"""JWT auth + user management."""
from __future__ import annotations

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 sqlmodel import Session, select

from config import settings
from database import get_session
from models.user import User

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


# --- password helpers ---


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


def verify_password(plain: str, hashed: str) -> bool:
    return pwd_context.verify(plain, hashed)


# --- token helpers ---


def _create_token(sub: str, role: str, token_type: str, expires: timedelta) -> str:
    now = datetime.now(timezone.utc)
    payload = {
        "sub": sub,
        "role": role,
        "type": token_type,
        "iat": now,
        "exp": now + expires,
    }
    return jwt.encode(payload, settings.SECRET_KEY, algorithm=settings.ALGORITHM)


def create_access_token(user: User) -> str:
    return _create_token(
        user.username,
        user.role,
        "access",
        timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES),
    )


def create_refresh_token(user: User) -> str:
    return _create_token(
        user.username,
        user.role,
        "refresh",
        timedelta(days=settings.REFRESH_TOKEN_EXPIRE_DAYS),
    )


def decode_token(token: str, expected_type: str = "access") -> dict:
    try:
        payload = jwt.decode(
            token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM]
        )
    except JWTError as exc:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid token",
        ) from exc
    if payload.get("type") != expected_type:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Wrong token type",
        )
    return payload


# --- user lookups ---


def get_user(session: Session, username: str) -> Optional[User]:
    return session.exec(select(User).where(User.username == username)).first()


def authenticate(session: Session, username: str, password: str) -> Optional[User]:
    user = get_user(session, username)
    if not user or not user.is_active:
        return None
    if not verify_password(password, user.hashed_password):
        return None
    return user


def users_exist(session: Session) -> bool:
    return session.exec(select(User)).first() is not None


# --- FastAPI dependencies ---


def get_current_user(
    token: Optional[str] = Depends(oauth2_scheme),
    session: Session = Depends(get_session),
) -> User:
    if not token:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Not authenticated",
            headers={"WWW-Authenticate": "Bearer"},
        )
    payload = decode_token(token, "access")
    user = get_user(session, payload.get("sub", ""))
    if not user or not user.is_active:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="User not found or inactive",
        )
    return user


def require_admin(user: User = Depends(get_current_user)) -> User:
    if user.role != "admin":
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Admin privileges required",
        )
    return user