# -*- coding: utf-8 -*-
#
# Picard, the next-generation MusicBrainz tagger
#
# Copyright (C) 2004 Robert Kaye
# Copyright (C) 2006-2009, 2011-2012, 2014 Lukáš Lalinský
# Copyright (C) 2008 Gary van der Merwe
# Copyright (C) 2008 Hendrik van Antwerpen
# Copyright (C) 2008 ojnkpjg
# Copyright (C) 2008-2011, 2014, 2018-2022 Philipp Wolfer
# Copyright (C) 2009 Nikolai Prokoschenko
# Copyright (C) 2011-2012 Chad Wilson
# Copyright (C) 2011-2013, 2019 Michael Wiencek
# Copyright (C) 2012-2013, 2016-2017 Wieland Hoffmann
# Copyright (C) 2013, 2018 Calvin Walton
# Copyright (C) 2013-2015, 2017 Sophist-UK
# Copyright (C) 2013-2015, 2017-2022 Laurent Monin
# Copyright (C) 2016 Suhas
# Copyright (C) 2016-2018 Sambhav Kothari
# Copyright (C) 2017 Antonio Larrosa
# Copyright (C) 2018 Vishal Choudhary
# Copyright (C) 2019 Joel Lintunen
# Copyright (C) 2020-2021 Gabriel Ferreira
# Copyright (C) 2021 Petit Minion
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.


from collections import (
    OrderedDict,
    defaultdict,
    namedtuple,
)
from enum import IntEnum
import traceback

from PyQt5 import (
    QtCore,
    QtNetwork,
)

from picard import log
from picard.cluster import Cluster
from picard.collection import add_release_to_user_collections
from picard.config import get_config
from picard.const import VARIOUS_ARTISTS_ID
from picard.dataobj import DataObject
from picard.file import File
from picard.mbjson import (
    medium_to_metadata,
    release_group_to_metadata,
    release_to_metadata,
    track_to_metadata,
)
from picard.metadata import (
    Metadata,
    run_album_metadata_processors,
    run_track_metadata_processors,
)
from picard.plugin import (
    PluginFunctions,
    PluginPriority,
)
from picard.script import (
    ScriptError,
    ScriptParser,
    enabled_tagger_scripts_texts,
)
from picard.track import Track
from picard.util import (
    find_best_match,
    format_time,
    mbid_validate,
)
from picard.util.imagelist import (
    add_metadata_images,
    remove_metadata_images,
    update_metadata_images,
)
from picard.util.textencoding import asciipunct

from picard.ui.item import Item


RECORDING_QUERY_LIMIT = 100


def _create_artist_node_dict(source_node):
    return {x['artist']['id']: x['artist'] for x in source_node['artist-credit']}


def _copy_artist_nodes(source, target_node):
    for credit in target_node['artist-credit']:
        artist_node = source.get(credit['artist']['id'])
        if artist_node:
            credit['artist'] = artist_node


class AlbumArtist(DataObject):
    def __init__(self, album_artist_id):
        super().__init__(album_artist_id)


class AlbumStatus(IntEnum):
    NONE = 0
    LOADING = 1
    ERROR = 2
    LOADED = 3


class ParseResult(IntEnum):
    PARSED = 0
    REDIRECT = 1
    MISSING_TRACK_RELS = 2


class Album(DataObject, Item):

    metadata_images_changed = QtCore.pyqtSignal()

    def __init__(self, album_id, discid=None):
        DataObject.__init__(self, album_id)
        self.metadata = Metadata()
        self.orig_metadata = Metadata()
        self.tracks = []
        self.loaded = False
        self.load_task = None
        self.release_group = None
        self._files_count = 0
        self._requests = 0
        self._tracks_loaded = False
        self._discids = set()
        self._recordings_map = {}
        if discid:
            self._discids.add(discid)
        self._after_load_callbacks = []
        self.unmatched_files = Cluster(_("Unmatched Files"), special=True, related_album=self, hide_if_empty=True)
        self.unmatched_files.metadata_images_changed.connect(self.update_metadata_images)
        self.status = AlbumStatus.NONE
        self._album_artists = []
        self.update_metadata_images_enabled = True

