"""
auth.py
--------
Password hashing (bcrypt via passlib) and JWT-based session auth.
Also provides the `get_current_user` FastAPI dependency used to protect
routes that require a logged-in user.
"""

from datetime import datetime, timedelta, timezone
from typing import Optional

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt
from passlib.context import CryptContext
from sqlalchemy.orm import Session

from .config import settings
from .database import get_db
from . import db_models

pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="auth/login")


def hash_password(plain_password: str) -> str:
    return pwd_context.hash(plain_password)


def verify_password(plain_password: str, password_hash: str) -> bool:
    return pwd_context.verify(plain_password, password_hash)


def create_access_token(subject: str, expires_minutes: Optional[int] = None) -> str:
    expire = datetime.now(timezone.utc) + timedelta(
        minutes=expires_minutes or settings.ACCESS_TOKEN_EXPIRE_MINUTES
    )
    to_encode = {"sub": subject, "exp": expire}
    return jwt.encode(to_encode, settings.JWT_SECRET_KEY, algorithm=settings.JWT_ALGORITHM)


def decode_access_token(token: str) -> str:
    try:
        payload = jwt.decode(token, settings.JWT_SECRET_KEY, algorithms=[settings.JWT_ALGORITHM])
        subject: str = payload.get("sub")
        if subject is None:
            raise credentials_exception
        return subject
    except JWTError:
        raise credentials_exception


credentials_exception = HTTPException(
    status_code=status.HTTP_401_UNAUTHORIZED,
    detail="Could not validate credentials",
    headers={"WWW-Authenticate": "Bearer"},
)


def get_current_user(
    token: str = Depends(oauth2_scheme), db: Session = Depends(get_db)
) -> db_models.User:
    email = decode_access_token(token)
    user = db.query(db_models.User).filter(db_models.User.email == email).first()
    if user is None or not user.is_active:
        raise credentials_exception
    return user