import binascii
import os
from twisted.internet.defer import Deferred, succeed

import libtorrent as lt

from Tribler.Core.DownloadConfig import DownloadStartupConfig
from Tribler.Core.Libtorrent.LibtorrentDownloadImpl import LibtorrentDownloadImpl
from Tribler.Core.TorrentDef import TorrentDef
from Tribler.Core.Utilities.configparser import CallbackConfigParser
from Tribler.Core.Utilities.torrent_utils import get_info_from_handle
from Tribler.Core.simpledefs import DLSTATUS_DOWNLOADING, DLMODE_VOD
from Tribler.Test.Core.base_test import TriblerCoreTest, MockObject
from Tribler.Test.common import TESTS_DATA_DIR
from Tribler.Test.test_as_server import TestAsServer
from Tribler.Test.twisted_thread import deferred, reactor


class TestLibtorrentDownloadImpl(TestAsServer):
    """
    This class provides unit tests that test the LibtorrentDownloadImpl class.
    """

    def setUpPreSession(self):
        super(TestLibtorrentDownloadImpl, self).setUpPreSession()
        self.config.set_torrent_checking_enabled(False)
        self.config.set_megacache_enabled(True)
        self.config.set_dispersy_enabled(False)
        self.config.set_tunnel_community_enabled(False)
        self.config.set_mainline_dht_enabled(False)
        self.config.set_torrent_collecting_enabled(False)
        self.config.set_libtorrent_enabled(True)
        self.config.set_video_server_enabled(False)

    def create_tdef(self):
        """
        create and save torrent definition used in this test file
        """
        tdef = TorrentDef()
        sourcefn = os.path.join(TESTS_DATA_DIR, 'video.avi')
        tdef.add_content(sourcefn)
        tdef.set_tracker("http://localhost/announce")
        tdef.finalize()

        torrentfn = os.path.join(self.session.config.get_state_dir(), "gen.torrent")
        tdef.save(torrentfn)

        return tdef

    @deferred(timeout=10)
    def test_can_create_engine_wrapper(self):
        impl = LibtorrentDownloadImpl(self.session, None)
        impl.cew_scheduled = False
        self.session.lm.ltmgr.is_dht_ready = lambda: True
        return impl.can_create_engine_wrapper()

    @deferred(timeout=15)
    def test_can_create_engine_wrapper_retry(self):
        impl = LibtorrentDownloadImpl(self.session, None)
        impl.cew_scheduled = True
        def set_cew_false():
            self.session.lm.ltmgr.is_dht_ready = lambda: True
            impl.cew_scheduled = False

        # Simulate Tribler changing the cew, the calllater should have fired by now
        # and before it executed the cew is false, firing the deferred.
        reactor.callLater(2, set_cew_false)
        return impl.can_create_engine_wrapper()

    def test_get_magnet_link_none(self):
        tdef = self.create_tdef()

        impl = LibtorrentDownloadImpl(self.session, tdef)
        link = impl.get_magnet_link()
        self.assertEqual(None, link, "Magnet link was not none while it should be!")

    def test_get_tdef(self):
        tdef = self.create_tdef()

        impl = LibtorrentDownloadImpl(self.session, None)
        impl.set_def(tdef)
        self.assertEqual(impl.tdef, tdef, "Torrent definitions were not equal!")

    @deferred(timeout=20)
    def test_setup(self):
        tdef = self.create_tdef()

        impl = LibtorrentDownloadImpl(self.session, tdef)

        def callback(_):
            impl.cancel_all_pending_tasks()

        deferred = impl.setup(None, None, 0)
        deferred.addCallback(callback)
        return deferred.addCallback(lambda _: impl.stop())

    def test_restart(self):
        tdef = self.create_tdef()

        impl = LibtorrentDownloadImpl(self.session, tdef)
        impl.handle = MockObject()
        impl.handle.set_priority = lambda _: None
        impl.handle.set_sequential_download = lambda _: None
        impl.handle.resume = lambda: None
        impl.handle.status = lambda: fake_status
        fake_status = MockObject()
        fake_status.share_mode = False
        # Create a dummy download config
        impl.dlconfig = DownloadStartupConfig().dlconfig.copy()
        impl.session.lm.on_download_wrapper_created = lambda _: True
        impl.restart()

