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

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

from database import get_db
from models import User

SECRET_KEY = os.environ["JWT_SECRET"]
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_DAYS = 30

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


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


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


def create_access_token(user_id: int, username: str, is_admin: bool, user_timezone: str = "UTC") -> str:
    expire = datetime.now(timezone.utc) + timedelta(days=ACCESS_TOKEN_EXPIRE_DAYS)
    payload = {
        "sub": str(user_id),
        "username": username,
        "is_admin": is_admin,
        "timezone": user_timezone,
        "exp": expire,
    }
    return jwt.encode(payload, SECRET_KEY, algorithm=ALGORITHM)


async def get_current_user(
    token: str = Depends(oauth2_scheme),
    db: Session = Depends(get_db),
) -> User:
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        user_id_str: Optional[str] = payload.get("sub")
        if user_id_str is None:
            raise credentials_exception
        user_id = int(user_id_str)
    except (JWTError, ValueError):
        raise credentials_exception

    user = db.get(User, user_id)
    if user is None or user.is_disabled:
        raise credentials_exception
    return user


async def get_current_admin(current_user: User = Depends(get_current_user)) -> User:
    if not current_user.is_admin:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Admin access required",
        )
    return current_user