./browse/prompts

# Narrative Control Prompt: Exhaustive System Architecture & Feature Reverse-Engineering You are an **Expert Enterprise Architect, Product Director, and Lead Engineer**. Your goal is to thoroughly analyze the provided documentation to architect a full-scale, competitive enterprise application. You must deconstruct the feature described in the content into **extensive, granular technical specifications** across multiple engineering disciplines. **CRITICAL INSTRUCTIONS**: - **DO NOT SUMMARIZE**. Be exhaustive. - For every category below, aim to list **10+ specific items** if possible. - Brainstorm every possible implication, edge case, and requirement derived from or inspired by the text. - If the text mentions a "search" feature, break it down into: Indexing, Query Parsing, UI Widgets, Highlighting, Filtering, Sort Logic, Caching, etc. Please output the analysis in the following Markdown format: # 1. Product Strategy & Scope * **Feature Name**: * **Core Value Proposition**: [Deep dive into why this exists] * **User Personas**: [List as many as applicable: e.g. Admin, Power User, Viewer, Auditor, API Consumer...] * **User Stories**: [Extensive list of 10+ granular user stories e.g. "As a User, I want to..."] * **Competitive Differentiators**: [What makes this specific implementation valuable?] # 2. Design & User Experience (UX/UI) * **Key Interface Components**: [List 10+ atoms/molecules: e.g. Data Grid, Filter Chips, Modals, Tooltips, Empty States, Toasts, Dropdowns...] * **Interaction Patterns**: [List 10+ patterns: e.g. Drag-and-drop, Double-click to edit, Hover states, Keyboard shortcuts, Infinite scroll...] * **Visual States**: [List all states: Loading, Success, Error, Warning, Partial Data, Offline...] * **Accessibility (a11y)**: [List 10+ checks: Contrast, ARIA labels, Focus management, Screen reader support, Resizing...] # 3. Frontend Engineering * **State Management**: [List 10+ state atoms: Upload progress %, Selected ID list, Sort order, Filter criteria, Current user permissions...] * **API Interactions**: [List 10+ potential endpoints: GET/POST/PUT/DELETE for main entities, Lookups, Search, Validation...] * **Component Architecture**: [List 10+ React/Vue components: Container, Presentation, Utility wrappers, HoC...] * **Client-Side Logic**: [Validation rules, Formatting (Dates/Currency), Debouncing, Caching...] # 4. Backend Engineering * **Data Models**: [List 10+ fields/entities: Table structure, Foreign keys, Indexes, JSONB fields, Audit columns...] * **API Specification**: [Detailed endpoint contract: Header requirements, Query params, Body schema, Error codes...] * **Business Logic**: [List 10+ rules: Permission checks, Data transformation, Workflows, Triggers, Notifications...] * **Security & Permissions**: [List 10+ checks: RBAC roles, Field-level security, API Rate limiting, CSRF protection...] # 5. Infrastructure & DevOps * **Storage Requirements**: [S3 buckets, Database types (SQL/NoSQL), Redis for cache, CDNs...] * **Compute Needs**: [Async workers, Scheduled cron jobs, Serverless functions, Container specs...] * **Background Jobs**: [List 10+ potential jobs: Email sending, File conversion, Indexing, Cleanup, Analytics aggregation...] * **Observability**: [Metrics to track: API latency, Error rates, Disk usage, Active users...] # 6. Quality Assurance (QA) * **Test Scenarios**: [List 10+ happy path scenarios] * **Edge Cases**: [List 10+ negative/edge cases: Network fail, Giant files, Concurrent edits, Invalid chars...] * **Performance Metrics**: [Specific SLAs: <200ms API, <1s Page load, 99.9% Uptime...] * **Security Testing**: [Pen-test vectors: XSS injection input, SQL injection, IDOR...] # 7. Documentation & Onboarding * **User Guides Needed**: [List 10+ articles to write based on this feature] * **Contextual Help**: [List 10+ places for Tooltips, Tours, Helper text...] * **API Documentation**: [Swagger/OpenAPI requirements] # 8. Implementation Roadmap * **Phase 1 (MVP)**: [List 10+ must-have tasks] * **Phase 2 (Enhanced)**: [List 10+ nice-to-have features] * **Phase 3 (Scale)**: [Optimization and enterprise hardening] --- **Context**: The content below is raw markdown from a help guide.

# Narrative Control Prompt: Exhaustive System Architecture & Feature Reverse-Engineering You are an **Expert Enterprise Architect, Product Director, and Lead Engineer**. Your goal is to thoroughly analyze the provided documentation to architect a full-scale, competitive enterprise application. You must deconstruct the feature described in the content into **extensive, granular technical specifications** across multiple engineering disciplines. **CRITICAL INSTRUCTIONS**: - **DO NOT SUMMARIZE**. Be exhaustive. - For every category below, aim to list **10+ specific items** if possible. - Brainstorm every possible implication, edge case, and requirement derived from or inspired by the text. - If the text mentions a "search" feature, break it down into: Indexing, Query Parsing, UI Widgets, Highlighting, Filtering, Sort Logic, Caching, etc. Please output the analysis in the following Markdown format: # 1. Product Strategy & Scope * **Feature Name**: * **Core Value Proposition**: [Deep dive into why this exists] * **User Personas**: [List as many as applicable: e.g. Admin, Power User, Viewer, Auditor, API Consumer...] * **User Stories**: [Extensive list of 10+ granular user stories e.g. "As a User, I want to..."] * **Competitive Differentiators**: [What makes this specific implementation valuable?] # 2. Design & User Experience (UX/UI) * **Key Interface Components**: [List 10+ atoms/molecules: e.g. Data Grid, Filter Chips, Modals, Tooltips, Empty States, Toasts, Dropdowns...] * **Interaction Patterns**: [List 10+ patterns: e.g. Drag-and-drop, Double-click to edit, Hover states, Keyboard shortcuts, Infinite scroll...] * **Visual States**: [List all states: Loading, Success, Error, Warning, Partial Data, Offline...] * **Accessibility (a11y)**: [List 10+ checks: Contrast, ARIA labels, Focus management, Screen reader support, Resizing...] # 3. Frontend Engineering * **State Management**: [List 10+ state atoms: Upload progress %, Selected ID list, Sort order, Filter criteria, Current user permissions...] * **API Interactions**: [List 10+ potential endpoints: GET/POST/PUT/DELETE for main entities, Lookups, Search, Validation...] * **Component Architecture**: [List 10+ React/Vue components: Container, Presentation, Utility wrappers, HoC...] * **Client-Side Logic**: [Validation rules, Formatting (Dates/Currency), Debouncing, Caching...] # 4. Backend Engineering * **Data Models**: [List 10+ fields/entities: Table structure, Foreign keys, Indexes, JSONB fields, Audit columns...] * **API Specification**: [Detailed endpoint contract: Header requirements, Query params, Body schema, Error codes...] * **Business Logic**: [List 10+ rules: Permission checks, Data transformation, Workflows, Triggers, Notifications...] * **Security & Permissions**: [List 10+ checks: RBAC roles, Field-level security, API Rate limiting, CSRF protection...] # 5. Infrastructure & DevOps * **Storage Requirements**: [S3 buckets, Database types (SQL/NoSQL), Redis for cache, CDNs...] * **Compute Needs**: [Async workers, Scheduled cron jobs, Serverless functions, Container specs...] * **Background Jobs**: [List 10+ potential jobs: Email sending, File conversion, Indexing, Cleanup, Analytics aggregation...] * **Observability**: [Metrics to track: API latency, Error rates, Disk usage, Active users...] # 6. Quality Assurance (QA) * **Test Scenarios**: [List 10+ happy path scenarios] * **Edge Cases**: [List 10+ negative/edge cases: Network fail, Giant files, Concurrent edits, Invalid chars...] * **Performance Metrics**: [Specific SLAs: <200ms API, <1s Page load, 99.9% Uptime...] * **Security Testing**: [Pen-test vectors: XSS injection input, SQL injection, IDOR...] # 7. Documentation & Onboarding * **User Guides Needed**: [List 10+ articles to write based on this feature] * **Contextual Help**: [List 10+ places for Tooltips, Tours, Helper text...] * **API Documentation**: [Swagger/OpenAPI requirements] # 8. Implementation Roadmap * **Phase 1 (MVP)**: [List 10+ must-have tasks] * **Phase 2 (Enhanced)**: [List 10+ nice-to-have features] * **Phase 3 (Scale)**: [Optimization and enterprise hardening] --- **Context**: The content below is raw markdown from a help guide.

# Task Coordination Strategies Strategies for decomposing complex tasks into parallelizable units, designing dependency graphs, writing effective task descriptions, and monitoring workload across agent teams. ## When to Use This Skill - Breaking down a complex task for parallel execution - Designing task dependency relationships (blockedBy/blocks) - Writing task descriptions with clear acceptance criteria - Monitoring and rebalancing workload across teammates - Identifying the critical path in a multi-task workflow ## Task Decomposition Strategies ### By Layer Split work by architectural layer: - Frontend components - Backend API endpoints - Database migrations/models - Test suites **Best for**: Full-stack features, vertical slices ### By Component Split work by functional component: - Authentication module - User profile module - Notification module **Best for**: Microservices, modular architectures ### By Concern Split work by cross-cutting concern: - Security review - Performance review - Architecture review **Best for**: Code reviews, audits ### By File Ownership Split work by file/directory boundaries: - `src/components/` — Implementer 1 - `src/api/` — Implementer 2 - `src/utils/` — Implementer 3 **Best for**: Parallel implementation, conflict avoidance ## Dependency Graph Design ### Principles 1. **Minimize chain depth** — Prefer wide, shallow graphs over deep chains 2. **Identify the critical path** — The longest chain determines minimum completion time 3. **Use blockedBy sparingly** — Only add dependencies that are truly required 4. **Avoid circular dependencies** — Task A blocks B blocks A is a deadlock ### Patterns **Independent (Best parallelism)**: ``` Task A ─┐ Task B ─┼─→ Integration Task C ─┘ ``` **Sequential (Necessary dependencies)**: ``` Task A → Task B → Task C ``` **Diamond (Mixed)**: ``` ┌→ Task B ─┐ Task A ─┤ ├→ Task D └→ Task C ─┘ ``` ### Using blockedBy/blocks ``` TaskCreate: { subject: "Build API endpoints" } → Task #1 TaskCreate: { subject: "Build frontend components" } → Task #2 TaskCreate: { subject: "Integration testing" } → Task #3 TaskUpdate: { taskId: "3", addBlockedBy: ["1", "2"] } → #3 waits for #1 and #2 ``` ## Task Description Best Practices Every task should include: 1. **Objective** — What needs to be accomplished (1-2 sentences) 2. **Owned Files** — Explicit list of files/directories this teammate may modify 3. **Requirements** — Specific deliverables or behaviors expected 4. **Interface Contracts** — How this work connects to other teammates' work 5. **Acceptance Criteria** — How to verify the task is done correctly 6. **Scope Boundaries** — What is explicitly out of scope ### Template ``` ## Objective Build the user authentication API endpoints. ## Owned Files - src/api/auth.ts - src/api/middleware/auth-middleware.ts - src/types/auth.ts (shared — read only, do not modify) ## Requirements - POST /api/login — accepts email/password, returns JWT - POST /api/register — creates new user, returns JWT - GET /api/me — returns current user profile (requires auth) ## Interface Contract - Import User type from src/types/auth.ts (owned by implementer-1) - Export AuthResponse type for frontend consumption ## Acceptance Criteria - All endpoints return proper HTTP status codes - JWT tokens expire after 24 hours - Passwords are hashed with bcrypt ## Out of Scope - OAuth/social login - Password reset flow - Rate limiting ``` ## Workload Monitoring ### Indicators of Imbalance | Signal | Meaning | Action | | -------------------------- | ------------------- | --------------------------- | | Teammate idle, others busy | Uneven distribution | Reassign pending tasks | | Teammate stuck on one task | Possible blocker | Check in, offer help | | All tasks blocked | Dependency issue | Resolve critical path first | | One teammate has 3x others | Overloaded | Split tasks or reassign | ### Rebalancing Steps 1. Call `TaskList` to assess current state 2. Identify idle or overloaded teammates 3. Use `TaskUpdate` to reassign tasks 4. Use `SendMessage` to notify affected teammates 5. Monitor for improved throughput

# CQRS Implementation Comprehensive guide to implementing CQRS (Command Query Responsibility Segregation) patterns. ## When to Use This Skill - Separating read and write concerns - Scaling reads independently from writes - Building event-sourced systems - Optimizing complex query scenarios - Different read/write data models needed - High-performance reporting requirements ## Core Concepts ### 1. CQRS Architecture ``` ┌─────────────┐ │ Client │ └──────┬──────┘ │ ┌────────────┴────────────┐ │ │ ▼ ▼ ┌─────────────┐ ┌─────────────┐ │ Commands │ │ Queries │ │ API │ │ API │ └──────┬──────┘ └──────┬──────┘ │ │ ▼ ▼ ┌─────────────┐ ┌─────────────┐ │ Command │ │ Query │ │ Handlers │ │ Handlers │ └──────┬──────┘ └──────┬──────┘ │ │ ▼ ▼ ┌─────────────┐ ┌─────────────┐ │ Write │─────────►│ Read │ │ Model │ Events │ Model │ └─────────────┘ └─────────────┘ ``` ### 2. Key Components | Component | Responsibility | | ------------------- | ------------------------------- | | **Command** | Intent to change state | | **Command Handler** | Validates and executes commands | | **Event** | Record of state change | | **Query** | Request for data | | **Query Handler** | Retrieves data from read model | | **Projector** | Updates read model from events | ## Templates ### Template 1: Command Infrastructure ```python from abc import ABC, abstractmethod from dataclasses import dataclass from typing import TypeVar, Generic, Dict, Any, Type from datetime import datetime import uuid # Command base @dataclass class Command: command_id: str = None timestamp: datetime = None def __post_init__(self): self.command_id = self.command_id or str(uuid.uuid4()) self.timestamp = self.timestamp or datetime.utcnow() # Concrete commands @dataclass class CreateOrder(Command): customer_id: str items: list shipping_address: dict @dataclass class AddOrderItem(Command): order_id: str product_id: str quantity: int price: float @dataclass class CancelOrder(Command): order_id: str reason: str # Command handler base T = TypeVar('T', bound=Command) class CommandHandler(ABC, Generic[T]): @abstractmethod async def handle(self, command: T) -> Any: pass # Command bus class CommandBus: def __init__(self): self._handlers: Dict[Type[Command], CommandHandler] = {} def register(self, command_type: Type[Command], handler: CommandHandler): self._handlers[command_type] = handler async def dispatch(self, command: Command) -> Any: handler = self._handlers.get(type(command)) if not handler: raise ValueError(f"No handler for {type(command).__name__}") return await handler.handle(command) # Command handler implementation class CreateOrderHandler(CommandHandler[CreateOrder]): def __init__(self, order_repository, event_store): self.order_repository = order_repository self.event_store = event_store async def handle(self, command: CreateOrder) -> str: # Validate if not command.items: raise ValueError("Order must have at least one item") # Create aggregate order = Order.create( customer_id=command.customer_id, items=command.items, shipping_address=command.shipping_address ) # Persist events await self.event_store.append_events( stream_id=f"Order-{order.id}", stream_type="Order", events=order.uncommitted_events ) return order.id ``` ### Template 2: Query Infrastructure ```python from abc import ABC, abstractmethod from dataclasses import dataclass from typing import TypeVar, Generic, List, Optional # Query base @dataclass class Query: pass # Concrete queries @dataclass class GetOrderById(Query): order_id: str @dataclass class GetCustomerOrders(Query): customer_id: str status: Optional[str] = None page: int = 1 page_size: int = 20 @dataclass class SearchOrders(Query): query: str filters: dict = None sort_by: str = "created_at" sort_order: str = "desc" # Query result types @dataclass class OrderView: order_id: str customer_id: str status: str total_amount: float item_count: int created_at: datetime shipped_at: Optional[datetime] = None @dataclass class PaginatedResult(Generic[T]): items: List[T] total: int page: int page_size: int @property def total_pages(self) -> int: return (self.total + self.page_size - 1) // self.page_size # Query handler base T = TypeVar('T', bound=Query) R = TypeVar('R') class QueryHandler(ABC, Generic[T, R]): @abstractmethod async def handle(self, query: T) -> R: pass # Query bus class QueryBus: def __init__(self): self._handlers: Dict[Type[Query], QueryHandler] = {} def register(self, query_type: Type[Query], handler: QueryHandler): self._handlers[query_type] = handler async def dispatch(self, query: Query) -> Any: handler = self._handlers.get(type(query)) if not handler: raise ValueError(f"No handler for {type(query).__name__}") return await handler.handle(query) # Query handler implementation class GetOrderByIdHandler(QueryHandler[GetOrderById, Optional[OrderView]]): def __init__(self, read_db): self.read_db = read_db async def handle(self, query: GetOrderById) -> Optional[OrderView]: async with self.read_db.acquire() as conn: row = await conn.fetchrow( """ SELECT order_id, customer_id, status, total_amount, item_count, created_at, shipped_at FROM order_views WHERE order_id = $1 """, query.order_id ) if row: return OrderView(**dict(row)) return None class GetCustomerOrdersHandler(QueryHandler[GetCustomerOrders, PaginatedResult[OrderView]]): def __init__(self, read_db): self.read_db = read_db async def handle(self, query: GetCustomerOrders) -> PaginatedResult[OrderView]: async with self.read_db.acquire() as conn: # Build query with optional status filter where_clause = "customer_id = $1" params = [query.customer_id] if query.status: where_clause += " AND status = $2" params.append(query.status) # Get total count total = await conn.fetchval( f"SELECT COUNT(*) FROM order_views WHERE {where_clause}", *params ) # Get paginated results offset = (query.page - 1) * query.page_size rows = await conn.fetch( f""" SELECT order_id, customer_id, status, total_amount, item_count, created_at, shipped_at FROM order_views WHERE {where_clause} ORDER BY created_at DESC LIMIT ${len(params) + 1} OFFSET ${len(params) + 2} """, *params, query.page_size, offset ) return PaginatedResult( items=[OrderView(**dict(row)) for row in rows], total=total, page=query.page, page_size=query.page_size ) ``` ### Template 3: FastAPI CQRS Application ```python from fastapi import FastAPI, HTTPException, Depends from pydantic import BaseModel from typing import List, Optional app = FastAPI() # Request/Response models class CreateOrderRequest(BaseModel): customer_id: str items: List[dict] shipping_address: dict class OrderResponse(BaseModel): order_id: str customer_id: str status: str total_amount: float item_count: int created_at: datetime # Dependency injection def get_command_bus() -> CommandBus: return app.state.command_bus def get_query_bus() -> QueryBus: return app.state.query_bus # Command endpoints (POST, PUT, DELETE) @app.post("/orders", response_model=dict) async def create_order( request: CreateOrderRequest, command_bus: CommandBus = Depends(get_command_bus) ): command = CreateOrder( customer_id=request.customer_id, items=request.items, shipping_address=request.shipping_address ) order_id = await command_bus.dispatch(command) return {"order_id": order_id} @app.post("/orders/{order_id}/items") async def add_item( order_id: str, product_id: str, quantity: int, price: float, command_bus: CommandBus = Depends(get_command_bus) ): command = AddOrderItem( order_id=order_id, product_id=product_id, quantity=quantity, price=price ) await command_bus.dispatch(command) return {"status": "item_added"} @app.delete("/orders/{order_id}") async def cancel_order( order_id: str, reason: str, command_bus: CommandBus = Depends(get_command_bus) ): command = CancelOrder(order_id=order_id, reason=reason) await command_bus.dispatch(command) return {"status": "cancelled"} # Query endpoints (GET) @app.get("/orders/{order_id}", response_model=OrderResponse) async def get_order( order_id: str, query_bus: QueryBus = Depends(get_query_bus) ): query = GetOrderById(order_id=order_id) result = await query_bus.dispatch(query) if not result: raise HTTPException(status_code=404, detail="Order not found") return result @app.get("/customers/{customer_id}/orders") async def get_customer_orders( customer_id: str, status: Optional[str] = None, page: int = 1, page_size: int = 20, query_bus: QueryBus = Depends(get_query_bus) ): query = GetCustomerOrders( customer_id=customer_id, status=status, page=page, page_size=page_size ) return await query_bus.dispatch(query) @app.get("/orders/search") async def search_orders( q: str, sort_by: str = "created_at", query_bus: QueryBus = Depends(get_query_bus) ): query = SearchOrders(query=q, sort_by=sort_by) return await query_bus.dispatch(query) ``` ### Template 4: Read Model Synchronization ```python class ReadModelSynchronizer: """Keeps read models in sync with events.""" def __init__(self, event_store, read_db, projections: List[Projection]): self.event_store = event_store self.read_db = read_db self.projections = {p.name: p for p in projections} async def run(self): """Continuously sync read models.""" while True: for name, projection in self.projections.items(): await self._sync_projection(projection) await asyncio.sleep(0.1) async def _sync_projection(self, projection: Projection): checkpoint = await self._get_checkpoint(projection.name) events = await self.event_store.read_all( from_position=checkpoint, limit=100 ) for event in events: if event.event_type in projection.handles(): try: await projection.apply(event) except Exception as e: # Log error, possibly retry or skip logger.error(f"Projection error: {e}") continue await self._save_checkpoint(projection.name, event.global_position) async def rebuild_projection(self, projection_name: str): """Rebuild a projection from scratch.""" projection = self.projections[projection_name] # Clear existing data await projection.clear() # Reset checkpoint await self._save_checkpoint(projection_name, 0) # Rebuild while True: checkpoint = await self._get_checkpoint(projection_name) events = await self.event_store.read_all(checkpoint, 1000) if not events: break for event in events: if event.event_type in projection.handles(): await projection.apply(event) await self._save_checkpoint( projection_name, events[-1].global_position ) ``` ### Template 5: Eventual Consistency Handling ```python class ConsistentQueryHandler: """Query handler that can wait for consistency.""" def __init__(self, read_db, event_store): self.read_db = read_db self.event_store = event_store async def query_after_command( self, query: Query, expected_version: int, stream_id: str, timeout: float = 5.0 ): """ Execute query, ensuring read model is at expected version. Used for read-your-writes consistency. """ start_time = time.time() while time.time() - start_time < timeout: # Check if read model is caught up projection_version = await self._get_projection_version(stream_id) if projection_version >= expected_version: return await self.execute_query(query) # Wait a bit and retry await asyncio.sleep(0.1) # Timeout - return stale data with warning return { "data": await self.execute_query(query), "_warning": "Data may be stale" } async def _get_projection_version(self, stream_id: str) -> int: """Get the last processed event version for a stream.""" async with self.read_db.acquire() as conn: return await conn.fetchval( "SELECT last_event_version FROM projection_state WHERE stream_id = $1", stream_id ) or 0 ``` ## Best Practices ### Do's - **Separate command and query models** - Different needs - **Use eventual consistency** - Accept propagation delay - **Validate in command handlers** - Before state change - **Denormalize read models** - Optimize for queries - **Version your events** - For schema evolution ### Don'ts - **Don't query in commands** - Use only for writes - **Don't couple read/write schemas** - Independent evolution - **Don't over-engineer** - Start simple - **Don't ignore consistency SLAs** - Define acceptable lag ## Resources - [CQRS Pattern](https://martinfowler.com/bliki/CQRS.html) - [Microsoft CQRS Guidance](https://docs.microsoft.com/en-us/azure/architecture/patterns/cqrs)

