WealthWise/backend/app/api/deps.py

"""WealthWise API dependencies.

This module provides reusable dependencies for FastAPI endpoints including:
- Database session injection
- Authentication dependencies with JWT validation
- Common dependency utilities
"""

from typing import Optional
from uuid import UUID

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt
from sqlalchemy import select
from sqlmodel.ext.asyncio.session import AsyncSession

from app.core.config import get_settings
from app.core.db import get_session
from app.models import User
from app.schemas.user import TokenPayload

settings = get_settings()

# OAuth2 scheme for JWT token authentication
# Uses the token endpoint for OAuth2 Password Flow
oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl=f"{settings.API_V1_STR}/auth/token",
    auto_error=False,  # Allow optional auth for public endpoints
)


# Database session dependency
# Re-export get_session for cleaner imports in endpoint modules
SessionDep = Depends(get_session)


async def get_current_user(
    token: Optional[str] = Depends(oauth2_scheme),
    session: AsyncSession = SessionDep,
) -> User:
    """Get current authenticated user from JWT token.
    
    This dependency extracts the Bearer token from the Authorization header,
    validates it locally using the application's secret key, queries the
    database for the user, and returns the User model.
    
    Args:
        token: JWT access token from Authorization header (Bearer token)
        session: Database session for user lookup
        
    Returns:
        User: Authenticated user model from database
        
    Raises:
        HTTPException: 401 if token is missing, invalid, or user not found/inactive
    """
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    
    if not token:
        raise credentials_exception
    
    try:
        # Decode and validate JWT
        payload = jwt.decode(
            token,
            settings.SECRET_KEY,
            algorithms=[settings.ALGORITHM],
        )
        
        # Extract user ID from subject claim
        user_id: Optional[str] = payload.get("sub")
        if user_id is None:
            raise credentials_exception
        
        # Validate token type
        token_type = payload.get("type")
        if token_type != "access":
            raise credentials_exception
            
    except JWTError:
        raise credentials_exception
    
    # Query database for user
    statement = select(User).where(User.id == UUID(user_id))
    result = await session.exec(statement)
    user = result.first()
    
    # Validate user exists and is active
    if user is None or not user.is_active:
        raise credentials_exception
    
    return user


async def get_current_active_user(
    current_user: User = Depends(get_current_user),
) -> User:
    """Verify user is active (non-superuser check optional).
    
    This dependency extends get_current_user. Currently just returns the user
    since get_current_user already checks is_active. Can be extended for
    additional checks like email verification.
    
    Args:
        current_user: User from get_current_user dependency
        
    Returns:
        Active User model
        
    Raises:
        HTTPException: 401 if user is inactive
    """
    return current_user


async def get_current_superuser(
    current_user: User = Depends(get_current_user),
) -> User:
    """Verify user is a superuser/admin.
    
    This dependency requires the user to have superuser privileges.
    
    Args:
        current_user: User from get_current_user dependency
        
    Returns:
        Superuser User model
        
    Raises:
        HTTPException: 403 if user is not a superuser
    """
    if not current_user.is_superuser:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Not enough permissions",
        )
    return current_user


# Convenience exports for endpoint modules
__all__ = [
    "get_session",
    "SessionDep",
    "oauth2_scheme",
    "get_current_user",
    "get_current_active_user",
    "get_current_superuser",
]