"""JWT authentication for admin routes."""

from __future__ import annotations

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

import bcrypt
from fastapi import Depends, HTTPException, status
from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
from jose import JWTError, jwt

logger = logging.getLogger(__name__)

JWT_SECRET = os.getenv("JWT_SECRET") or secrets.token_urlsafe(32)
JWT_ALGORITHM = "HS256"
JWT_EXPIRE_HOURS = 24

bearer_scheme = HTTPBearer(auto_error=False)


def hash_password(password: str) -> str:
    """Hash a plain-text password with bcrypt."""
    return bcrypt.hashpw(password.encode("utf-8"), bcrypt.gensalt()).decode("utf-8")


def verify_password(plain: str, hashed: str) -> bool:
    """Verify a plain-text password against its bcrypt hash."""
    return bcrypt.checkpw(plain.encode("utf-8"), hashed.encode("utf-8"))


def create_access_token(subject: str) -> str:
    """Create a JWT access token for the given subject (username)."""
    expire = datetime.now(timezone.utc) + timedelta(hours=JWT_EXPIRE_HOURS)
    return jwt.encode(
        {"sub": subject, "exp": expire},
        JWT_SECRET,
        algorithm=JWT_ALGORITHM,
    )


async def require_admin(
    credentials: Optional[HTTPAuthorizationCredentials] = Depends(bearer_scheme),
) -> str:
    """FastAPI dependency that validates the JWT and returns the username.

    Use as: ``admin_user: str = Depends(require_admin)``
    """
    if credentials is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Authentication required",
            headers={"WWW-Authenticate": "Bearer"},
        )

    token = credentials.credentials
    try:
        payload = jwt.decode(token, JWT_SECRET, algorithms=[JWT_ALGORITHM])
        username: Optional[str] = payload.get("sub")
        if username is None:
            raise HTTPException(status_code=401, detail="Invalid token payload")
        return username
    except JWTError:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid or expired token",
            headers={"WWW-Authenticate": "Bearer"},
        )