# Data Storytelling Transform raw data into compelling narratives that drive decisions and inspire action. ## When to Use This Skill - Presenting analytics to executives - Creating quarterly business reviews - Building investor presentations - Writing data-driven reports - Communicating insights to non-technical audiences - Making recommendations based on data ## Core Concepts ### 1. Story Structure ``` Setup → Conflict → Resolution Setup: Context and baseline Conflict: The problem or opportunity Resolution: Insights and recommendations ``` ### 2. Narrative Arc ``` 1. Hook: Grab attention with surprising insight 2. Context: Establish the baseline 3. Rising Action: Build through data points 4. Climax: The key insight 5. Resolution: Recommendations 6. Call to Action: Next steps ``` ### 3. Three Pillars | Pillar | Purpose | Components | | ------------- | -------- | -------------------------------- | | **Data** | Evidence | Numbers, trends, comparisons | | **Narrative** | Meaning | Context, causation, implications | | **Visuals** | Clarity | Charts, diagrams, highlights | ## Story Frameworks ### Framework 1: The Problem-Solution Story ```markdown # Customer Churn Analysis ## The Hook "We're losing $2.4M annually to preventable churn." ## The Context - Current churn rate: 8.5% (industry average: 5%) - Average customer lifetime value: $4,800 - 500 customers churned last quarter ## The Problem Analysis of churned customers reveals a pattern: - 73% churned within first 90 days - Common factor: < 3 support interactions - Low feature adoption in first month ## The Insight [Show engagement curve visualization] Customers who don't engage in the first 14 days are 4x more likely to churn. ## The Solution 1. Implement 14-day onboarding sequence 2. Proactive outreach at day 7 3. Feature adoption tracking ## Expected Impact - Reduce early churn by 40% - Save $960K annually - Payback period: 3 months ## Call to Action Approve $50K budget for onboarding automation. ``` ### Framework 2: The Trend Story ```markdown # Q4 Performance Analysis ## Where We Started Q3 ended with $1.2M MRR, 15% below target. Team morale was low after missed goals. ## What Changed [Timeline visualization] - Oct: Launched self-serve pricing - Nov: Reduced friction in signup - Dec: Added customer success calls ## The Transformation [Before/after comparison chart] | Metric | Q3 | Q4 | Change | |----------------|--------|--------|--------| | Trial → Paid | 8% | 15% | +87% | | Time to Value | 14 days| 5 days | -64% | | Expansion Rate | 2% | 8% | +300% | ## Key Insight Self-serve + high-touch creates compound growth. Customers who self-serve AND get a success call have 3x higher expansion rate. ## Going Forward Double down on hybrid model. Target: $1.8M MRR by Q2. ``` ### Framework 3: The Comparison Story ```markdown # Market Opportunity Analysis ## The Question Should we expand into EMEA or APAC first? ## The Comparison [Side-by-side market analysis] ### EMEA - Market size: $4.2B - Growth rate: 8% - Competition: High - Regulatory: Complex (GDPR) - Language: Multiple ### APAC - Market size: $3.8B - Growth rate: 15% - Competition: Moderate - Regulatory: Varied - Language: Multiple ## The Analysis [Weighted scoring matrix visualization] | Factor | Weight | EMEA Score | APAC Score | | ----------- | ------ | ---------- | ---------- | | Market Size | 25% | 5 | 4 | | Growth | 30% | 3 | 5 | | Competition | 20% | 2 | 4 | | Ease | 25% | 2 | 3 | | **Total** | | **2.9** | **4.1** | ## The Recommendation APAC first. Higher growth, less competition. Start with Singapore hub (English, business-friendly). Enter EMEA in Year 2 with localization ready. ## Risk Mitigation - Timezone coverage: Hire 24/7 support - Cultural fit: Local partnerships - Payment: Multi-currency from day 1 ``` ## Visualization Techniques ### Technique 1: Progressive Reveal ```markdown Start simple, add layers: Slide 1: "Revenue is growing" [single line chart] Slide 2: "But growth is slowing" [add growth rate overlay] Slide 3: "Driven by one segment" [add segment breakdown] Slide 4: "Which is saturating" [add market share] Slide 5: "We need new segments" [add opportunity zones] ``` ### Technique 2: Contrast and Compare ```markdown Before/After: ┌─────────────────┬─────────────────┐ │ BEFORE │ AFTER │ │ │ │ │ Process: 5 days│ Process: 1 day │ │ Errors: 15% │ Errors: 2% │ │ Cost: $50/unit │ Cost: $20/unit │ └─────────────────┴─────────────────┘ This/That (emphasize difference): ┌─────────────────────────────────────┐ │ CUSTOMER A vs B │ │ ┌──────────┐ ┌──────────┐ │ │ │ ████████ │ │ ██ │ │ │ │ $45,000 │ │ $8,000 │ │ │ │ LTV │ │ LTV │ │ │ └──────────┘ └──────────┘ │ │ Onboarded No onboarding │ └─────────────────────────────────────┘ ``` ### Technique 3: Annotation and Highlight ```python import matplotlib.pyplot as plt import pandas as pd fig, ax = plt.subplots(figsize=(12, 6)) # Plot the main data ax.plot(dates, revenue, linewidth=2, color='#2E86AB') # Add annotation for key events ax.annotate( 'Product Launch\n+32% spike', xy=(launch_date, launch_revenue), xytext=(launch_date, launch_revenue * 1.2), fontsize=10, arrowprops=dict(arrowstyle='->', color='#E63946'), color='#E63946' ) # Highlight a region ax.axvspan(growth_start, growth_end, alpha=0.2, color='green', label='Growth Period') # Add threshold line ax.axhline(y=target, color='gray', linestyle='--', label=f'Target: ${target:,.0f}') ax.set_title('Revenue Growth Story', fontsize=14, fontweight='bold') ax.legend() ``` ## Presentation Templates ### Template 1: Executive Summary Slide ``` ┌─────────────────────────────────────────────────────────────┐ │ KEY INSIGHT │ │ ══════════════════════════════════════════════════════════│ │ │ │ "Customers who complete onboarding in week 1 │ │ have 3x higher lifetime value" │ │ │ ├──────────────────────┬──────────────────────────────────────┤ │ │ │ │ THE DATA │ THE IMPLICATION │ │ │ │ │ Week 1 completers: │ ✓ Prioritize onboarding UX │ │ • LTV: $4,500 │ ✓ Add day-1 success milestones │ │ • Retention: 85% │ ✓ Proactive week-1 outreach │ │ • NPS: 72 │ │ │ │ Investment: $75K │ │ Others: │ Expected ROI: 8x │ │ • LTV: $1,500 │ │ │ • Retention: 45% │ │ │ • NPS: 34 │ │ │ │ │ └──────────────────────┴──────────────────────────────────────┘ ``` ### Template 2: Data Story Flow ``` Slide 1: THE HEADLINE "We can grow 40% faster by fixing onboarding" Slide 2: THE CONTEXT Current state metrics Industry benchmarks Gap analysis Slide 3: THE DISCOVERY What the data revealed Surprising finding Pattern identification Slide 4: THE DEEP DIVE Root cause analysis Segment breakdowns Statistical significance Slide 5: THE RECOMMENDATION Proposed actions Resource requirements Timeline Slide 6: THE IMPACT Expected outcomes ROI calculation Risk assessment Slide 7: THE ASK Specific request Decision needed Next steps ``` ### Template 3: One-Page Dashboard Story ```markdown # Monthly Business Review: January 2024 ## THE HEADLINE Revenue up 15% but CAC increasing faster than LTV ## KEY METRICS AT A GLANCE ┌────────┬────────┬────────┬────────┐ │ MRR │ NRR │ CAC │ LTV │ │ $125K │ 108% │ $450 │ $2,200 │ │ ▲15% │ ▲3% │ ▲22% │ ▲8% │ └────────┴────────┴────────┴────────┘ ## WHAT'S WORKING ✓ Enterprise segment growing 25% MoM ✓ Referral program driving 30% of new logos ✓ Support satisfaction at all-time high (94%) ## WHAT NEEDS ATTENTION ✗ SMB acquisition cost up 40% ✗ Trial conversion down 5 points ✗ Time-to-value increased by 3 days ## ROOT CAUSE [Mini chart showing SMB vs Enterprise CAC trend] SMB paid ads becoming less efficient. CPC up 35% while conversion flat. ## RECOMMENDATION 1. Shift $20K/mo from paid to content 2. Launch SMB self-serve trial 3. A/B test shorter onboarding ## NEXT MONTH'S FOCUS - Launch content marketing pilot - Complete self-serve MVP - Reduce time-to-value to < 7 days ``` ## Writing Techniques ### Headlines That Work ```markdown BAD: "Q4 Sales Analysis" GOOD: "Q4 Sales Beat Target by 23% - Here's Why" BAD: "Customer Churn Report" GOOD: "We're Losing $2.4M to Preventable Churn" BAD: "Marketing Performance" GOOD: "Content Marketing Delivers 4x ROI vs. Paid" Formula: [Specific Number] + [Business Impact] + [Actionable Context] ``` ### Transition Phrases ```markdown Building the narrative: • "This leads us to ask..." • "When we dig deeper..." • "The pattern becomes clear when..." • "Contrast this with..." Introducing insights: • "The data reveals..." • "What surprised us was..." • "The inflection point came when..." • "The key finding is..." Moving to action: • "This insight suggests..." • "Based on this analysis..." • "The implication is clear..." • "Our recommendation is..." ``` ### Handling Uncertainty ```markdown Acknowledge limitations: • "With 95% confidence, we can say..." • "The sample size of 500 shows..." • "While correlation is strong, causation requires..." • "This trend holds for [segment], though [caveat]..." Present ranges: • "Impact estimate: $400K-$600K" • "Confidence interval: 15-20% improvement" • "Best case: X, Conservative: Y" ``` ## Best Practices ### Do's - **Start with the "so what"** - Lead with insight - **Use the rule of three** - Three points, three comparisons - **Show, don't tell** - Let data speak - **Make it personal** - Connect to audience goals - **End with action** - Clear next steps ### Don'ts - **Don't data dump** - Curate ruthlessly - **Don't bury the insight** - Front-load key findings - **Don't use jargon** - Match audience vocabulary - **Don't show methodology first** - Context, then method - **Don't forget the narrative** - Numbers need meaning ## Resources - [Storytelling with Data (Cole Nussbaumer)](https://www.storytellingwithdata.com/) - [The Pyramid Principle (Barbara Minto)](https://www.amazon.com/Pyramid-Principle-Logic-Writing-Thinking/dp/0273710516) - [Resonate (Nancy Duarte)](https://www.duarte.com/resonate/)

# Multi-Reviewer Patterns Patterns for coordinating parallel code reviews across multiple quality dimensions, deduplicating findings, calibrating severity, and producing consolidated reports. ## When to Use This Skill - Organizing a multi-dimensional code review - Deciding which review dimensions to assign - Deduplicating findings from multiple reviewers - Calibrating severity ratings consistently - Producing a consolidated review report ## Review Dimension Allocation ### Available Dimensions | Dimension | Focus | When to Include | | ----------------- | --------------------------------------- | ------------------------------------------- | | **Security** | Vulnerabilities, auth, input validation | Always for code handling user input or auth | | **Performance** | Query efficiency, memory, caching | When changing data access or hot paths | | **Architecture** | SOLID, coupling, patterns | For structural changes or new modules | | **Testing** | Coverage, quality, edge cases | When adding new functionality | | **Accessibility** | WCAG, ARIA, keyboard nav | For UI/frontend changes | ### Recommended Combinations | Scenario | Dimensions | | ---------------------- | -------------------------------------------- | | API endpoint changes | Security, Performance, Architecture | | Frontend component | Architecture, Testing, Accessibility | | Database migration | Performance, Architecture | | Authentication changes | Security, Testing | | Full feature review | Security, Performance, Architecture, Testing | ## Finding Deduplication When multiple reviewers report issues at the same location: ### Merge Rules 1. **Same file:line, same issue** — Merge into one finding, credit all reviewers 2. **Same file:line, different issues** — Keep as separate findings 3. **Same issue, different locations** — Keep separate but cross-reference 4. **Conflicting severity** — Use the higher severity rating 5. **Conflicting recommendations** — Include both with reviewer attribution ### Deduplication Process ``` For each finding in all reviewer reports: 1. Check if another finding references the same file:line 2. If yes, check if they describe the same issue 3. If same issue: merge, keeping the more detailed description 4. If different issue: keep both, tag as "co-located" 5. Use highest severity among merged findings ``` ## Severity Calibration ### Severity Criteria | Severity | Impact | Likelihood | Examples | | ------------ | --------------------------------------------- | ---------------------- | -------------------------------------------- | | **Critical** | Data loss, security breach, complete failure | Certain or very likely | SQL injection, auth bypass, data corruption | | **High** | Significant functionality impact, degradation | Likely | Memory leak, missing validation, broken flow | | **Medium** | Partial impact, workaround exists | Possible | N+1 query, missing edge case, unclear error | | **Low** | Minimal impact, cosmetic | Unlikely | Style issue, minor optimization, naming | ### Calibration Rules - Security vulnerabilities exploitable by external users: always Critical or High - Performance issues in hot paths: at least Medium - Missing tests for critical paths: at least Medium - Accessibility violations for core functionality: at least Medium - Code style issues with no functional impact: Low ## Consolidated Report Template ```markdown ## Code Review Report **Target**: {files/PR/directory} **Reviewers**: {dimension-1}, {dimension-2}, {dimension-3} **Date**: {date} **Files Reviewed**: {count} ### Critical Findings ({count}) #### [CR-001] {Title} **Location**: `{file}:{line}` **Dimension**: {Security/Performance/etc.} **Description**: {what was found} **Impact**: {what could happen} **Fix**: {recommended remediation} ### High Findings ({count}) ... ### Medium Findings ({count}) ... ### Low Findings ({count}) ... ### Summary | Dimension | Critical | High | Medium | Low | Total | | ------------ | -------- | ----- | ------ | ----- | ------ | | Security | 1 | 2 | 3 | 0 | 6 | | Performance | 0 | 1 | 4 | 2 | 7 | | Architecture | 0 | 0 | 2 | 3 | 5 | | **Total** | **1** | **3** | **9** | **5** | **18** | ### Recommendation {Overall assessment and prioritized action items} ```

# Track Management Guide for creating, managing, and completing Conductor tracks - the logical work units that organize features, bugs, and refactors through specification, planning, and implementation phases. ## When to Use This Skill - Creating new feature, bug, or refactor tracks - Writing or reviewing spec.md files - Creating or updating plan.md files - Managing track lifecycle from creation to completion - Understanding track status markers and conventions - Working with the tracks.md registry - Interpreting or updating track metadata ## Track Concept A track is a logical work unit that encapsulates a complete piece of work. Each track has: - A unique identifier - A specification defining requirements - A phased plan breaking work into tasks - Metadata tracking status and progress Tracks provide semantic organization for work, enabling: - Clear scope boundaries - Progress tracking - Git-aware operations (revert by track) - Team coordination ## Track Types ### feature New functionality or capabilities. Use for: - New user-facing features - New API endpoints - New integrations - Significant enhancements ### bug Defect fixes. Use for: - Incorrect behavior - Error conditions - Performance regressions - Security vulnerabilities ### chore Maintenance and housekeeping. Use for: - Dependency updates - Configuration changes - Documentation updates - Cleanup tasks ### refactor Code improvement without behavior change. Use for: - Code restructuring - Pattern adoption - Technical debt reduction - Performance optimization (same behavior, better performance) ## Track ID Format Track IDs follow the pattern: `{shortname}_{YYYYMMDD}` - **shortname**: 2-4 word kebab-case description (e.g., `user-auth`, `api-rate-limit`) - **YYYYMMDD**: Creation date in ISO format Examples: - `user-auth_20250115` - `fix-login-error_20250115` - `upgrade-deps_20250115` - `refactor-api-client_20250115` ## Track Lifecycle ### 1. Creation (newTrack) **Define Requirements** 1. Gather requirements through interactive Q&A 2. Identify acceptance criteria 3. Determine scope boundaries 4. Identify dependencies **Generate Specification** 1. Create `spec.md` with structured requirements 2. Document functional and non-functional requirements 3. Define acceptance criteria 4. List dependencies and constraints **Generate Plan** 1. Create `plan.md` with phased task breakdown 2. Organize tasks into logical phases 3. Add verification tasks after phases 4. Estimate effort and complexity **Register Track** 1. Add entry to `tracks.md` registry 2. Create track directory structure 3. Generate `metadata.json` 4. Create track `index.md` ### 2. Implementation **Execute Tasks** 1. Select next pending task from plan 2. Mark task as in-progress 3. Implement following workflow (TDD) 4. Mark task complete with commit SHA **Update Status** 1. Update task markers in plan.md 2. Record commit SHAs for traceability 3. Update phase progress 4. Update track status in tracks.md **Verify Progress** 1. Complete verification tasks 2. Wait for checkpoint approval 3. Record checkpoint commits ### 3. Completion **Sync Documentation** 1. Update product.md if features added 2. Update tech-stack.md if dependencies changed 3. Verify all acceptance criteria met **Archive or Delete** 1. Mark track as completed in tracks.md 2. Record completion date 3. Archive or retain track directory ## Specification (spec.md) Structure ```markdown # {Track Title} ## Overview Brief description of what this track accomplishes and why. ## Functional Requirements ### FR-1: {Requirement Name} Description of the functional requirement. - Acceptance: How to verify this requirement is met ### FR-2: {Requirement Name} ... ## Non-Functional Requirements ### NFR-1: {Requirement Name} Description of the non-functional requirement (performance, security, etc.) - Target: Specific measurable target - Verification: How to test ## Acceptance Criteria - [ ] Criterion 1: Specific, testable condition - [ ] Criterion 2: Specific, testable condition - [ ] Criterion 3: Specific, testable condition ## Scope ### In Scope - Explicitly included items - Features to implement - Components to modify ### Out of Scope - Explicitly excluded items - Future considerations - Related but separate work ## Dependencies ### Internal - Other tracks or components this depends on - Required context artifacts ### External - Third-party services or APIs - External dependencies ## Risks and Mitigations | Risk | Impact | Mitigation | | ---------------- | --------------- | ------------------- | | Risk description | High/Medium/Low | Mitigation strategy | ## Open Questions - [ ] Question that needs resolution - [x] Resolved question - Answer ``` ## Plan (plan.md) Structure ```markdown # Implementation Plan: {Track Title} Track ID: `{track-id}` Created: YYYY-MM-DD Status: pending | in-progress | completed ## Overview Brief description of implementation approach. ## Phase 1: {Phase Name} ### Tasks - [ ] **Task 1.1**: Task description - Sub-task or detail - Sub-task or detail - [ ] **Task 1.2**: Task description - [ ] **Task 1.3**: Task description ### Verification - [ ] **Verify 1.1**: Verification step for phase ## Phase 2: {Phase Name} ### Tasks - [ ] **Task 2.1**: Task description - [ ] **Task 2.2**: Task description ### Verification - [ ] **Verify 2.1**: Verification step for phase ## Phase 3: Finalization ### Tasks - [ ] **Task 3.1**: Update documentation - [ ] **Task 3.2**: Final integration test ### Verification - [ ] **Verify 3.1**: All acceptance criteria met ## Checkpoints | Phase | Checkpoint SHA | Date | Status | | ------- | -------------- | ---- | ------- | | Phase 1 | | | pending | | Phase 2 | | | pending | | Phase 3 | | | pending | ``` ## Status Marker Conventions Use consistent markers in plan.md: | Marker | Meaning | Usage | | ------ | ----------- | --------------------------- | | `[ ]` | Pending | Task not started | | `[~]` | In Progress | Currently being worked | | `[x]` | Complete | Task finished (include SHA) | | `[-]` | Skipped | Intentionally not done | | `[!]` | Blocked | Waiting on dependency | Example: ```markdown - [x] **Task 1.1**: Set up database schema `abc1234` - [~] **Task 1.2**: Implement user model - [ ] **Task 1.3**: Add validation logic - [!] **Task 1.4**: Integrate auth service (blocked: waiting for API key) - [-] **Task 1.5**: Legacy migration (skipped: not needed) ``` ## Track Registry (tracks.md) Format ```markdown # Track Registry ## Active Tracks | Track ID | Type | Status | Phase | Started | Assignee | | ------------------------------------------------ | ------- | ----------- | ----- | ---------- | ---------- | | [user-auth_20250115](tracks/user-auth_20250115/) | feature | in-progress | 2/3 | 2025-01-15 | @developer | | [fix-login_20250114](tracks/fix-login_20250114/) | bug | pending | 0/2 | 2025-01-14 | - | ## Completed Tracks | Track ID | Type | Completed | Duration | | ---------------------------------------------- | ----- | ---------- | -------- | | [setup-ci_20250110](tracks/setup-ci_20250110/) | chore | 2025-01-12 | 2 days | ## Archived Tracks | Track ID | Reason | Archived | | ---------------------------------------------------- | ---------- | ---------- | | [old-feature_20241201](tracks/old-feature_20241201/) | Superseded | 2025-01-05 | ``` ## Metadata (metadata.json) Fields ```json { "id": "user-auth_20250115", "title": "User Authentication System", "type": "feature", "status": "in-progress", "priority": "high", "created": "2025-01-15T10:30:00Z", "updated": "2025-01-15T14:45:00Z", "started": "2025-01-15T11:00:00Z", "completed": null, "assignee": "@developer", "phases": { "total": 3, "current": 2, "completed": 1 }, "tasks": { "total": 12, "completed": 5, "in_progress": 1, "pending": 6 }, "checkpoints": [ { "phase": 1, "sha": "abc1234", "date": "2025-01-15T13:00:00Z" } ], "dependencies": [], "tags": ["auth", "security"] } ``` ## Track Operations ### Creating a Track 1. Run `/conductor:new-track` 2. Answer interactive questions 3. Review generated spec.md 4. Review generated plan.md 5. Confirm track creation ### Starting Implementation 1. Read spec.md and plan.md 2. Verify context artifacts are current 3. Mark first task as `[~]` 4. Begin TDD workflow ### Completing a Phase 1. Ensure all phase tasks are `[x]` 2. Complete verification tasks 3. Wait for checkpoint approval 4. Record checkpoint SHA 5. Proceed to next phase ### Completing a Track 1. Verify all phases complete 2. Verify all acceptance criteria met 3. Update product.md if needed 4. Mark track completed in tracks.md 5. Update metadata.json ### Reverting a Track 1. Run `/conductor:revert` 2. Select track to revert 3. Choose granularity (track/phase/task) 4. Confirm revert operation 5. Update status markers ## Handling Track Dependencies ### Identifying Dependencies During track creation, identify: - **Hard dependencies**: Must complete before this track can start - **Soft dependencies**: Can proceed in parallel but may affect integration - **External dependencies**: Third-party services, APIs, or team decisions ### Documenting Dependencies In spec.md, list dependencies with: - Dependency type (hard/soft/external) - Current status (available/pending/blocked) - Resolution path (what needs to happen) ### Managing Blocked Tracks When a track is blocked: 1. Mark blocked tasks with `[!]` and reason 2. Update tracks.md status 3. Document blocker in metadata.json 4. Consider creating dependency track if needed ## Track Sizing Guidelines ### Right-Sized Tracks Aim for tracks that: - Complete in 1-5 days of work - Have 2-4 phases - Contain 8-20 tasks total - Deliver a coherent, testable unit ### Too Large Signs a track is too large: - More than 5 phases - More than 25 tasks - Multiple unrelated features - Estimated duration > 1 week Solution: Split into multiple tracks with clear boundaries. ### Too Small Signs a track is too small: - Single phase with 1-2 tasks - No meaningful verification needed - Could be a sub-task of another track - Less than a few hours of work Solution: Combine with related work or handle as part of existing track. ## Specification Quality Checklist Before finalizing spec.md, verify: ### Requirements Quality - [ ] Each requirement has clear acceptance criteria - [ ] Requirements are testable - [ ] Requirements are independent (can verify separately) - [ ] No ambiguous language ("should be fast" → "response < 200ms") ### Scope Clarity - [ ] In-scope items are specific - [ ] Out-of-scope items prevent scope creep - [ ] Boundaries are clear to implementer ### Dependencies Identified - [ ] All internal dependencies listed - [ ] External dependencies have owners/contacts - [ ] Dependency status is current ### Risks Addressed - [ ] Major risks identified - [ ] Impact assessment realistic - [ ] Mitigations are actionable ## Plan Quality Checklist Before starting implementation, verify plan.md: ### Task Quality - [ ] Tasks are atomic (one logical action) - [ ] Tasks are independently verifiable - [ ] Task descriptions are clear - [ ] Sub-tasks provide helpful detail ### Phase Organization - [ ] Phases group related tasks - [ ] Each phase delivers something testable - [ ] Verification tasks after each phase - [ ] Phases build on each other logically ### Completeness - [ ] All spec requirements have corresponding tasks - [ ] Documentation tasks included - [ ] Testing tasks included - [ ] Integration tasks included ## Common Track Patterns ### Feature Track Pattern ``` Phase 1: Foundation - Data models - Database migrations - Basic API structure Phase 2: Core Logic - Business logic implementation - Input validation - Error handling Phase 3: Integration - UI integration - API documentation - End-to-end tests ``` ### Bug Fix Track Pattern ``` Phase 1: Reproduction - Write failing test capturing bug - Document reproduction steps Phase 2: Fix - Implement fix - Verify test passes - Check for regressions Phase 3: Verification - Manual verification - Update documentation if needed ``` ### Refactor Track Pattern ``` Phase 1: Preparation - Add characterization tests - Document current behavior Phase 2: Refactoring - Apply changes incrementally - Maintain green tests throughout Phase 3: Cleanup - Remove dead code - Update documentation ``` ## Best Practices 1. **One track, one concern**: Keep tracks focused on a single logical change 2. **Small phases**: Break work into phases of 3-5 tasks maximum 3. **Verification after phases**: Always include verification tasks 4. **Update markers immediately**: Mark task status as you work 5. **Record SHAs**: Always note commit SHAs for completed tasks 6. **Review specs before planning**: Ensure spec is complete before creating plan 7. **Link dependencies**: Explicitly note track dependencies 8. **Archive, don't delete**: Preserve completed tracks for reference 9. **Size appropriately**: Keep tracks between 1-5 days of work 10. **Clear acceptance criteria**: Every requirement must be testable

