/codebase-documenter

Architecture Overview

What This Document Covers

This document explains the high-level architecture of [Project Name], including how different components interact, key design decisions, and where to make common changes.

Target audience: Developers who need to understand the system design before making significant changes.

System Design

High-Level Architecture

[Create a simple ASCII diagram or describe components]

┌─────────────┐      ┌─────────────┐      ┌─────────────┐
│   Frontend  │─────▶│   Backend   │─────▶│  Database   │
│  (React)    │◀─────│   (Node.js) │◀─────│ (Postgres)  │
└─────────────┘      └─────────────┘      └─────────────┘
       │                    │
       │                    ▼
       │             ┌─────────────┐
       └────────────▶│  API Layer  │
                     └─────────────┘

Components:

1. Frontend - [Explain what this component does and its responsibilities]
2. Backend - [Explain what this component does and its responsibilities]
3. Database - [Explain what data is stored and how it's organized]
4. API Layer - [Explain how components communicate]

Technology Stack

Directory Structure

project-root/
├── src/
│   ├── components/          # Reusable UI components
│   │   ├── common/         # Shared components (buttons, inputs, etc.)
│   │   ├── features/       # Feature-specific components
│   │   └── layout/         # Layout components (header, footer, etc.)
│   │
│   ├── pages/              # Page-level components (one per route)
│   │   ├── Home/          # Home page and related components
│   │   ├── Dashboard/     # Dashboard page and related components
│   │   └── Settings/      # Settings page and related components
│   │
│   ├── services/           # Business logic and external integrations
│   │   ├── api.js         # API client configuration
│   │   ├── auth.js        # Authentication logic
│   │   └── [feature].js   # Feature-specific business logic
│   │
│   ├── store/              # State management (Redux/Context/etc.)
│   │   ├── slices/        # State slices by feature
│   │   └── store.js       # Store configuration
│   │
│   ├── utils/              # Helper functions and utilities
│   │   ├── validation.js  # Input validation helpers
│   │   ├── formatting.js  # Data formatting utilities
│   │   └── constants.js   # App-wide constants
│   │
│   ├── hooks/              # Custom React hooks
│   │   └── use[Feature].js # Feature-specific hooks
│   │
│   ├── types/              # TypeScript type definitions
│   │   ├── models.ts      # Data model types
│   │   └── api.ts         # API request/response types
│   │
│   └── index.js            # Application entry point
│
├── tests/                  # Test files (mirrors src/ structure)
├── public/                 # Static assets
├── config/                 # Configuration files
└── [build-output]/         # Build artifacts (gitignored)

Directory Purpose and Rules

components/

Purpose: Reusable UI components that don't contain business logic.

What goes here:

• Presentational components (buttons, cards, modals)
• Layout components (headers, sidebars, containers)
• Feature-specific components used in multiple places

What doesn't go here:

• Business logic (put in services/)
• Page-level components (put in pages/)
• One-off components used in a single place (colocate with parent)

When to add a file: When you need a reusable component used in 2+ places.

services/

Purpose: Business logic, API calls, and external service integrations.

What goes here:

• API client functions
• Authentication and authorization logic
• Data transformation and validation
• Third-party service integrations

What doesn't go here:

• UI components (put in components/)
• State management (put in store/)
• Pure utility functions (put in utils/)

When to add a file: When you need to interact with external services or implement complex business logic.

utils/

Purpose: Pure utility functions with no side effects.

What goes here:

• Data formatting and parsing
• Validation helpers
• Constants and enumerations
• Date/time utilities

What doesn't go here:

• Functions that make API calls (put in services/)
• Functions that depend on React (make a custom hook in hooks/)
• Functions specific to one component (colocate with component)

When to add a file: When you have a pure function used in 3+ places.

Data Flow

[Feature Name] Flow

Explain how data flows through the system for a key feature:

User Action → Component → Service → API → Database
                ↓
            State Update
                ↓
            UI Re-render

Step-by-step:

1. User triggers action in components/FeatureComponent.tsx

   • User clicks button, submits form, etc.
   • Component calls handleAction() function

2. Component dispatches action to state management

   • Calls dispatch(featureAction(data))
   • State is updated optimistically

3. Service layer processes request in services/feature.js

   • Validates input data
   • Transforms data to API format
   • Makes HTTP request to backend

4. Backend processes request in api/feature/route.js

   • Validates authentication
   • Applies business logic
   • Updates database

5. Response flows back through the layers

   • Backend returns success/error
   • Service layer transforms response
   • State is updated with final result
   • Component re-renders with new data

State Management

Architecture: [Describe state management approach - Redux, Context API, Zustand, etc.]

State organization:

Global State
├── auth          # User authentication state
├── user          # User profile data
├── [feature1]    # Feature-specific state
├── [feature2]    # Feature-specific state
└── ui            # UI state (modals, loading, etc.)

