from collections.abc import AsyncGenerator

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.security import decode_token
from app.db.session import async_session_factory
from app.models.user import User

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/v1/auth/login")


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    async with async_session_factory() as session:
        yield session


async def get_current_user(
    token: str = Depends(oauth2_scheme),
    db: AsyncSession = Depends(get_db),
) -> User:
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = decode_token(token)
        user_id: str | None = payload.get("sub")
        if user_id is None or payload.get("type") != "access":
            raise credentials_exception
    except ValueError:
        raise credentials_exception

    result = await db.execute(select(User).where(User.id == int(user_id)))
    user = result.scalar_one_or_none()
    if user is None:
        raise credentials_exception
    return user


async def get_current_active_user(
    current_user: User = Depends(get_current_user),
) -> User:
    if not current_user.is_active:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="User account is disabled",
        )
    return current_user


async def get_optional_current_user(
    token: str | None = Depends(OAuth2PasswordBearer(tokenUrl="/api/v1/auth/login", auto_error=False)),
    db: AsyncSession = Depends(get_db),
) -> User | None:
    if not token:
        return None
    try:
        payload = decode_token(token)
        user_id = payload.get("sub")
        if user_id is None or payload.get("type") != "access":
            return None
    except ValueError:
        return None
    result = await db.execute(select(User).where(User.id == int(user_id)))
    return result.scalar_one_or_none()