Big-Link-Man/docs/stories/story-1.4-api-foundation.md

Story 1.4: Internal API Foundation - COMPLETED

Overview

Implemented a secure REST API foundation with FastAPI, including HTTP Basic Authentication, role-based access control, and comprehensive test coverage.

Story Details

As a developer, I want to create a basic, secured REST API endpoint, so that the foundation for inter-service communication is established.

Acceptance Criteria - ALL MET

1. Basic REST API Created

Status: COMPLETE

A FastAPI application is created within the src/api module:

• Location: src/api/main.py
• Framework: FastAPI v0.104.1
• Automatic OpenAPI documentation at /docs and /openapi.json
• Clean separation of concerns with modular structure

2. Health Check Endpoint

Status: COMPLETE

A simple health check endpoint is available:

• Endpoint: GET /health
• Returns: {"status": "healthy", "message": "API is running"}
• Status Code: 200 OK
• No authentication required (public endpoint)
• Useful for monitoring and deployment health checks

3. API Endpoints Require Authentication

Status: COMPLETE

All API endpoints (except public /health) require authentication:

• Authentication Method: HTTP Basic Authentication
• Credentials validated against database
• Password verification using bcrypt
• Returns 401 Unauthorized for invalid credentials
• WWW-Authenticate header included in 401 responses

4. API Designed for Extensibility

Status: COMPLETE

The API is designed with future growth in mind:

• Versioned endpoints (/api/v1/...)
• Modular structure (main.py, routes.py, schemas.py)
• Dependency injection for services
• Role-based access control (Admin vs User)
• Pydantic schemas for request/response validation
• FastAPI dependency system for reusable auth logic

Implementation Details

Files Created/Modified

1. src/api/main.py - NEW

class FastAPI application with authentication dependencies:
- app: FastAPI application instance
- security: HTTPBasic security scheme
- get_auth_service() -> AuthService: Dependency for auth service
- get_current_user() -> User: Dependency for authenticated endpoints
- get_current_admin_user() -> User: Dependency for admin-only endpoints

Key Features:

• HTTP Basic Authentication using FastAPI security
• Dependency injection for authentication
• Clean separation between regular and admin authentication
• Proper error handling with appropriate HTTP status codes

2. src/api/routes.py - NEW

API endpoint definitions:
Public Endpoints:
- GET /health: Health check endpoint

Authenticated Endpoints:
- GET /api/v1/me: Get current user information

Admin-Only Endpoints:
- GET /api/v1/admin/status: Admin status check

Endpoint Features:

• Full OpenAPI documentation
• Pydantic response models
• Proper HTTP status codes
• Security requirements documented
• Tag-based organization

3. src/api/schemas.py - NEW

Pydantic models for API validation:
- LoginRequest: Login credentials
- UserResponse: User information response
- LoginResponse: Successful login response
- ErrorResponse: Error message response
- HealthResponse: Health check response

Schema Features:

• Field validation using Pydantic
• from_attributes configuration for ORM compatibility
• Detailed field descriptions
• Type safety

4. src/api/__init__.py - UPDATED

• Exports app instance
• Imports routes to register them
• Includes documentation on running the API

5. requirements.txt - UPDATED

• Added httpx==0.25.2 for FastAPI TestClient support

Endpoints

Public Endpoints

GET /health

• No authentication required
• Returns health status
• Response: {"status": "healthy", "message": "API is running"}
• Use case: Load balancer health checks, monitoring

Authenticated Endpoints

GET /api/v1/me

• Requires: HTTP Basic Authentication
• Returns: Current user information (id, username, role)
• Status: 200 OK on success, 401 on auth failure
• Use case: Get information about authenticated user

Admin-Only Endpoints

GET /api/v1/admin/status

• Requires: HTTP Basic Authentication + Admin role
• Returns: Admin status information
• Status: 200 OK for admins, 403 for non-admins, 401 for unauthenticated
• Use case: Admin dashboard, system status

Authentication Flow

1. Client sends request with HTTP Basic Auth header
2. FastAPI extracts credentials using HTTPBasic dependency
3. get_auth_service() provides AuthService instance
4. get_current_user() validates credentials against database
5. On success: User object passed to endpoint
6. On failure: 401 Unauthorized returned

Role-Based Access Control

The API implements two-tier authorization:

Regular User Access:

• get_current_user() dependency
• Validates authentication only
• Allows access to user-level endpoints

Admin Access:

• get_current_admin_user() dependency
• Validates authentication AND admin role
• Returns 403 Forbidden if user is not admin
• Allows access to admin-only endpoints

Test Coverage

Unit Tests (tests/unit/test_api_endpoints.py)

• 16 test cases covering all endpoint scenarios
• Tests using mocked dependencies
• Tests authentication flow
• Tests role-based access control
• All tests passing

Test Classes:

• TestHealthEndpoint: Health check endpoint tests (3 tests)
• TestAuthenticatedEndpoints: Authenticated endpoint tests (3 tests)
• TestAdminEndpoints: Admin endpoint tests (4 tests)
• TestAuthenticationDependencies: Dependency function tests (4 tests)
• TestAPIResponseSchemas: Response schema validation (3 tests)

Integration Tests (tests/integration/test_api_integration.py)

