"""Authentication Backends for the Meet core app."""

from django.conf import settings
from django.core.exceptions import SuspiciousOperation
from django.utils.translation import gettext_lazy as _

import requests
from mozilla_django_oidc.auth import (
    OIDCAuthenticationBackend as MozillaOIDCAuthenticationBackend,
)

from core.models import User


class OIDCAuthenticationBackend(MozillaOIDCAuthenticationBackend):
    """Custom OpenID Connect (OIDC) Authentication Backend.

    This class overrides the default OIDC Authentication Backend to accommodate differences
    in the User and Identity models, and handles signed and/or encrypted UserInfo response.
    """

    def get_userinfo(self, access_token, id_token, payload):
        """Return user details dictionary.

        Parameters:
        - access_token (str): The access token.
        - id_token (str): The id token (unused).
        - payload (dict): The token payload (unused).

        Note: The id_token and payload parameters are unused in this implementation,
        but were kept to preserve base method signature.

        Note: It handles signed and/or encrypted UserInfo Response. It is required by
        Agent Connect, which follows the OIDC standard. It forces us to override the
        base method, which deal with 'application/json' response.

        Returns:
        - dict: User details dictionary obtained from the OpenID Connect user endpoint.
        """

        user_response = requests.get(
            self.OIDC_OP_USER_ENDPOINT,
            headers={"Authorization": f"Bearer {access_token}"},
            verify=self.get_settings("OIDC_VERIFY_SSL", True),
            timeout=self.get_settings("OIDC_TIMEOUT", None),
            proxies=self.get_settings("OIDC_PROXY", None),
        )
        user_response.raise_for_status()
        userinfo = self.verify_token(user_response.text)
        return userinfo

    def get_or_create_user(self, access_token, id_token, payload):
        """Return a User based on userinfo. Get or create a new user if no user matches the Sub.

        Parameters:
        - access_token (str): The access token.
        - id_token (str): The ID token.
        - payload (dict): The user payload.

        Returns:
        - User: An existing or newly created User instance.

        Raises:
        - Exception: Raised when user creation is not allowed and no existing user is found.
        """

        user_info = self.get_userinfo(access_token, id_token, payload)
        sub = user_info.get("sub")

        if not sub:
            raise SuspiciousOperation(
                _("User info contained no recognizable user identification")
            )

        email = user_info.get("email")
        user = self.get_existing_user(sub, email)

        if not user and self.get_settings("OIDC_CREATE_USER", True):
            user = User.objects.create(
                sub=sub,
                email=email,
                password="!",  # noqa: S106
            )
        elif not user:
            return None

        if not user.is_active:
            raise SuspiciousOperation(_("User account is disabled"))

        return user

    def get_existing_user(self, sub, email):
        """Fetch existing user by sub or email."""
        try:
            return User.objects.get(sub=sub)
        except User.DoesNotExist:
            if email and settings.OIDC_FALLBACK_TO_EMAIL_FOR_IDENTIFICATION:
                try:
                    return User.objects.get(email=email)
                except User.DoesNotExist:
                    pass
        return None