# -*- coding: utf-8 -*-
# Copyright 2020 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import logging
from typing import TYPE_CHECKING, Optional

from synapse.handlers._base import BaseHandler
from synapse.http.server import respond_with_html

if TYPE_CHECKING:
    from synapse.server import HomeServer

logger = logging.getLogger(__name__)


class MappingException(Exception):
    """Used to catch errors when mapping the UserInfo object
    """


class SsoHandler(BaseHandler):
    def __init__(self, hs: "HomeServer"):
        super().__init__(hs)
        self._error_template = hs.config.sso_error_template

    def render_error(
        self, request, error: str, error_description: Optional[str] = None
    ) -> None:
        """Renders the error template and responds with it.

        This is used to show errors to the user. The template of this page can
        be found under `synapse/res/templates/sso_error.html`.

        Args:
            request: The incoming request from the browser.
                We'll respond with an HTML page describing the error.
            error: A technical identifier for this error.
            error_description: A human-readable description of the error.
        """
        html = self._error_template.render(
            error=error, error_description=error_description
        )
        respond_with_html(request, 400, html)

    async def get_sso_user_by_remote_user_id(
        self, auth_provider_id: str, remote_user_id: str
    ) -> Optional[str]:
        """
        Maps the user ID of a remote IdP to a mxid for a previously seen user.

        If the user has not been seen yet, this will return None.

        Args:
            auth_provider_id: A unique identifier for this SSO provider, e.g.
                "oidc" or "saml".
            remote_user_id: The user ID according to the remote IdP. This might
                be an e-mail address, a GUID, or some other form. It must be
                unique and immutable.

        Returns:
            The mxid of a previously seen user.
        """
        # Check if we already have a mapping for this user.
        logger.info(
            "Looking for existing mapping for user %s:%s",
            auth_provider_id,
            remote_user_id,
        )
        previously_registered_user_id = await self.store.get_user_by_external_id(
            auth_provider_id, remote_user_id,
        )

        # A match was found, return the user ID.
        if previously_registered_user_id is not None:
            logger.info("Found existing mapping %s", previously_registered_user_id)
            return previously_registered_user_id

        # No match.
        return None