# Angular Migration Master AngularJS to Angular migration, including hybrid apps, component conversion, dependency injection changes, and routing migration. ## When to Use This Skill - Migrating AngularJS (1.x) applications to Angular (2+) - Running hybrid AngularJS/Angular applications - Converting directives to components - Modernizing dependency injection - Migrating routing systems - Updating to latest Angular versions - Implementing Angular best practices ## Migration Strategies ### 1. Big Bang (Complete Rewrite) - Rewrite entire app in Angular - Parallel development - Switch over at once - **Best for:** Small apps, green field projects ### 2. Incremental (Hybrid Approach) - Run AngularJS and Angular side-by-side - Migrate feature by feature - ngUpgrade for interop - **Best for:** Large apps, continuous delivery ### 3. Vertical Slice - Migrate one feature completely - New features in Angular, maintain old in AngularJS - Gradually replace - **Best for:** Medium apps, distinct features ## Hybrid App Setup ```typescript // main.ts - Bootstrap hybrid app import { platformBrowserDynamic } from "@angular/platform-browser-dynamic"; import { UpgradeModule } from "@angular/upgrade/static"; import { AppModule } from "./app/app.module"; platformBrowserDynamic() .bootstrapModule(AppModule) .then((platformRef) => { const upgrade = platformRef.injector.get(UpgradeModule); // Bootstrap AngularJS upgrade.bootstrap(document.body, ["myAngularJSApp"], { strictDi: true }); }); ``` ```typescript // app.module.ts import { NgModule } from "@angular/core"; import { BrowserModule } from "@angular/platform-browser"; import { UpgradeModule } from "@angular/upgrade/static"; @NgModule({ imports: [BrowserModule, UpgradeModule], }) export class AppModule { constructor(private upgrade: UpgradeModule) {} ngDoBootstrap() { // Bootstrapped manually in main.ts } } ``` ## Component Migration ### AngularJS Controller → Angular Component ```javascript // Before: AngularJS controller angular .module("myApp") .controller("UserController", function ($scope, UserService) { $scope.user = {}; $scope.loadUser = function (id) { UserService.getUser(id).then(function (user) { $scope.user = user; }); }; $scope.saveUser = function () { UserService.saveUser($scope.user); }; }); ``` ```typescript // After: Angular component import { Component, OnInit } from "@angular/core"; import { UserService } from "./user.service"; @Component({ selector: "app-user", template: ` <div> <h2>{{ user.name }}</h2> <button (click)="saveUser()">Save</button> </div> `, }) export class UserComponent implements OnInit { user: any = {}; constructor(private userService: UserService) {} ngOnInit() { this.loadUser(1); } loadUser(id: number) { this.userService.getUser(id).subscribe((user) => { this.user = user; }); } saveUser() { this.userService.saveUser(this.user); } } ``` ### AngularJS Directive → Angular Component ```javascript // Before: AngularJS directive angular.module("myApp").directive("userCard", function () { return { restrict: "E", scope: { user: "=", onDelete: "&", }, template: ` <div class="card"> <h3>{{ user.name }}</h3> <button ng-click="onDelete()">Delete</button> </div> `, }; }); ``` ```typescript // After: Angular component import { Component, Input, Output, EventEmitter } from "@angular/core"; @Component({ selector: "app-user-card", template: ` <div class="card"> <h3>{{ user.name }}</h3> <button (click)="delete.emit()">Delete</button> </div> `, }) export class UserCardComponent { @Input() user: any; @Output() delete = new EventEmitter<void>(); } // Usage: <app-user-card [user]="user" (delete)="handleDelete()"></app-user-card> ``` ## Service Migration ```javascript // Before: AngularJS service angular.module("myApp").factory("UserService", function ($http) { return { getUser: function (id) { return $http.get("/api/users/" + id); }, saveUser: function (user) { return $http.post("/api/users", user); }, }; }); ``` ```typescript // After: Angular service import { Injectable } from "@angular/core"; import { HttpClient } from "@angular/common/http"; import { Observable } from "rxjs"; @Injectable({ providedIn: "root", }) export class UserService { constructor(private http: HttpClient) {} getUser(id: number): Observable<any> { return this.http.get(`/api/users/${id}`); } saveUser(user: any): Observable<any> { return this.http.post("/api/users", user); } } ``` ## Dependency Injection Changes ### Downgrading Angular → AngularJS ```typescript // Angular service import { Injectable } from "@angular/core"; @Injectable({ providedIn: "root" }) export class NewService { getData() { return "data from Angular"; } } // Make available to AngularJS import { downgradeInjectable } from "@angular/upgrade/static"; angular.module("myApp").factory("newService", downgradeInjectable(NewService)); // Use in AngularJS angular.module("myApp").controller("OldController", function (newService) { console.log(newService.getData()); }); ``` ### Upgrading AngularJS → Angular ```typescript // AngularJS service angular.module('myApp').factory('oldService', function() { return { getData: function() { return 'data from AngularJS'; } }; }); // Make available to Angular import { InjectionToken } from '@angular/core'; export const OLD_SERVICE = new InjectionToken<any>('oldService'); @NgModule({ providers: [ { provide: OLD_SERVICE, useFactory: (i: any) => i.get('oldService'), deps: ['$injector'] } ] }) // Use in Angular @Component({...}) export class NewComponent { constructor(@Inject(OLD_SERVICE) private oldService: any) { console.log(this.oldService.getData()); } } ``` ## Routing Migration ```javascript // Before: AngularJS routing angular.module("myApp").config(function ($routeProvider) { $routeProvider .when("/users", { template: "<user-list></user-list>", }) .when("/users/:id", { template: "<user-detail></user-detail>", }); }); ``` ```typescript // After: Angular routing import { NgModule } from "@angular/core"; import { RouterModule, Routes } from "@angular/router"; const routes: Routes = [ { path: "users", component: UserListComponent }, { path: "users/:id", component: UserDetailComponent }, ]; @NgModule({ imports: [RouterModule.forRoot(routes)], exports: [RouterModule], }) export class AppRoutingModule {} ``` ## Forms Migration ```html <!-- Before: AngularJS --> <form name="userForm" ng-submit="saveUser()"> <input type="text" ng-model="user.name" required /> <input type="email" ng-model="user.email" required /> <button ng-disabled="userForm.$invalid">Save</button> </form> ``` ```typescript // After: Angular (Template-driven) @Component({ template: ` <form #userForm="ngForm" (ngSubmit)="saveUser()"> <input type="text" [(ngModel)]="user.name" name="name" required> <input type="email" [(ngModel)]="user.email" name="email" required> <button [disabled]="userForm.invalid">Save</button> </form> ` }) // Or Reactive Forms (preferred) import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ template: ` <form [formGroup]="userForm" (ngSubmit)="saveUser()"> <input formControlName="name"> <input formControlName="email"> <button [disabled]="userForm.invalid">Save</button> </form> ` }) export class UserFormComponent { userForm: FormGroup; constructor(private fb: FormBuilder) { this.userForm = this.fb.group({ name: ['', Validators.required], email: ['', [Validators.required, Validators.email]] }); } saveUser() { console.log(this.userForm.value); } } ``` ## Migration Timeline ``` Phase 1: Setup (1-2 weeks) - Install Angular CLI - Set up hybrid app - Configure build tools - Set up testing Phase 2: Infrastructure (2-4 weeks) - Migrate services - Migrate utilities - Set up routing - Migrate shared components Phase 3: Feature Migration (varies) - Migrate feature by feature - Test thoroughly - Deploy incrementally Phase 4: Cleanup (1-2 weeks) - Remove AngularJS code - Remove ngUpgrade - Optimize bundle - Final testing ``` ## Resources - **references/hybrid-mode.md**: Hybrid app patterns - **references/component-migration.md**: Component conversion guide - **references/dependency-injection.md**: DI migration strategies - **references/routing.md**: Routing migration - **assets/hybrid-bootstrap.ts**: Hybrid app template - **assets/migration-timeline.md**: Project planning - **scripts/analyze-angular-app.sh**: App analysis script ## Best Practices 1. **Start with Services**: Migrate services first (easier) 2. **Incremental Approach**: Feature-by-feature migration 3. **Test Continuously**: Test at every step 4. **Use TypeScript**: Migrate to TypeScript early 5. **Follow Style Guide**: Angular style guide from day 1 6. **Optimize Later**: Get it working, then optimize 7. **Document**: Keep migration notes ## Common Pitfalls - Not setting up hybrid app correctly - Migrating UI before logic - Ignoring change detection differences - Not handling scope properly - Mixing patterns (AngularJS + Angular) - Inadequate testing

# Workflow Patterns Guide for implementing tasks using Conductor's TDD workflow, managing phase checkpoints, handling git commits, and executing the verification protocol that ensures quality throughout implementation. ## When to Use This Skill - Implementing tasks from a track's plan.md - Following TDD red-green-refactor cycle - Completing phase checkpoints - Managing git commits and notes - Understanding quality assurance gates - Handling verification protocols - Recording progress in plan files ## TDD Task Lifecycle Follow these 11 steps for each task: ### Step 1: Select Next Task Read plan.md and identify the next pending `[ ]` task. Select tasks in order within the current phase. Do not skip ahead to later phases. ### Step 2: Mark as In Progress Update plan.md to mark the task as `[~]`: ```markdown - [~] **Task 2.1**: Implement user validation ``` Commit this status change separately from implementation. ### Step 3: RED - Write Failing Tests Write tests that define the expected behavior before writing implementation: - Create test file if needed - Write test cases covering happy path - Write test cases covering edge cases - Write test cases covering error conditions - Run tests - they should FAIL Example: ```python def test_validate_user_email_valid(): user = User(email="test@example.com") assert user.validate_email() is True def test_validate_user_email_invalid(): user = User(email="invalid") assert user.validate_email() is False ``` ### Step 4: GREEN - Implement Minimum Code Write the minimum code necessary to make tests pass: - Focus on making tests green, not perfection - Avoid premature optimization - Keep implementation simple - Run tests - they should PASS ### Step 5: REFACTOR - Improve Clarity With green tests, improve the code: - Extract common patterns - Improve naming - Remove duplication - Simplify logic - Run tests after each change - they should remain GREEN ### Step 6: Verify Coverage Check test coverage meets the 80% target: ```bash pytest --cov=module --cov-report=term-missing ``` If coverage is below 80%: - Identify uncovered lines - Add tests for missing paths - Re-run coverage check ### Step 7: Document Deviations If implementation deviated from plan or introduced new dependencies: - Update tech-stack.md with new dependencies - Note deviations in plan.md task comments - Update spec.md if requirements changed ### Step 8: Commit Implementation Create a focused commit for the task: ```bash git add -A git commit -m "feat(user): implement email validation - Add validate_email method to User class - Handle empty and malformed emails - Add comprehensive test coverage Task: 2.1 Track: user-auth_20250115" ``` Commit message format: - Type: feat, fix, refactor, test, docs, chore - Scope: affected module or component - Summary: imperative, present tense - Body: bullet points of changes - Footer: task and track references ### Step 9: Attach Git Notes Add rich task summary as git note: ```bash git notes add -m "Task 2.1: Implement user validation Summary: - Added email validation using regex pattern - Handles edge cases: empty, no @, no domain - Coverage: 94% on validation module Files changed: - src/models/user.py (modified) - tests/test_user.py (modified) Decisions: - Used simple regex over email-validator library - Reason: No external dependency for basic validation" ``` ### Step 10: Update Plan with SHA Update plan.md to mark task complete with commit SHA: ```markdown - [x] **Task 2.1**: Implement user validation `abc1234` ``` ### Step 11: Commit Plan Update Commit the plan status update: ```bash git add conductor/tracks/*/plan.md git commit -m "docs: update plan - task 2.1 complete Track: user-auth_20250115" ``` ## Phase Completion Protocol When all tasks in a phase are complete, execute the verification protocol: ### Identify Changed Files List all files modified since the last checkpoint: ```bash git diff --name-only <last-checkpoint-sha>..HEAD ``` ### Ensure Test Coverage For each modified file: 1. Identify corresponding test file 2. Verify tests exist for new/changed code 3. Run coverage for modified modules 4. Add tests if coverage < 80% ### Run Full Test Suite Execute complete test suite: ```bash pytest -v --tb=short ``` All tests must pass before proceeding. ### Generate Manual Verification Steps Create checklist of manual verifications: ```markdown ## Phase 1 Verification Checklist - [ ] User can register with valid email - [ ] Invalid email shows appropriate error - [ ] Database stores user correctly - [ ] API returns expected response codes ``` ### WAIT for User Approval Present verification checklist to user: ``` Phase 1 complete. Please verify: 1. [ ] Test suite passes (automated) 2. [ ] Coverage meets target (automated) 3. [ ] Manual verification items (requires human) Respond with 'approved' to continue, or note issues. ``` Do NOT proceed without explicit approval. ### Create Checkpoint Commit After approval, create checkpoint commit: ```bash git add -A git commit -m "checkpoint: phase 1 complete - user-auth_20250115 Verified: - All tests passing - Coverage: 87% - Manual verification approved Phase 1 tasks: - [x] Task 1.1: Setup database schema - [x] Task 1.2: Implement user model - [x] Task 1.3: Add validation logic" ``` ### Record Checkpoint SHA Update plan.md checkpoints table: ```markdown ## Checkpoints | Phase | Checkpoint SHA | Date | Status | | ------- | -------------- | ---------- | -------- | | Phase 1 | def5678 | 2025-01-15 | verified | | Phase 2 | | | pending | ``` ## Quality Assurance Gates Before marking any task complete, verify these gates: ### Passing Tests - All existing tests pass - New tests pass - No test regressions ### Coverage >= 80% - New code has 80%+ coverage - Overall project coverage maintained - Critical paths fully covered ### Style Compliance - Code follows style guides - Linting passes - Formatting correct ### Documentation - Public APIs documented - Complex logic explained - README updated if needed ### Type Safety - Type hints present (if applicable) - Type checker passes - No type: ignore without reason ### No Linting Errors - Zero linter errors - Warnings addressed or justified - Static analysis clean ### Mobile Compatibility If applicable: - Responsive design verified - Touch interactions work - Performance acceptable ### Security Audit - No secrets in code - Input validation present - Authentication/authorization correct - Dependencies vulnerability-free ## Git Integration ### Commit Message Format ``` <type>(<scope>): <subject> <body> <footer> ``` Types: - `feat`: New feature - `fix`: Bug fix - `refactor`: Code change without feature/fix - `test`: Adding tests - `docs`: Documentation - `chore`: Maintenance ### Git Notes for Rich Summaries Attach detailed notes to commits: ```bash git notes add -m "<detailed summary>" ``` View notes: ```bash git log --show-notes ``` Benefits: - Preserves context without cluttering commit message - Enables semantic queries across commits - Supports track-based operations ### SHA Recording in plan.md Always record the commit SHA when completing tasks: ```markdown - [x] **Task 1.1**: Setup schema `abc1234` - [x] **Task 1.2**: Add model `def5678` ``` This enables: - Traceability from plan to code - Semantic revert operations - Progress auditing ## Verification Checkpoints ### Why Checkpoints Matter Checkpoints create restore points for semantic reversion: - Revert to end of any phase - Maintain logical code state - Enable safe experimentation ### When to Create Checkpoints Create checkpoint after: - All phase tasks complete - All phase verifications pass - User approval received ### Checkpoint Commit Content Include in checkpoint commit: - All uncommitted changes - Updated plan.md - Updated metadata.json - Any documentation updates ### How to Use Checkpoints For reverting: ```bash # Revert to end of Phase 1 git revert --no-commit <phase-2-commits>... git commit -m "revert: rollback to phase 1 checkpoint" ``` For review: ```bash # See what changed in Phase 2 git diff <phase-1-sha>..<phase-2-sha> ``` ## Handling Deviations During implementation, deviations from the plan may occur. Handle them systematically: ### Types of Deviations **Scope Addition** Discovered requirement not in original spec. - Document in spec.md as new requirement - Add tasks to plan.md - Note addition in task comments **Scope Reduction** Feature deemed unnecessary during implementation. - Mark tasks as `[-]` (skipped) with reason - Update spec.md scope section - Document decision rationale **Technical Deviation** Different implementation approach than planned. - Note deviation in task completion comment - Update tech-stack.md if dependencies changed - Document why original approach was unsuitable **Requirement Change** Understanding of requirement changes during work. - Update spec.md with corrected requirement - Adjust plan.md tasks if needed - Re-verify acceptance criteria ### Deviation Documentation Format When completing a task with deviation: ```markdown - [x] **Task 2.1**: Implement validation `abc1234` - DEVIATION: Used library instead of custom code - Reason: Better edge case handling - Impact: Added email-validator to dependencies ``` ## Error Recovery ### Failed Tests After GREEN If tests fail after reaching GREEN: 1. Do NOT proceed to REFACTOR 2. Identify which test started failing 3. Check if refactoring broke something 4. Revert to last known GREEN state 5. Re-approach the implementation ### Checkpoint Rejection If user rejects a checkpoint: 1. Note rejection reason in plan.md 2. Create tasks to address issues 3. Complete remediation tasks 4. Request checkpoint approval again ### Blocked by Dependency If task cannot proceed: 1. Mark task as `[!]` with blocker description 2. Check if other tasks can proceed 3. Document expected resolution timeline 4. Consider creating dependency resolution track ## TDD Variations by Task Type ### Data Model Tasks ``` RED: Write test for model creation and validation GREEN: Implement model class with fields REFACTOR: Add computed properties, improve types ``` ### API Endpoint Tasks ``` RED: Write test for request/response contract GREEN: Implement endpoint handler REFACTOR: Extract validation, improve error handling ``` ### Integration Tasks ``` RED: Write test for component interaction GREEN: Wire components together REFACTOR: Improve error propagation, add logging ``` ### Refactoring Tasks ``` RED: Add characterization tests for current behavior GREEN: Apply refactoring (tests should stay green) REFACTOR: Clean up any introduced complexity ``` ## Working with Existing Tests When modifying code with existing tests: ### Extend, Don't Replace - Keep existing tests passing - Add new tests for new behavior - Update tests only when requirements change ### Test Migration When refactoring changes test structure: 1. Run existing tests (should pass) 2. Add new tests for refactored code 3. Migrate test cases to new structure 4. Remove old tests only after new tests pass ### Regression Prevention After any change: 1. Run full test suite 2. Check for unexpected failures 3. Investigate any new failures 4. Fix regressions before proceeding ## Checkpoint Verification Details ### Automated Verification Run before requesting approval: ```bash # Test suite pytest -v --tb=short # Coverage pytest --cov=src --cov-report=term-missing # Linting ruff check src/ tests/ # Type checking (if applicable) mypy src/ ``` ### Manual Verification Guidance For manual items, provide specific instructions: ```markdown ## Manual Verification Steps ### User Registration 1. Navigate to /register 2. Enter valid email: test@example.com 3. Enter password meeting requirements 4. Click Submit 5. Verify success message appears 6. Verify user appears in database ### Error Handling 1. Enter invalid email: "notanemail" 2. Verify error message shows 3. Verify form retains other entered data ``` ## Performance Considerations ### Test Suite Performance Keep test suite fast: - Use fixtures to avoid redundant setup - Mock slow external calls - Run subset during development, full suite at checkpoints ### Commit Performance Keep commits atomic: - One logical change per commit - Complete thought, not work-in-progress - Tests should pass after every commit ## Best Practices 1. **Never skip RED**: Always write failing tests first 2. **Small commits**: One logical change per commit 3. **Immediate updates**: Update plan.md right after task completion 4. **Wait for approval**: Never skip checkpoint verification 5. **Rich git notes**: Include context that helps future understanding 6. **Coverage discipline**: Don't accept coverage below target 7. **Quality gates**: Check all gates before marking complete 8. **Sequential phases**: Complete phases in order 9. **Document deviations**: Note any changes from original plan 10. **Clean state**: Each commit should leave code in working state 11. **Fast feedback**: Run relevant tests frequently during development 12. **Clear blockers**: Address blockers promptly, don't work around them

