backend/dependencies.py

"""
FastAPI dependencies for authentication.
"""
from datetime import datetime, timedelta, timezone
from typing import Optional

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

import database
from config import JWT_SECRET

_bearer = HTTPBearer(auto_error=False)

_ALGORITHM = "HS256"
_TOKEN_EXPIRE_DAYS = 30


def create_access_token(data: dict) -> str:
    payload = data.copy()
    payload["exp"] = datetime.now(timezone.utc) + timedelta(days=_TOKEN_EXPIRE_DAYS)
    return jwt.encode(payload, JWT_SECRET, algorithm=_ALGORITHM)


async def _decode_token(credentials: Optional[HTTPAuthorizationCredentials]) -> Optional[dict]:
    if credentials is None:
        return None
    try:
        payload = jwt.decode(credentials.credentials, JWT_SECRET, algorithms=[_ALGORITHM])
        user_id: str = payload.get("sub")
        if not user_id:
            return None
        return await run_in_threadpool(database.get_user_by_id, user_id)
    except JWTError:
        return None


async def get_current_user(
    credentials: Optional[HTTPAuthorizationCredentials] = Depends(_bearer),
) -> dict:
    """Require a valid JWT; raise 401 otherwise."""
    user = await _decode_token(credentials)
    if user is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Not authenticated.",
            headers={"WWW-Authenticate": "Bearer"},
        )
    return user


async def get_optional_user(
    credentials: Optional[HTTPAuthorizationCredentials] = Depends(_bearer),
) -> Optional[dict]:
    """Return the authenticated user or None (for routes that work with or without auth)."""
    return await _decode_token(credentials)