from datetime import datetime, timedelta
from passlib.context import CryptContext
from jose import JWTError, jwt
import os
from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from model import User, SessionLocal

# JWT settings
SECRET_KEY = os.getenv("SECRET_KEY", "")
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 60

if SECRET_KEY == "":
    raise ValueError("SECRET_KEY environment variable is not set")

pwd_context = CryptContext(schemes=["argon2"], deprecated="auto")
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="login")


def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password):
    return pwd_context.hash(password)


def create_access_token(data: dict, expires_delta: timedelta | None = None):
    to_encode = data.copy()
    expire = datetime.utcnow() + (
        expires_delta or timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    )
    to_encode.update({"exp": expire})
    return jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)


def get_user(db, username: str):
    return db.query(User).filter(User.username == username).first()


def authenticate_user(db, username: str, password: str):
    user = get_user(db, username)
    if not user or not verify_password(password, user.password_hash):
        return None
    return user


def get_current_user(token: str = Depends(oauth2_scheme)):
    db = SessionLocal()
    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 | None = payload.get("sub")
        if username is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception
    user = get_user(db, username)
    db.close()
    if user is None:
        raise credentials_exception
    return user