    @deferred(timeout=20)
    def test_restart_no_handle(self):
        test_deferred = Deferred()
        tdef = self.create_tdef()
        impl = LibtorrentDownloadImpl(self.session, tdef)
        impl.session.lm.on_download_handle_created = lambda _: test_deferred.callback(None)
        impl.restart()
        return test_deferred

    @deferred(timeout=20)
    def test_multifile_torrent(self):
        tdef = TorrentDef()

        dn = os.path.join(TESTS_DATA_DIR, "contentdir")
        tdef.add_content(dn, "dirintorrent")

        fn = os.path.join(TESTS_DATA_DIR, "video.avi")
        tdef.add_content(fn, os.path.join("dirintorrent", "video.avi"))

        tdef.set_tracker("http://tribler.org/announce")
        tdef.finalize()

        impl = LibtorrentDownloadImpl(self.session, tdef)
        # Override the add_torrent because it will be called
        impl.ltmgr = MockObject()
        impl.ltmgr.add_torrent = lambda _, _dummy2: succeed(fake_handler)
        impl.set_selected_files = lambda: None
        fake_handler = MockObject()
        fake_handler.is_valid = lambda: True
        fake_handler.status = lambda: fake_status
        fake_handler.set_share_mode = lambda _: None
        fake_handler.set_priority = lambda _: None
        fake_handler.set_sequential_download = lambda _: None
        fake_handler.resume = lambda: None
        fake_handler.set_max_connections = lambda _: None
        fake_status = MockObject()
        fake_status.share_mode = False
        # Create a dummy download config
        impl.dlconfig = DownloadStartupConfig().dlconfig.copy()
        # Create a dummy pstate
        pstate = CallbackConfigParser()
        pstate.add_section("state")
        test_dict = dict()
        test_dict["a"] = "b"
        pstate.set("state", "engineresumedata", test_dict)
        return impl.network_create_engine_wrapper(pstate)

    @deferred(timeout=10)
    def test_save_resume(self):
        """
        testing call resume data alert
        """
        tdef = self.create_tdef()

        impl = LibtorrentDownloadImpl(self.session, tdef)

        def resume_ready(_):
            """
            check if resume data is ready
            """
            basename = binascii.hexlify(tdef.get_infohash()) + '.state'
            filename = os.path.join(self.session.get_downloads_pstate_dir(), basename)

            engine_data = CallbackConfigParser()
            engine_data.read_file(filename)

            self.assertEqual(tdef.get_infohash(), engine_data.get('state', 'engineresumedata').get('info-hash'))

        def callback(_):
            """
            callback after finishing setup in LibtorrentDownloadImpl
            """
            defer_alert = impl.save_resume_data()
            defer_alert.addCallback(resume_ready)
            return defer_alert

        result_deferred = impl.setup(None, None, 0)
        result_deferred.addCallback(callback)

        return result_deferred.addCallback(lambda _: impl.stop())

    @deferred(timeout=10)
    def test_save_resume_disabled(self):
        """
        testing call resume data alert, if checkpointing is disabled
        """
        tdef = self.create_tdef()

        impl = LibtorrentDownloadImpl(self.session, tdef)

        def callback(_):
            """
            callback after finishing setup in LibtorrentDownloadImpl
            """
            basename = binascii.hexlify(tdef.get_infohash()) + '.state'
            filename = os.path.join(self.session.get_downloads_pstate_dir(), basename)

            self.assertFalse(os.path.isfile(filename))

        # This should not cause a checkpoint
        result_deferred = impl.setup(None, None, 0, checkpoint_disabled=True)
        result_deferred.addCallback(callback)

        # This shouldn't either
        impl.checkpoint()
        callback(None)

        return result_deferred.addCallback(lambda _: impl.stop())


class TestLibtorrentDownloadImplNoSession(TriblerCoreTest):

    def setUp(self, annotate=True):
        TriblerCoreTest.setUp(self, annotate=annotate)
        self.libtorrent_download_impl = LibtorrentDownloadImpl(None, None)
        mock_handle = MockObject()
        mock_status = MockObject()
        mock_status.pieces = [True, False, True, True, False]
        torrent_info = MockObject()
        file_info = MockObject()
        file_info.size = 1234
        torrent_info.file_at = lambda _: file_info
        map_file_result = MockObject()
        map_file_result.piece = 123
        torrent_info.map_file = lambda _dummy1, _dummy2, _dummy3: map_file_result
        torrent_info.num_pieces = lambda: 5