    def __repr__(self):
        return '<Album %s %r>' % (self.id, self.metadata["album"])

    def iterfiles(self, save=False):
        for track in self.tracks:
            yield from track.iterfiles()
        if not save:
            yield from self.unmatched_files.iterfiles()

    def enable_update_metadata_images(self, enabled):
        self.update_metadata_images_enabled = enabled

    def append_album_artist(self, album_artist_id):
        """Append artist id to the list of album artists
        and return an AlbumArtist instance"""
        album_artist = AlbumArtist(album_artist_id)
        self._album_artists.append(album_artist)
        return album_artist

    def add_discid(self, discid):
        if not discid:
            return
        self._discids.add(discid)
        for track in self.tracks:
            medium_discids = track.metadata.getall('~musicbrainz_discids')
            track_discids = list(self._discids.intersection(medium_discids))
            if track_discids:
                track.metadata['musicbrainz_discid'] = track_discids
                track.update()
                for file in track.files:
                    file.metadata['musicbrainz_discid'] = track_discids
                    file.update()

    def get_next_track(self, track):
        try:
            index = self.tracks.index(track)
            return self.tracks[index + 1]
        except (IndexError, ValueError):
            return None

    def get_album_artists(self):
        """Returns the list of album artists (as AlbumArtist objects)"""
        return self._album_artists

    def _run_album_metadata_processors(self):
        try:
            run_album_metadata_processors(self, self._new_metadata, self._release_node)
        except BaseException:
            self.error_append(traceback.format_exc())

    def _parse_release(self, release_node):
        log.debug("Loading release %r ...", self.id)
        self._tracks_loaded = False
        release_id = release_node['id']
        if release_id != self.id:
            self.tagger.mbid_redirects[self.id] = release_id
            album = self.tagger.albums.get(release_id)
            if album:
                log.debug("Release %r already loaded", release_id)
                album.match_files(self.unmatched_files.files)
                album.update()
                self.tagger.remove_album(self)
                return ParseResult.REDIRECT
            else:
                del self.tagger.albums[self.id]
                self.tagger.albums[release_id] = self
                self.id = release_id

        self._release_node = release_node
        # Make the release artist nodes available, since they may
        # contain supplementary data (aliases, tags, genres, ratings)
        # which aren't present in the release group, track, or
        # recording artist nodes. We can copy them into those places
        # wherever the IDs match, so that the data is shared and
        # available for use in mbjson.py and external plugins.
        self._release_artist_nodes = _create_artist_node_dict(release_node)

        # Get release metadata
        m = self._new_metadata
        m.length = 0

        rg_node = release_node['release-group']
        rg = self.release_group = self.tagger.get_release_group_by_id(rg_node['id'])
        rg.loaded_albums.add(self.id)
        rg.refcount += 1

        _copy_artist_nodes(self._release_artist_nodes, rg_node)
        release_group_to_metadata(rg_node, rg.metadata, rg)
        m.copy(rg.metadata)
        release_to_metadata(release_node, m, album=self)

        config = get_config()

        # Custom VA name
        if m['musicbrainz_albumartistid'] == VARIOUS_ARTISTS_ID:
            m['albumartistsort'] = m['albumartist'] = config.setting['va_name']

        # Convert Unicode punctuation
        if config.setting['convert_punctuation']:
            m.apply_func(asciipunct)

        m['totaldiscs'] = len(release_node['media'])

        # Add album to collections
        add_release_to_user_collections(release_node)

        if config.setting['track_ars']:
            # Detect if track relationships did not get loaded
            try:
                for medium_node in release_node['media']:
                    if medium_node['track-count']:
                        if 'relations' in medium_node['tracks'][0]['recording']:
                            return ParseResult.PARSED
                        else:
                            return ParseResult.MISSING_TRACK_RELS
            except KeyError:
                pass