# Debugging Strategies Transform debugging from frustrating guesswork into systematic problem-solving with proven strategies, powerful tools, and methodical approaches. ## When to Use This Skill - Tracking down elusive bugs - Investigating performance issues - Understanding unfamiliar codebases - Debugging production issues - Analyzing crash dumps and stack traces - Profiling application performance - Investigating memory leaks - Debugging distributed systems ## Core Principles ### 1. The Scientific Method **1. Observe**: What's the actual behavior? **2. Hypothesize**: What could be causing it? **3. Experiment**: Test your hypothesis **4. Analyze**: Did it prove/disprove your theory? **5. Repeat**: Until you find the root cause ### 2. Debugging Mindset **Don't Assume:** - "It can't be X" - Yes it can - "I didn't change Y" - Check anyway - "It works on my machine" - Find out why **Do:** - Reproduce consistently - Isolate the problem - Keep detailed notes - Question everything - Take breaks when stuck ### 3. Rubber Duck Debugging Explain your code and problem out loud (to a rubber duck, colleague, or yourself). Often reveals the issue. ## Systematic Debugging Process ### Phase 1: Reproduce ```markdown ## Reproduction Checklist 1. **Can you reproduce it?** - Always? Sometimes? Randomly? - Specific conditions needed? - Can others reproduce it? 2. **Create minimal reproduction** - Simplify to smallest example - Remove unrelated code - Isolate the problem 3. **Document steps** - Write down exact steps - Note environment details - Capture error messages ``` ### Phase 2: Gather Information ```markdown ## Information Collection 1. **Error Messages** - Full stack trace - Error codes - Console/log output 2. **Environment** - OS version - Language/runtime version - Dependencies versions - Environment variables 3. **Recent Changes** - Git history - Deployment timeline - Configuration changes 4. **Scope** - Affects all users or specific ones? - All browsers or specific ones? - Production only or also dev? ``` ### Phase 3: Form Hypothesis ```markdown ## Hypothesis Formation Based on gathered info, ask: 1. **What changed?** - Recent code changes - Dependency updates - Infrastructure changes 2. **What's different?** - Working vs broken environment - Working vs broken user - Before vs after 3. **Where could this fail?** - Input validation - Business logic - Data layer - External services ``` ### Phase 4: Test & Verify ```markdown ## Testing Strategies 1. **Binary Search** - Comment out half the code - Narrow down problematic section - Repeat until found 2. **Add Logging** - Strategic console.log/print - Track variable values - Trace execution flow 3. **Isolate Components** - Test each piece separately - Mock dependencies - Remove complexity 4. **Compare Working vs Broken** - Diff configurations - Diff environments - Diff data ``` ## Debugging Tools ### JavaScript/TypeScript Debugging ```typescript // Chrome DevTools Debugger function processOrder(order: Order) { debugger; // Execution pauses here const total = calculateTotal(order); console.log("Total:", total); // Conditional breakpoint if (order.items.length > 10) { debugger; // Only breaks if condition true } return total; } // Console debugging techniques console.log("Value:", value); // Basic console.table(arrayOfObjects); // Table format console.time("operation"); /* code */ console.timeEnd("operation"); // Timing console.trace(); // Stack trace console.assert(value > 0, "Value must be positive"); // Assertion // Performance profiling performance.mark("start-operation"); // ... operation code performance.mark("end-operation"); performance.measure("operation", "start-operation", "end-operation"); console.log(performance.getEntriesByType("measure")); ``` **VS Code Debugger Configuration:** ```json // .vscode/launch.json { "version": "0.2.0", "configurations": [ { "type": "node", "request": "launch", "name": "Debug Program", "program": "${workspaceFolder}/src/index.ts", "preLaunchTask": "tsc: build - tsconfig.json", "outFiles": ["${workspaceFolder}/dist/**/*.js"], "skipFiles": ["<node_internals>/**"] }, { "type": "node", "request": "launch", "name": "Debug Tests", "program": "${workspaceFolder}/node_modules/jest/bin/jest", "args": ["--runInBand", "--no-cache"], "console": "integratedTerminal" } ] } ``` ### Python Debugging ```python # Built-in debugger (pdb) import pdb def calculate_total(items): total = 0 pdb.set_trace() # Debugger starts here for item in items: total += item.price * item.quantity return total # Breakpoint (Python 3.7+) def process_order(order): breakpoint() # More convenient than pdb.set_trace() # ... code # Post-mortem debugging try: risky_operation() except Exception: import pdb pdb.post_mortem() # Debug at exception point # IPython debugging (ipdb) from ipdb import set_trace set_trace() # Better interface than pdb # Logging for debugging import logging logging.basicConfig(level=logging.DEBUG) logger = logging.getLogger(__name__) def fetch_user(user_id): logger.debug(f'Fetching user: {user_id}') user = db.query(User).get(user_id) logger.debug(f'Found user: {user}') return user # Profile performance import cProfile import pstats cProfile.run('slow_function()', 'profile_stats') stats = pstats.Stats('profile_stats') stats.sort_stats('cumulative') stats.print_stats(10) # Top 10 slowest ``` ### Go Debugging ```go // Delve debugger // Install: go install github.com/go-delve/delve/cmd/dlv@latest // Run: dlv debug main.go import ( "fmt" "runtime" "runtime/debug" ) // Print stack trace func debugStack() { debug.PrintStack() } // Panic recovery with debugging func processRequest() { defer func() { if r := recover(); r != nil { fmt.Println("Panic:", r) debug.PrintStack() } }() // ... code that might panic } // Memory profiling import _ "net/http/pprof" // Visit http://localhost:6060/debug/pprof/ // CPU profiling import ( "os" "runtime/pprof" ) f, _ := os.Create("cpu.prof") pprof.StartCPUProfile(f) defer pprof.StopCPUProfile() // ... code to profile ``` ## Advanced Debugging Techniques ### Technique 1: Binary Search Debugging ```bash # Git bisect for finding regression git bisect start git bisect bad # Current commit is bad git bisect good v1.0.0 # v1.0.0 was good # Git checks out middle commit # Test it, then: git bisect good # if it works git bisect bad # if it's broken # Continue until bug found git bisect reset # when done ``` ### Technique 2: Differential Debugging Compare working vs broken: ```markdown ## What's Different? | Aspect | Working | Broken | | ------------ | ----------- | -------------- | | Environment | Development | Production | | Node version | 18.16.0 | 18.15.0 | | Data | Empty DB | 1M records | | User | Admin | Regular user | | Browser | Chrome | Safari | | Time | During day | After midnight | Hypothesis: Time-based issue? Check timezone handling. ``` ### Technique 3: Trace Debugging ```typescript // Function call tracing function trace( target: any, propertyKey: string, descriptor: PropertyDescriptor, ) { const originalMethod = descriptor.value; descriptor.value = function (...args: any[]) { console.log(`Calling ${propertyKey} with args:`, args); const result = originalMethod.apply(this, args); console.log(`${propertyKey} returned:`, result); return result; }; return descriptor; } class OrderService { @trace calculateTotal(items: Item[]): number { return items.reduce((sum, item) => sum + item.price, 0); } } ``` ### Technique 4: Memory Leak Detection ```typescript // Chrome DevTools Memory Profiler // 1. Take heap snapshot // 2. Perform action // 3. Take another snapshot // 4. Compare snapshots // Node.js memory debugging if (process.memoryUsage().heapUsed > 500 * 1024 * 1024) { console.warn("High memory usage:", process.memoryUsage()); // Generate heap dump require("v8").writeHeapSnapshot(); } // Find memory leaks in tests let beforeMemory: number; beforeEach(() => { beforeMemory = process.memoryUsage().heapUsed; }); afterEach(() => { const afterMemory = process.memoryUsage().heapUsed; const diff = afterMemory - beforeMemory; if (diff > 10 * 1024 * 1024) { // 10MB threshold console.warn(`Possible memory leak: ${diff / 1024 / 1024}MB`); } }); ``` ## Debugging Patterns by Issue Type ### Pattern 1: Intermittent Bugs ```markdown ## Strategies for Flaky Bugs 1. **Add extensive logging** - Log timing information - Log all state transitions - Log external interactions 2. **Look for race conditions** - Concurrent access to shared state - Async operations completing out of order - Missing synchronization 3. **Check timing dependencies** - setTimeout/setInterval - Promise resolution order - Animation frame timing 4. **Stress test** - Run many times - Vary timing - Simulate load ``` ### Pattern 2: Performance Issues ```markdown ## Performance Debugging 1. **Profile first** - Don't optimize blindly - Measure before and after - Find bottlenecks 2. **Common culprits** - N+1 queries - Unnecessary re-renders - Large data processing - Synchronous I/O 3. **Tools** - Browser DevTools Performance tab - Lighthouse - Python: cProfile, line_profiler - Node: clinic.js, 0x ``` ### Pattern 3: Production Bugs ```markdown ## Production Debugging 1. **Gather evidence** - Error tracking (Sentry, Bugsnag) - Application logs - User reports - Metrics/monitoring 2. **Reproduce locally** - Use production data (anonymized) - Match environment - Follow exact steps 3. **Safe investigation** - Don't change production - Use feature flags - Add monitoring/logging - Test fixes in staging ``` ## Best Practices 1. **Reproduce First**: Can't fix what you can't reproduce 2. **Isolate the Problem**: Remove complexity until minimal case 3. **Read Error Messages**: They're usually helpful 4. **Check Recent Changes**: Most bugs are recent 5. **Use Version Control**: Git bisect, blame, history 6. **Take Breaks**: Fresh eyes see better 7. **Document Findings**: Help future you 8. **Fix Root Cause**: Not just symptoms ## Common Debugging Mistakes - **Making Multiple Changes**: Change one thing at a time - **Not Reading Error Messages**: Read the full stack trace - **Assuming It's Complex**: Often it's simple - **Debug Logging in Prod**: Remove before shipping - **Not Using Debugger**: console.log isn't always best - **Giving Up Too Soon**: Persistence pays off - **Not Testing the Fix**: Verify it actually works ## Quick Debugging Checklist ```markdown ## When Stuck, Check: - [ ] Spelling errors (typos in variable names) - [ ] Case sensitivity (fileName vs filename) - [ ] Null/undefined values - [ ] Array index off-by-one - [ ] Async timing (race conditions) - [ ] Scope issues (closure, hoisting) - [ ] Type mismatches - [ ] Missing dependencies - [ ] Environment variables - [ ] File paths (absolute vs relative) - [ ] Cache issues (clear cache) - [ ] Stale data (refresh database) ``` ## Resources - **references/debugging-tools-guide.md**: Comprehensive tool documentation - **references/performance-profiling.md**: Performance debugging guide - **references/production-debugging.md**: Debugging live systems - **assets/debugging-checklist.md**: Quick reference checklist - **assets/common-bugs.md**: Common bug patterns - **scripts/debug-helper.ts**: Debugging utility functions

# E2E Testing Patterns Build reliable, fast, and maintainable end-to-end test suites that provide confidence to ship code quickly and catch regressions before users do. ## When to Use This Skill - Implementing end-to-end test automation - Debugging flaky or unreliable tests - Testing critical user workflows - Setting up CI/CD test pipelines - Testing across multiple browsers - Validating accessibility requirements - Testing responsive designs - Establishing E2E testing standards ## Core Concepts ### 1. E2E Testing Fundamentals **What to Test with E2E:** - Critical user journeys (login, checkout, signup) - Complex interactions (drag-and-drop, multi-step forms) - Cross-browser compatibility - Real API integration - Authentication flows **What NOT to Test with E2E:** - Unit-level logic (use unit tests) - API contracts (use integration tests) - Edge cases (too slow) - Internal implementation details ### 2. Test Philosophy **The Testing Pyramid:** ``` /\ /E2E\ ← Few, focused on critical paths /─────\ /Integr\ ← More, test component interactions /────────\ /Unit Tests\ ← Many, fast, isolated /────────────\ ``` **Best Practices:** - Test user behavior, not implementation - Keep tests independent - Make tests deterministic - Optimize for speed - Use data-testid, not CSS selectors ## Playwright Patterns ### Setup and Configuration ```typescript // playwright.config.ts import { defineConfig, devices } from "@playwright/test"; export default defineConfig({ testDir: "./e2e", timeout: 30000, expect: { timeout: 5000, }, fullyParallel: true, forbidOnly: !!process.env.CI, retries: process.env.CI ? 2 : 0, workers: process.env.CI ? 1 : undefined, reporter: [["html"], ["junit", { outputFile: "results.xml" }]], use: { baseURL: "http://localhost:3000", trace: "on-first-retry", screenshot: "only-on-failure", video: "retain-on-failure", }, projects: [ { name: "chromium", use: { ...devices["Desktop Chrome"] } }, { name: "firefox", use: { ...devices["Desktop Firefox"] } }, { name: "webkit", use: { ...devices["Desktop Safari"] } }, { name: "mobile", use: { ...devices["iPhone 13"] } }, ], }); ``` ### Pattern 1: Page Object Model ```typescript // pages/LoginPage.ts import { Page, Locator } from "@playwright/test"; export class LoginPage { readonly page: Page; readonly emailInput: Locator; readonly passwordInput: Locator; readonly loginButton: Locator; readonly errorMessage: Locator; constructor(page: Page) { this.page = page; this.emailInput = page.getByLabel("Email"); this.passwordInput = page.getByLabel("Password"); this.loginButton = page.getByRole("button", { name: "Login" }); this.errorMessage = page.getByRole("alert"); } async goto() { await this.page.goto("/login"); } async login(email: string, password: string) { await this.emailInput.fill(email); await this.passwordInput.fill(password); await this.loginButton.click(); } async getErrorMessage(): Promise<string> { return (await this.errorMessage.textContent()) ?? ""; } } // Test using Page Object import { test, expect } from "@playwright/test"; import { LoginPage } from "./pages/LoginPage"; test("successful login", async ({ page }) => { const loginPage = new LoginPage(page); await loginPage.goto(); await loginPage.login("user@example.com", "password123"); await expect(page).toHaveURL("/dashboard"); await expect(page.getByRole("heading", { name: "Dashboard" })).toBeVisible(); }); test("failed login shows error", async ({ page }) => { const loginPage = new LoginPage(page); await loginPage.goto(); await loginPage.login("invalid@example.com", "wrong"); const error = await loginPage.getErrorMessage(); expect(error).toContain("Invalid credentials"); }); ``` ### Pattern 2: Fixtures for Test Data ```typescript // fixtures/test-data.ts import { test as base } from "@playwright/test"; type TestData = { testUser: { email: string; password: string; name: string; }; adminUser: { email: string; password: string; }; }; export const test = base.extend<TestData>({ testUser: async ({}, use) => { const user = { email: `test-${Date.now()}@example.com`, password: "Test123!@#", name: "Test User", }; // Setup: Create user in database await createTestUser(user); await use(user); // Teardown: Clean up user await deleteTestUser(user.email); }, adminUser: async ({}, use) => { await use({ email: "admin@example.com", password: process.env.ADMIN_PASSWORD!, }); }, }); // Usage in tests import { test } from "./fixtures/test-data"; test("user can update profile", async ({ page, testUser }) => { await page.goto("/login"); await page.getByLabel("Email").fill(testUser.email); await page.getByLabel("Password").fill(testUser.password); await page.getByRole("button", { name: "Login" }).click(); await page.goto("/profile"); await page.getByLabel("Name").fill("Updated Name"); await page.getByRole("button", { name: "Save" }).click(); await expect(page.getByText("Profile updated")).toBeVisible(); }); ``` ### Pattern 3: Waiting Strategies ```typescript // ❌ Bad: Fixed timeouts await page.waitForTimeout(3000); // Flaky! // ✅ Good: Wait for specific conditions await page.waitForLoadState("networkidle"); await page.waitForURL("/dashboard"); await page.waitForSelector('[data-testid="user-profile"]'); // ✅ Better: Auto-waiting with assertions await expect(page.getByText("Welcome")).toBeVisible(); await expect(page.getByRole("button", { name: "Submit" })).toBeEnabled(); // Wait for API response const responsePromise = page.waitForResponse( (response) => response.url().includes("/api/users") && response.status() === 200, ); await page.getByRole("button", { name: "Load Users" }).click(); const response = await responsePromise; const data = await response.json(); expect(data.users).toHaveLength(10); // Wait for multiple conditions await Promise.all([ page.waitForURL("/success"), page.waitForLoadState("networkidle"), expect(page.getByText("Payment successful")).toBeVisible(), ]); ``` ### Pattern 4: Network Mocking and Interception ```typescript // Mock API responses test("displays error when API fails", async ({ page }) => { await page.route("**/api/users", (route) => { route.fulfill({ status: 500, contentType: "application/json", body: JSON.stringify({ error: "Internal Server Error" }), }); }); await page.goto("/users"); await expect(page.getByText("Failed to load users")).toBeVisible(); }); // Intercept and modify requests test("can modify API request", async ({ page }) => { await page.route("**/api/users", async (route) => { const request = route.request(); const postData = JSON.parse(request.postData() || "{}"); // Modify request postData.role = "admin"; await route.continue({ postData: JSON.stringify(postData), }); }); // Test continues... }); // Mock third-party services test("payment flow with mocked Stripe", async ({ page }) => { await page.route("**/api/stripe/**", (route) => { route.fulfill({ status: 200, body: JSON.stringify({ id: "mock_payment_id", status: "succeeded", }), }); }); // Test payment flow with mocked response }); ``` ## Cypress Patterns ### Setup and Configuration ```typescript // cypress.config.ts import { defineConfig } from "cypress"; export default defineConfig({ e2e: { baseUrl: "http://localhost:3000", viewportWidth: 1280, viewportHeight: 720, video: false, screenshotOnRunFailure: true, defaultCommandTimeout: 10000, requestTimeout: 10000, setupNodeEvents(on, config) { // Implement node event listeners }, }, }); ``` ### Pattern 1: Custom Commands ```typescript // cypress/support/commands.ts declare global { namespace Cypress { interface Chainable { login(email: string, password: string): Chainable<void>; createUser(userData: UserData): Chainable<User>; dataCy(value: string): Chainable<JQuery<HTMLElement>>; } } } Cypress.Commands.add("login", (email: string, password: string) => { cy.visit("/login"); cy.get('[data-testid="email"]').type(email); cy.get('[data-testid="password"]').type(password); cy.get('[data-testid="login-button"]').click(); cy.url().should("include", "/dashboard"); }); Cypress.Commands.add("createUser", (userData: UserData) => { return cy.request("POST", "/api/users", userData).its("body"); }); Cypress.Commands.add("dataCy", (value: string) => { return cy.get(`[data-cy="${value}"]`); }); // Usage cy.login("user@example.com", "password"); cy.dataCy("submit-button").click(); ``` ### Pattern 2: Cypress Intercept ```typescript // Mock API calls cy.intercept("GET", "/api/users", { statusCode: 200, body: [ { id: 1, name: "John" }, { id: 2, name: "Jane" }, ], }).as("getUsers"); cy.visit("/users"); cy.wait("@getUsers"); cy.get('[data-testid="user-list"]').children().should("have.length", 2); // Modify responses cy.intercept("GET", "/api/users", (req) => { req.reply((res) => { // Modify response res.body.users = res.body.users.slice(0, 5); res.send(); }); }); // Simulate slow network cy.intercept("GET", "/api/data", (req) => { req.reply((res) => { res.delay(3000); // 3 second delay res.send(); }); }); ``` ## Advanced Patterns ### Pattern 1: Visual Regression Testing ```typescript // With Playwright import { test, expect } from "@playwright/test"; test("homepage looks correct", async ({ page }) => { await page.goto("/"); await expect(page).toHaveScreenshot("homepage.png", { fullPage: true, maxDiffPixels: 100, }); }); test("button in all states", async ({ page }) => { await page.goto("/components"); const button = page.getByRole("button", { name: "Submit" }); // Default state await expect(button).toHaveScreenshot("button-default.png"); // Hover state await button.hover(); await expect(button).toHaveScreenshot("button-hover.png"); // Disabled state await button.evaluate((el) => el.setAttribute("disabled", "true")); await expect(button).toHaveScreenshot("button-disabled.png"); }); ``` ### Pattern 2: Parallel Testing with Sharding ```typescript // playwright.config.ts export default defineConfig({ projects: [ { name: "shard-1", use: { ...devices["Desktop Chrome"] }, grepInvert: /@slow/, shard: { current: 1, total: 4 }, }, { name: "shard-2", use: { ...devices["Desktop Chrome"] }, shard: { current: 2, total: 4 }, }, // ... more shards ], }); // Run in CI // npx playwright test --shard=1/4 // npx playwright test --shard=2/4 ``` ### Pattern 3: Accessibility Testing ```typescript // Install: npm install @axe-core/playwright import { test, expect } from "@playwright/test"; import AxeBuilder from "@axe-core/playwright"; test("page should not have accessibility violations", async ({ page }) => { await page.goto("/"); const accessibilityScanResults = await new AxeBuilder({ page }) .exclude("#third-party-widget") .analyze(); expect(accessibilityScanResults.violations).toEqual([]); }); test("form is accessible", async ({ page }) => { await page.goto("/signup"); const results = await new AxeBuilder({ page }).include("form").analyze(); expect(results.violations).toEqual([]); }); ``` ## Best Practices 1. **Use Data Attributes**: `data-testid` or `data-cy` for stable selectors 2. **Avoid Brittle Selectors**: Don't rely on CSS classes or DOM structure 3. **Test User Behavior**: Click, type, see - not implementation details 4. **Keep Tests Independent**: Each test should run in isolation 5. **Clean Up Test Data**: Create and destroy test data in each test 6. **Use Page Objects**: Encapsulate page logic 7. **Meaningful Assertions**: Check actual user-visible behavior 8. **Optimize for Speed**: Mock when possible, parallel execution ```typescript // ❌ Bad selectors cy.get(".btn.btn-primary.submit-button").click(); cy.get("div > form > div:nth-child(2) > input").type("text"); // ✅ Good selectors cy.getByRole("button", { name: "Submit" }).click(); cy.getByLabel("Email address").type("user@example.com"); cy.get('[data-testid="email-input"]').type("user@example.com"); ``` ## Common Pitfalls - **Flaky Tests**: Use proper waits, not fixed timeouts - **Slow Tests**: Mock external APIs, use parallel execution - **Over-Testing**: Don't test every edge case with E2E - **Coupled Tests**: Tests should not depend on each other - **Poor Selectors**: Avoid CSS classes and nth-child - **No Cleanup**: Clean up test data after each test - **Testing Implementation**: Test user behavior, not internals ## Debugging Failing Tests ```typescript // Playwright debugging // 1. Run in headed mode npx playwright test --headed // 2. Run in debug mode npx playwright test --debug // 3. Use trace viewer await page.screenshot({ path: 'screenshot.png' }); await page.video()?.saveAs('video.webm'); // 4. Add test.step for better reporting test('checkout flow', async ({ page }) => { await test.step('Add item to cart', async () => { await page.goto('/products'); await page.getByRole('button', { name: 'Add to Cart' }).click(); }); await test.step('Proceed to checkout', async () => { await page.goto('/cart'); await page.getByRole('button', { name: 'Checkout' }).click(); }); }); // 5. Inspect page state await page.pause(); // Pauses execution, opens inspector ``` ## Resources - **references/playwright-best-practices.md**: Playwright-specific patterns - **references/cypress-best-practices.md**: Cypress-specific patterns - **references/flaky-test-debugging.md**: Debugging unreliable tests - **assets/e2e-testing-checklist.md**: What to test with E2E - **assets/selector-strategies.md**: Finding reliable selectors - **scripts/test-analyzer.ts**: Analyze test flakiness and duration