        mock_handle.is_valid = lambda: True
        mock_handle.status = lambda: mock_status
        mock_handle.get_torrent_info = lambda: torrent_info
        mock_handle.set_sequential_download = lambda _: None
        mock_handle.set_priority = lambda _: None
        mock_handle.prioritize_pieces = lambda _: None

        self.libtorrent_download_impl.handle = mock_handle

        # Create a fake tdef
        self.libtorrent_download_impl.tdef = MockObject()
        self.libtorrent_download_impl.tdef.get_name = lambda: "ubuntu.iso"
        self.libtorrent_download_impl.tdef.is_multifile_torrent = lambda: False

    def tearDown(self, annotate=True):
        self.libtorrent_download_impl.shutdown_task_manager()
        super(TestLibtorrentDownloadImplNoSession, self).tearDown(annotate=annotate)

    def test_selected_files(self):
        """
        Test whether the selected files are set correctly
        """
        def mocked_set_file_prios(_):
            mocked_set_file_prios.called = True

        mocked_set_file_prios.called = False

        mocked_file = MockObject()
        mocked_file.path = 'my/path'
        mock_torrent_info = MockObject()
        mock_torrent_info.files = lambda: [mocked_file, mocked_file]
        self.libtorrent_download_impl.handle.prioritize_files = mocked_set_file_prios
        self.libtorrent_download_impl.handle.get_torrent_info = lambda: mock_torrent_info
        self.libtorrent_download_impl.handle.rename_file = lambda *_: None

        self.libtorrent_download_impl.get_share_mode = lambda: False
        self.libtorrent_download_impl.tdef.get_infohash = lambda: 'a' * 20
        self.libtorrent_download_impl.orig_files = ['a', 'b']
        self.libtorrent_download_impl.get_save_path = lambda: 'my/path'
        self.libtorrent_download_impl.set_selected_files(['a'])
        self.assertTrue(mocked_set_file_prios.called)

        self.libtorrent_download_impl.get_share_mode = lambda: False
        mocked_set_file_prios.called = False
        self.assertFalse(mocked_set_file_prios.called)

    def test_get_share_mode(self):
        """
        Test whether we return the right share mode when requested in the LibtorrentDownloadImpl
        """
        self.libtorrent_download_impl.handle.status().share_mode = False
        self.assertFalse(self.libtorrent_download_impl.get_share_mode())
        self.libtorrent_download_impl.handle.status().share_mode = True
        self.assertTrue(self.libtorrent_download_impl.get_share_mode())

    def test_set_share_mode(self):
        """
        Test whether we set the right share mode in LibtorrentDownloadImpl
        """
        def mocked_set_share_mode(val):
            self.assertTrue(val)
            mocked_set_share_mode.called = True

        mocked_set_share_mode.called = False
        self.libtorrent_download_impl.handle.set_share_mode = mocked_set_share_mode

        self.libtorrent_download_impl.set_share_mode(True)
        self.assertTrue(mocked_set_share_mode.called)

    def test_set_priority(self):
        """
        Test whether setting the priority calls the right methods in LibtorrentDownloadImpl
        """
        def mocked_set_priority(prio):
            self.assertEqual(prio, 1234)
            mocked_set_priority.called = True

        mocked_set_priority.called = False
        self.libtorrent_download_impl.handle.set_priority = mocked_set_priority

        self.libtorrent_download_impl.set_priority(1234)
        self.assertTrue(mocked_set_priority.called)

    def test_dlconfig_cb_change(self):
        """
        Testing whether changing the configuration on runtime calls the right methods in LibtorrentDownloadImpl
        """
        def mocked_set_upload_limit(prio):
            self.assertEqual(prio, 3 * 1024)
            mocked_set_upload_limit.called = True

        mocked_set_upload_limit.called = False
        self.libtorrent_download_impl.handle.set_upload_limit = mocked_set_upload_limit

        def mocked_set_download_limit(prio):
            self.assertEqual(prio, 3 * 1024)
            mocked_set_download_limit.called = True

        mocked_set_download_limit.called = False
        self.libtorrent_download_impl.handle.set_download_limit = mocked_set_download_limit

