"""Shared FastAPI dependencies.

``get_current_user`` decodes the Bearer JWT and returns a ``UserProfile``.
Step 9 will layer rate-limiting and sanitization middleware on top of this.
Step 12 will add a DB look-up to fetch the live tier from PostgreSQL.
"""

from __future__ import annotations

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt

from app.config.settings import settings
from app.schemas import BillingTier, UserProfile

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


async def get_current_user(
    token: str = Depends(oauth2_scheme),
) -> UserProfile:
    """Validate a Bearer JWT and return the authenticated user.

    Raises ``HTTP 401`` on any invalid or expired token.
    The tier embedded in the JWT is used for feature-gating until Step 12
    adds a live DB lookup.
    """
    credentials_exc = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(
            token, settings.JWT_SECRET, algorithms=[settings.JWT_ALGORITHM]
        )
        user_id: str | None = payload.get("sub")
        email: str | None = payload.get("email")
        tier: str = payload.get("tier", "free")
        if not user_id or not email:
            raise credentials_exc
    except JWTError:
        raise credentials_exc

    return UserProfile(id=user_id, email=email, tier=tier)  # type: ignore[arg-type]