import os
from typing import Tuple

import jwt
from jwt import InvalidTokenError
from pydantic import BaseModel, Field
from starlette.authentication import AuthenticationBackend
from starlette.middleware.authentication import (
    AuthenticationMiddleware as BaseAuthenticationMiddleware,
)
from starlette.requests import HTTPConnection


class Session(BaseModel):
    authenticated: bool = Field(False, description="Is user authenticated?")


class AuthBackend(AuthenticationBackend):
    async def authenticate(
        self, conn: HTTPConnection
    ) -> Tuple[bool, Session]:
        session = Session()
        authorization: str = conn.headers.get("Authorization")
        if not authorization:
            return False, session

        try:
            scheme, token = authorization.split(" ")
            if scheme.lower() != "bearer":
                return False, session
        except ValueError:
            return False, session

        jwt_secret_key = os.getenv("JWT_SECRET_KEY")
        if not jwt_secret_key:
            return False, session

        try:
            jwt.decode(token, jwt_secret_key, algorithms=["HS256"])
        except InvalidTokenError:
            return False, session

        session.authenticated = True
        return True, session


class AuthenticationMiddleware(BaseAuthenticationMiddleware):
    pass