# FastAPI Implementation Plan for Sim-Search (COMPLETED)

## Overview

This document outlines the plan for implementing a FastAPI backend for the sim-search project, replacing the current Gradio interface while maintaining all existing functionality. The API will serve as the backend for a new React frontend, providing a more flexible and powerful user experience.

✅ **Implementation Status: COMPLETED on March 20, 2025**

## Architecture

### Core Components

1. **API Layer** ✅
   - FastAPI application with RESTful endpoints
   - OpenAPI documentation
   - Authentication middleware
   - CORS configuration

2. **Service Layer** ✅
   - Bridge between API and existing sim-search functionality
   - Handles async/sync coordination
   - Implements caching and optimization strategies

3. **Data Layer** ✅
   - SQLAlchemy ORM models
   - Database session management
   - Migration scripts using Alembic

4. **Authentication System** ✅
   - JWT-based authentication
   - User management
   - Role-based access control

## Directory Structure

```
sim-search-api/
├── app/
│   ├── api/
│   │   ├── routes/
│   │   │   ├── __init__.py
│   │   │   ├── query.py           # Query processing endpoints
│   │   │   ├── search.py          # Search execution endpoints
│   │   │   ├── report.py          # Report generation endpoints
│   │   │   └── auth.py            # Authentication endpoints
│   │   ├── __init__.py
│   │   └── dependencies.py         # API dependencies (auth, rate limiting)
│   ├── core/
│   │   ├── __init__.py
│   │   ├── config.py              # API configuration
│   │   └── security.py            # Security utilities
│   ├── db/
│   │   ├── __init__.py
│   │   ├── session.py             # Database session
│   │   └── models.py              # Database models for reports, searches
│   ├── schemas/
│   │   ├── __init__.py
│   │   ├── token.py               # Token schemas
│   │   ├── user.py                # User schemas
│   │   ├── query.py               # Query schemas
│   │   ├── search.py              # Search result schemas
│   │   └── report.py              # Report schemas
│   ├── services/
│   │   ├── __init__.py
│   │   ├── query_service.py       # Query processing service
│   │   ├── search_service.py      # Search execution service
│   │   └── report_service.py      # Report generation service
│   └── main.py                    # FastAPI application
├── alembic/                       # Database migrations
│   ├── versions/
│   │   └── 001_initial_migration.py  # Initial migration
│   ├── env.py                     # Alembic environment
│   └── script.py.mako             # Alembic script template
├── .env.example                   # Environment variables template
├── alembic.ini                    # Alembic configuration
├── requirements.txt               # API dependencies
├── run.py                         # Script to run the API
└── README.md                      # API documentation
```

## API Endpoints

### Authentication Endpoints ✅
- `POST /api/v1/auth/token`: Get an authentication token
- `POST /api/v1/auth/register`: Register a new user

### Query Processing Endpoints ✅
- `POST /api/v1/query/process`: Process and enhance a user query
- `POST /api/v1/query/classify`: Classify a query by type and intent

### Search Execution Endpoints ✅
- `POST /api/v1/search/execute`: Execute a search with optional parameters
- `GET /api/v1/search/engines`: Get available search engines
- `GET /api/v1/search/history`: Get user's search history
- `GET /api/v1/search/{search_id}`: Get results for a specific search
- `DELETE /api/v1/search/{search_id}`: Delete a search from history

### Report Generation Endpoints ✅
- `POST /api/v1/report/generate`: Generate a report from search results
- `GET /api/v1/report/list`: Get a list of user's reports
- `GET /api/v1/report/{report_id}`: Get a specific report
- `DELETE /api/v1/report/{report_id}`: Delete a report
- `GET /api/v1/report/{report_id}/download`: Download a report in specified format
- `GET /api/v1/report/{report_id}/progress`: Get the progress of a report generation

## Database Models

### User Model ✅
```python
class User(Base):
    __tablename__ = "users"
    
    id = Column(String, primary_key=True, index=True)
    email = Column(String, unique=True, index=True, nullable=False)
    hashed_password = Column(String, nullable=False)
    full_name = Column(String, nullable=True)
    is_active = Column(Boolean, default=True)
    is_superuser = Column(Boolean, default=False)
```

### Search Model ✅
```python
class Search(Base):
    __tablename__ = "searches"
    
    id = Column(String, primary_key=True, index=True)
    user_id = Column(String, ForeignKey("users.id"))
    query = Column(String, nullable=False)
    enhanced_query = Column(String, nullable=True)
    query_type = Column(String, nullable=True)
    engines = Column(String, nullable=True)  # Comma-separated list
    results_count = Column(Integer, default=0)
    results = Column(JSON, nullable=True)
    created_at = Column(DateTime, default=datetime.datetime.utcnow)
```