        return ParseResult.PARSED

    def _release_request_finished(self, document, http, error):
        if self.load_task is None:
            return
        self.load_task = None
        parse_result = None
        try:
            if error:
                self.error_append(http.errorString())
                # Fix for broken NAT releases
                if error == QtNetwork.QNetworkReply.NetworkError.ContentNotFoundError:
                    config = get_config()
                    nats = False
                    nat_name = config.setting["nat_name"]
                    files = list(self.unmatched_files.files)
                    for file in files:
                        recordingid = file.metadata["musicbrainz_recordingid"]
                        if mbid_validate(recordingid) and file.metadata["album"] == nat_name:
                            nats = True
                            self.tagger.move_file_to_nat(file, recordingid)
                            self.tagger.nats.update()
                    if nats and not self.get_num_unmatched_files():
                        self.tagger.remove_album(self)
                        error = False
            else:
                try:
                    parse_result = self._parse_release(document)
                    config = get_config()
                    if parse_result == ParseResult.MISSING_TRACK_RELS:
                        log.debug('Recording relationships not loaded in initial request for %r, issuing separate requests' % self)
                        self._request_recording_relationships(config=config)
                    elif parse_result == ParseResult.PARSED:
                        self._run_album_metadata_processors()
                    elif parse_result == ParseResult.REDIRECT:
                        error = False
                except Exception:
                    error = True
                    self.error_append(traceback.format_exc())
        finally:
            self._requests -= 1
            if parse_result == ParseResult.PARSED or error:
                self._finalize_loading(error)

    def _request_recording_relationships(self, offset=0, limit=RECORDING_QUERY_LIMIT, config=None):
        if not config:
            config = get_config()
        inc = (
            'artist-rels',
            'recording-rels',
            'release-rels',
            'url-rels',
            'work-rels',
            'work-level-rels',
        )
        log.debug('Loading recording relationships for %r (offset=%i, limit=%i)' % (self, offset, limit))
        self._requests += 1
        self.load_task = self.tagger.mb_api.browse_recordings(
            self._recordings_request_finished,
            inc=inc,
            release=self.id,
            limit=limit,
            offset=offset
        )

    def _recordings_request_finished(self, document, http, error):
        if error:
            self.error_append(http.errorString())
            self._requests -= 1
            self._finalize_loading(error)
        else:
            for recording in document.get('recordings', []):
                recording_id = recording.get('id')
                if recording_id:
                    self._recordings_map[recording_id] = recording
            count = document.get('recording-count', 0)
            offset = document.get('recording-offset', 0)
            next_offset = offset + RECORDING_QUERY_LIMIT
            if next_offset < count:
                self._requests -= 1
                self._request_recording_relationships(offset=next_offset)
            else:
                # Merge separately loaded recording relationships into release node
                self._merge_release_recording_relationships()
                self._run_album_metadata_processors()
                self._requests -= 1
                self._finalize_loading(error)

    def _merge_recording_relationships(self, track_node):
        if 'relations' not in track_node['recording']:
            recording = self._recordings_map.get(track_node['recording']['id'])
            if recording:
                track_node['recording']['relations'] = recording.get('relations', [])

    def _merge_release_recording_relationships(self):
        for medium_node in self._release_node['media']:
            pregap_node = medium_node.get('pregap')
            if pregap_node:
                self._merge_recording_relationships(pregap_node)

            for track_node in medium_node.get('tracks', []):
                self._merge_recording_relationships(track_node)

            for track_node in medium_node.get('data-tracks', []):
                self._merge_recording_relationships(track_node)

        self._recordings_map = {}

    def _finalize_loading_track(self, track_node, metadata, artists, extra_metadata=None):
        # As noted in `_parse_release` above, the release artist nodes
        # may contain supplementary data that isn't present in track
        # artist nodes. Similarly, the track artists may contain
        # information which the recording artists don't. Copy this
        # information across to wherever the artist IDs match.
        _copy_artist_nodes(self._release_artist_nodes, track_node)
        _copy_artist_nodes(self._release_artist_nodes, track_node['recording'])
        _copy_artist_nodes(_create_artist_node_dict(track_node), track_node['recording'])

        track = Track(track_node['recording']['id'], self)
        self._new_tracks.append(track)

        # Get track metadata
        tm = track.metadata
        tm.copy(metadata)
        track_to_metadata(track_node, track)
        track._customize_metadata()

        self._new_metadata.length += tm.length
        artists.add(tm["artist"])
        if extra_metadata:
            tm.update(extra_metadata)

