mygpo/users/sync.py

   1 from collections import namedtuple
   2
   3 from couchdbkit.ext.django.schema import *
   4
   5 from mygpo.core.models import Podcast, SubscriptionException
   6
   7 import logging
   8 logger = logging.getLogger(__name__)
   9
  10
  11 GroupedDevices = namedtuple('GroupedDevices', 'is_synced devices')
  12
  13
  14
  15 class SyncedDevicesMixin(DocumentSchema):
  16     """ Contains the device-syncing functionality of a user """
  17
  18     sync_groups = ListProperty()
  19
  20
  21     def get_grouped_devices(self):
  22         """ Returns groups of synced devices and a unsynced group """
  23
  24         indexed_devices = dict( (dev.id, dev) for dev in self.active_devices )
  25
  26         for group in self.sync_groups:
  27
  28             devices = [indexed_devices.pop(device_id, None) for device_id in group]
  29             devices = filter(None, devices)
  30             if not devices:
  31                 continue
  32
  33             yield GroupedDevices(
  34                     True,
  35                     devices
  36                 )
  37
  38         # un-synced devices
  39         yield GroupedDevices(
  40                 False,
  41                 indexed_devices.values()
  42             )
  43
  44
  45     def sync_devices(self, device1, device2):
  46         """ Puts two devices in a common sync group"""
  47
  48         devices = set([device1, device2])
  49         if not devices.issubset(set(self.devices)):
  50             raise ValueError('the devices do not belong to the user')
  51
  52         sg1 = self.get_device_sync_group(device1)
  53         sg2 = self.get_device_sync_group(device2)
  54
  55         if sg1 is not None and sg2 is not None:
  56             # merge sync_groups
  57             self.sync_groups[sg1].extend(self.sync_groups[sg2])
  58             self.sync_groups.pop(sg2)
  59
  60         elif sg1 is None and sg2 is None:
  61             self.sync_groups.append([device1.id, device2.id])
  62
  63         elif sg1 is not None:
  64             self.sync_groups[sg1].append(device2.id)
  65
  66         elif sg2 is not None:
  67             self.sync_groups[sg2].append(device1.id)
  68
  69
  70     def unsync_device(self, device):
  71         """ Removts the device from its sync-group
  72
  73         Raises a ValueError if the device is not synced """
  74
  75         sg = self.get_device_sync_group(device)
  76
  77         if sg is None:
  78             raise ValueError('the device is not synced')
  79
  80         group = self.sync_groups[sg]
  81
  82         if len(group) <= 2:
  83             self.sync_groups.pop(sg)
  84
  85         else:
  86             group.remove(device.id)
  87
  88
  89     def get_device_sync_group(self, device):
  90         """ Returns the sync-group Id of the device """
  91
  92         for n, group in enumerate(self.sync_groups):
  93             if device.id in group:
  94                 return n
  95
  96
  97     def is_synced(self, device):
  98         return self.get_device_sync_group(device) is not None
  99
 100
 101     def get_synced(self, device):
 102         """ Returns the devices that are synced with the given one """
 103
 104         sg = self.get_device_sync_group(device)
 105
 106         if sg is None:
 107             return []
 108
 109         devices = self.get_devices_in_group(sg)
 110         devices.remove(device)
 111         return devices
 112
 113
 114
 115     def get_sync_targets(self, device):
 116         """ Returns the devices and groups with which the device can be synced
 117
 118         Groups are represented as lists of devices """
 119
 120         sg = self.get_device_sync_group(device)
 121
 122         for n, group in enumerate(self.get_grouped_devices()):
 123
 124             if sg == n:
 125                 # the device's group can't be a sync-target
 126                 continue
 127
 128             elif group.is_synced:
 129                 yield group.devices
 130
 131             else:
 132                 # every unsynced device is a sync-target
 133                 for dev in group.devices:
 134                     if not dev == device:
 135                         yield dev
 136
 137
 138     def get_devices_in_group(self, sg):
 139         """ Returns the devices in the group with the given Id """
 140
 141         ids = self.sync_groups[sg]
 142         return map(self.get_device, ids)
 143
 144
 145     def sync_group(self, device):
 146         """ Sync the group of the device """
 147
 148         group_index = self.get_device_sync_group(device)
 149
 150         if group_index is None:
 151             return
 152
 153         group_state = self.get_group_state(group_index)
 154
 155         for device in self.get_devices_in_group(group_index):
 156             sync_actions = self.get_sync_actions(device, group_state)
 157             self.apply_sync_actions(device, sync_actions)
 158
 159
 160     def apply_sync_actions(self, device, sync_actions):
 161         """ Applies the sync-actions to the device """
 162
 163         from mygpo.db.couchdb.podcast_state import subscribe, unsubscribe
 164         add, rem = sync_actions
 165
 166         podcasts = Podcast.objects.filter(id__in=(add+rem))
 167         podcasts = {podcast.id: podcast for podcast in podcasts}
 168
 169         for podcast_id in add:
 170             podcast = podcasts.get(podcast_id, None)
 171             if podcast is None:
 172                 continue
 173             try:
 174                 subscribe(podcast, self, device)
 175             except SubscriptionException as e:
 176                 logger.warn('Web: %(username)s: cannot sync device: %(error)s' %
 177                     dict(username=self.username, error=repr(e)))
 178
 179         for podcast_id in rem:
 180             podcast = podcasts.get(podcast_id, None)
 181             if not podcast:
 182                 continue
 183
 184             try:
 185                 unsubscribe(podcast, self, device)
 186             except SubscriptionException as e:
 187                 logger.warn('Web: %(username)s: cannot sync device: %(error)s' %
 188                     dict(username=self.username, error=repr(e)))
 189
 190
 191     def get_group_state(self, group_index):
 192         """ Returns the group's subscription state
 193
 194         The state is represented by the latest actions for each podcast """
 195
 196         device_ids = self.sync_groups[group_index]
 197         devices = self.get_devices(device_ids)
 198
 199         state = {}
 200
 201         for d in devices:
 202             actions = dict(d.get_latest_changes())
 203             for podcast_id, action in actions.items():
 204                 if not podcast_id in state or \
 205                         action.timestamp > state[podcast_id].timestamp:
 206                     state[podcast_id] = action
 207
 208         return state
 209
 210
 211     def get_sync_actions(self, device, group_state):
 212         """ Get the actions required to bring the device to the group's state
 213
 214         After applying the actions the device reflects the group's state """
 215
 216         sg = self.get_device_sync_group(device)
 217         if sg is None:
 218             return [], []
 219
 220         # Filter those that describe actual changes to the current state
 221         add, rem = [], []
 222         current_state = dict(device.get_latest_changes())
 223
 224         for podcast_id, action in group_state.items():
 225
 226             # Sync-Actions must be newer than current state
 227             if podcast_id in current_state and \
 228                action.timestamp <= current_state[podcast_id].timestamp:
 229                 continue
 230
 231             # subscribe only what hasn't been subscribed before
 232             if action.action == 'subscribe' and \
 233                         (podcast_id not in current_state or \
 234                          current_state[podcast_id].action == 'unsubscribe'):
 235                 add.append(podcast_id)
 236
 237             # unsubscribe only what has been subscribed before
 238             elif action.action == 'unsubscribe' and \
 239                         podcast_id in current_state and \
 240                         current_state[podcast_id].action == 'subscribe':
 241                 rem.append(podcast_id)
 242
 243         return add, rem