from datetime import datetime, timedelta
from typing import Annotated, Union
import os

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.orm import Session
from sqlalchemy.ext.asyncio import AsyncSession
from dotenv import load_dotenv

from .db import SessionLocal
from . import orm_models, pydantic_schemas

load_dotenv("unimportant.env")
SECRET_KEY = os.getenv("SECRET_KEY")
ALGORITHM = os.getenv("ALGORITHM")
ACCESS_TOKEN_EXPIRE_MINUTES = os.getenv("ACCESS_TOKEN_EXPIRE_MINUTES")
pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/token")


async def get_session() -> AsyncSession:
    async with SessionLocal() as session:
        yield session


async def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)


async def get_password_hash(password):
    return pwd_context.hash(password)


async def get_user_by_nickname(db: Annotated[AsyncSession, Depends(get_session)], nickname: str):
    user_with_required_id = db.select(orm_models.User).where(orm_models.User.nickname == nickname).first()
    if user_with_required_id:
        return user_with_required_id
    return None


async def get_user_by_id(db: Annotated[AsyncSession, Depends(get_session)], user_id: int):
    user_with_required_id = db.select(orm_models.User).where(orm_models.User.id == user_id).first()
    if user_with_required_id:
        return user_with_required_id
    return None
    

async def authenticate_user(db: Annotated[AsyncSession, Depends(get_session)], nickname: str, password: str):
    user = get_user_by_nickname(db=db, nickname=nickname)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


async def create_access_token(data: dict, expires_delta: Union[timedelta, None] = 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(db: Annotated[AsyncSession, Depends(get_session)], token: Annotated[str, Depends(oauth2_scheme)]):
    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])
        user_id: int = payload.get("user_id")
        if user_id is None:
            raise credentials_exception
        token_data = pydantic_schemas.TokenData(user_id=user_id)
    except JWTError:
        raise credentials_exception
    user = get_user_by_id(db, user_id=token_data.user_id)
    if user is None:
        raise credentials_exception
    return pydantic_schemas.User(id=user.id, nickname=user.nickname, name=user.name, surname=user.surname,
        disabled=user.disabled, items=user.announcements, reg_date=user.reg_date, points=user.points)


async def get_current_active_user(
    current_user: Annotated[pydantic_schemas.User, Depends(get_current_user)]
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user