siftlode/backend/app/auth.py

from datetime import datetime, timezone

from authlib.integrations.starlette_client import OAuth, OAuthError
from fastapi import APIRouter, Depends, HTTPException, Request
from fastapi.responses import JSONResponse, RedirectResponse
from sqlalchemy.orm import Session

from app.config import settings
from app.db import get_db
from app.models import OAuthToken, User
from app.security import encrypt

# Single YouTube scope that allows reading subscriptions/playlists AND writing
# (unsubscribe, playlist export). openid/email/profile give us the account identity.
SCOPES = "openid email profile https://www.googleapis.com/auth/youtube"

router = APIRouter(prefix="/auth", tags=["auth"])

oauth = OAuth()
oauth.register(
    name="google",
    client_id=settings.google_client_id,
    client_secret=settings.google_client_secret,
    server_metadata_url="https://accounts.google.com/.well-known/openid-configuration",
    client_kwargs={"scope": SCOPES},
)


@router.get("/login")
async def login(request: Request):
    # access_type=offline ensures a refresh_token on first authorization. We avoid
    # prompt=consent so returning users get a quick sign-in; the stored refresh token
    # is kept when Google doesn't re-issue one (see the callback).
    return await oauth.google.authorize_redirect(
        request,
        settings.oauth_redirect_url,
        access_type="offline",
        prompt="select_account",
        include_granted_scopes="true",
    )


@router.get("/callback")
async def callback(request: Request, db: Session = Depends(get_db)):
    try:
        token = await oauth.google.authorize_access_token(request)
    except OAuthError as exc:
        raise HTTPException(status_code=400, detail=f"OAuth error: {exc.error}")

    userinfo = token.get("userinfo")
    if not userinfo or not userinfo.get("sub"):
        raise HTTPException(status_code=400, detail="No user info returned by Google")

    email = (userinfo.get("email") or "").lower()
    if not email or email not in settings.allowed_email_set:
        raise HTTPException(
            status_code=403, detail="This Google account is not on the invite list."
        )

    user = db.query(User).filter(User.google_sub == userinfo["sub"]).one_or_none()
    if user is None:
        user = User(google_sub=userinfo["sub"], email=email)
        db.add(user)
    user.email = email
    user.display_name = userinfo.get("name")
    user.avatar_url = userinfo.get("picture")
    user.role = "admin" if email in settings.admin_email_set else "user"
    db.flush()

    tok = user.token or OAuthToken(user=user)
    # Google only returns a refresh_token on (re)consent; keep the previous one otherwise.
    if token.get("refresh_token"):
        tok.refresh_token_enc = encrypt(token["refresh_token"])
    tok.access_token = token.get("access_token")
    expires_at = token.get("expires_at")
    tok.expiry = (
        datetime.fromtimestamp(expires_at, tz=timezone.utc) if expires_at else None
    )
    tok.scopes = token.get("scope") or SCOPES
    db.add(tok)
    db.commit()

    request.session["user_id"] = user.id
    return RedirectResponse(url="/")


@router.post("/logout")
async def logout(request: Request):
    request.session.clear()
    return JSONResponse({"ok": True})


def current_user(request: Request, db: Session = Depends(get_db)) -> User:
    user_id = request.session.get("user_id")
    if not user_id:
        raise HTTPException(status_code=401, detail="Not authenticated")
    user = db.get(User, user_id)
    if user is None:
        request.session.clear()
        raise HTTPException(status_code=401, detail="Not authenticated")
    return user


@router.get("/me")
async def me(user: User = Depends(current_user)) -> dict:
    return {
        "id": user.id,
        "email": user.email,
        "display_name": user.display_name,
        "avatar_url": user.avatar_url,
        "role": user.role,
    }