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

import bcrypt
from fastapi import Depends, HTTPException, Request, status
from jose import JWTError, jwt
from pydantic import BaseModel, EmailStr
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from database import get_db
from models import User

SECRET_KEY = os.environ["SECRET_KEY"]  # Required - see .env.example
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 60 * 24 * 7  # 7 days
COOKIE_NAME = "auth_token"


class UserCredentials(BaseModel):
    email: EmailStr
    password: str


UserCreate = UserCredentials
UserLogin = UserCredentials


class UserResponse(BaseModel):
    id: int
    email: str


class TokenResponse(BaseModel):
    access_token: str
    token_type: str
    user: UserResponse


def verify_password(plain_password: str, hashed_password: str) -> bool:
    return bcrypt.checkpw(
        plain_password.encode("utf-8"),
        hashed_password.encode("utf-8"),
    )


def get_password_hash(password: str) -> str:
    return bcrypt.hashpw(
        password.encode("utf-8"),
        bcrypt.gensalt(),
    ).decode("utf-8")


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


async def get_user_by_email(db: AsyncSession, email: str) -> Optional[User]:
    result = await db.execute(select(User).where(User.email == email))
    return result.scalar_one_or_none()


async def authenticate_user(db: AsyncSession, email: str, password: str) -> Optional[User]:
    user = await get_user_by_email(db, email)
    if not user or not verify_password(password, user.hashed_password):
        return None
    return user


async def get_current_user(
    request: Request,
    db: AsyncSession = Depends(get_db),
) -> User:
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Invalid authentication credentials",
    )
    
    token = request.cookies.get(COOKIE_NAME)
    if not token:
        raise credentials_exception
    
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        user_id_str = payload.get("sub")
        if user_id_str is None:
            raise credentials_exception
        user_id = int(user_id_str)
    except (JWTError, ValueError):
        raise credentials_exception

    result = await db.execute(select(User).where(User.id == user_id))
    user = result.scalar_one_or_none()
    if user is None:
        raise credentials_exception
    return user