        # Run track metadata plugins
        try:
            run_track_metadata_processors(self, tm, track_node, self._release_node)
        except BaseException:
            self.error_append(traceback.format_exc())

        return track

    def _load_tracks(self):
        artists = set()
        all_media = []
        absolutetracknumber = 0

        def _load_track(node, mm, artists, extra_metadata):
            nonlocal absolutetracknumber
            absolutetracknumber += 1
            extra_metadata['~absolutetracknumber'] = absolutetracknumber
            self._finalize_loading_track(node, mm, artists, extra_metadata)

        va = self._new_metadata['musicbrainz_albumartistid'] == VARIOUS_ARTISTS_ID

        djmix_ars = {}
        if hasattr(self._new_metadata, "_djmix_ars"):
            djmix_ars = self._new_metadata._djmix_ars

        for medium_node in self._release_node['media']:
            mm = Metadata()
            mm.copy(self._new_metadata)
            medium_to_metadata(medium_node, mm)
            format = medium_node.get('format')
            if format:
                all_media.append(format)

            for dj in djmix_ars.get(mm["discnumber"], []):
                mm.add("djmixer", dj)

            if va:
                mm["compilation"] = "1"
            else:
                del mm["compilation"]

            if 'discs' in medium_node:
                discids = [disc.get('id') for disc in medium_node['discs']]
                mm['~musicbrainz_discids'] = discids
                mm['musicbrainz_discid'] = list(self._discids.intersection(discids))

            pregap_node = medium_node.get('pregap')
            if pregap_node:
                mm['~discpregap'] = '1'
                _load_track(pregap_node, mm, artists, {'~pregap': '1'})

            for track_node in medium_node.get('tracks', []):
                _load_track(track_node, mm, artists, {})

            for track_node in medium_node.get('data-tracks', []):
                _load_track(track_node, mm, artists, {'~datatrack': '1'})

        totalalbumtracks = absolutetracknumber
        self._new_metadata['~totalalbumtracks'] = totalalbumtracks
        # Generate a list of unique media, but keep order of first appearance
        self._new_metadata['media'] = " / ".join(list(OrderedDict.fromkeys(all_media)))

        multiartists = len(artists) > 1
        for track in self._new_tracks:
            track.metadata["~totalalbumtracks"] = totalalbumtracks
            if multiartists:
                track.metadata["~multiartist"] = "1"
        del self._release_node
        del self._release_artist_nodes
        self._tracks_loaded = True

    def _finalize_loading_album(self):
        self.enable_update_metadata_images(False)
        for track in self._new_tracks:
            track.orig_metadata.copy(track.metadata)
            track.metadata_images_changed.connect(self.update_metadata_images)

        # Prepare parser for user's script
        for s_name, s_text in enabled_tagger_scripts_texts():
            parser = ScriptParser()
            for track in self._new_tracks:
                # Run tagger script for each track
                try:
                    parser.eval(s_text, track.metadata)
                except ScriptError:
                    log.exception("Failed to run tagger script %s on track", s_name)
                track.metadata.strip_whitespace()
                track.scripted_metadata.update(track.metadata)
            # Run tagger script for the album itself
            try:
                parser.eval(s_text, self._new_metadata)
            except ScriptError:
                log.exception("Failed to run tagger script %s on album", s_name)
            self._new_metadata.strip_whitespace()

        unmatched_files = [file for track in self.tracks for file in track.files]
        self.metadata = self._new_metadata
        self.orig_metadata.copy(self.metadata)
        self.orig_metadata.images.clear()
        self.tracks = self._new_tracks
        del self._new_metadata
        del self._new_tracks
        self.loaded = True
        self.status = AlbumStatus.LOADED
        self.match_files(unmatched_files + self.unmatched_files.files)
        self.enable_update_metadata_images(True)
        self.update_metadata_images()
        self.update()
        self.tagger.window.set_statusbar_message(
            N_('Album %(id)s loaded: %(artist)s - %(album)s'),
            {
                'id': self.id,
                'artist': self.metadata['albumartist'],
                'album': self.metadata['album']
            },
            timeout=3000
        )
        for func, always in self._after_load_callbacks:
            func()
        self._after_load_callbacks = []
        if self.item.isSelected():
            self.tagger.window.refresh_metadatabox()
            self.tagger.window.cover_art_box.update_metadata()