        self.libtorrent_download_impl.dlconfig_changed_callback('libtorrent', 'max_upload_rate', 3, 4)
        self.assertTrue(mocked_set_upload_limit)
        self.libtorrent_download_impl.dlconfig_changed_callback('libtorrent', 'max_download_rate', 3, 4)
        self.assertTrue(mocked_set_download_limit)
        self.assertFalse(self.libtorrent_download_impl.dlconfig_changed_callback(
            'download_defaults', 'super_seeder', 3, 4))

    def test_add_trackers(self):
        """
        Testing whether trackers are added to the libtorrent handler in LibtorrentDownloadImpl
        """
        def mocked_add_trackers(tracker_info):
            self.assertIsInstance(tracker_info, dict)
            self.assertEqual(tracker_info['url'], 'http://google.com')
            mocked_add_trackers.called = True

        mocked_add_trackers.called = False
        self.libtorrent_download_impl.handle.add_tracker = mocked_add_trackers
        self.libtorrent_download_impl.add_trackers(['http://google.com'])
        self.assertTrue(mocked_add_trackers.called)

    def test_process_error_alert(self):
        """
        Testing whether error alerts are processed correctly
        """
        url = "http://google.com"
        mock_alert = MockObject()
        mock_alert.msg = None
        mock_alert.category = lambda: lt.alert.category_t.error_notification
        mock_alert.status_code = 123
        mock_alert.url = url
        self.libtorrent_download_impl.process_alert(mock_alert, 'tracker_error_alert')
        self.assertEqual(self.libtorrent_download_impl.tracker_status[url][1], 'HTTP status code 123')

        mock_alert.status_code = 0
        self.libtorrent_download_impl.process_alert(mock_alert, 'tracker_error_alert')
        self.assertEqual(self.libtorrent_download_impl.tracker_status[url][1], 'Timeout')

    def test_tracker_warning_alert(self):
        """
        Test whether a tracking warning alert is processed correctly
        """
        url = "http://google.com"
        mock_alert = MockObject()
        mock_alert.category = lambda: lt.alert.category_t.error_notification
        mock_alert.url = url
        mock_alert.message = lambda: 'test'
        self.libtorrent_download_impl.process_alert(mock_alert, 'tracker_warning_alert')
        self.assertEqual(self.libtorrent_download_impl.tracker_status[url][1], 'Warning: test')

    @deferred(timeout=10)
    def test_on_metadata_received_alert(self):
        """
        Testing whether the right operations happen when we receive metadata
        """
        test_deferred = Deferred()

        def mocked_checkpoint():
            test_deferred.callback(None)

        mocked_file = MockObject()
        mocked_file.path = 'test'

        self.libtorrent_download_impl.handle.trackers = lambda: []
        self.libtorrent_download_impl.handle.save_resume_data = lambda: None
        torrent_dict = {'name': 'test', 'piece length': 42, 'pieces': '', 'files': []}
        get_info_from_handle(self.libtorrent_download_impl.handle).metadata = lambda: lt.bencode(torrent_dict)
        get_info_from_handle(self.libtorrent_download_impl.handle).files = lambda: [mocked_file]

        self.libtorrent_download_impl.checkpoint = mocked_checkpoint
        self.libtorrent_download_impl.session = MockObject()
        self.libtorrent_download_impl.session.lm = MockObject()
        self.libtorrent_download_impl.session.lm.rtorrent_handler = None
        self.libtorrent_download_impl.session.lm.torrent_db = None
        self.libtorrent_download_impl.handle.save_path = lambda: None
        self.libtorrent_download_impl.handle.prioritize_files = lambda _: None
        self.libtorrent_download_impl.get_save_path = lambda: ''
        self.libtorrent_download_impl.get_share_mode = lambda: False
        self.libtorrent_download_impl.on_metadata_received_alert(None)

        return test_deferred

    def test_metadata_received_invalid_info(self):
        """
        Testing whether the right operations happen when we receive metadata but the torrent info is invalid
        """
        def mocked_checkpoint():
            raise RuntimeError("This code should not be reached!")

        self.libtorrent_download_impl.checkpoint = mocked_checkpoint
        self.libtorrent_download_impl.handle.get_torrent_info = lambda: None
        self.libtorrent_download_impl.on_metadata_received_alert(None)


    def test_metadata_received_invalid_torrent_with_value_error(self):
        """
        Testing whether the right operations happen when we receive metadata but the torrent info is invalid and throws
        Value Error
        """
        def mocked_checkpoint():
            raise RuntimeError("This code should not be reached!")

