text: # -*- coding: utf-8 -*-
  # Copyright 2016 OpenMarket 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.
  
  from twisted.internet import defer, reactor
  from twisted.internet.error import AlreadyCalled, AlreadyCancelled
  
  import logging
  
  from synapse.util.metrics import Measure
  from synapse.util.logcontext import LoggingContext
  
  from mailer import Mailer
  
  logger = logging.getLogger(__name__)
  
  # The amount of time we always wait before ever emailing about a notification
  # (to give the user a chance to respond to other push or notice the window)
  DELAY_BEFORE_MAIL_MS = 10 * 60 * 1000
  
  # THROTTLE is the minimum time between mail notifications sent for a given room.
  # Each room maintains its own throttle counter, but each new mail notification
  # sends the pending notifications for all rooms.
  THROTTLE_START_MS = 10 * 60 * 1000
  THROTTLE_MAX_MS = 24 * 60 * 60 * 1000  # 24h
  # THROTTLE_MULTIPLIER = 6              # 10 mins, 1 hour, 6 hours, 24 hours
  THROTTLE_MULTIPLIER = 144              # 10 mins, 24 hours - i.e. jump straight to 1 day
  
  # If no event triggers a notification for this long after the previous,
  # the throttle is released.
  # 12 hours - a gap of 12 hours in conversation is surely enough to merit a new
  # notification when things get going again...
  THROTTLE_RESET_AFTER_MS = (12 * 60 * 60 * 1000)
  
  # does each email include all unread notifs, or just the ones which have happened
  # since the last mail?
  # XXX: this is currently broken as it includes ones from parted rooms(!)
  INCLUDE_ALL_UNREAD_NOTIFS = False
  
  
  class EmailPusher(object):
      """
      A pusher that sends email notifications about events (approximately)
      when they happen.
      This shares quite a bit of code with httpusher: it would be good to
      factor out the common parts
      """
      def __init__(self, hs, pusherdict):
          self.hs = hs
          self.store = self.hs.get_datastore()
          self.clock = self.hs.get_clock()
          self.pusher_id = pusherdict['id']
          self.user_id = pusherdict['user_name']
          self.app_id = pusherdict['app_id']
          self.email = pusherdict['pushkey']
          self.last_stream_ordering = pusherdict['last_stream_ordering']
          self.timed_call = None
          self.throttle_params = None
  
          # See httppusher
          self.max_stream_ordering = None
  
          self.processing = False
  
          if self.hs.config.email_enable_notifs:
              if 'data' in pusherdict and 'brand' in pusherdict['data']:
                  app_name = pusherdict['data']['brand']
              else:
                  app_name = self.hs.config.email_app_name
  
              self.mailer = Mailer(self.hs, app_name)
          else:
              self.mailer = None
  
      @defer.inlineCallbacks
      def on_started(self):
          if self.mailer is not None:
              self.throttle_params = yield self.store.get_throttle_params_by_room(
                  self.pusher_id
              )
              yield self._process()
  
      def on_stop(self):
          if self.timed_call:
              try:
                  self.timed_call.cancel()
              except (AlreadyCalled, AlreadyCancelled):
                  pass
              self.timed_call = None
  
      @defer.inlineCallbacks
      def on_new_notifications(self, min_stream_ordering, max_stream_ordering):
          self.max_stream_ordering = max(max_stream_ordering, self.max_stream_ordering)
          yield self._process()
  
      def on_new_receipts(self, min_stream_id, max_stream_id):
          # We could wake up and cancel the timer but there tend to be quite a
          # lot of read receipts so it's probably less work to just let the
          # timer fire
          return defer.succeed(None)
  
      @defer.inlineCallbacks
      def on_timer(self):
          self.timed_call = None
          yield self._process()
  
      @defer.inlineCallbacks
      def _process(self):
          if self.processing:
              return
  
          with LoggingContext("emailpush._process"):
              with Measure(self.clock, "emailpush._process"):
                  try:
                      self.processing = True
                      # if the max ordering changes while we're running _unsafe_process,
                      # call it again, and so on until we've caught up.
                      while True:
                          starting_max_ordering = self.max_stream_ordering
                          try:
                              yield self._unsafe_process()
                          except:
                              logger.exception("Exception processing notifs")
                          if self.max_stream_ordering == starting_max_ordering:
                              break
                  finally:
                      self.processing = False
  
      @defer.inlineCallbacks
      def _unsafe_process(self):
          """
          Main logic of the push loop without the wrapper function that sets
          up logging, measures and guards against multiple instances of it
          being run.
          """
          start = 0 if INCLUDE_ALL_UNREAD_NOTIFS else self.last_stream_ordering
          fn = self.store.get_unread_push_actions_for_user_in_range_for_email
          unprocessed = yield fn(self.user_id, start, self.max_stream_ordering)
  
          soonest_due_at = None
  
          if not unprocessed:
              yield self.save_last_stream_ordering_and_success(self.max_stream_ordering)
              return
  
          for push_action in unprocessed:
              received_at = push_action['received_ts']
              if received_at is None:
                  received_at = 0
              notif_ready_at = received_at + DELAY_BEFORE_MAIL_MS
  
              room_ready_at = self.room_ready_to_notify_at(
                  push_action['room_id']
              )
  
              should_notify_at = max(notif_ready_at, room_ready_at)
  
              if should_notify_at < self.clock.time_msec():
                  # one of our notifications is ready for sending, so we send
                  # *one* email updating the user on their notifications,
                  # we then consider all previously outstanding notifications
                  # to be delivered.
  
