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.
  
  import logging
  from typing import TYPE_CHECKING, Dict, List, Optional
  
  from twisted.internet.base import DelayedCall
  from twisted.internet.error import AlreadyCalled, AlreadyCancelled
  
  from synapse.metrics.background_process_metrics import run_as_background_process
  from synapse.push import Pusher, PusherConfig, ThrottleParams
  from synapse.push.mailer import Mailer
  
  if TYPE_CHECKING:
      from synapse.app.homeserver import HomeServer
  
  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(Pusher):
      """
      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: "HomeServer", pusher_config: PusherConfig, mailer: Mailer):
          super().__init__(hs, pusher_config)
          self.mailer = mailer
  
          self.store = self.hs.get_datastore()
          self.email = pusher_config.pushkey
          self.timed_call = None  # type: Optional[DelayedCall]
          self.throttle_params = {}  # type: Dict[str, ThrottleParams]
          self._inited = False
  
          self._is_processing = False
  
      def on_started(self, should_check_for_notifs: bool) -> None:
          """Called when this pusher has been started.
  
          Args:
              should_check_for_notifs: Whether we should immediately
                  check for push to send. Set to False only if it's known there
                  is nothing to send
          """
          if should_check_for_notifs and self.mailer is not None:
              self._start_processing()
  
      def on_stop(self) -> None:
          if self.timed_call:
              try:
                  self.timed_call.cancel()
              except (AlreadyCalled, AlreadyCancelled):
                  pass
              self.timed_call = None
  
      def on_new_receipts(self, min_stream_id: int, max_stream_id: int) -> None:
          # 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
          pass
  
      def on_timer(self) -> None:
          self.timed_call = None
          self._start_processing()
  
      def _start_processing(self) -> None:
          if self._is_processing:
              return
  
          run_as_background_process("emailpush.process", self._process)
  
      def _pause_processing(self) -> None:
          """Used by tests to temporarily pause processing of events.
  
          Asserts that its not currently processing.
          """
          assert not self._is_processing
          self._is_processing = True
  
      def _resume_processing(self) -> None:
          """Used by tests to resume processing of events after pausing.
          """
          assert self._is_processing
          self._is_processing = False
          self._start_processing()
  
      async def _process(self) -> None:
          # we should never get here if we are already processing
          assert not self._is_processing
  
          try:
              self._is_processing = True
  
              if not self._inited:
                  # this is our first loop: load up the throttle params
                  assert self.pusher_id is not None
                  self.throttle_params = await self.store.get_throttle_params_by_room(
                      self.pusher_id
                  )
                  self._inited = 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:
                      await self._unsafe_process()
                  except Exception:
                      logger.exception("Exception processing notifs")
                  if self.max_stream_ordering == starting_max_ordering:
                      break
          finally:
              self._is_processing = False
  
      async def _unsafe_process(self) -> None:
          """
          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
          assert start is not None
          unprocessed = await self.store.get_unread_push_actions_for_user_in_range_for_email(
              self.user_id, start, self.max_stream_ordering
          )
  
          soonest_due_at = None  # type: Optional[int]
  
          if not unprocessed:
              await 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"]),
                  }
  
                  await self.send_notification(unprocessed, reason)
  
                  await 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:
                      await 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 = self.hs.get_reactor().callLater(
                  self.seconds_until(soonest_due_at), self.on_timer
              )
  
      async def save_last_stream_ordering_and_success(
          self, last_stream_ordering: Optional[int]
      ) -> None:
          if last_stream_ordering is None:
              # This happens if we haven't yet processed anything
              return
  
          self.last_stream_ordering = last_stream_ordering
          pusher_still_exists = await self.store.update_pusher_last_stream_ordering_and_success(
              self.app_id,
              self.email,
              self.user_id,
              last_stream_ordering,
              self.clock.time_msec(),
          )
          if not pusher_still_exists:
              # The pusher has been deleted while we were processing, so
              # lets just stop and return.
              self.on_stop()
  
      def seconds_until(self, ts_msec: int) -> float:
          secs = (ts_msec - self.clock.time_msec()) / 1000
          return max(secs, 0)
  
      def get_room_throttle_ms(self, room_id: str) -> int:
          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: str) -> int:
          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: str) -> int:
          """
          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
  
      async def sent_notif_update_throttle(
          self, room_id: str, notified_push_action: dict
      ) -> None:
          # 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 = await 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] = ThrottleParams(
              self.clock.time_msec(), new_throttle_ms,
          )
          assert self.pusher_id is not None
          await self.store.set_throttle_params(
              self.pusher_id, room_id, self.throttle_params[room_id]
          )
  
      async def send_notification(self, push_actions: List[dict], reason: dict) -> None:
          logger.info("Sending notif email for user %r", self.user_id)
  
          await self.mailer.send_notification_mail(
              self.app_id, self.user_id, self.email, push_actions, reason
          )
  