    def _finalize_loading(self, error):
        if self.loaded:
            # This is not supposed to happen, _finalize_loading should only
            # be called once after all requests finished.
            import inspect
            stack = inspect.stack()
            args = [self]
            msg = 'Album._finalize_loading called for already loaded album %r'
            if len(stack) > 1:
                f = stack[1]
                msg += ' at %s:%d in %s'
                args.extend((f.filename, f.lineno, f.function))
            log.warning(msg, *args)
            return

        if error:
            self.metadata.clear()
            self.status = AlbumStatus.ERROR
            self.update()
            if not self._requests:
                del self._new_metadata
                del self._new_tracks
                self.loaded = True
                for func, always in self._after_load_callbacks:
                    if always:
                        func()
            return

        if self._requests > 0:
            return

        if not self._tracks_loaded:
            self._load_tracks()

        if not self._requests:
            self._finalize_loading_album()

    def load(self, priority=False, refresh=False):
        if self._requests:
            log.info("Not reloading, some requests are still active.")
            return
        self.tagger.window.set_statusbar_message(
            N_('Loading album %(id)s ...'),
            {'id': self.id}
        )
        self.loaded = False
        self.status = AlbumStatus.LOADING
        if self.release_group:
            self.release_group.loaded = False
            self.release_group.genres.clear()
        self.metadata.clear()
        self.genres.clear()
        self.update(update_selection=False)
        self._new_metadata = Metadata()
        self._new_tracks = []
        self._requests = 1
        self.clear_errors()
        config = get_config()
        require_authentication = False
        inc = {
            'aliases',
            'annotation',
            'artist-credits',
            'artists',
            'collections',
            'discids',
            'isrcs',
            'labels',
            'media',
            'recordings',
            'release-groups',
        }
        if self.tagger.webservice.oauth_manager.is_authorized():
            require_authentication = True
            inc |= {'user-collections'}
        if config.setting['release_ars'] or config.setting['track_ars']:
            inc |= {
                'artist-rels',
                'recording-rels',
                'release-rels',
                'url-rels',
                'work-rels'
            }
            if config.setting['track_ars']:
                inc |= {
                    'recording-level-rels',
                    'work-level-rels',
                }
        require_authentication = self.set_genre_inc_params(inc, config) or require_authentication
        if config.setting['enable_ratings']:
            require_authentication = True
            inc |= {'user-ratings'}

        self.load_task = self.tagger.mb_api.get_release_by_id(
            self.id,
            self._release_request_finished,
            inc=tuple(inc),
            mblogin=require_authentication,
            priority=priority,
            refresh=refresh
        )

    def run_when_loaded(self, func, always=False):
        if self.loaded:
            func()
        else:
            self._after_load_callbacks.append((func, always))

    def stop_loading(self):
        if self.load_task:
            self.tagger.webservice.remove_task(self.load_task)
            self.load_task = None

    def update(self, update_tracks=True, update_selection=True):
        if self.item:
            self.item.update(update_tracks, update_selection=update_selection)

    def add_file(self, track, file, new_album=True):
        self._files_count += 1
        if new_album:
            self.update(update_tracks=False)
            add_metadata_images(self, [file])

    def remove_file(self, track, file, new_album=True):
        self._files_count -= 1
        if new_album:
            self.update(update_tracks=False)
            remove_metadata_images(self, [file])

    @staticmethod
    def _match_files(files, tracks, unmatched_files, threshold=0):
        """Match files to tracks on this album, based on metadata similarity or recordingid."""
        tracks_cache = defaultdict(lambda: None)

        def build_tracks_cache():
            for track in tracks:
                tm_recordingid = track.orig_metadata['musicbrainz_recordingid']
                tm_trackid = track.orig_metadata['musicbrainz_trackid']
                tm_tracknumber = track.orig_metadata['tracknumber']
                tm_discnumber = track.orig_metadata['discnumber']
                for tup in (
                    (tm_recordingid, tm_tracknumber, tm_discnumber),
                    (tm_recordingid, tm_tracknumber),
                    (tm_recordingid, ),
                    (tm_trackid, tm_tracknumber, tm_discnumber),
                    (tm_trackid, tm_tracknumber),
                    (tm_trackid, )):
                    tracks_cache[tup] = track