Data flow rules:

• Components read state via [hooks/selectors]
• Components update state via [dispatch/setState functions]
• Async operations handled in [middleware/thunks/services]

Key Design Decisions

Decision 1: [Architecture Choice]

What we decided: [Describe the decision made]

Context: [Explain the situation that required this decision]

• [Constraint or requirement 1]
• [Constraint or requirement 2]

Why we decided this:

• Reason 1: [Explain benefit]
• Reason 2: [Explain benefit]
• Reason 3: [Explain benefit]

Trade-offs:

• ✅ Pros: [What we gained]
• ❌ Cons: [What we sacrificed]
• 🤔 When to reconsider: [Conditions that might make this decision obsolete]

Alternatives considered:

• [Alternative 1]: Rejected because [reason]
• [Alternative 2]: Rejected because [reason]

Decision 2: [Technology Choice]

What we decided: [Describe the decision made]

Context: [Explain the situation that required this decision]

Why we decided this:

• [Reason 1]
• [Reason 2]

Trade-offs:

• ✅ Pros: [What we gained]
• ❌ Cons: [What we sacrificed]

Alternatives considered:

• [Alternative 1]: Rejected because [reason]
• [Alternative 2]: Rejected because [reason]

Module Dependencies

Dependency Graph

pages/
  └─→ components/
        └─→ hooks/
              └─→ services/
                    └─→ utils/

store/
  └─→ services/
        └─→ utils/

Dependency rules:

1. Lower layers can't depend on higher layers

   • ❌ services/ can't import from components/
   • ✅ components/ can import from services/

2. Same-level imports require careful consideration

   • 🤔 Components importing other components: Usually OK
   • ⚠️ Services importing other services: Consider refactoring

3. Avoid circular dependencies

   • Use dependency injection or event systems when needed

External Dependencies

Extension Points

Adding a New Feature

To add a new feature to the codebase:

1. Create feature structure:

   src/
   ├── components/features/[FeatureName]/
   ├── services/[featureName].js
   └── store/slices/[featureName]Slice.js

2. Implement components:

   • Create UI components in components/features/[FeatureName]/
   • Follow existing component patterns
   • Use shared components from components/common/

3. Add business logic:

   • Create service file in services/[featureName].js
   • Implement API calls and data transformations
   • Follow existing error handling patterns

4. Set up state management:

   • Create slice in store/slices/[featureName]Slice.js
   • Define actions and reducers
   • Export selectors for components

5. Add routes (if applicable):

   • Register new routes in routes.js
   • Create page component in pages/[FeatureName]/

6. Add tests:

   • Mirror structure in tests/
   • Test components, services, and state

Common Modification Points

Adding a new API endpoint:

• Backend: Create route in api/[feature]/route.js
• Frontend: Add service function in services/[feature].js
• Update types in types/api.ts

Adding a new database table:

• Create migration in migrations/
• Add model in models/[tableName].js
• Update seed data if applicable

Adding a new component library:

• Install package: npm install [package]
• Create wrapper in components/common/[ComponentName]/
• Configure theme/styling in config/theme.js

Performance Considerations

Critical Performance Paths

1. [Path 1: e.g., Initial page load]

   • Current performance: [metrics]
   • Bottlenecks: [known issues]
   • Optimization strategy: [approach]

2. [Path 2: e.g., Search functionality]

   • Current performance: [metrics]
   • Bottlenecks: [known issues]
   • Optimization strategy: [approach]

Caching Strategy

What we cache:

• [Data type 1]: Cached in [location] for [duration]
• [Data type 2]: Cached in [location] for [duration]

Cache invalidation:

• [Trigger 1]: Clears [cache type]
• [Trigger 2]: Clears [cache type]

Security Architecture

Authentication Flow

[Describe how users authenticate]

1. User submits credentials
2. Backend validates and issues [JWT/session/etc.]
3. Token stored in [location]
4. Subsequent requests include token

Authorization

Permission levels:

• [Role 1]: Can [actions]
• [Role 2]: Can [actions]
• [Role 3]: Can [actions]

Implementation:

• Frontend: Check permissions in [location]
• Backend: Enforce permissions in [location]

Data Security

• Sensitive data encrypted at rest: [Yes/No - how]
• API communications: [HTTPS/TLS version]
• Input validation: [Where and how]
• XSS protection: [Strategy]
• CSRF protection: [Strategy]

Deployment Architecture

Environments

Build Process

# Development build
[build-command-dev]

# Production build
[build-command-prod]

Build artifacts:

• Output location: [path]
• Artifacts: [list of generated files]

Deployment Steps

1. [Step 1]
2. [Step 2]
3. [Step 3]

Monitoring and Observability

Logging

Log levels:

• ERROR: [What gets logged]
• WARN: [What gets logged]
• INFO: [What gets logged]

Log destinations:

• Development: [Console/file]
• Production: [Service name/location]

Metrics

Key metrics tracked:

• [Metric 1]: [What it measures]
• [Metric 2]: [What it measures]

Monitoring tools:

• [Tool name]: [What we monitor with it]

Troubleshooting

Common Architecture Issues

Issue: [Common problem]

• Symptoms: [How to recognize it]
• Cause: [Why it happens]
• Solution: [How to fix it]

Additional Resources

• [Link to API documentation]
• [Link to database schema]
• [Link to deployment guide]
• [Link to contributing guidelines]

Questions and Feedback

If you have questions about the architecture or suggestions for improvements:

• [Contact method]
• [Issue tracker link]