import os
from datetime import datetime, timedelta
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 sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from . import models
from .database import get_db

# Configuration
SECRET_KEY = os.getenv("RAGLINT_SECRET_KEY", "dev_secret_key_change_in_prod")
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30

pwd_context = CryptContext(schemes=["pbkdf2_sha256"], deprecated="auto")
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="auth/token")


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: 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: AsyncSession = Depends(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])
        email: str = payload.get("sub")
        if email is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception

    result = await db.execute(select(models.User).where(models.User.email == email))
    user = result.scalar_one_or_none()

    if user is None:
        raise credentials_exception
    return user


# Optional auth for backward compatibility or public dashboards
async def get_current_user_optional(
    token: Optional[str] = Depends(oauth2_scheme), db: AsyncSession = Depends(get_db)
):
    if not token:
        return None
    try:
        return await get_current_user(token, db)
    except HTTPException:
        return None