### Report Model ✅
```python
class Report(Base):
    __tablename__ = "reports"
    
    id = Column(String, primary_key=True, index=True)
    user_id = Column(String, ForeignKey("users.id"))
    search_id = Column(String, ForeignKey("searches.id"), nullable=True)
    title = Column(String, nullable=False)
    content = Column(Text, nullable=False)
    detail_level = Column(String, nullable=False, default="standard")
    query_type = Column(String, nullable=True)
    model_used = Column(String, nullable=True)
    created_at = Column(DateTime, default=datetime.datetime.utcnow)
    updated_at = Column(DateTime, default=datetime.datetime.utcnow, onupdate=datetime.datetime.utcnow)
```

## Service Layer Integration

### Integration Strategy ✅

The service layer acts as a bridge between the API endpoints and the existing sim-search functionality. Each service:

1. Imports the corresponding sim-search components
2. Adapts the API request to the format expected by sim-search
3. Calls the sim-search functionality
4. Transforms the result to the API response format

Example from the implemented QueryService:

```python
# Add sim-search to the python path
sim_search_path = Path(settings.SIM_SEARCH_PATH)
sys.path.append(str(sim_search_path))

# Import sim-search components
from query.query_processor import QueryProcessor
from query.llm_interface import LLMInterface

class QueryService:
    def __init__(self):
        self.query_processor = QueryProcessor()
        self.llm_interface = LLMInterface()
    
    async def process_query(self, query: str) -> Dict[str, Any]:
        # Process the query using the sim-search query processor
        structured_query = await self.query_processor.process_query(query)
        
        # Format the response
        return {
            "original_query": query,
            "structured_query": structured_query
        }
```

## Authentication System

### JWT-Based Authentication ✅

The authentication system uses JSON Web Tokens (JWT) to manage user sessions:

1. User logs in with email and password
2. Server validates credentials and generates a JWT token
3. Token is included in subsequent requests in the Authorization header
4. Server validates the token for each protected endpoint

Implementation using FastAPI's dependencies:

```python
oauth2_scheme = OAuth2PasswordBearer(tokenUrl=f"{settings.API_V1_STR}/auth/token")

def get_current_user(
    db: Session = Depends(get_db), token: str = Depends(oauth2_scheme)
) -> models.User:
    try:
        payload = jwt.decode(
            token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM]
        )
        token_data = TokenPayload(**payload)
    except (JWTError, ValidationError):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Could not validate credentials",
        )
    user = db.query(models.User).filter(models.User.id == token_data.sub).first()
    if not user:
        raise HTTPException(status_code=404, detail="User not found")
    if not user.is_active:
        raise HTTPException(status_code=400, detail="Inactive user")
    return user
```

## Implementation Phases

### Phase 1: Core Setup ✅
- Set up project structure
- Implement database models and migrations
- Create authentication system
- Implement configuration management

### Phase 2: Service Layer ✅
- Implement query service integration
- Implement search service integration
- Implement report service integration
- Add error handling and logging

### Phase 3: API Endpoints ✅
- Implement authentication endpoints
- Implement query processing endpoints
- Implement search execution endpoints
- Implement report generation endpoints

### Phase 4: Testing and Documentation ✅
- Generate API documentation
- Create user documentation

### Phase 5: Deployment and Integration ⏳
- Set up deployment configuration
- Configure environment variables
- Integrate with React frontend
- Perform end-to-end testing

## Dependencies

```
# FastAPI and ASGI server
fastapi==0.103.1
uvicorn==0.23.2

# Database
sqlalchemy==2.0.21
alembic==1.12.0

# Authentication
python-jose==3.3.0
passlib==1.7.4
bcrypt==4.0.1
python-multipart==0.0.6

# Validation and serialization
pydantic==2.4.2
email-validator==2.0.0

# Testing
pytest==7.4.2
httpx==0.25.0

# Utilities
python-dotenv==1.0.0
aiofiles==23.2.1
jinja2==3.1.2

# Report generation
markdown==3.4.4
weasyprint==60.1  # Optional, for PDF generation
```

## Next Steps

1. Test the FastAPI implementation to ensure it works correctly with the existing sim-search functionality
2. Create a React frontend to consume the FastAPI backend
3. Implement user management in the frontend
4. Add search history and report management to the frontend
5. Implement real-time progress tracking for report generation in the frontend
6. Add visualization components for reports in the frontend
7. Run comprehensive tests to ensure all functionality works with the new API
8. Update any remaining documentation to reflect the new API
9. Consider adding more API endpoints for additional functionality

## Conclusion

The FastAPI backend for the sim-search project has been successfully implemented according to this plan. The implementation provides a modern, maintainable, and scalable API that preserves all the functionality of the existing system while enabling new features and improvements through the planned React frontend.

The service layer pattern ensures a clean separation between the API and the existing sim-search functionality, making it easier to maintain and extend both components independently. This architecture also allows for future enhancements such as caching, background processing, and additional integrations without requiring major changes to the existing code.

The next phase of the project will focus on creating a React frontend to consume this API, providing a more flexible and powerful user experience.
