"""Auth + RBAC dependencies for FastAPI routes."""
from __future__ import annotations

from collections.abc import Callable

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_access_token
from app.database import get_db
from app.models.enums import Role
from app.models.user import User

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

# Privilege ordering: higher number = more privilege
_ROLE_RANK = {Role.readonly: 0, Role.support: 1, Role.admin: 2}


async def get_current_user(
    token: str = Depends(oauth2_scheme),
    db: AsyncSession = Depends(get_db),
) -> User:
    creds_error = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    payload = decode_access_token(token)
    if not payload or "sub" not in payload:
        raise creds_error
    result = await db.execute(select(User).where(User.email == payload["sub"]))
    user = result.scalar_one_or_none()
    if user is None or not user.is_active:
        raise creds_error
    return user


def require_role(minimum: Role) -> Callable:
    """Return a dependency that enforces a minimum role."""

    async def _guard(user: User = Depends(get_current_user)) -> User:
        if _ROLE_RANK[user.role] < _ROLE_RANK[minimum]:
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail=f"Requires at least '{minimum.value}' role",
            )
        return user

    return _guard


require_admin = require_role(Role.admin)
require_support = require_role(Role.support)
require_readonly = require_role(Role.readonly)