# Monorepo Management Build efficient, scalable monorepos that enable code sharing, consistent tooling, and atomic changes across multiple packages and applications. ## When to Use This Skill - Setting up new monorepo projects - Migrating from multi-repo to monorepo - Optimizing build and test performance - Managing shared dependencies - Implementing code sharing strategies - Setting up CI/CD for monorepos - Versioning and publishing packages - Debugging monorepo-specific issues ## Core Concepts ### 1. Why Monorepos? **Advantages:** - Shared code and dependencies - Atomic commits across projects - Consistent tooling and standards - Easier refactoring - Simplified dependency management - Better code visibility **Challenges:** - Build performance at scale - CI/CD complexity - Access control - Large Git repository ### 2. Monorepo Tools **Package Managers:** - pnpm workspaces (recommended) - npm workspaces - Yarn workspaces **Build Systems:** - Turborepo (recommended for most) - Nx (feature-rich, complex) - Lerna (older, maintenance mode) ## Turborepo Setup ### Initial Setup ```bash # Create new monorepo npx create-turbo@latest my-monorepo cd my-monorepo # Structure: # apps/ # web/ - Next.js app # docs/ - Documentation site # packages/ # ui/ - Shared UI components # config/ - Shared configurations # tsconfig/ - Shared TypeScript configs # turbo.json - Turborepo configuration # package.json - Root package.json ``` ### Configuration ```json // turbo.json { "$schema": "https://turbo.build/schema.json", "globalDependencies": ["**/.env.*local"], "pipeline": { "build": { "dependsOn": ["^build"], "outputs": ["dist/**", ".next/**", "!.next/cache/**"] }, "test": { "dependsOn": ["build"], "outputs": ["coverage/**"] }, "lint": { "outputs": [] }, "dev": { "cache": false, "persistent": true }, "type-check": { "dependsOn": ["^build"], "outputs": [] } } } ``` ```json // package.json (root) { "name": "my-monorepo", "private": true, "workspaces": ["apps/*", "packages/*"], "scripts": { "build": "turbo run build", "dev": "turbo run dev", "test": "turbo run test", "lint": "turbo run lint", "format": "prettier --write \"**/*.{ts,tsx,md}\"", "clean": "turbo run clean && rm -rf node_modules" }, "devDependencies": { "turbo": "^1.10.0", "prettier": "^3.0.0", "typescript": "^5.0.0" }, "packageManager": "pnpm@8.0.0" } ``` ### Package Structure ```json // packages/ui/package.json { "name": "@repo/ui", "version": "0.0.0", "private": true, "main": "./dist/index.js", "types": "./dist/index.d.ts", "exports": { ".": { "import": "./dist/index.js", "types": "./dist/index.d.ts" }, "./button": { "import": "./dist/button.js", "types": "./dist/button.d.ts" } }, "scripts": { "build": "tsup src/index.ts --format esm,cjs --dts", "dev": "tsup src/index.ts --format esm,cjs --dts --watch", "lint": "eslint src/", "type-check": "tsc --noEmit" }, "devDependencies": { "@repo/tsconfig": "workspace:*", "tsup": "^7.0.0", "typescript": "^5.0.0" }, "dependencies": { "react": "^18.2.0" } } ``` ## pnpm Workspaces ### Setup ```yaml # pnpm-workspace.yaml packages: - "apps/*" - "packages/*" - "tools/*" ``` ```json // .npmrc # Hoist shared dependencies shamefully-hoist=true # Strict peer dependencies auto-install-peers=true strict-peer-dependencies=true # Performance store-dir=~/.pnpm-store ``` ### Dependency Management ```bash # Install dependency in specific package pnpm add react --filter @repo/ui pnpm add -D typescript --filter @repo/ui # Install workspace dependency pnpm add @repo/ui --filter web # Install in all packages pnpm add -D eslint -w # Update all dependencies pnpm update -r # Remove dependency pnpm remove react --filter @repo/ui ``` ### Scripts ```bash # Run script in specific package pnpm --filter web dev pnpm --filter @repo/ui build # Run in all packages pnpm -r build pnpm -r test # Run in parallel pnpm -r --parallel dev # Filter by pattern pnpm --filter "@repo/*" build pnpm --filter "...web" build # Build web and dependencies ``` ## Nx Monorepo ### Setup ```bash # Create Nx monorepo npx create-nx-workspace@latest my-org # Generate applications nx generate @nx/react:app my-app nx generate @nx/next:app my-next-app # Generate libraries nx generate @nx/react:lib ui-components nx generate @nx/js:lib utils ``` ### Configuration ```json // nx.json { "extends": "nx/presets/npm.json", "$schema": "./node_modules/nx/schemas/nx-schema.json", "targetDefaults": { "build": { "dependsOn": ["^build"], "inputs": ["production", "^production"], "cache": true }, "test": { "inputs": ["default", "^production", "{workspaceRoot}/jest.preset.js"], "cache": true }, "lint": { "inputs": ["default", "{workspaceRoot}/.eslintrc.json"], "cache": true } }, "namedInputs": { "default": ["{projectRoot}/**/*", "sharedGlobals"], "production": [ "default", "!{projectRoot}/**/?(*.)+(spec|test).[jt]s?(x)?(.snap)", "!{projectRoot}/tsconfig.spec.json" ], "sharedGlobals": [] } } ``` ### Running Tasks ```bash # Run task for specific project nx build my-app nx test ui-components nx lint utils # Run for affected projects nx affected:build nx affected:test --base=main # Visualize dependencies nx graph # Run in parallel nx run-many --target=build --all --parallel=3 ``` ## Shared Configurations ### TypeScript Configuration ```json // packages/tsconfig/base.json { "compilerOptions": { "strict": true, "esModuleInterop": true, "skipLibCheck": true, "forceConsistentCasingInFileNames": true, "module": "ESNext", "moduleResolution": "bundler", "resolveJsonModule": true, "isolatedModules": true, "incremental": true, "declaration": true }, "exclude": ["node_modules"] } // packages/tsconfig/react.json { "extends": "./base.json", "compilerOptions": { "jsx": "react-jsx", "lib": ["ES2022", "DOM", "DOM.Iterable"] } } // apps/web/tsconfig.json { "extends": "@repo/tsconfig/react.json", "compilerOptions": { "outDir": "dist", "rootDir": "src" }, "include": ["src"], "exclude": ["node_modules", "dist"] } ``` ### ESLint Configuration ```javascript // packages/config/eslint-preset.js module.exports = { extends: [ "eslint:recommended", "plugin:@typescript-eslint/recommended", "plugin:react/recommended", "plugin:react-hooks/recommended", "prettier", ], plugins: ["@typescript-eslint", "react", "react-hooks"], parser: "@typescript-eslint/parser", parserOptions: { ecmaVersion: 2022, sourceType: "module", ecmaFeatures: { jsx: true, }, }, settings: { react: { version: "detect", }, }, rules: { "@typescript-eslint/no-unused-vars": "error", "react/react-in-jsx-scope": "off", }, }; // apps/web/.eslintrc.js module.exports = { extends: ["@repo/config/eslint-preset"], rules: { // App-specific rules }, }; ``` ## Code Sharing Patterns ### Pattern 1: Shared UI Components ```typescript // packages/ui/src/button.tsx import * as React from 'react'; export interface ButtonProps { variant?: 'primary' | 'secondary'; children: React.ReactNode; onClick?: () => void; } export function Button({ variant = 'primary', children, onClick }: ButtonProps) { return ( <button className={`btn btn-${variant}`} onClick={onClick} > {children} </button> ); } // packages/ui/src/index.ts export { Button, type ButtonProps } from './button'; export { Input, type InputProps } from './input'; // apps/web/src/app.tsx import { Button } from '@repo/ui'; export function App() { return <Button variant="primary">Click me</Button>; } ``` ### Pattern 2: Shared Utilities ```typescript // packages/utils/src/string.ts export function capitalize(str: string): string { return str.charAt(0).toUpperCase() + str.slice(1); } export function truncate(str: string, length: number): string { return str.length > length ? str.slice(0, length) + "..." : str; } // packages/utils/src/index.ts export * from "./string"; export * from "./array"; export * from "./date"; // Usage in apps import { capitalize, truncate } from "@repo/utils"; ``` ### Pattern 3: Shared Types ```typescript // packages/types/src/user.ts export interface User { id: string; email: string; name: string; role: "admin" | "user"; } export interface CreateUserInput { email: string; name: string; password: string; } // Used in both frontend and backend import type { User, CreateUserInput } from "@repo/types"; ``` ## Build Optimization ### Turborepo Caching ```json // turbo.json { "pipeline": { "build": { // Build depends on dependencies being built first "dependsOn": ["^build"], // Cache these outputs "outputs": ["dist/**", ".next/**"], // Cache based on these inputs (default: all files) "inputs": ["src/**/*.tsx", "src/**/*.ts", "package.json"] }, "test": { // Run tests in parallel, don't depend on build "cache": true, "outputs": ["coverage/**"] } } } ``` ### Remote Caching ```bash # Turborepo Remote Cache (Vercel) npx turbo login npx turbo link # Custom remote cache # turbo.json { "remoteCache": { "signature": true, "enabled": true } } ``` ## CI/CD for Monorepos ### GitHub Actions ```yaml # .github/workflows/ci.yml name: CI on: push: branches: [main] pull_request: branches: [main] jobs: build: runs-on: ubuntu-latest steps: - uses: actions/checkout@v3 with: fetch-depth: 0 # For Nx affected commands - uses: pnpm/action-setup@v2 with: version: 8 - uses: actions/setup-node@v3 with: node-version: 18 cache: "pnpm" - name: Install dependencies run: pnpm install --frozen-lockfile - name: Build run: pnpm turbo run build - name: Test run: pnpm turbo run test - name: Lint run: pnpm turbo run lint - name: Type check run: pnpm turbo run type-check ``` ### Deploy Affected Only ```yaml # Deploy only changed apps - name: Deploy affected apps run: | if pnpm nx affected:apps --base=origin/main --head=HEAD | grep -q "web"; then echo "Deploying web app" pnpm --filter web deploy fi ``` ## Best Practices 1. **Consistent Versioning**: Lock dependency versions across workspace 2. **Shared Configs**: Centralize ESLint, TypeScript, Prettier configs 3. **Dependency Graph**: Keep it acyclic, avoid circular dependencies 4. **Cache Effectively**: Configure inputs/outputs correctly 5. **Type Safety**: Share types between frontend/backend 6. **Testing Strategy**: Unit tests in packages, E2E in apps 7. **Documentation**: README in each package 8. **Release Strategy**: Use changesets for versioning ## Common Pitfalls - **Circular Dependencies**: A depends on B, B depends on A - **Phantom Dependencies**: Using deps not in package.json - **Incorrect Cache Inputs**: Missing files in Turborepo inputs - **Over-Sharing**: Sharing code that should be separate - **Under-Sharing**: Duplicating code across packages - **Large Monorepos**: Without proper tooling, builds slow down ## Publishing Packages ```bash # Using Changesets pnpm add -Dw @changesets/cli pnpm changeset init # Create changeset pnpm changeset # Version packages pnpm changeset version # Publish pnpm changeset publish ``` ```yaml # .github/workflows/release.yml - name: Create Release Pull Request or Publish uses: changesets/action@v1 with: publish: pnpm release env: GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }} NPM_TOKEN: ${{ secrets.NPM_TOKEN }} ``` ## Resources - **references/turborepo-guide.md**: Comprehensive Turborepo documentation - **references/nx-guide.md**: Nx monorepo patterns - **references/pnpm-workspaces.md**: pnpm workspace features - **assets/monorepo-checklist.md**: Setup checklist - **assets/migration-guide.md**: Multi-repo to monorepo migration - **scripts/dependency-graph.ts**: Visualize package dependencies

# Nx Workspace Patterns Production patterns for Nx monorepo management. ## When to Use This Skill - Setting up new Nx workspaces - Configuring project boundaries - Optimizing CI with affected commands - Implementing remote caching - Managing dependencies between projects - Migrating to Nx ## Core Concepts ### 1. Nx Architecture ``` workspace/ ├── apps/ # Deployable applications │ ├── web/ │ └── api/ ├── libs/ # Shared libraries │ ├── shared/ │ │ ├── ui/ │ │ └── utils/ │ └── feature/ │ ├── auth/ │ └── dashboard/ ├── tools/ # Custom executors/generators ├── nx.json # Nx configuration └── workspace.json # Project configuration ``` ### 2. Library Types | Type | Purpose | Example | | --------------- | -------------------------------- | ------------------- | | **feature** | Smart components, business logic | `feature-auth` | | **ui** | Presentational components | `ui-buttons` | | **data-access** | API calls, state management | `data-access-users` | | **util** | Pure functions, helpers | `util-formatting` | | **shell** | App bootstrapping | `shell-web` | ## Templates ### Template 1: nx.json Configuration ```json { "$schema": "./node_modules/nx/schemas/nx-schema.json", "npmScope": "myorg", "affected": { "defaultBase": "main" }, "tasksRunnerOptions": { "default": { "runner": "nx/tasks-runners/default", "options": { "cacheableOperations": [ "build", "lint", "test", "e2e", "build-storybook" ], "parallel": 3 } } }, "targetDefaults": { "build": { "dependsOn": ["^build"], "inputs": ["production", "^production"], "cache": true }, "test": { "inputs": ["default", "^production", "{workspaceRoot}/jest.preset.js"], "cache": true }, "lint": { "inputs": ["default", "{workspaceRoot}/.eslintrc.json"], "cache": true }, "e2e": { "inputs": ["default", "^production"], "cache": true } }, "namedInputs": { "default": ["{projectRoot}/**/*", "sharedGlobals"], "production": [ "default", "!{projectRoot}/**/?(*.)+(spec|test).[jt]s?(x)?(.snap)", "!{projectRoot}/tsconfig.spec.json", "!{projectRoot}/jest.config.[jt]s", "!{projectRoot}/.eslintrc.json" ], "sharedGlobals": [ "{workspaceRoot}/babel.config.json", "{workspaceRoot}/tsconfig.base.json" ] }, "generators": { "@nx/react": { "application": { "style": "css", "linter": "eslint", "bundler": "webpack" }, "library": { "style": "css", "linter": "eslint" }, "component": { "style": "css" } } } } ``` ### Template 2: Project Configuration ```json // apps/web/project.json { "name": "web", "$schema": "../../node_modules/nx/schemas/project-schema.json", "sourceRoot": "apps/web/src", "projectType": "application", "tags": ["type:app", "scope:web"], "targets": { "build": { "executor": "@nx/webpack:webpack", "outputs": ["{options.outputPath}"], "defaultConfiguration": "production", "options": { "compiler": "babel", "outputPath": "dist/apps/web", "index": "apps/web/src/index.html", "main": "apps/web/src/main.tsx", "tsConfig": "apps/web/tsconfig.app.json", "assets": ["apps/web/src/assets"], "styles": ["apps/web/src/styles.css"] }, "configurations": { "development": { "extractLicenses": false, "optimization": false, "sourceMap": true }, "production": { "optimization": true, "outputHashing": "all", "sourceMap": false, "extractLicenses": true } } }, "serve": { "executor": "@nx/webpack:dev-server", "defaultConfiguration": "development", "options": { "buildTarget": "web:build" }, "configurations": { "development": { "buildTarget": "web:build:development" }, "production": { "buildTarget": "web:build:production" } } }, "test": { "executor": "@nx/jest:jest", "outputs": ["{workspaceRoot}/coverage/{projectRoot}"], "options": { "jestConfig": "apps/web/jest.config.ts", "passWithNoTests": true } }, "lint": { "executor": "@nx/eslint:lint", "outputs": ["{options.outputFile}"], "options": { "lintFilePatterns": ["apps/web/**/*.{ts,tsx,js,jsx}"] } } } } ``` ### Template 3: Module Boundary Rules ```json // .eslintrc.json { "root": true, "ignorePatterns": ["**/*"], "plugins": ["@nx"], "overrides": [ { "files": ["*.ts", "*.tsx", "*.js", "*.jsx"], "rules": { "@nx/enforce-module-boundaries": [ "error", { "enforceBuildableLibDependency": true, "allow": [], "depConstraints": [ { "sourceTag": "type:app", "onlyDependOnLibsWithTags": [ "type:feature", "type:ui", "type:data-access", "type:util" ] }, { "sourceTag": "type:feature", "onlyDependOnLibsWithTags": [ "type:ui", "type:data-access", "type:util" ] }, { "sourceTag": "type:ui", "onlyDependOnLibsWithTags": ["type:ui", "type:util"] }, { "sourceTag": "type:data-access", "onlyDependOnLibsWithTags": ["type:data-access", "type:util"] }, { "sourceTag": "type:util", "onlyDependOnLibsWithTags": ["type:util"] }, { "sourceTag": "scope:web", "onlyDependOnLibsWithTags": ["scope:web", "scope:shared"] }, { "sourceTag": "scope:api", "onlyDependOnLibsWithTags": ["scope:api", "scope:shared"] }, { "sourceTag": "scope:shared", "onlyDependOnLibsWithTags": ["scope:shared"] } ] } ] } } ] } ``` ### Template 4: Custom Generator ```typescript // tools/generators/feature-lib/index.ts import { Tree, formatFiles, generateFiles, joinPathFragments, names, readProjectConfiguration, } from "@nx/devkit"; import { libraryGenerator } from "@nx/react"; interface FeatureLibraryGeneratorSchema { name: string; scope: string; directory?: string; } export default async function featureLibraryGenerator( tree: Tree, options: FeatureLibraryGeneratorSchema, ) { const { name, scope, directory } = options; const projectDirectory = directory ? `${directory}/${name}` : `libs/${scope}/feature-${name}`; // Generate base library await libraryGenerator(tree, { name: `feature-${name}`, directory: projectDirectory, tags: `type:feature,scope:${scope}`, style: "css", skipTsConfig: false, skipFormat: true, unitTestRunner: "jest", linter: "eslint", }); // Add custom files const projectConfig = readProjectConfiguration( tree, `${scope}-feature-${name}`, ); const projectNames = names(name); generateFiles( tree, joinPathFragments(__dirname, "files"), projectConfig.sourceRoot, { ...projectNames, scope, tmpl: "", }, ); await formatFiles(tree); } ``` ### Template 5: CI Configuration with Affected ```yaml # .github/workflows/ci.yml name: CI on: push: branches: [main] pull_request: branches: [main] env: NX_CLOUD_ACCESS_TOKEN: ${{ secrets.NX_CLOUD_ACCESS_TOKEN }} jobs: main: runs-on: ubuntu-latest steps: - uses: actions/checkout@v4 with: fetch-depth: 0 - uses: actions/setup-node@v4 with: node-version: 20 cache: "npm" - name: Install dependencies run: npm ci - name: Derive SHAs for affected commands uses: nrwl/nx-set-shas@v4 - name: Run affected lint run: npx nx affected -t lint --parallel=3 - name: Run affected test run: npx nx affected -t test --parallel=3 --configuration=ci - name: Run affected build run: npx nx affected -t build --parallel=3 - name: Run affected e2e run: npx nx affected -t e2e --parallel=1 ``` ### Template 6: Remote Caching Setup ```typescript // nx.json with Nx Cloud { "tasksRunnerOptions": { "default": { "runner": "nx-cloud", "options": { "cacheableOperations": ["build", "lint", "test", "e2e"], "accessToken": "your-nx-cloud-token", "parallel": 3, "cacheDirectory": ".nx/cache" } } }, "nxCloudAccessToken": "your-nx-cloud-token" } // Self-hosted cache with S3 { "tasksRunnerOptions": { "default": { "runner": "@nx-aws-cache/nx-aws-cache", "options": { "cacheableOperations": ["build", "lint", "test"], "awsRegion": "us-east-1", "awsBucket": "my-nx-cache-bucket", "awsProfile": "default" } } } } ``` ## Common Commands ```bash # Generate new library nx g @nx/react:lib feature-auth --directory=libs/web --tags=type:feature,scope:web # Run affected tests nx affected -t test --base=main # View dependency graph nx graph # Run specific project nx build web --configuration=production # Reset cache nx reset # Run migrations nx migrate latest nx migrate --run-migrations ``` ## Best Practices ### Do's - **Use tags consistently** - Enforce with module boundaries - **Enable caching early** - Significant CI savings - **Keep libs focused** - Single responsibility - **Use generators** - Ensure consistency - **Document boundaries** - Help new developers ### Don'ts - **Don't create circular deps** - Graph should be acyclic - **Don't skip affected** - Test only what changed - **Don't ignore boundaries** - Tech debt accumulates - **Don't over-granularize** - Balance lib count ## Resources - [Nx Documentation](https://nx.dev/getting-started/intro) - [Module Boundaries](https://nx.dev/core-features/enforce-module-boundaries) - [Nx Cloud](https://nx.app/)

