from datetime import datetime, timedelta, timezone

import bcrypt
from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt
from sqlalchemy.orm import Session
from sqlalchemy import select

from app import models
from app.core.config import settings
from app.core.database import get_db


oauth2_scheme = OAuth2PasswordBearer(tokenUrl="auth/login")  # tokenUrl es solo para la doc interactiva de Swagger; no restringe cómo se emite el token.


def verify_password(plain_password:str, hashed_password:str) -> bool:
    return bcrypt.checkpw(plain_password.encode(), hashed_password.encode())

def get_password_hash(password:str) -> str:
    return bcrypt.hashpw(password.encode(), bcrypt.gensalt()).decode()

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

def authenticate_user(db:Session, email:str, password:str) -> models.User | None:
    user = db.scalar(select(models.User).where(models.User.email == email.lower()))
    if user is None or not verify_password(password, user.password_hash):
        return None
    return user

def get_current_user(token:str = Depends(oauth2_scheme), db:Session = Depends(get_db)) -> models.User:
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Token inválido o expirado",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM])
        sub = payload.get("sub")
        if sub is None:
            raise credentials_exception
        user_id = int(sub)
    except (JWTError, ValueError) as exc:
        raise credentials_exception from exc

    user = db.get(models.User, user_id)
    if user is None:
        raise credentials_exception
    return user

def get_current_active_user(current_user:models.User = Depends(get_current_user)) -> models.User:
    if not current_user.is_active:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Usuario inactivo")
    return current_user

def get_current_admin_user(current_user:models.User = Depends(get_current_active_user)) -> models.User:
    if not current_user.is_admin:
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="Se requieren privilegios de administrador")
    return current_user