# -*- coding: utf-8 -*-
# Copyright 2014 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

from synapse.streams.config import PaginationConfig
from synapse.types import StreamToken

import synapse.util.async

import logging

logger = logging.getLogger(__name__)


class Pusher(object):
    INITIAL_BACKOFF = 1000
    MAX_BACKOFF = 60 * 60 * 1000
    GIVE_UP_AFTER = 24 * 60 * 60 * 1000

    def __init__(self, _hs, user_name, app_id,
                 app_display_name, device_display_name, pushkey, data,
                 last_token, last_success, failing_since):
        self.hs = _hs
        self.evStreamHandler = self.hs.get_handlers().event_stream_handler
        self.store = self.hs.get_datastore()
        self.clock = self.hs.get_clock()
        self.user_name = user_name
        self.app_id = app_id
        self.app_display_name = app_display_name
        self.device_display_name = device_display_name
        self.pushkey = pushkey
        self.data = data
        self.last_token = last_token
        self.last_success = last_success  # not actually used
        self.backoff_delay = Pusher.INITIAL_BACKOFF
        self.failing_since = failing_since
        self.alive = True

    def _should_notify_for_event(self, ev):
        """
        This should take into account notification settings that the user
        has configured both globally and per-room when we have the ability
        to do such things.
        """
        if ev['user_id'] == self.user_name:
            # let's assume you probably know about messages you sent yourself
            return False
        return True

    @defer.inlineCallbacks
    def start(self):
        if not self.last_token:
            # First-time setup: get a token to start from (we can't
            # just start from no token, ie. 'now'
            # because we need the result to be reproduceable in case
            # we fail to dispatch the push)
            config = PaginationConfig(from_token=None, limit='1')
            chunk = yield self.evStreamHandler.get_stream(
                self.user_name, config, timeout=0)
            self.last_token = chunk['end']
            self.store.update_pusher_last_token(
                self.user_name, self.pushkey, self.last_token)
            logger.info("Pusher %s for user %s starting from token %s",
                        self.pushkey, self.user_name, self.last_token)

        while self.alive:
            from_tok = StreamToken.from_string(self.last_token)
            config = PaginationConfig(from_token=from_tok, limit='1')
            chunk = yield self.evStreamHandler.get_stream(
                self.user_name, config, timeout=100*365*24*60*60*1000)

            # limiting to 1 may get 1 event plus 1 presence event, so
            # pick out the actual event
            single_event = None
            for c in chunk['chunk']:
                if 'event_id' in c:  # Hmmm...
                    single_event = c
                    break
            if not single_event:
                self.last_token = chunk['end']
                continue

            if not self.alive:
                continue

            processed = False
            if self._should_notify_for_event(single_event):
                processed = yield self.dispatch_push(single_event)
            else:
                processed = True
            if processed:
                self.backoff_delay = Pusher.INITIAL_BACKOFF
                self.last_token = chunk['end']
                self.store.update_pusher_last_token_and_success(
                    self.user_name,
                    self.pushkey,
                    self.last_token,
                    self.clock.time_msec()
                )
                if self.failing_since:
                    self.failing_since = None
                    self.store.update_pusher_failing_since(
                        self.user_name,
                        self.pushkey,
                        self.failing_since)
            else:
                if not self.failing_since:
                    self.failing_since = self.clock.time_msec()
                    self.store.update_pusher_failing_since(
                        self.user_name,
                        self.pushkey,
                        self.failing_since
                    )

                if self.failing_since and \
                   self.failing_since < \
                   self.clock.time_msec() - Pusher.GIVE_UP_AFTER:
                    # we really only give up so that if the URL gets
                    # fixed, we don't suddenly deliver a load
                    # of old notifications.
                    logger.warn("Giving up on a notification to user %s, "
                                "pushkey %s",
                                self.user_name, self.pushkey)
                    self.backoff_delay = Pusher.INITIAL_BACKOFF
                    self.last_token = chunk['end']
                    self.store.update_pusher_last_token(
                        self.user_name,
                        self.pushkey,
                        self.last_token
                    )

                    self.failing_since = None
                    self.store.update_pusher_failing_since(
                        self.user_name,
                        self.pushkey,
                        self.failing_since
                    )
                else:
                    logger.warn("Failed to dispatch push for user %s "
                                "(failing for %dms)."
                                "Trying again in %dms",
                                self.user_name,
                                self.clock.time_msec() - self.failing_since,
                                self.backoff_delay
                                )
                    yield synapse.util.async.sleep(self.backoff_delay / 1000.0)
                    self.backoff_delay *= 2
                    if self.backoff_delay > Pusher.MAX_BACKOFF:
                        self.backoff_delay = Pusher.MAX_BACKOFF

    def stop(self):
        self.alive = False

    def dispatch_push(self, p):
        pass


class PusherConfigException(Exception):
    def __init__(self, msg):
        super(PusherConfigException, self).__init__(msg)