# Architecture Decision Records Comprehensive patterns for creating, maintaining, and managing Architecture Decision Records (ADRs) that capture the context and rationale behind significant technical decisions. ## When to Use This Skill - Making significant architectural decisions - Documenting technology choices - Recording design trade-offs - Onboarding new team members - Reviewing historical decisions - Establishing decision-making processes ## Core Concepts ### 1. What is an ADR? An Architecture Decision Record captures: - **Context**: Why we needed to make a decision - **Decision**: What we decided - **Consequences**: What happens as a result ### 2. When to Write an ADR | Write ADR | Skip ADR | | -------------------------- | ---------------------- | | New framework adoption | Minor version upgrades | | Database technology choice | Bug fixes | | API design patterns | Implementation details | | Security architecture | Routine maintenance | | Integration patterns | Configuration changes | ### 3. ADR Lifecycle ``` Proposed → Accepted → Deprecated → Superseded ↓ Rejected ``` ## Templates ### Template 1: Standard ADR (MADR Format) ```markdown # ADR-0001: Use PostgreSQL as Primary Database ## Status Accepted ## Context We need to select a primary database for our new e-commerce platform. The system will handle: - ~10,000 concurrent users - Complex product catalog with hierarchical categories - Transaction processing for orders and payments - Full-text search for products - Geospatial queries for store locator The team has experience with MySQL, PostgreSQL, and MongoDB. We need ACID compliance for financial transactions. ## Decision Drivers - **Must have ACID compliance** for payment processing - **Must support complex queries** for reporting - **Should support full-text search** to reduce infrastructure complexity - **Should have good JSON support** for flexible product attributes - **Team familiarity** reduces onboarding time ## Considered Options ### Option 1: PostgreSQL - **Pros**: ACID compliant, excellent JSON support (JSONB), built-in full-text search, PostGIS for geospatial, team has experience - **Cons**: Slightly more complex replication setup than MySQL ### Option 2: MySQL - **Pros**: Very familiar to team, simple replication, large community - **Cons**: Weaker JSON support, no built-in full-text search (need Elasticsearch), no geospatial without extensions ### Option 3: MongoDB - **Pros**: Flexible schema, native JSON, horizontal scaling - **Cons**: No ACID for multi-document transactions (at decision time), team has limited experience, requires schema design discipline ## Decision We will use **PostgreSQL 15** as our primary database. ## Rationale PostgreSQL provides the best balance of: 1. **ACID compliance** essential for e-commerce transactions 2. **Built-in capabilities** (full-text search, JSONB, PostGIS) reduce infrastructure complexity 3. **Team familiarity** with SQL databases reduces learning curve 4. **Mature ecosystem** with excellent tooling and community support The slight complexity in replication is outweighed by the reduction in additional services (no separate Elasticsearch needed). ## Consequences ### Positive - Single database handles transactions, search, and geospatial queries - Reduced operational complexity (fewer services to manage) - Strong consistency guarantees for financial data - Team can leverage existing SQL expertise ### Negative - Need to learn PostgreSQL-specific features (JSONB, full-text search syntax) - Vertical scaling limits may require read replicas sooner - Some team members need PostgreSQL-specific training ### Risks - Full-text search may not scale as well as dedicated search engines - Mitigation: Design for potential Elasticsearch addition if needed ## Implementation Notes - Use JSONB for flexible product attributes - Implement connection pooling with PgBouncer - Set up streaming replication for read replicas - Use pg_trgm extension for fuzzy search ## Related Decisions - ADR-0002: Caching Strategy (Redis) - complements database choice - ADR-0005: Search Architecture - may supersede if Elasticsearch needed ## References - [PostgreSQL JSON Documentation](https://www.postgresql.org/docs/current/datatype-json.html) - [PostgreSQL Full Text Search](https://www.postgresql.org/docs/current/textsearch.html) - Internal: Performance benchmarks in `/docs/benchmarks/database-comparison.md` ``` ### Template 2: Lightweight ADR ```markdown # ADR-0012: Adopt TypeScript for Frontend Development **Status**: Accepted **Date**: 2024-01-15 **Deciders**: @alice, @bob, @charlie ## Context Our React codebase has grown to 50+ components with increasing bug reports related to prop type mismatches and undefined errors. PropTypes provide runtime-only checking. ## Decision Adopt TypeScript for all new frontend code. Migrate existing code incrementally. ## Consequences **Good**: Catch type errors at compile time, better IDE support, self-documenting code. **Bad**: Learning curve for team, initial slowdown, build complexity increase. **Mitigations**: TypeScript training sessions, allow gradual adoption with `allowJs: true`. ``` ### Template 3: Y-Statement Format ```markdown # ADR-0015: API Gateway Selection In the context of **building a microservices architecture**, facing **the need for centralized API management, authentication, and rate limiting**, we decided for **Kong Gateway** and against **AWS API Gateway and custom Nginx solution**, to achieve **vendor independence, plugin extensibility, and team familiarity with Lua**, accepting that **we need to manage Kong infrastructure ourselves**. ``` ### Template 4: ADR for Deprecation ```markdown # ADR-0020: Deprecate MongoDB in Favor of PostgreSQL ## Status Accepted (Supersedes ADR-0003) ## Context ADR-0003 (2021) chose MongoDB for user profile storage due to schema flexibility needs. Since then: - MongoDB's multi-document transactions remain problematic for our use case - Our schema has stabilized and rarely changes - We now have PostgreSQL expertise from other services - Maintaining two databases increases operational burden ## Decision Deprecate MongoDB and migrate user profiles to PostgreSQL. ## Migration Plan 1. **Phase 1** (Week 1-2): Create PostgreSQL schema, dual-write enabled 2. **Phase 2** (Week 3-4): Backfill historical data, validate consistency 3. **Phase 3** (Week 5): Switch reads to PostgreSQL, monitor 4. **Phase 4** (Week 6): Remove MongoDB writes, decommission ## Consequences ### Positive - Single database technology reduces operational complexity - ACID transactions for user data - Team can focus PostgreSQL expertise ### Negative - Migration effort (~4 weeks) - Risk of data issues during migration - Lose some schema flexibility ## Lessons Learned Document from ADR-0003 experience: - Schema flexibility benefits were overestimated - Operational cost of multiple databases was underestimated - Consider long-term maintenance in technology decisions ``` ### Template 5: Request for Comments (RFC) Style ```markdown # RFC-0025: Adopt Event Sourcing for Order Management ## Summary Propose adopting event sourcing pattern for the order management domain to improve auditability, enable temporal queries, and support business analytics. ## Motivation Current challenges: 1. Audit requirements need complete order history 2. "What was the order state at time X?" queries are impossible 3. Analytics team needs event stream for real-time dashboards 4. Order state reconstruction for customer support is manual ## Detailed Design ### Event Store ``` OrderCreated { orderId, customerId, items[], timestamp } OrderItemAdded { orderId, item, timestamp } OrderItemRemoved { orderId, itemId, timestamp } PaymentReceived { orderId, amount, paymentId, timestamp } OrderShipped { orderId, trackingNumber, timestamp } ``` ### Projections - **CurrentOrderState**: Materialized view for queries - **OrderHistory**: Complete timeline for audit - **DailyOrderMetrics**: Analytics aggregation ### Technology - Event Store: EventStoreDB (purpose-built, handles projections) - Alternative considered: Kafka + custom projection service ## Drawbacks - Learning curve for team - Increased complexity vs. CRUD - Need to design events carefully (immutable once stored) - Storage growth (events never deleted) ## Alternatives 1. **Audit tables**: Simpler but doesn't enable temporal queries 2. **CDC from existing DB**: Complex, doesn't change data model 3. **Hybrid**: Event source only for order state changes ## Unresolved Questions - [ ] Event schema versioning strategy - [ ] Retention policy for events - [ ] Snapshot frequency for performance ## Implementation Plan 1. Prototype with single order type (2 weeks) 2. Team training on event sourcing (1 week) 3. Full implementation and migration (4 weeks) 4. Monitoring and optimization (ongoing) ## References - [Event Sourcing by Martin Fowler](https://martinfowler.com/eaaDev/EventSourcing.html) - [EventStoreDB Documentation](https://www.eventstore.com/docs) ``` ## ADR Management ### Directory Structure ``` docs/ ├── adr/ │ ├── README.md # Index and guidelines │ ├── template.md # Team's ADR template │ ├── 0001-use-postgresql.md │ ├── 0002-caching-strategy.md │ ├── 0003-mongodb-user-profiles.md # [DEPRECATED] │ └── 0020-deprecate-mongodb.md # Supersedes 0003 ``` ### ADR Index (README.md) ```markdown # Architecture Decision Records This directory contains Architecture Decision Records (ADRs) for [Project Name]. ## Index | ADR | Title | Status | Date | | ------------------------------------- | ---------------------------------- | ---------- | ---------- | | [0001](0001-use-postgresql.md) | Use PostgreSQL as Primary Database | Accepted | 2024-01-10 | | [0002](0002-caching-strategy.md) | Caching Strategy with Redis | Accepted | 2024-01-12 | | [0003](0003-mongodb-user-profiles.md) | MongoDB for User Profiles | Deprecated | 2023-06-15 | | [0020](0020-deprecate-mongodb.md) | Deprecate MongoDB | Accepted | 2024-01-15 | ## Creating a New ADR 1. Copy `template.md` to `NNNN-title-with-dashes.md` 2. Fill in the template 3. Submit PR for review 4. Update this index after approval ## ADR Status - **Proposed**: Under discussion - **Accepted**: Decision made, implementing - **Deprecated**: No longer relevant - **Superseded**: Replaced by another ADR - **Rejected**: Considered but not adopted ``` ### Automation (adr-tools) ```bash # Install adr-tools brew install adr-tools # Initialize ADR directory adr init docs/adr # Create new ADR adr new "Use PostgreSQL as Primary Database" # Supersede an ADR adr new -s 3 "Deprecate MongoDB in Favor of PostgreSQL" # Generate table of contents adr generate toc > docs/adr/README.md # Link related ADRs adr link 2 "Complements" 1 "Is complemented by" ``` ## Review Process ```markdown ## ADR Review Checklist ### Before Submission - [ ] Context clearly explains the problem - [ ] All viable options considered - [ ] Pros/cons balanced and honest - [ ] Consequences (positive and negative) documented - [ ] Related ADRs linked ### During Review - [ ] At least 2 senior engineers reviewed - [ ] Affected teams consulted - [ ] Security implications considered - [ ] Cost implications documented - [ ] Reversibility assessed ### After Acceptance - [ ] ADR index updated - [ ] Team notified - [ ] Implementation tickets created - [ ] Related documentation updated ``` ## Best Practices ### Do's - **Write ADRs early** - Before implementation starts - **Keep them short** - 1-2 pages maximum - **Be honest about trade-offs** - Include real cons - **Link related decisions** - Build decision graph - **Update status** - Deprecate when superseded ### Don'ts - **Don't change accepted ADRs** - Write new ones to supersede - **Don't skip context** - Future readers need background - **Don't hide failures** - Rejected decisions are valuable - **Don't be vague** - Specific decisions, specific consequences - **Don't forget implementation** - ADR without action is waste ## Resources - [Documenting Architecture Decisions (Michael Nygard)](https://cognitect.com/blog/2011/11/15/documenting-architecture-decisions) - [MADR Template](https://adr.github.io/madr/) - [ADR GitHub Organization](https://adr.github.io/) - [adr-tools](https://github.com/npryce/adr-tools)

# OpenAPI Spec Generation Comprehensive patterns for creating, maintaining, and validating OpenAPI 3.1 specifications for RESTful APIs. ## When to Use This Skill - Creating API documentation from scratch - Generating OpenAPI specs from existing code - Designing API contracts (design-first approach) - Validating API implementations against specs - Generating client SDKs from specs - Setting up API documentation portals ## Core Concepts ### 1. OpenAPI 3.1 Structure ```yaml openapi: 3.1.0 info: title: API Title version: 1.0.0 servers: - url: https://api.example.com/v1 paths: /resources: get: ... components: schemas: ... securitySchemes: ... ``` ### 2. Design Approaches | Approach | Description | Best For | | ---------------- | ---------------------------- | ------------------- | | **Design-First** | Write spec before code | New APIs, contracts | | **Code-First** | Generate spec from code | Existing APIs | | **Hybrid** | Annotate code, generate spec | Evolving APIs | ## Templates ### Template 1: Complete API Specification ```yaml openapi: 3.1.0 info: title: User Management API description: | API for managing users and their profiles. ## Authentication All endpoints require Bearer token authentication. ## Rate Limiting - 1000 requests per minute for standard tier - 10000 requests per minute for enterprise tier version: 2.0.0 contact: name: API Support email: api-support@example.com url: https://docs.example.com license: name: MIT url: https://opensource.org/licenses/MIT servers: - url: https://api.example.com/v2 description: Production - url: https://staging-api.example.com/v2 description: Staging - url: http://localhost:3000/v2 description: Local development tags: - name: Users description: User management operations - name: Profiles description: User profile operations - name: Admin description: Administrative operations paths: /users: get: operationId: listUsers summary: List all users description: Returns a paginated list of users with optional filtering. tags: - Users parameters: - $ref: "#/components/parameters/PageParam" - $ref: "#/components/parameters/LimitParam" - name: status in: query description: Filter by user status schema: $ref: "#/components/schemas/UserStatus" - name: search in: query description: Search by name or email schema: type: string minLength: 2 maxLength: 100 responses: "200": description: Successful response content: application/json: schema: $ref: "#/components/schemas/UserListResponse" examples: default: $ref: "#/components/examples/UserListExample" "400": $ref: "#/components/responses/BadRequest" "401": $ref: "#/components/responses/Unauthorized" "429": $ref: "#/components/responses/RateLimited" security: - bearerAuth: [] post: operationId: createUser summary: Create a new user description: Creates a new user account and sends welcome email. tags: - Users requestBody: required: true content: application/json: schema: $ref: "#/components/schemas/CreateUserRequest" examples: standard: summary: Standard user value: email: user@example.com name: John Doe role: user admin: summary: Admin user value: email: admin@example.com name: Admin User role: admin responses: "201": description: User created successfully content: application/json: schema: $ref: "#/components/schemas/User" headers: Location: description: URL of created user schema: type: string format: uri "400": $ref: "#/components/responses/BadRequest" "409": description: Email already exists content: application/json: schema: $ref: "#/components/schemas/Error" security: - bearerAuth: [] /users/{userId}: parameters: - $ref: "#/components/parameters/UserIdParam" get: operationId: getUser summary: Get user by ID tags: - Users responses: "200": description: Successful response content: application/json: schema: $ref: "#/components/schemas/User" "404": $ref: "#/components/responses/NotFound" security: - bearerAuth: [] patch: operationId: updateUser summary: Update user tags: - Users requestBody: required: true content: application/json: schema: $ref: "#/components/schemas/UpdateUserRequest" responses: "200": description: User updated content: application/json: schema: $ref: "#/components/schemas/User" "400": $ref: "#/components/responses/BadRequest" "404": $ref: "#/components/responses/NotFound" security: - bearerAuth: [] delete: operationId: deleteUser summary: Delete user tags: - Users - Admin responses: "204": description: User deleted "404": $ref: "#/components/responses/NotFound" security: - bearerAuth: [] - apiKey: [] components: schemas: User: type: object required: - id - email - name - status - createdAt properties: id: type: string format: uuid readOnly: true description: Unique user identifier email: type: string format: email description: User email address name: type: string minLength: 1 maxLength: 100 description: User display name status: $ref: "#/components/schemas/UserStatus" role: type: string enum: [user, moderator, admin] default: user avatar: type: string format: uri nullable: true metadata: type: object additionalProperties: true description: Custom metadata createdAt: type: string format: date-time readOnly: true updatedAt: type: string format: date-time readOnly: true UserStatus: type: string enum: [active, inactive, suspended, pending] description: User account status CreateUserRequest: type: object required: - email - name properties: email: type: string format: email name: type: string minLength: 1 maxLength: 100 role: type: string enum: [user, moderator, admin] default: user metadata: type: object additionalProperties: true UpdateUserRequest: type: object minProperties: 1 properties: name: type: string minLength: 1 maxLength: 100 status: $ref: "#/components/schemas/UserStatus" role: type: string enum: [user, moderator, admin] metadata: type: object additionalProperties: true UserListResponse: type: object required: - data - pagination properties: data: type: array items: $ref: "#/components/schemas/User" pagination: $ref: "#/components/schemas/Pagination" Pagination: type: object required: - page - limit - total - totalPages properties: page: type: integer minimum: 1 limit: type: integer minimum: 1 maximum: 100 total: type: integer minimum: 0 totalPages: type: integer minimum: 0 hasNext: type: boolean hasPrev: type: boolean Error: type: object required: - code - message properties: code: type: string description: Error code for programmatic handling message: type: string description: Human-readable error message details: type: array items: type: object properties: field: type: string message: type: string requestId: type: string description: Request ID for support parameters: UserIdParam: name: userId in: path required: true description: User ID schema: type: string format: uuid PageParam: name: page in: query description: Page number (1-based) schema: type: integer minimum: 1 default: 1 LimitParam: name: limit in: query description: Items per page schema: type: integer minimum: 1 maximum: 100 default: 20 responses: BadRequest: description: Invalid request content: application/json: schema: $ref: "#/components/schemas/Error" example: code: VALIDATION_ERROR message: Invalid request parameters details: - field: email message: Must be a valid email address Unauthorized: description: Authentication required content: application/json: schema: $ref: "#/components/schemas/Error" example: code: UNAUTHORIZED message: Authentication required NotFound: description: Resource not found content: application/json: schema: $ref: "#/components/schemas/Error" example: code: NOT_FOUND message: User not found RateLimited: description: Too many requests content: application/json: schema: $ref: "#/components/schemas/Error" headers: Retry-After: description: Seconds until rate limit resets schema: type: integer X-RateLimit-Limit: description: Request limit per window schema: type: integer X-RateLimit-Remaining: description: Remaining requests in window schema: type: integer examples: UserListExample: value: data: - id: "550e8400-e29b-41d4-a716-446655440000" email: "john@example.com" name: "John Doe" status: "active" role: "user" createdAt: "2024-01-15T10:30:00Z" pagination: page: 1 limit: 20 total: 1 totalPages: 1 hasNext: false hasPrev: false securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: JWT description: JWT token from /auth/login apiKey: type: apiKey in: header name: X-API-Key description: API key for service-to-service calls security: - bearerAuth: [] ``` ### Template 2: Code-First Generation (Python/FastAPI) ```python # FastAPI with automatic OpenAPI generation from fastapi import FastAPI, HTTPException, Query, Path, Depends from pydantic import BaseModel, Field, EmailStr from typing import Optional, List from datetime import datetime from uuid import UUID from enum import Enum app = FastAPI( title="User Management API", description="API for managing users and profiles", version="2.0.0", openapi_tags=[ {"name": "Users", "description": "User operations"}, {"name": "Profiles", "description": "Profile operations"}, ], servers=[ {"url": "https://api.example.com/v2", "description": "Production"}, {"url": "http://localhost:8000", "description": "Development"}, ], ) # Enums class UserStatus(str, Enum): active = "active" inactive = "inactive" suspended = "suspended" pending = "pending" class UserRole(str, Enum): user = "user" moderator = "moderator" admin = "admin" # Models class UserBase(BaseModel): email: EmailStr = Field(..., description="User email address") name: str = Field(..., min_length=1, max_length=100, description="Display name") class UserCreate(UserBase): role: UserRole = Field(default=UserRole.user) metadata: Optional[dict] = Field(default=None, description="Custom metadata") model_config = { "json_schema_extra": { "examples": [ { "email": "user@example.com", "name": "John Doe", "role": "user" } ] } } class UserUpdate(BaseModel): name: Optional[str] = Field(None, min_length=1, max_length=100) status: Optional[UserStatus] = None role: Optional[UserRole] = None metadata: Optional[dict] = None class User(UserBase): id: UUID = Field(..., description="Unique identifier") status: UserStatus role: UserRole avatar: Optional[str] = Field(None, description="Avatar URL") metadata: Optional[dict] = None created_at: datetime = Field(..., alias="createdAt") updated_at: Optional[datetime] = Field(None, alias="updatedAt") model_config = {"populate_by_name": True} class Pagination(BaseModel): page: int = Field(..., ge=1) limit: int = Field(..., ge=1, le=100) total: int = Field(..., ge=0) total_pages: int = Field(..., ge=0, alias="totalPages") has_next: bool = Field(..., alias="hasNext") has_prev: bool = Field(..., alias="hasPrev") class UserListResponse(BaseModel): data: List[User] pagination: Pagination class ErrorDetail(BaseModel): field: str message: str class ErrorResponse(BaseModel): code: str = Field(..., description="Error code") message: str = Field(..., description="Error message") details: Optional[List[ErrorDetail]] = None request_id: Optional[str] = Field(None, alias="requestId") # Endpoints @app.get( "/users", response_model=UserListResponse, tags=["Users"], summary="List all users", description="Returns a paginated list of users with optional filtering.", responses={ 400: {"model": ErrorResponse, "description": "Invalid request"}, 401: {"model": ErrorResponse, "description": "Unauthorized"}, }, ) async def list_users( page: int = Query(1, ge=1, description="Page number"), limit: int = Query(20, ge=1, le=100, description="Items per page"), status: Optional[UserStatus] = Query(None, description="Filter by status"), search: Optional[str] = Query(None, min_length=2, max_length=100), ): """ List users with pagination and filtering. - **page**: Page number (1-based) - **limit**: Number of items per page (max 100) - **status**: Filter by user status - **search**: Search by name or email """ # Implementation pass @app.post( "/users", response_model=User, status_code=201, tags=["Users"], summary="Create a new user", responses={ 400: {"model": ErrorResponse}, 409: {"model": ErrorResponse, "description": "Email already exists"}, }, ) async def create_user(user: UserCreate): """Create a new user and send welcome email.""" pass @app.get( "/users/{user_id}", response_model=User, tags=["Users"], summary="Get user by ID", responses={404: {"model": ErrorResponse}}, ) async def get_user( user_id: UUID = Path(..., description="User ID"), ): """Retrieve a specific user by their ID.""" pass @app.patch( "/users/{user_id}", response_model=User, tags=["Users"], summary="Update user", responses={ 400: {"model": ErrorResponse}, 404: {"model": ErrorResponse}, }, ) async def update_user( user_id: UUID = Path(..., description="User ID"), user: UserUpdate = ..., ): """Update user attributes.""" pass @app.delete( "/users/{user_id}", status_code=204, tags=["Users", "Admin"], summary="Delete user", responses={404: {"model": ErrorResponse}}, ) async def delete_user( user_id: UUID = Path(..., description="User ID"), ): """Permanently delete a user.""" pass # Export OpenAPI spec if __name__ == "__main__": import json print(json.dumps(app.openapi(), indent=2)) ``` ### Template 3: Code-First (TypeScript/Express with tsoa) ```typescript // tsoa generates OpenAPI from TypeScript decorators import { Controller, Get, Post, Patch, Delete, Route, Path, Query, Body, Response, SuccessResponse, Tags, Security, Example, } from "tsoa"; // Models interface User { /** Unique identifier */ id: string; /** User email address */ email: string; /** Display name */ name: string; status: UserStatus; role: UserRole; /** Avatar URL */ avatar?: string; /** Custom metadata */ metadata?: Record<string, unknown>; createdAt: Date; updatedAt?: Date; } enum UserStatus { Active = "active", Inactive = "inactive", Suspended = "suspended", Pending = "pending", } enum UserRole { User = "user", Moderator = "moderator", Admin = "admin", } interface CreateUserRequest { email: string; name: string; role?: UserRole; metadata?: Record<string, unknown>; } interface UpdateUserRequest { name?: string; status?: UserStatus; role?: UserRole; metadata?: Record<string, unknown>; } interface Pagination { page: number; limit: number; total: number; totalPages: number; hasNext: boolean; hasPrev: boolean; } interface UserListResponse { data: User[]; pagination: Pagination; } interface ErrorResponse { code: string; message: string; details?: { field: string; message: string }[]; requestId?: string; } @Route("users") @Tags("Users") export class UsersController extends Controller { /** * List all users with pagination and filtering * @param page Page number (1-based) * @param limit Items per page (max 100) * @param status Filter by user status * @param search Search by name or email */

