# -*- coding: utf-8 -*-
# Copyright 2019 New Vector Ltd
#
# 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

import twisted
import twisted.internet.error
from twisted.internet import defer
from twisted.web import server, static
from twisted.web.resource import Resource

from synapse.app import check_bind_error
from synapse.config import ConfigError

logger = logging.getLogger(__name__)


class AcmeHandler(object):
    def __init__(self, hs):
        self.hs = hs
        self.reactor = hs.get_reactor()
        self._acme_domain = hs.config.acme_domain

    @defer.inlineCallbacks
    def start_listening(self):
        from synapse.handlers import acme_issuing_service

        # Configure logging for txacme, if you need to debug
        # from eliot import add_destinations
        # from eliot.twisted import TwistedDestination
        #
        # add_destinations(TwistedDestination())

        well_known = Resource()

        self._issuer = acme_issuing_service.create_issuing_service(
            self.reactor,
            acme_url=self.hs.config.acme_url,
            account_key_file=self.hs.config.acme_account_key_file,
            well_known_resource=well_known,
        )

        responder_resource = Resource()
        responder_resource.putChild(b".well-known", well_known)
        responder_resource.putChild(b"check", static.Data(b"OK", b"text/plain"))
        srv = server.Site(responder_resource)

        bind_addresses = self.hs.config.acme_bind_addresses
        for host in bind_addresses:
            logger.info(
                "Listening for ACME requests on %s:%i", host, self.hs.config.acme_port
            )
            try:
                self.reactor.listenTCP(self.hs.config.acme_port, srv, interface=host)
            except twisted.internet.error.CannotListenError as e:
                check_bind_error(e, host, bind_addresses)

        # Make sure we are registered to the ACME server. There's no public API
        # for this, it is usually triggered by startService, but since we don't
        # want it to control where we save the certificates, we have to reach in
        # and trigger the registration machinery ourselves.
        self._issuer._registered = False

        try:
            yield self._issuer._ensure_registered()
        except Exception:
            raise ConfigError("Failed to register with the ACME provider. This is likely"
                " happening because the install is new, and ACME v1 has been deprecated"
                " by Let's Encrypt and is disabled for installs set up after November"
                " 2019. At the moment, Synapse doesn't support ACME v2. For more info"
                " and alternative solution, check out https://github.com/matrix-org"
                "/synapse/blob/master/docs/ACME.md#deprecation-of-acme-v1"
            )

    @defer.inlineCallbacks
    def provision_certificate(self):

        logger.warning("Reprovisioning %s", self._acme_domain)

        try:
            yield self._issuer.issue_cert(self._acme_domain)
        except Exception:
            logger.exception("Fail!")
            raise
        logger.warning("Reprovisioned %s, saving.", self._acme_domain)
        cert_chain = self._issuer.cert_store.certs[self._acme_domain]

        try:
            with open(self.hs.config.tls_private_key_file, "wb") as private_key_file:
                for x in cert_chain:
                    if x.startswith(b"-----BEGIN RSA PRIVATE KEY-----"):
                        private_key_file.write(x)

            with open(self.hs.config.tls_certificate_file, "wb") as certificate_file:
                for x in cert_chain:
                    if x.startswith(b"-----BEGIN CERTIFICATE-----"):
                        certificate_file.write(x)
        except Exception:
            logger.exception("Failed saving!")
            raise

        return True