from datetime import datetime, timedelta
from typing import Optional
from jose import JWTError, jwt
from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from sqlalchemy.orm import Session
from backend import models, database
import bcrypt

SECRET_KEY = "YOUR_SECRET_KEY_CHANGE_THIS"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30

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

def verify_password(plain_password, hashed_password):
    return bcrypt.checkpw(plain_password.encode('utf-8'), hashed_password.encode('utf-8'))

def get_password_hash(password):
    return bcrypt.hashpw(password.encode('utf-8'), bcrypt.gensalt()).decode('utf-8')

def create_access_token(data: dict, expires_delta: Optional[timedelta] = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.utcnow() + expires_delta
    else:
        expire = datetime.utcnow() + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt

async def get_current_user(token: str = Depends(oauth2_scheme), db: Session = Depends(database.get_db)):
    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])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception
    user = db.query(models.User).filter(models.User.username == username).first()
    if user is None:
        raise credentials_exception
    return user

async def get_current_admin_user(current_user: models.User = Depends(get_current_user)):
    if not current_user.is_admin:
        raise HTTPException(status_code=403, detail="Not enough permissions")
    return current_user