def change_playlist(self, playlist_id, desired_playlist, safe=True):
"""Changes the order and contents of an existing playlist. Returns the id of the playlist when finished - which may not be the argument, in the case of a failure and recovery.
:param playlist_id: the id of the playlist being modified.
:param desired_playlist: the desired contents and order as a list of song dictionaries, like is returned from :func:`get_playlist_songs`.
:param safe: if True, ensure playlists will not be lost if a problem occurs. This may slow down updates.
The server only provides 3 basic (atomic) playlist mutations: addition, deletion, and reordering. This function will automagically use these to apply a list representation of the desired changes.
However, this might involve multiple calls to the server, and if a call fails, the playlist will be left in an inconsistent state. The `safe` option makes a backup of the playlist before doing anything, so it can be rolled back if a problem occurs. This is enabled by default. Note that this might slow down updates of very large playlists.
There will always be a warning logged if a problem occurs, even if `safe` is False.
"""
#We'll be modifying the entries in the playlist, and need to copy it.
#Copying ensures two things:
# 1. the user won't see our changes
# 2. changing a key for one entry won't change it for another - which would be the case
# if the user appended the same song twice, for example.
desired_playlist = [copy.deepcopy(t) for t in desired_playlist]
server_tracks = self.get_playlist_songs(playlist_id)
if safe: #make the backup.
#The backup is stored on the server as a new playlist with "_gmusicapi_backup" appended to the backed up name.
#We can't just store the backup here, since when rolling back we'd be relying on this function - and it just failed.
names_to_ids = self.get_all_playlist_ids(always_id_lists=True)['user']
playlist_name = (ni_pair[0]
for ni_pair in names_to_ids.iteritems()
if playlist_id in ni_pair[1]).next()
backup_id = self.copy_playlist(playlist_id, playlist_name + "_gmusicapi_backup")
#Ensure CallFailures do not get suppressed in our subcalls.
#Did not unsuppress the above copy_playlist call, since we should fail
# out if we can't ensure the backup was made.
with self._unsuppress_failures():
try:
#Counter, Counter, and set of id pairs to delete, add, and keep.
to_del, to_add, to_keep = tools.find_playlist_changes(server_tracks, desired_playlist)
##Delete unwanted entries.
to_del_eids = [pair[1] for pair in to_del.elements()]
if to_del_eids: self._remove_entries_from_playlist(playlist_id, to_del_eids)
##Add new entries.
to_add_sids = [pair[0] for pair in to_add.elements()]
if to_add_sids:
new_pairs = self.add_songs_to_playlist(playlist_id, to_add_sids)
##Update desired tracks with added tracks server-given eids.
#Map new sid -> [eids]
new_sid_to_eids = {}
for sid, eid in new_pairs:
if not sid in new_sid_to_eids:
new_sid_to_eids[sid] = []
new_sid_to_eids[sid].append(eid)
for d_t in desired_playlist:
if d_t["id"] in new_sid_to_eids:
#Found a matching sid.
match = d_t
sid = match["id"]
eid = match.get("playlistEntryId")
pair = (sid, eid)
if pair in to_keep:
to_keep.remove(pair) #only keep one of the to_keep eids.
else:
match["playlistEntryId"] = new_sid_to_eids[sid].pop()
if len(new_sid_to_eids[sid]) == 0:
del new_sid_to_eids[sid]
##Now, the right eids are in the playlist.
##Set the order of the tracks:
#The web client has no way to dictate the order without block insertion,
# but the api actually supports setting the order to a given list.
#For whatever reason, though, it needs to be set backwards; might be
# able to get around this by messing with afterEntry and beforeEntry parameters.
sids, eids = zip(*tools.get_id_pairs(desired_playlist[::-1]))
if sids: self._wc_call("changeplaylistorder", playlist_id, sids, eids)
##Clean up the backup.
if safe: self.delete_playlist(backup_id)
except CallFailure:
self.log.warning("a subcall of change_playlist failed - playlist %s is in an inconsistent state", playlist_id)
if not safe: raise #there's nothing we can do
else: #try to revert to the backup
self.log.warning("attempting to revert changes from playlist '%s_gmusicapi_backup'", playlist_name)
try:
self.delete_playlist(playlist_id)
self.change_playlist_name(backup_id, playlist_name)
except CallFailure:
self.log.error("failed to revert changes.")
raise
else:
self.log.warning("reverted changes safely; playlist id of '%s' is now '%s'", playlist_name, backup_id)
playlist_id = backup_id
return playlist_id
def change_playlist(self, playlist_id, desired_playlist, safe=True):
"""Changes the order and contents of an existing playlist.