        mocked_file = MockObject()
        mocked_file.path = 'test'

        # The line below should trigger Value Error
        self.libtorrent_download_impl.handle.trackers = lambda: [{'url': 'no-DHT'}]

        torrent_dict = {'name': 'test', 'piece length': 42, 'pieces': '', 'files': []}
        get_info_from_handle(self.libtorrent_download_impl.handle).metadata = lambda: lt.bencode(torrent_dict)
        get_info_from_handle(self.libtorrent_download_impl.handle).files = lambda: [mocked_file]

        self.libtorrent_download_impl.checkpoint = mocked_checkpoint
        self.libtorrent_download_impl.on_metadata_received_alert(None)

    def test_torrent_checked_alert(self):
        """
        Testing whether the right operations happen after a torrent checked alert is received
        """
        def mocked_pause_checkpoint():
            mocked_pause_checkpoint.called = True

        mocked_pause_checkpoint.called = False
        self.libtorrent_download_impl.handle.pause = mocked_pause_checkpoint
        self.libtorrent_download_impl.checkpoint = mocked_pause_checkpoint

        mock_alert = MockObject()
        mock_alert.category = lambda: lt.alert.category_t.error_notification
        self.libtorrent_download_impl.pause_after_next_hashcheck = True
        self.libtorrent_download_impl.process_alert(mock_alert, 'torrent_checked_alert')
        self.assertFalse(self.libtorrent_download_impl.pause_after_next_hashcheck)
        self.assertTrue(mocked_pause_checkpoint.called)

        mocked_pause_checkpoint.called = False
        self.libtorrent_download_impl.checkpoint_after_next_hashcheck = True
        self.libtorrent_download_impl.process_alert(mock_alert, 'torrent_checked_alert')
        self.assertFalse(self.libtorrent_download_impl.checkpoint_after_next_hashcheck)
        self.assertTrue(mocked_pause_checkpoint.called)

    def test_get_dest_files(self):
        """
        Testing whether the right list of files is returned when fetching files from a download
        """
        self.libtorrent_download_impl.handle.file_priority = lambda _: 123
        mocked_file = MockObject()
        mocked_file.path = 'test'
        mock_torrent_info = MockObject()
        mock_torrent_info.files = lambda: [mocked_file]
        self.libtorrent_download_impl.handle.get_torrent_info = lambda: mock_torrent_info
        dest_files = self.libtorrent_download_impl.get_dest_files()
        self.assertIsInstance(dest_files[0], tuple)
        self.assertEqual(dest_files[0][0], 'test')

    def test_get_vod_fileindex(self):
        """
        Testing whether the right vod file index is returned in LibtorrentDownloadImpl
        """
        self.libtorrent_download_impl.vod_index = None
        self.assertEqual(self.libtorrent_download_impl.get_vod_fileindex(), -1)
        self.libtorrent_download_impl.vod_index = 42
        self.assertEqual(self.libtorrent_download_impl.get_vod_fileindex(), 42)

    def test_get_vod_filesize(self):
        """
        Testing whether the right vod file size is returned in LibtorrentDownloadImpl
        """
        mock_file_entry = MockObject()
        mock_file_entry.size = 42
        mock_torrent_info = MockObject()
        mock_torrent_info.file_at = lambda _: mock_file_entry
        self.libtorrent_download_impl.handle.get_torrent_info = lambda: mock_torrent_info

        self.libtorrent_download_impl.vod_index = None
        self.assertEqual(self.libtorrent_download_impl.get_vod_filesize(), 0)
        self.libtorrent_download_impl.vod_index = 42
        self.assertEqual(self.libtorrent_download_impl.get_vod_filesize(), 42)

    def test_get_piece_progress(self):
        """
        Testing whether the right piece progress is returned in LibtorrentDownloadImpl
        """
        self.assertEqual(self.libtorrent_download_impl.get_piece_progress(None), 1.0)

        self.libtorrent_download_impl.handle.status().pieces = [True, False]
        self.assertEqual(self.libtorrent_download_impl.get_piece_progress([0, 1], True), 0.5)

        self.libtorrent_download_impl.handle.status = lambda: None
        self.assertEqual(self.libtorrent_download_impl.get_piece_progress([3, 1]), 0.0)

    def test_get_byte_progress(self):
        """
        Testing whether the right byte progress is returned in LibtorrentDownloadImpl
        """
        self.assertEqual(self.libtorrent_download_impl.get_byte_progress([(-1, 0, 0)], False), 1.0)