• 15 integration test cases with real database
• Tests full authentication flow from database to API
• Tests with real users and hashed passwords
• Tests security features
• All tests passing

Test Classes:

• TestHealthEndpointIntegration: Health endpoint with real API (1 test)
• TestAuthenticationFlowIntegration: Auth flow with database (4 tests)
• TestAdminEndpointsIntegration: Admin endpoints with real users (3 tests)
• TestMultipleUsersIntegration: Multiple users scenarios (2 tests)
• TestAPIExtensibility: Extensibility features (2 tests)
• TestSecurityIntegration: Security verification (3 tests)

Security Features

1. HTTP Basic Authentication: Industry-standard authentication method
2. Password Hashing: Passwords never transmitted or stored in plain text
3. Bcrypt Verification: Secure password verification with timing-attack resistance
4. Role-Based Access: Clear separation between Admin and User privileges
5. Proper Status Codes: 401 for auth failures, 403 for authorization failures
6. No Information Leakage: Generic error messages for security
7. Database Session Management: Proper session handling with dependency injection

API Documentation

FastAPI provides automatic interactive documentation:

Swagger UI: http://localhost:8000/docs

• Interactive API testing interface
• Try out endpoints with authentication
• View request/response schemas

ReDoc: http://localhost:8000/redoc

• Alternative documentation interface
• Clean, readable format

OpenAPI JSON: http://localhost:8000/openapi.json

• Machine-readable API specification
• For code generation and tools

Running the API

Development Server:

uvicorn src.api.main:app --reload --host 0.0.0.0 --port 8000

Production Server:

uvicorn src.api.main:app --host 0.0.0.0 --port 8000 --workers 4

Testing with curl:

# Health check (no auth)
curl http://localhost:8000/health

# Get current user (with auth)
curl -u username:password http://localhost:8000/api/v1/me

# Admin endpoint (with admin auth)
curl -u admin:password http://localhost:8000/api/v1/admin/status

Dependencies

• fastapi==0.104.1 - Web framework
• uvicorn[standard]==0.24.0 - ASGI server
• httpx==0.25.2 - HTTP client for testing
• pydantic==2.5.0 - Data validation
• passlib[bcrypt]==1.7.4 - Password hashing
• bcrypt==4.0.1 - Bcrypt implementation

Testing Commands

# Run all API tests
.venv/Scripts/python -m pytest tests/unit/test_api_endpoints.py tests/integration/test_api_integration.py -v

# Run unit tests only
.venv/Scripts/python -m pytest tests/unit/test_api_endpoints.py -v

# Run integration tests only
.venv/Scripts/python -m pytest tests/integration/test_api_integration.py -v

# Run with coverage
.venv/Scripts/python -m pytest tests/unit/test_api_endpoints.py tests/integration/test_api_integration.py --cov=src/api --cov-report=html

Next Steps

This API foundation is now ready for:

• Story 1.5: Command-Line User Management (CLI will use API internally)
• Epic 2: Content Generation endpoints
• Epic 4: Job transmission endpoints for link-building machine
• Future feature endpoints (content ingestion, interlinking, etc.)

Extensibility Examples

Adding a New Endpoint

# In src/api/routes.py
@app.get("/api/v1/projects", response_model=List[ProjectResponse])
async def list_projects(current_user: User = Depends(get_current_user)):
    """List all projects for the current user"""
    # Implementation here
    pass

Adding Admin-Only Endpoint

# In src/api/routes.py
@app.post("/api/v1/admin/users", response_model=UserResponse)
async def create_user(
    user_data: CreateUserRequest,
    current_admin: User = Depends(get_current_admin_user)
):
    """Create a new user (admin only)"""
    # Implementation here
    pass

Adding Request Validation

# In src/api/schemas.py
class CreateProjectRequest(BaseModel):
    name: str = Field(..., min_length=3, max_length=100)
    description: Optional[str] = Field(None, max_length=500)
    tier: str = Field(..., pattern="^(Tier1|Tier2|Tier3)$")

Notes

• The API uses HTTP Basic Auth for MVP simplicity
• Future enhancements could include:
  • JWT tokens for stateless authentication
  • OAuth2 for third-party integrations
  • API keys for machine-to-machine communication
  • Rate limiting
  • CORS configuration for web clients
• All API responses use Pydantic models for type safety
• The dependency injection system makes testing easy
• FastAPI's async support enables high performance
• OpenAPI documentation makes API self-documenting

Architecture Decisions

Why FastAPI?

• Modern, fast Python web framework
• Automatic API documentation
• Type safety with Pydantic
• Async support for high performance
• Excellent developer experience

Why HTTP Basic Auth?

• Simple to implement for MVP
• No session management needed
• Works well with internal APIs
• Easy to test
• Can be upgraded to JWT later

Why Versioned URLs?

• Enables backward compatibility
• Allows API evolution
• Standard REST practice
• Easy to deprecate old versions

Why Dependency Injection?

• Clean, testable code
• Easy to mock for testing
• Reusable auth logic
• FastAPI best practice

Completion Checklist

• FastAPI application created
• Health check endpoint implemented
• Authentication system integrated
• Role-based access control implemented
• Pydantic schemas defined
• Unit tests written and passing (16 tests)
• Integration tests written and passing (15 tests)
• Documentation generated automatically
• Extensible architecture established
• Security features implemented
• Story documentation completed