auth.py

import os
from fastapi import Depends, HTTPException, status
from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
from jose import jwt, JWTError

security = HTTPBearer()

def get_jwt_secret() -> str:
    """Get JWT secret from environment variable."""
    secret = os.getenv("JWT_SECRET")
    if not secret:
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail="JWT_SECRET not configured"
        )
    return secret


def verify_token(credentials: HTTPAuthorizationCredentials = Depends(security)) -> dict:
    """
    Verify Bearer token signature.
    Returns the decoded token payload if valid.
    Raises HTTPException if invalid.
    """
    token = credentials.credentials
    jwt_secret = get_jwt_secret()

    try:
        # Decode and verify the JWT token
        payload = jwt.decode(
            token,
            jwt_secret,
            algorithms=["HS256"],
            options={"verify_aud": False}  # Clerk tokens may not have standard audience
        )
        return payload
    except JWTError as e:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail=f"Invalid token: {str(e)}",
            headers={"WWW-Authenticate": "Bearer"},
        )


def get_current_user(token_payload: dict = Depends(verify_token)) -> dict:
    """
    Extract user information from verified token.
    """
    user_id = token_payload.get("sub")
    if not user_id:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid token: missing user ID",
            headers={"WWW-Authenticate": "Bearer"},
        )
    
    return {
        "user_id": user_id,
        "email": token_payload.get("email"),
        "claims": token_payload
    }