                  reason = {
                      'room_id': push_action['room_id'],
                      'now': self.clock.time_msec(),
                      'received_at': received_at,
                      'delay_before_mail_ms': DELAY_BEFORE_MAIL_MS,
                      'last_sent_ts': self.get_room_last_sent_ts(push_action['room_id']),
                      'throttle_ms': self.get_room_throttle_ms(push_action['room_id']),
                  }
  
                  yield self.send_notification(unprocessed, reason)
  
                  yield self.save_last_stream_ordering_and_success(max([
                      ea['stream_ordering'] for ea in unprocessed
                  ]))
  
                  # we update the throttle on all the possible unprocessed push actions
                  for ea in unprocessed:
                      yield self.sent_notif_update_throttle(
                          ea['room_id'], ea
                      )
                  break
              else:
                  if soonest_due_at is None or should_notify_at < soonest_due_at:
                      soonest_due_at = should_notify_at
  
                  if self.timed_call is not None:
                      try:
                          self.timed_call.cancel()
                      except (AlreadyCalled, AlreadyCancelled):
                          pass
                      self.timed_call = None
  
          if soonest_due_at is not None:
              self.timed_call = reactor.callLater(
                  self.seconds_until(soonest_due_at), self.on_timer
              )
  
      @defer.inlineCallbacks
      def save_last_stream_ordering_and_success(self, last_stream_ordering):
          self.last_stream_ordering = last_stream_ordering
          yield self.store.update_pusher_last_stream_ordering_and_success(
              self.app_id, self.email, self.user_id,
              last_stream_ordering, self.clock.time_msec()
          )
  
      def seconds_until(self, ts_msec):
          return (ts_msec - self.clock.time_msec()) / 1000
  
      def get_room_throttle_ms(self, room_id):
          if room_id in self.throttle_params:
              return self.throttle_params[room_id]["throttle_ms"]
          else:
              return 0
  
      def get_room_last_sent_ts(self, room_id):
          if room_id in self.throttle_params:
              return self.throttle_params[room_id]["last_sent_ts"]
          else:
              return 0
  
      def room_ready_to_notify_at(self, room_id):
          """
          Determines whether throttling should prevent us from sending an email
          for the given room
          Returns: The timestamp when we are next allowed to send an email notif
          for this room
          """
          last_sent_ts = self.get_room_last_sent_ts(room_id)
          throttle_ms = self.get_room_throttle_ms(room_id)
  
          may_send_at = last_sent_ts + throttle_ms
          return may_send_at
  
      @defer.inlineCallbacks
      def sent_notif_update_throttle(self, room_id, notified_push_action):
          # We have sent a notification, so update the throttle accordingly.
          # If the event that triggered the notif happened more than
          # THROTTLE_RESET_AFTER_MS after the previous one that triggered a
          # notif, we release the throttle. Otherwise, the throttle is increased.
          time_of_previous_notifs = yield self.store.get_time_of_last_push_action_before(
              notified_push_action['stream_ordering']
          )
  
          time_of_this_notifs = notified_push_action['received_ts']
  
          if time_of_previous_notifs is not None and time_of_this_notifs is not None:
              gap = time_of_this_notifs - time_of_previous_notifs
          else:
              # if we don't know the arrival time of one of the notifs (it was not
              # stored prior to email notification code) then assume a gap of
              # zero which will just not reset the throttle
              gap = 0
  
          current_throttle_ms = self.get_room_throttle_ms(room_id)
  
          if gap > THROTTLE_RESET_AFTER_MS:
              new_throttle_ms = THROTTLE_START_MS
          else:
              if current_throttle_ms == 0:
                  new_throttle_ms = THROTTLE_START_MS
              else:
                  new_throttle_ms = min(
                      current_throttle_ms * THROTTLE_MULTIPLIER,
                      THROTTLE_MAX_MS
                  )
          self.throttle_params[room_id] = {
              "last_sent_ts": self.clock.time_msec(),
              "throttle_ms": new_throttle_ms
          }
          yield self.store.set_throttle_params(
              self.pusher_id, room_id, self.throttle_params[room_id]
          )
  
      @defer.inlineCallbacks
      def send_notification(self, push_actions, reason):
          logger.info("Sending notif email for user %r", self.user_id)
  
          yield self.mailer.send_notification_mail(
              self.app_id, self.user_id, self.email, push_actions, reason
          )
  