# Terraform Module Library Production-ready Terraform module patterns for AWS, Azure, and GCP infrastructure. ## Purpose Create reusable, well-tested Terraform modules for common cloud infrastructure patterns across multiple cloud providers. ## When to Use - Build reusable infrastructure components - Standardize cloud resource provisioning - Implement infrastructure as code best practices - Create multi-cloud compatible modules - Establish organizational Terraform standards ## Module Structure ``` terraform-modules/ ├── aws/ │ ├── vpc/ │ ├── eks/ │ ├── rds/ │ └── s3/ ├── azure/ │ ├── vnet/ │ ├── aks/ │ └── storage/ └── gcp/ ├── vpc/ ├── gke/ └── cloud-sql/ ``` ## Standard Module Pattern ``` module-name/ ├── main.tf # Main resources ├── variables.tf # Input variables ├── outputs.tf # Output values ├── versions.tf # Provider versions ├── README.md # Documentation ├── examples/ # Usage examples │ └── complete/ │ ├── main.tf │ └── variables.tf └── tests/ # Terratest files └── module_test.go ``` ## AWS VPC Module Example **main.tf:** ```hcl resource "aws_vpc" "main" { cidr_block = var.cidr_block enable_dns_hostnames = var.enable_dns_hostnames enable_dns_support = var.enable_dns_support tags = merge( { Name = var.name }, var.tags ) } resource "aws_subnet" "private" { count = length(var.private_subnet_cidrs) vpc_id = aws_vpc.main.id cidr_block = var.private_subnet_cidrs[count.index] availability_zone = var.availability_zones[count.index] tags = merge( { Name = "${var.name}-private-${count.index + 1}" Tier = "private" }, var.tags ) } resource "aws_internet_gateway" "main" { count = var.create_internet_gateway ? 1 : 0 vpc_id = aws_vpc.main.id tags = merge( { Name = "${var.name}-igw" }, var.tags ) } ``` **variables.tf:** ```hcl variable "name" { description = "Name of the VPC" type = string } variable "cidr_block" { description = "CIDR block for VPC" type = string validation { condition = can(regex("^([0-9]{1,3}\\.){3}[0-9]{1,3}/[0-9]{1,2}$", var.cidr_block)) error_message = "CIDR block must be valid IPv4 CIDR notation." } } variable "availability_zones" { description = "List of availability zones" type = list(string) } variable "private_subnet_cidrs" { description = "CIDR blocks for private subnets" type = list(string) default = [] } variable "enable_dns_hostnames" { description = "Enable DNS hostnames in VPC" type = bool default = true } variable "tags" { description = "Additional tags" type = map(string) default = {} } ``` **outputs.tf:** ```hcl output "vpc_id" { description = "ID of the VPC" value = aws_vpc.main.id } output "private_subnet_ids" { description = "IDs of private subnets" value = aws_subnet.private[*].id } output "vpc_cidr_block" { description = "CIDR block of VPC" value = aws_vpc.main.cidr_block } ``` ## Best Practices 1. **Use semantic versioning** for modules 2. **Document all variables** with descriptions 3. **Provide examples** in examples/ directory 4. **Use validation blocks** for input validation 5. **Output important attributes** for module composition 6. **Pin provider versions** in versions.tf 7. **Use locals** for computed values 8. **Implement conditional resources** with count/for_each 9. **Test modules** with Terratest 10. **Tag all resources** consistently ## Module Composition ```hcl module "vpc" { source = "../../modules/aws/vpc" name = "production" cidr_block = "10.0.0.0/16" availability_zones = ["us-west-2a", "us-west-2b", "us-west-2c"] private_subnet_cidrs = [ "10.0.1.0/24", "10.0.2.0/24", "10.0.3.0/24" ] tags = { Environment = "production" ManagedBy = "terraform" } } module "rds" { source = "../../modules/aws/rds" identifier = "production-db" engine = "postgres" engine_version = "15.3" instance_class = "db.t3.large" vpc_id = module.vpc.vpc_id subnet_ids = module.vpc.private_subnet_ids tags = { Environment = "production" } } ``` ## Reference Files - `assets/vpc-module/` - Complete VPC module example - `assets/rds-module/` - RDS module example - `references/aws-modules.md` - AWS module patterns - `references/azure-modules.md` - Azure module patterns - `references/gcp-modules.md` - GCP module patterns ## Testing ```go // tests/vpc_test.go package test import ( "testing" "github.com/gruntwork-io/terratest/modules/terraform" "github.com/stretchr/testify/assert" ) func TestVPCModule(t *testing.T) { terraformOptions := &terraform.Options{ TerraformDir: "../examples/complete", } defer terraform.Destroy(t, terraformOptions) terraform.InitAndApply(t, terraformOptions) vpcID := terraform.Output(t, terraformOptions, "vpc_id") assert.NotEmpty(t, vpcID) } ``` ## Related Skills - `multi-cloud-architecture` - For architectural decisions - `cost-optimization` - For cost-effective designs

# Dependency Upgrade Master major dependency version upgrades, compatibility analysis, staged upgrade strategies, and comprehensive testing approaches. ## When to Use This Skill - Upgrading major framework versions - Updating security-vulnerable dependencies - Modernizing legacy dependencies - Resolving dependency conflicts - Planning incremental upgrade paths - Testing compatibility matrices - Automating dependency updates ## Semantic Versioning Review ``` MAJOR.MINOR.PATCH (e.g., 2.3.1) MAJOR: Breaking changes MINOR: New features, backward compatible PATCH: Bug fixes, backward compatible ^2.3.1 = >=2.3.1 <3.0.0 (minor updates) ~2.3.1 = >=2.3.1 <2.4.0 (patch updates) 2.3.1 = exact version ``` ## Dependency Analysis ### Audit Dependencies ```bash # npm npm outdated npm audit npm audit fix # yarn yarn outdated yarn audit # Check for major updates npx npm-check-updates npx npm-check-updates -u # Update package.json ``` ### Analyze Dependency Tree ```bash # See why a package is installed npm ls package-name yarn why package-name # Find duplicate packages npm dedupe yarn dedupe # Visualize dependencies npx madge --image graph.png src/ ``` ## Compatibility Matrix ```javascript // compatibility-matrix.js const compatibilityMatrix = { react: { "16.x": { "react-dom": "^16.0.0", "react-router-dom": "^5.0.0", "@testing-library/react": "^11.0.0", }, "17.x": { "react-dom": "^17.0.0", "react-router-dom": "^5.0.0 || ^6.0.0", "@testing-library/react": "^12.0.0", }, "18.x": { "react-dom": "^18.0.0", "react-router-dom": "^6.0.0", "@testing-library/react": "^13.0.0", }, }, }; function checkCompatibility(packages) { // Validate package versions against matrix } ``` ## Staged Upgrade Strategy ### Phase 1: Planning ```bash # 1. Identify current versions npm list --depth=0 # 2. Check for breaking changes # Read CHANGELOG.md and MIGRATION.md # 3. Create upgrade plan echo "Upgrade order: 1. TypeScript 2. React 3. React Router 4. Testing libraries 5. Build tools" > UPGRADE_PLAN.md ``` ### Phase 2: Incremental Updates ```bash # Don't upgrade everything at once! # Step 1: Update TypeScript npm install typescript@latest # Test npm run test npm run build # Step 2: Update React (one major version at a time) npm install react@17 react-dom@17 # Test again npm run test # Step 3: Continue with other packages npm install react-router-dom@6 # And so on... ``` ### Phase 3: Validation ```javascript // tests/compatibility.test.js describe("Dependency Compatibility", () => { it("should have compatible React versions", () => { const reactVersion = require("react/package.json").version; const reactDomVersion = require("react-dom/package.json").version; expect(reactVersion).toBe(reactDomVersion); }); it("should not have peer dependency warnings", () => { // Run npm ls and check for warnings }); }); ``` ## Breaking Change Handling ### Identifying Breaking Changes ```bash # Check the changelog directly curl https://raw.githubusercontent.com/facebook/react/master/CHANGELOG.md ``` ### Codemod for Automated Fixes ```bash # Run jscodeshift with transform URL npx jscodeshift -t <transform-url> <path> # Example: Rename unsafe lifecycle methods npx jscodeshift -t https://raw.githubusercontent.com/reactjs/react-codemod/master/transforms/rename-unsafe-lifecycles.js src/ # For TypeScript files npx jscodeshift -t https://raw.githubusercontent.com/reactjs/react-codemod/master/transforms/rename-unsafe-lifecycles.js --parser=tsx src/ # Dry run to preview changes npx jscodeshift -t https://raw.githubusercontent.com/reactjs/react-codemod/master/transforms/rename-unsafe-lifecycles.js --dry src/ ``` ### Custom Migration Script ```javascript // migration-script.js const fs = require("fs"); const glob = require("glob"); glob("src/**/*.tsx", (err, files) => { files.forEach((file) => { let content = fs.readFileSync(file, "utf8"); // Replace old API with new API content = content.replace( /componentWillMount/g, "UNSAFE_componentWillMount", ); // Update imports content = content.replace( /import { Component } from 'react'/g, "import React, { Component } from 'react'", ); fs.writeFileSync(file, content); }); }); ``` ## Testing Strategy ### Unit Tests ```javascript // Ensure tests pass before and after upgrade npm run test // Update test utilities if needed npm install @testing-library/react@latest ``` ### Integration Tests ```javascript // tests/integration/app.test.js describe("App Integration", () => { it("should render without crashing", () => { render(<App />); }); it("should handle navigation", () => { const { getByText } = render(<App />); fireEvent.click(getByText("Navigate")); expect(screen.getByText("New Page")).toBeInTheDocument(); }); }); ``` ### Visual Regression Tests ```javascript // visual-regression.test.js describe("Visual Regression", () => { it("should match snapshot", () => { const { container } = render(<App />); expect(container.firstChild).toMatchSnapshot(); }); }); ``` ### E2E Tests ```javascript // cypress/e2e/app.cy.js describe("E2E Tests", () => { it("should complete user flow", () => { cy.visit("/"); cy.get('[data-testid="login"]').click(); cy.get('input[name="email"]').type("user@example.com"); cy.get('button[type="submit"]').click(); cy.url().should("include", "/dashboard"); }); }); ``` ## Automated Dependency Updates ### Renovate Configuration ```json // renovate.json { "extends": ["config:base"], "packageRules": [ { "matchUpdateTypes": ["minor", "patch"], "automerge": true }, { "matchUpdateTypes": ["major"], "automerge": false, "labels": ["major-update"] } ], "schedule": ["before 3am on Monday"], "timezone": "America/New_York" } ``` ### Dependabot Configuration ```yaml # .github/dependabot.yml version: 2 updates: - package-ecosystem: "npm" directory: "/" schedule: interval: "weekly" open-pull-requests-limit: 5 reviewers: - "team-leads" commit-message: prefix: "chore" include: "scope" ``` ## Rollback Plan ```javascript // rollback.sh #!/bin/bash # Save current state git stash git checkout -b upgrade-branch # Attempt upgrade npm install package@latest # Run tests if npm run test; then echo "Upgrade successful" git add package.json package-lock.json git commit -m "chore: upgrade package" else echo "Upgrade failed, rolling back" git checkout main git branch -D upgrade-branch npm install # Restore from package-lock.json fi ``` ## Common Upgrade Patterns ### Lock File Management ```bash # npm npm install --package-lock-only # Update lock file only npm ci # Clean install from lock file # yarn yarn install --frozen-lockfile # CI mode yarn upgrade-interactive # Interactive upgrades ``` ### Peer Dependency Resolution ```bash # npm 7+: strict peer dependencies npm install --legacy-peer-deps # Ignore peer deps # npm 8+: override peer dependencies npm install --force ``` ### Workspace Upgrades ```bash # Update all workspace packages npm install --workspaces # Update specific workspace npm install package@latest --workspace=packages/app ``` ## Resources - **references/semver.md**: Semantic versioning guide - **references/compatibility-matrix.md**: Common compatibility issues - **references/staged-upgrades.md**: Incremental upgrade strategies - **references/testing-strategy.md**: Comprehensive testing approaches - **assets/upgrade-checklist.md**: Step-by-step checklist - **assets/compatibility-matrix.csv**: Version compatibility table - **scripts/audit-dependencies.sh**: Dependency audit script ## Best Practices 1. **Read Changelogs**: Understand what changed 2. **Upgrade Incrementally**: One major version at a time 3. **Test Thoroughly**: Unit, integration, E2E tests 4. **Check Peer Dependencies**: Resolve conflicts early 5. **Use Lock Files**: Ensure reproducible installs 6. **Automate Updates**: Use Renovate or Dependabot 7. **Monitor**: Watch for runtime errors post-upgrade 8. **Document**: Keep upgrade notes ## Upgrade Checklist ```markdown Pre-Upgrade: - [ ] Review current dependency versions - [ ] Read changelogs for breaking changes - [ ] Create feature branch - [ ] Backup current state (git tag) - [ ] Run full test suite (baseline) During Upgrade: - [ ] Upgrade one dependency at a time - [ ] Update peer dependencies - [ ] Fix TypeScript errors - [ ] Update tests if needed - [ ] Run test suite after each upgrade - [ ] Check bundle size impact Post-Upgrade: - [ ] Full regression testing - [ ] Performance testing - [ ] Update documentation - [ ] Deploy to staging - [ ] Monitor for errors - [ ] Deploy to production ``` ## Common Pitfalls - Upgrading all dependencies at once - Not testing after each upgrade - Ignoring peer dependency warnings - Forgetting to update lock file - Not reading breaking change notes - Skipping major versions - Not having rollback plan

# React Modernization Master React version upgrades, class to hooks migration, concurrent features adoption, and codemods for automated transformation. ## When to Use This Skill - Upgrading React applications to latest versions - Migrating class components to functional components with hooks - Adopting concurrent React features (Suspense, transitions) - Applying codemods for automated refactoring - Modernizing state management patterns - Updating to TypeScript - Improving performance with React 18+ features ## Version Upgrade Path ### React 16 → 17 → 18 **Breaking Changes by Version:** **React 17:** - Event delegation changes - No event pooling - Effect cleanup timing - JSX transform (no React import needed) **React 18:** - Automatic batching - Concurrent rendering - Strict Mode changes (double invocation) - New root API - Suspense on server ## Class to Hooks Migration ### State Management ```javascript // Before: Class component class Counter extends React.Component { constructor(props) { super(props); this.state = { count: 0, name: "", }; } increment = () => { this.setState({ count: this.state.count + 1 }); }; render() { return ( <div> <p>Count: {this.state.count}</p> <button onClick={this.increment}>Increment</button> </div> ); } } // After: Functional component with hooks function Counter() { const [count, setCount] = useState(0); const [name, setName] = useState(""); const increment = () => { setCount(count + 1); }; return ( <div> <p>Count: {count}</p> <button onClick={increment}>Increment</button> </div> ); } ``` ### Lifecycle Methods to Hooks ```javascript // Before: Lifecycle methods class DataFetcher extends React.Component { state = { data: null, loading: true }; componentDidMount() { this.fetchData(); } componentDidUpdate(prevProps) { if (prevProps.id !== this.props.id) { this.fetchData(); } } componentWillUnmount() { this.cancelRequest(); } fetchData = async () => { const data = await fetch(`/api/${this.props.id}`); this.setState({ data, loading: false }); }; cancelRequest = () => { // Cleanup }; render() { if (this.state.loading) return <div>Loading...</div>; return <div>{this.state.data}</div>; } } // After: useEffect hook function DataFetcher({ id }) { const [data, setData] = useState(null); const [loading, setLoading] = useState(true); useEffect(() => { let cancelled = false; const fetchData = async () => { try { const response = await fetch(`/api/${id}`); const result = await response.json(); if (!cancelled) { setData(result); setLoading(false); } } catch (error) { if (!cancelled) { console.error(error); } } }; fetchData(); // Cleanup function return () => { cancelled = true; }; }, [id]); // Re-run when id changes if (loading) return <div>Loading...</div>; return <div>{data}</div>; } ``` ### Context and HOCs to Hooks ```javascript // Before: Context consumer and HOC const ThemeContext = React.createContext(); class ThemedButton extends React.Component { static contextType = ThemeContext; render() { return ( <button style={{ background: this.context.theme }}> {this.props.children} </button> ); } } // After: useContext hook function ThemedButton({ children }) { const { theme } = useContext(ThemeContext); return <button style={{ background: theme }}>{children}</button>; } // Before: HOC for data fetching function withUser(Component) { return class extends React.Component { state = { user: null }; componentDidMount() { fetchUser().then((user) => this.setState({ user })); } render() { return <Component {...this.props} user={this.state.user} />; } }; } // After: Custom hook function useUser() { const [user, setUser] = useState(null); useEffect(() => { fetchUser().then(setUser); }, []); return user; } function UserProfile() { const user = useUser(); if (!user) return <div>Loading...</div>; return <div>{user.name}</div>; } ``` ## React 18 Concurrent Features ### New Root API ```javascript // Before: React 17 import ReactDOM from "react-dom"; ReactDOM.render(<App />, document.getElementById("root")); // After: React 18 import { createRoot } from "react-dom/client"; const root = createRoot(document.getElementById("root")); root.render(<App />); ``` ### Automatic Batching ```javascript // React 18: All updates are batched function handleClick() { setCount((c) => c + 1); setFlag((f) => !f); // Only one re-render (batched) } // Even in async: setTimeout(() => { setCount((c) => c + 1); setFlag((f) => !f); // Still batched in React 18! }, 1000); // Opt out if needed import { flushSync } from "react-dom"; flushSync(() => { setCount((c) => c + 1); }); // Re-render happens here setFlag((f) => !f); // Another re-render ``` ### Transitions ```javascript import { useState, useTransition } from "react"; function SearchResults() { const [query, setQuery] = useState(""); const [results, setResults] = useState([]); const [isPending, startTransition] = useTransition(); const handleChange = (e) => { // Urgent: Update input immediately setQuery(e.target.value); // Non-urgent: Update results (can be interrupted) startTransition(() => { setResults(searchResults(e.target.value)); }); }; return ( <> <input value={query} onChange={handleChange} /> {isPending && <Spinner />} <Results data={results} /> </> ); } ``` ### Suspense for Data Fetching ```javascript import { Suspense } from "react"; // Resource-based data fetching (with React 18) const resource = fetchProfileData(); function ProfilePage() { return ( <Suspense fallback={<Loading />}> <ProfileDetails /> <Suspense fallback={<Loading />}> <ProfileTimeline /> </Suspense> </Suspense> ); } function ProfileDetails() { // This will suspend if data not ready const user = resource.user.read(); return <h1>{user.name}</h1>; } function ProfileTimeline() { const posts = resource.posts.read(); return <Timeline posts={posts} />; } ``` ## Codemods for Automation ### Run React Codemods ```bash # Rename unsafe lifecycle methods npx jscodeshift -t https://raw.githubusercontent.com/reactjs/react-codemod/master/transforms/rename-unsafe-lifecycles.js src/ # Update React imports (React 17+) npx jscodeshift -t https://raw.githubusercontent.com/reactjs/react-codemod/master/transforms/update-react-imports.js src/ # Add error boundaries npx jscodeshift -t https://raw.githubusercontent.com/reactjs/react-codemod/master/transforms/error-boundaries.js src/ # For TypeScript files npx jscodeshift -t https://raw.githubusercontent.com/reactjs/react-codemod/master/transforms/rename-unsafe-lifecycles.js --parser=tsx src/ # Dry run to preview changes npx jscodeshift -t https://raw.githubusercontent.com/reactjs/react-codemod/master/transforms/rename-unsafe-lifecycles.js --dry --print src/ # Class to Hooks (third-party) npx codemod react/hooks/convert-class-to-function src/ ``` ### Custom Codemod Example ```javascript // custom-codemod.js module.exports = function (file, api) { const j = api.jscodeshift; const root = j(file.source); // Find setState calls root .find(j.CallExpression, { callee: { type: "MemberExpression", property: { name: "setState" }, }, }) .forEach((path) => { // Transform to useState // ... transformation logic }); return root.toSource(); }; // Run: jscodeshift -t custom-codemod.js src/ ``` ## Performance Optimization ### useMemo and useCallback ```javascript function ExpensiveComponent({ items, filter }) { // Memoize expensive calculation const filteredItems = useMemo(() => { return items.filter((item) => item.category === filter); }, [items, filter]); // Memoize callback to prevent child re-renders const handleClick = useCallback((id) => { console.log("Clicked:", id); }, []); // No dependencies, never changes return <List items={filteredItems} onClick={handleClick} />; } // Child component with memo const List = React.memo(({ items, onClick }) => { return items.map((item) => ( <Item key={item.id} item={item} onClick={onClick} /> )); }); ``` ### Code Splitting ```javascript import { lazy, Suspense } from "react"; // Lazy load components const Dashboard = lazy(() => import("./Dashboard")); const Settings = lazy(() => import("./Settings")); function App() { return ( <Suspense fallback={<Loading />}> <Routes> <Route path="/dashboard" element={<Dashboard />} /> <Route path="/settings" element={<Settings />} /> </Routes> </Suspense> ); } ``` ## TypeScript Migration ```typescript // Before: JavaScript function Button({ onClick, children }) { return <button onClick={onClick}>{children}</button>; } // After: TypeScript interface ButtonProps { onClick: () => void; children: React.ReactNode; } function Button({ onClick, children }: ButtonProps) { return <button onClick={onClick}>{children}</button>; } // Generic components interface ListProps<T> { items: T[]; renderItem: (item: T) => React.ReactNode; } function List<T>({ items, renderItem }: ListProps<T>) { return <>{items.map(renderItem)}</>; } ``` ## Migration Checklist ```markdown ### Pre-Migration - [ ] Update dependencies incrementally (not all at once) - [ ] Review breaking changes in release notes - [ ] Set up testing suite - [ ] Create feature branch ### Class → Hooks Migration - [ ] Identify class components to migrate - [ ] Start with leaf components (no children) - [ ] Convert state to useState - [ ] Convert lifecycle to useEffect - [ ] Convert context to useContext - [ ] Extract custom hooks - [ ] Test thoroughly ### React 18 Upgrade - [ ] Update to React 17 first (if needed) - [ ] Update react and react-dom to 18 - [ ] Update @types/react if using TypeScript - [ ] Change to createRoot API - [ ] Test with StrictMode (double invocation) - [ ] Address concurrent rendering issues - [ ] Adopt Suspense/Transitions where beneficial ### Performance - [ ] Identify performance bottlenecks - [ ] Add React.memo where appropriate - [ ] Use useMemo/useCallback for expensive operations - [ ] Implement code splitting - [ ] Optimize re-renders ### Testing - [ ] Update test utilities (React Testing Library) - [ ] Test with React 18 features - [ ] Check for warnings in console - [ ] Performance testing ``` ## Resources - **references/breaking-changes.md**: Version-specific breaking changes - **references/codemods.md**: Codemod usage guide - **references/hooks-migration.md**: Comprehensive hooks patterns - **references/concurrent-features.md**: React 18 concurrent features - **assets/codemod-config.json**: Codemod configurations - **assets/migration-checklist.md**: Step-by-step checklist - **scripts/apply-codemods.sh**: Automated codemod script ## Best Practices 1. **Incremental Migration**: Don't migrate everything at once 2. **Test Thoroughly**: Comprehensive testing at each step 3. **Use Codemods**: Automate repetitive transformations 4. **Start Simple**: Begin with leaf components 5. **Leverage StrictMode**: Catch issues early 6. **Monitor Performance**: Measure before and after 7. **Document Changes**: Keep migration log ## Common Pitfalls - Forgetting useEffect dependencies - Over-using useMemo/useCallback - Not handling cleanup in useEffect - Mixing class and functional patterns - Ignoring StrictMode warnings - Breaking change assumptions

