from datetime import datetime, timedelta, timezone
import jwt
from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jwt.exceptions import JWTException
from passlib.context import CryptContext

from app.models.user_model import User
from app.database.manager import DatabaseManager

# Security settings
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30

# Password hashing setup
pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

# OAuth2 for token-based authentication
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


def get_password_hash(password: str) -> str:
    """Hashes a password using bcrypt."""
    return pwd_context.hash(password)


def verify_password(plain_password: str, hashed_password: str) -> bool:
    """Verifies that a given password matches the stored hashed password."""
    return pwd_context.verify(plain_password, hashed_password)


def create_access_token(data: dict, expires_delta: timedelta | None = None) -> str:
    """Generates a JWT token."""
    to_encode = data.copy()
    expire = datetime.now(timezone.utc) + (expires_delta or timedelta(minutes=15))
    to_encode.update({"exp": expire})
    return jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)


def get_user_by_username(username: str) -> User | None:
    """Retrieves a user from the database by username."""
    with DatabaseManager.get_session() as session:
        return session.query(User).filter(User.username == username).first()


def authenticate_user(username: str, password: str) -> User | bool:
    """Authenticates a user by verifying their credentials."""
    user = get_user_by_username(username)
    if not user or not verify_password(password, user.password):
        return False
    return user


async def get_current_user(token: str = Depends(oauth2_scheme)) -> User:
    """Retrieves the current authenticated user based on the token."""
    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 JWTException:
        raise credentials_exception

    user = get_user_by_username(username)
    if user is None:
        raise credentials_exception
    return user