        # Scenario: we have a file with 4 pieces, 250 bytes in each piece.
        def map_file(_dummy1, start_byte, _dummy2):
            res = MockObject()
            res.piece = int(start_byte / 250)
            return res

        self.libtorrent_download_impl.handle.get_torrent_info().num_pieces = lambda: 4
        self.libtorrent_download_impl.handle.get_torrent_info().map_file = map_file
        self.assertEqual(self.libtorrent_download_impl.get_byte_progress([(0, 10, 270)], True), 0.5)

    def test_setup_exception(self):
        """
        Testing whether an exception in the setup method of LibtorrentDownloadImpl is handled correctly
        """
        self.libtorrent_download_impl.setup()
        self.assertIsInstance(self.libtorrent_download_impl.error, Exception)

    def test_tracker_reply_alert(self):
        """
        Testing the tracker reply alert in LibtorrentDownloadImpl
        """
        mock_alert = MockObject()
        mock_alert.url = 'http://google.com'
        mock_alert.num_peers = 42
        self.libtorrent_download_impl.on_tracker_reply_alert(mock_alert)
        self.assertEqual(self.libtorrent_download_impl.tracker_status['http://google.com'], [42, 'Working'])

    def test_stop(self):
        """
        Testing whether the stop method in LibtorrentDownloadImpl invokes the correct method
        """
        def mocked_stop_remove(removestate, removecontent):
            self.assertFalse(removestate)
            self.assertFalse(removecontent)
            mocked_stop_remove.called = True

        mocked_stop_remove.called = False
        self.libtorrent_download_impl.stop_remove = mocked_stop_remove
        self.libtorrent_download_impl.stop()
        self.assertTrue(mocked_stop_remove.called)

    def test_download_finish_alert(self):
        """
        Testing whether the right operations are performed when we get a torrent finished alert
        """
        status = self.libtorrent_download_impl.handle.status()
        status.paused = False
        status.state = DLSTATUS_DOWNLOADING
        status.progress = 0.9
        status.error = None
        status.total_wanted = 33
        status.download_payload_rate = 928
        status.upload_payload_rate = 928
        status.all_time_upload = 42
        status.all_time_download = 43
        status.finished_time = 1234

        # Scenario: we have a file with 4 pieces, 250 bytes in each piece.
        def map_file(_dummy1, start_byte, _dummy2):
            res = MockObject()
            res.piece = int(start_byte / 250)
            return res

        self.libtorrent_download_impl.handle.get_torrent_info().num_pieces = lambda: 4
        self.libtorrent_download_impl.handle.get_torrent_info().map_file = map_file
        self.libtorrent_download_impl.handle.piece_priorities = lambda: [0, 0, 0, 0]

        self.libtorrent_download_impl.set_vod_mode(True)
        self.libtorrent_download_impl.set_mode(DLMODE_VOD)
        self.libtorrent_download_impl.on_torrent_finished_alert(None)

        has_priorities_task = False
        for task_name in self.libtorrent_download_impl._pending_tasks.iterkeys():
            if 'reset_priorities' in task_name:
                has_priorities_task = True
        self.assertTrue(has_priorities_task)

    def test_get_pieces_bitmask(self):
        """
        Testing whether a correct pieces bitmask is returned when requested
        """
        self.libtorrent_download_impl.handle.status().pieces = [True, False, True, False, False]
        self.assertEqual(self.libtorrent_download_impl.get_pieces_base64(), "oA==")

        self.libtorrent_download_impl.handle.status().pieces = [True * 16]
        self.assertEqual(self.libtorrent_download_impl.get_pieces_base64(), "gA==")

    @deferred(timeout=10)
    def test_resume_data_failed(self):
        """
        Testing whether the correct operations happen when an error is raised during resume data saving
        """
        test_deferred = Deferred()

        def on_error(_):
            test_deferred.callback(None)

        mock_alert = MockObject()
        mock_alert.msg = "test error"

        self.libtorrent_download_impl.deferreds_resume.append(Deferred().addErrback(
            self.libtorrent_download_impl._on_resume_err).addCallback(on_error))
        self.libtorrent_download_impl.on_save_resume_data_failed_alert(mock_alert)
        return test_deferred