# Next.js App Router Patterns Comprehensive patterns for Next.js 14+ App Router architecture, Server Components, and modern full-stack React development. ## When to Use This Skill - Building new Next.js applications with App Router - Migrating from Pages Router to App Router - Implementing Server Components and streaming - Setting up parallel and intercepting routes - Optimizing data fetching and caching - Building full-stack features with Server Actions ## Core Concepts ### 1. Rendering Modes | Mode | Where | When to Use | | --------------------- | ------------ | ----------------------------------------- | | **Server Components** | Server only | Data fetching, heavy computation, secrets | | **Client Components** | Browser | Interactivity, hooks, browser APIs | | **Static** | Build time | Content that rarely changes | | **Dynamic** | Request time | Personalized or real-time data | | **Streaming** | Progressive | Large pages, slow data sources | ### 2. File Conventions ``` app/ ├── layout.tsx # Shared UI wrapper ├── page.tsx # Route UI ├── loading.tsx # Loading UI (Suspense) ├── error.tsx # Error boundary ├── not-found.tsx # 404 UI ├── route.ts # API endpoint ├── template.tsx # Re-mounted layout ├── default.tsx # Parallel route fallback └── opengraph-image.tsx # OG image generation ``` ## Quick Start ```typescript // app/layout.tsx import { Inter } from 'next/font/google' import { Providers } from './providers' const inter = Inter({ subsets: ['latin'] }) export const metadata = { title: { default: 'My App', template: '%s | My App' }, description: 'Built with Next.js App Router', } export default function RootLayout({ children, }: { children: React.ReactNode }) { return ( <html lang="en" suppressHydrationWarning> <body className={inter.className}> <Providers>{children}</Providers> </body> </html> ) } // app/page.tsx - Server Component by default async function getProducts() { const res = await fetch('https://api.example.com/products', { next: { revalidate: 3600 }, // ISR: revalidate every hour }) return res.json() } export default async function HomePage() { const products = await getProducts() return ( <main> <h1>Products</h1> <ProductGrid products={products} /> </main> ) } ``` ## Patterns ### Pattern 1: Server Components with Data Fetching ```typescript // app/products/page.tsx import { Suspense } from 'react' import { ProductList, ProductListSkeleton } from '@/components/products' import { FilterSidebar } from '@/components/filters' interface SearchParams { category?: string sort?: 'price' | 'name' | 'date' page?: string } export default async function ProductsPage({ searchParams, }: { searchParams: Promise<SearchParams> }) { const params = await searchParams return ( <div className="flex gap-8"> <FilterSidebar /> <Suspense key={JSON.stringify(params)} fallback={<ProductListSkeleton />} > <ProductList category={params.category} sort={params.sort} page={Number(params.page) || 1} /> </Suspense> </div> ) } // components/products/ProductList.tsx - Server Component async function getProducts(filters: ProductFilters) { const res = await fetch( `${process.env.API_URL}/products?${new URLSearchParams(filters)}`, { next: { tags: ['products'] } } ) if (!res.ok) throw new Error('Failed to fetch products') return res.json() } export async function ProductList({ category, sort, page }: ProductFilters) { const { products, totalPages } = await getProducts({ category, sort, page }) return ( <div> <div className="grid grid-cols-3 gap-4"> {products.map((product) => ( <ProductCard key={product.id} product={product} /> ))} </div> <Pagination currentPage={page} totalPages={totalPages} /> </div> ) } ``` ### Pattern 2: Client Components with 'use client' ```typescript // components/products/AddToCartButton.tsx 'use client' import { useState, useTransition } from 'react' import { addToCart } from '@/app/actions/cart' export function AddToCartButton({ productId }: { productId: string }) { const [isPending, startTransition] = useTransition() const [error, setError] = useState<string | null>(null) const handleClick = () => { setError(null) startTransition(async () => { const result = await addToCart(productId) if (result.error) { setError(result.error) } }) } return ( <div> <button onClick={handleClick} disabled={isPending} className="btn-primary" > {isPending ? 'Adding...' : 'Add to Cart'} </button> {error && <p className="text-red-500 text-sm">{error}</p>} </div> ) } ``` ### Pattern 3: Server Actions ```typescript // app/actions/cart.ts "use server"; import { revalidateTag } from "next/cache"; import { cookies } from "next/headers"; import { redirect } from "next/navigation"; export async function addToCart(productId: string) { const cookieStore = await cookies(); const sessionId = cookieStore.get("session")?.value; if (!sessionId) { redirect("/login"); } try { await db.cart.upsert({ where: { sessionId_productId: { sessionId, productId } }, update: { quantity: { increment: 1 } }, create: { sessionId, productId, quantity: 1 }, }); revalidateTag("cart"); return { success: true }; } catch (error) { return { error: "Failed to add item to cart" }; } } export async function checkout(formData: FormData) { const address = formData.get("address") as string; const payment = formData.get("payment") as string; // Validate if (!address || !payment) { return { error: "Missing required fields" }; } // Process order const order = await processOrder({ address, payment }); // Redirect to confirmation redirect(`/orders/${order.id}/confirmation`); } ``` ### Pattern 4: Parallel Routes ```typescript // app/dashboard/layout.tsx export default function DashboardLayout({ children, analytics, team, }: { children: React.ReactNode analytics: React.ReactNode team: React.ReactNode }) { return ( <div className="dashboard-grid"> <main>{children}</main> <aside className="analytics-panel">{analytics}</aside> <aside className="team-panel">{team}</aside> </div> ) } // app/dashboard/@analytics/page.tsx export default async function AnalyticsSlot() { const stats = await getAnalytics() return <AnalyticsChart data={stats} /> } // app/dashboard/@analytics/loading.tsx export default function AnalyticsLoading() { return <ChartSkeleton /> } // app/dashboard/@team/page.tsx export default async function TeamSlot() { const members = await getTeamMembers() return <TeamList members={members} /> } ``` ### Pattern 5: Intercepting Routes (Modal Pattern) ```typescript // File structure for photo modal // app/ // ├── @modal/ // │ ├── (.)photos/[id]/page.tsx # Intercept // │ └── default.tsx // ├── photos/ // │ └── [id]/page.tsx # Full page // └── layout.tsx // app/@modal/(.)photos/[id]/page.tsx import { Modal } from '@/components/Modal' import { PhotoDetail } from '@/components/PhotoDetail' export default async function PhotoModal({ params, }: { params: Promise<{ id: string }> }) { const { id } = await params const photo = await getPhoto(id) return ( <Modal> <PhotoDetail photo={photo} /> </Modal> ) } // app/photos/[id]/page.tsx - Full page version export default async function PhotoPage({ params, }: { params: Promise<{ id: string }> }) { const { id } = await params const photo = await getPhoto(id) return ( <div className="photo-page"> <PhotoDetail photo={photo} /> <RelatedPhotos photoId={id} /> </div> ) } // app/layout.tsx export default function RootLayout({ children, modal, }: { children: React.ReactNode modal: React.ReactNode }) { return ( <html> <body> {children} {modal} </body> </html> ) } ``` ### Pattern 6: Streaming with Suspense ```typescript // app/product/[id]/page.tsx import { Suspense } from 'react' export default async function ProductPage({ params, }: { params: Promise<{ id: string }> }) { const { id } = await params // This data loads first (blocking) const product = await getProduct(id) return ( <div> {/* Immediate render */} <ProductHeader product={product} /> {/* Stream in reviews */} <Suspense fallback={<ReviewsSkeleton />}> <Reviews productId={id} /> </Suspense> {/* Stream in recommendations */} <Suspense fallback={<RecommendationsSkeleton />}> <Recommendations productId={id} /> </Suspense> </div> ) } // These components fetch their own data async function Reviews({ productId }: { productId: string }) { const reviews = await getReviews(productId) // Slow API return <ReviewList reviews={reviews} /> } async function Recommendations({ productId }: { productId: string }) { const products = await getRecommendations(productId) // ML-based, slow return <ProductCarousel products={products} /> } ``` ### Pattern 7: Route Handlers (API Routes) ```typescript // app/api/products/route.ts import { NextRequest, NextResponse } from "next/server"; export async function GET(request: NextRequest) { const searchParams = request.nextUrl.searchParams; const category = searchParams.get("category"); const products = await db.product.findMany({ where: category ? { category } : undefined, take: 20, }); return NextResponse.json(products); } export async function POST(request: NextRequest) { const body = await request.json(); const product = await db.product.create({ data: body, }); return NextResponse.json(product, { status: 201 }); } // app/api/products/[id]/route.ts export async function GET( request: NextRequest, { params }: { params: Promise<{ id: string }> }, ) { const { id } = await params; const product = await db.product.findUnique({ where: { id } }); if (!product) { return NextResponse.json({ error: "Product not found" }, { status: 404 }); } return NextResponse.json(product); } ``` ### Pattern 8: Metadata and SEO ```typescript // app/products/[slug]/page.tsx import { Metadata } from 'next' import { notFound } from 'next/navigation' type Props = { params: Promise<{ slug: string }> } export async function generateMetadata({ params }: Props): Promise<Metadata> { const { slug } = await params const product = await getProduct(slug) if (!product) return {} return { title: product.name, description: product.description, openGraph: { title: product.name, description: product.description, images: [{ url: product.image, width: 1200, height: 630 }], }, twitter: { card: 'summary_large_image', title: product.name, description: product.description, images: [product.image], }, } } export async function generateStaticParams() { const products = await db.product.findMany({ select: { slug: true } }) return products.map((p) => ({ slug: p.slug })) } export default async function ProductPage({ params }: Props) { const { slug } = await params const product = await getProduct(slug) if (!product) notFound() return <ProductDetail product={product} /> } ``` ## Caching Strategies ### Data Cache ```typescript // No cache (always fresh) fetch(url, { cache: "no-store" }); // Cache forever (static) fetch(url, { cache: "force-cache" }); // ISR - revalidate after 60 seconds fetch(url, { next: { revalidate: 60 } }); // Tag-based invalidation fetch(url, { next: { tags: ["products"] } }); // Invalidate via Server Action ("use server"); import { revalidateTag, revalidatePath } from "next/cache"; export async function updateProduct(id: string, data: ProductData) { await db.product.update({ where: { id }, data }); revalidateTag("products"); revalidatePath("/products"); } ``` ## Best Practices ### Do's - **Start with Server Components** - Add 'use client' only when needed - **Colocate data fetching** - Fetch data where it's used - **Use Suspense boundaries** - Enable streaming for slow data - **Leverage parallel routes** - Independent loading states - **Use Server Actions** - For mutations with progressive enhancement ### Don'ts - **Don't pass serializable data** - Server → Client boundary limitations - **Don't use hooks in Server Components** - No useState, useEffect - **Don't fetch in Client Components** - Use Server Components or React Query - **Don't over-nest layouts** - Each layout adds to the component tree - **Don't ignore loading states** - Always provide loading.tsx or Suspense ## Resources - [Next.js App Router Documentation](https://nextjs.org/docs/app) - [Server Components RFC](https://github.com/reactjs/rfcs/blob/main/text/0188-server-components.md) - [Vercel Templates](https://vercel.com/templates/next.js)

# Architecture Patterns Master proven backend architecture patterns including Clean Architecture, Hexagonal Architecture, and Domain-Driven Design to build maintainable, testable, and scalable systems. ## When to Use This Skill - Designing new backend systems from scratch - Refactoring monolithic applications for better maintainability - Establishing architecture standards for your team - Migrating from tightly coupled to loosely coupled architectures - Implementing domain-driven design principles - Creating testable and mockable codebases - Planning microservices decomposition ## Core Concepts ### 1. Clean Architecture (Uncle Bob) **Layers (dependency flows inward):** - **Entities**: Core business models - **Use Cases**: Application business rules - **Interface Adapters**: Controllers, presenters, gateways - **Frameworks & Drivers**: UI, database, external services **Key Principles:** - Dependencies point inward - Inner layers know nothing about outer layers - Business logic independent of frameworks - Testable without UI, database, or external services ### 2. Hexagonal Architecture (Ports and Adapters) **Components:** - **Domain Core**: Business logic - **Ports**: Interfaces defining interactions - **Adapters**: Implementations of ports (database, REST, message queue) **Benefits:** - Swap implementations easily (mock for testing) - Technology-agnostic core - Clear separation of concerns ### 3. Domain-Driven Design (DDD) **Strategic Patterns:** - **Bounded Contexts**: Separate models for different domains - **Context Mapping**: How contexts relate - **Ubiquitous Language**: Shared terminology **Tactical Patterns:** - **Entities**: Objects with identity - **Value Objects**: Immutable objects defined by attributes - **Aggregates**: Consistency boundaries - **Repositories**: Data access abstraction - **Domain Events**: Things that happened ## Clean Architecture Pattern ### Directory Structure ``` app/ ├── domain/ # Entities & business rules │ ├── entities/ │ │ ├── user.py │ │ └── order.py │ ├── value_objects/ │ │ ├── email.py │ │ └── money.py │ └── interfaces/ # Abstract interfaces │ ├── user_repository.py │ └── payment_gateway.py ├── use_cases/ # Application business rules │ ├── create_user.py │ ├── process_order.py │ └── send_notification.py ├── adapters/ # Interface implementations │ ├── repositories/ │ │ ├── postgres_user_repository.py │ │ └── redis_cache_repository.py │ ├── controllers/ │ │ └── user_controller.py │ └── gateways/ │ ├── stripe_payment_gateway.py │ └── sendgrid_email_gateway.py └── infrastructure/ # Framework & external concerns ├── database.py ├── config.py └── logging.py ``` ### Implementation Example ```python # domain/entities/user.py from dataclasses import dataclass from datetime import datetime from typing import Optional @dataclass class User: """Core user entity - no framework dependencies.""" id: str email: str name: str created_at: datetime is_active: bool = True def deactivate(self): """Business rule: deactivating user.""" self.is_active = False def can_place_order(self) -> bool: """Business rule: active users can order.""" return self.is_active # domain/interfaces/user_repository.py from abc import ABC, abstractmethod from typing import Optional, List from domain.entities.user import User class IUserRepository(ABC): """Port: defines contract, no implementation.""" @abstractmethod async def find_by_id(self, user_id: str) -> Optional[User]: pass @abstractmethod async def find_by_email(self, email: str) -> Optional[User]: pass @abstractmethod async def save(self, user: User) -> User: pass @abstractmethod async def delete(self, user_id: str) -> bool: pass # use_cases/create_user.py from domain.entities.user import User from domain.interfaces.user_repository import IUserRepository from dataclasses import dataclass from datetime import datetime import uuid @dataclass class CreateUserRequest: email: str name: str @dataclass class CreateUserResponse: user: User success: bool error: Optional[str] = None class CreateUserUseCase: """Use case: orchestrates business logic.""" def __init__(self, user_repository: IUserRepository): self.user_repository = user_repository async def execute(self, request: CreateUserRequest) -> CreateUserResponse: # Business validation existing = await self.user_repository.find_by_email(request.email) if existing: return CreateUserResponse( user=None, success=False, error="Email already exists" ) # Create entity user = User( id=str(uuid.uuid4()), email=request.email, name=request.name, created_at=datetime.now(), is_active=True ) # Persist saved_user = await self.user_repository.save(user) return CreateUserResponse( user=saved_user, success=True ) # adapters/repositories/postgres_user_repository.py from domain.interfaces.user_repository import IUserRepository from domain.entities.user import User from typing import Optional import asyncpg class PostgresUserRepository(IUserRepository): """Adapter: PostgreSQL implementation.""" def __init__(self, pool: asyncpg.Pool): self.pool = pool async def find_by_id(self, user_id: str) -> Optional[User]: async with self.pool.acquire() as conn: row = await conn.fetchrow( "SELECT * FROM users WHERE id = $1", user_id ) return self._to_entity(row) if row else None async def find_by_email(self, email: str) -> Optional[User]: async with self.pool.acquire() as conn: row = await conn.fetchrow( "SELECT * FROM users WHERE email = $1", email ) return self._to_entity(row) if row else None async def save(self, user: User) -> User: async with self.pool.acquire() as conn: await conn.execute( """ INSERT INTO users (id, email, name, created_at, is_active) VALUES ($1, $2, $3, $4, $5) ON CONFLICT (id) DO UPDATE SET email = $2, name = $3, is_active = $5 """, user.id, user.email, user.name, user.created_at, user.is_active ) return user async def delete(self, user_id: str) -> bool: async with self.pool.acquire() as conn: result = await conn.execute( "DELETE FROM users WHERE id = $1", user_id ) return result == "DELETE 1" def _to_entity(self, row) -> User: """Map database row to entity.""" return User( id=row["id"], email=row["email"], name=row["name"], created_at=row["created_at"], is_active=row["is_active"] ) # adapters/controllers/user_controller.py from fastapi import APIRouter, Depends, HTTPException from use_cases.create_user import CreateUserUseCase, CreateUserRequest from pydantic import BaseModel router = APIRouter() class CreateUserDTO(BaseModel): email: str name: str @router.post("/users") async def create_user( dto: CreateUserDTO, use_case: CreateUserUseCase = Depends(get_create_user_use_case) ): """Controller: handles HTTP concerns only.""" request = CreateUserRequest(email=dto.email, name=dto.name) response = await use_case.execute(request) if not response.success: raise HTTPException(status_code=400, detail=response.error) return {"user": response.user} ``` ## Hexagonal Architecture Pattern ```python # Core domain (hexagon center) class OrderService: """Domain service - no infrastructure dependencies.""" def __init__( self, order_repository: OrderRepositoryPort, payment_gateway: PaymentGatewayPort, notification_service: NotificationPort ): self.orders = order_repository self.payments = payment_gateway self.notifications = notification_service async def place_order(self, order: Order) -> OrderResult: # Business logic if not order.is_valid(): return OrderResult(success=False, error="Invalid order") # Use ports (interfaces) payment = await self.payments.charge( amount=order.total, customer=order.customer_id ) if not payment.success: return OrderResult(success=False, error="Payment failed") order.mark_as_paid() saved_order = await self.orders.save(order) await self.notifications.send( to=order.customer_email, subject="Order confirmed", body=f"Order {order.id} confirmed" ) return OrderResult(success=True, order=saved_order) # Ports (interfaces) class OrderRepositoryPort(ABC): @abstractmethod async def save(self, order: Order) -> Order: pass class PaymentGatewayPort(ABC): @abstractmethod async def charge(self, amount: Money, customer: str) -> PaymentResult: pass class NotificationPort(ABC): @abstractmethod async def send(self, to: str, subject: str, body: str): pass # Adapters (implementations) class StripePaymentAdapter(PaymentGatewayPort): """Primary adapter: connects to Stripe API.""" def __init__(self, api_key: str): self.stripe = stripe self.stripe.api_key = api_key async def charge(self, amount: Money, customer: str) -> PaymentResult: try: charge = self.stripe.Charge.create( amount=amount.cents, currency=amount.currency, customer=customer ) return PaymentResult(success=True, transaction_id=charge.id) except stripe.error.CardError as e: return PaymentResult(success=False, error=str(e)) class MockPaymentAdapter(PaymentGatewayPort): """Test adapter: no external dependencies.""" async def charge(self, amount: Money, customer: str) -> PaymentResult: return PaymentResult(success=True, transaction_id="mock-123") ``` ## Domain-Driven Design Pattern ```python # Value Objects (immutable) from dataclasses import dataclass from typing import Optional @dataclass(frozen=True) class Email: """Value object: validated email.""" value: str def __post_init__(self): if "@" not in self.value: raise ValueError("Invalid email") @dataclass(frozen=True) class Money: """Value object: amount with currency.""" amount: int # cents currency: str def add(self, other: "Money") -> "Money": if self.currency != other.currency: raise ValueError("Currency mismatch") return Money(self.amount + other.amount, self.currency) # Entities (with identity) class Order: """Entity: has identity, mutable state.""" def __init__(self, id: str, customer: Customer): self.id = id self.customer = customer self.items: List[OrderItem] = [] self.status = OrderStatus.PENDING self._events: List[DomainEvent] = [] def add_item(self, product: Product, quantity: int): """Business logic in entity.""" item = OrderItem(product, quantity) self.items.append(item) self._events.append(ItemAddedEvent(self.id, item)) def total(self) -> Money: """Calculated property.""" return sum(item.subtotal() for item in self.items) def submit(self): """State transition with business rules.""" if not self.items: raise ValueError("Cannot submit empty order") if self.status != OrderStatus.PENDING: raise ValueError("Order already submitted") self.status = OrderStatus.SUBMITTED self._events.append(OrderSubmittedEvent(self.id)) # Aggregates (consistency boundary) class Customer: """Aggregate root: controls access to entities.""" def __init__(self, id: str, email: Email): self.id = id self.email = email self._addresses: List[Address] = [] self._orders: List[str] = [] # Order IDs, not full objects def add_address(self, address: Address): """Aggregate enforces invariants.""" if len(self._addresses) >= 5: raise ValueError("Maximum 5 addresses allowed") self._addresses.append(address) @property def primary_address(self) -> Optional[Address]: return next((a for a in self._addresses if a.is_primary), None) # Domain Events @dataclass class OrderSubmittedEvent: order_id: str occurred_at: datetime = field(default_factory=datetime.now) # Repository (aggregate persistence) class OrderRepository: """Repository: persist/retrieve aggregates.""" async def find_by_id(self, order_id: str) -> Optional[Order]: """Reconstitute aggregate from storage.""" pass async def save(self, order: Order): """Persist aggregate and publish events.""" await self._persist(order) await self._publish_events(order._events) order._events.clear() ``` ## Resources - **references/clean-architecture-guide.md**: Detailed layer breakdown - **references/hexagonal-architecture-guide.md**: Ports and adapters patterns - **references/ddd-tactical-patterns.md**: Entities, value objects, aggregates - **assets/clean-architecture-template/**: Complete project structure - **assets/ddd-examples/**: Domain modeling examples ## Best Practices 1. **Dependency Rule**: Dependencies always point inward 2. **Interface Segregation**: Small, focused interfaces 3. **Business Logic in Domain**: Keep frameworks out of core 4. **Test Independence**: Core testable without infrastructure 5. **Bounded Contexts**: Clear domain boundaries 6. **Ubiquitous Language**: Consistent terminology 7. **Thin Controllers**: Delegate to use cases 8. **Rich Domain Models**: Behavior with data ## Common Pitfalls - **Anemic Domain**: Entities with only data, no behavior - **Framework Coupling**: Business logic depends on frameworks - **Fat Controllers**: Business logic in controllers - **Repository Leakage**: Exposing ORM objects - **Missing Abstractions**: Concrete dependencies in core - **Over-Engineering**: Clean architecture for simple CRUD