Returns the id of the playlist when finished -
this may be the same as the argument in the case of a failure and recovery.
:param playlist_id: the id of the playlist being modified.
:param desired_playlist: the desired contents and order as a list of
:ref:`song dictionaries <songdict-format>`, like is returned
from :func:`get_playlist_songs`.
:param safe: if ``True``, ensure playlists will not be lost if a problem occurs.
This may slow down updates.
The server only provides 3 basic playlist mutations: addition, deletion, and reordering.
This function will use these to automagically apply the desired changes.
However, this might involve multiple calls to the server, and if a call fails,
the playlist will be left in an inconsistent state.
The ``safe`` option makes a backup of the playlist before doing anything, so it can be
rolled back if a problem occurs. This is enabled by default.
This might slow down updates of very large playlists.
There will always be a warning logged if a problem occurs, even if ``safe`` is ``False``.
"""
#We'll be modifying the entries in the playlist, and need to copy it.
#Copying ensures two things:
# 1. the user won't see our changes
# 2. changing a key for one entry won't change it for another - which would be the case
# if the user appended the same song twice, for example.
desired_playlist = [copy.deepcopy(t) for t in desired_playlist]
server_tracks = self.get_playlist_songs(playlist_id)
if safe:
#Make a backup.
#The backup is stored on the server as a new playlist with "_gmusicapi_backup"
# appended to the backed up name.
names_to_ids = self.get_all_playlist_ids()['user']
playlist_name = (ni_pair[0]
for ni_pair in names_to_ids.iteritems()
if playlist_id in ni_pair[1]).next()
backup_id = self.copy_playlist(playlist_id, playlist_name + u"_gmusicapi_backup")
try:
#Counter, Counter, and set of id pairs to delete, add, and keep.
to_del, to_add, to_keep = \
tools.find_playlist_changes(server_tracks, desired_playlist)
##Delete unwanted entries.
to_del_eids = [pair[1] for pair in to_del.elements()]
if to_del_eids:
self._remove_entries_from_playlist(playlist_id, to_del_eids)
##Add new entries.
to_add_sids = [pair[0] for pair in to_add.elements()]
if to_add_sids:
new_pairs = self.add_songs_to_playlist(playlist_id, to_add_sids)
##Update desired tracks with added tracks server-given eids.
#Map new sid -> [eids]
new_sid_to_eids = {}
for sid, eid in new_pairs:
if not sid in new_sid_to_eids:
new_sid_to_eids[sid] = []
new_sid_to_eids[sid].append(eid)
for d_t in desired_playlist:
if d_t["id"] in new_sid_to_eids:
#Found a matching sid.
match = d_t
sid = match["id"]
eid = match.get("playlistEntryId")
pair = (sid, eid)
if pair in to_keep:
to_keep.remove(pair) # only keep one of the to_keep eids.
else:
match["playlistEntryId"] = new_sid_to_eids[sid].pop()
if len(new_sid_to_eids[sid]) == 0:
del new_sid_to_eids[sid]
##Now, the right eids are in the playlist.
##Set the order of the tracks:
#The web client has no way to dictate the order without block insertion,
# but the api actually supports setting the order to a given list.
#For whatever reason, though, it needs to be set backwards; might be
# able to get around this by messing with afterEntry and beforeEntry parameters.
if desired_playlist:
#can't *-unpack an empty list
sids, eids = zip(*tools.get_id_pairs(desired_playlist[::-1]))
if sids:
self._make_call(webclient.ChangePlaylistOrder, playlist_id, sids, eids)
##Clean up the backup.
if safe:
self.delete_playlist(backup_id)
except CallFailure:
self.logger.info("a subcall of change_playlist failed - "
"playlist %s is in an inconsistent state", playlist_id)
if not safe:
raise # there's nothing we can do
else: # try to revert to the backup
self.logger.info("attempting to revert changes from playlist "
"'%s_gmusicapi_backup'", playlist_name)
try:
self.delete_playlist(playlist_id)
self.change_playlist_name(backup_id, playlist_name)
except CallFailure:
self.logger.warning("failed to revert failed change_playlist call on '%s'",
playlist_name)
raise
else:
self.logger.info("reverted changes safely; playlist id of '%s' is now '%s'",
playlist_name, backup_id)
playlist_id = backup_id
return playlist_id