        SimMatchAlbum = namedtuple('SimMatchAlbum', 'similarity track')
        no_match = SimMatchAlbum(similarity=-1, track=unmatched_files)

        for file in list(files):
            if file.state == File.REMOVED:
                continue
            # if we have a recordingid or trackid to match against, use that in priority
            # if recordingid and trackid do point to different tracks, compare the file
            # and track durations to find the better match.
            recid = file.match_recordingid or file.metadata['musicbrainz_recordingid']
            trackid = file.metadata['musicbrainz_trackid']
            tracknumber = file.metadata['tracknumber']
            discnumber = file.metadata['discnumber']

            def mbid_candidates():
                for mbid in (recid, trackid):
                    if mbid and mbid_validate(mbid):
                        if not tracks_cache:
                            build_tracks_cache()
                        track = (tracks_cache[(mbid, tracknumber, discnumber)]
                                or tracks_cache[(mbid, tracknumber)]
                                or tracks_cache[(mbid, )])
                        if track:
                            similarity = track.metadata.length_score(track.metadata.length, file.metadata.length)
                            yield SimMatchAlbum(similarity=similarity, track=track)

            best_match = find_best_match(mbid_candidates(), no_match)
            if best_match.result != no_match:
                yield (file, best_match.result.track)
                continue

            # try to match by similarity
            def similarity_candidates():
                for track in tracks:
                    similarity = track.metadata.compare(file.orig_metadata)
                    if similarity >= threshold:
                        yield SimMatchAlbum(similarity=similarity, track=track)

            best_match = find_best_match(similarity_candidates(), no_match)
            yield (file, best_match.result.track)

    def match_files(self, files):
        """Match and move files to tracks on this album, based on metadata similarity or recordingid."""
        if self.loaded:
            config = get_config()
            threshold = config.setting['track_matching_threshold']
            moves = self._match_files(files, self.tracks, self.unmatched_files, threshold=threshold)
            with self.tagger.window.metadata_box.ignore_updates:
                for file, target in moves:
                    file.move(target)
        else:
            with self.tagger.window.metadata_box.ignore_updates:
                for file in list(files):
                    file.move(self.unmatched_files)

    def can_save(self):
        return self._files_count > 0

    def can_remove(self):
        return True

    def can_edit_tags(self):
        return True

    def can_analyze(self):
        return False

    def can_autotag(self):
        return False

    def can_refresh(self):
        return True

    def can_view_info(self):
        return self.loaded or bool(self.errors)

    def is_album_like(self):
        return True

    def get_num_matched_tracks(self):
        return sum(1 for track in self.tracks if track.is_linked())

    def get_num_unmatched_files(self):
        return len(self.unmatched_files.files)

    def get_num_total_files(self):
        return self._files_count + len(self.unmatched_files.files)

    def is_complete(self):
        if not self.tracks:
            return False
        for track in self.tracks:
            if not track.is_complete():
                return False
        return not self.get_num_unmatched_files()

    def is_modified(self):
        return any(self._iter_unsaved_files())

    def get_num_unsaved_files(self):
        return sum(1 for file in self._iter_unsaved_files())

    def _iter_unsaved_files(self):
        yield from (file for file in self.iterfiles(save=True) if not file.is_saved())

    def column(self, column):
        if column == 'title':
            if self.status == AlbumStatus.LOADING:
                title = _("[loading album information]")
            elif self.status == AlbumStatus.ERROR:
                title = _("[could not load album %s]") % self.id
            else:
                title = self.metadata['album']

            if self.tracks:
                elems = ['%d/%d' % (self.get_num_matched_tracks(), len(self.tracks))]
                unmatched = self.get_num_unmatched_files()
                if unmatched:
                    elems.append('%d?' % (unmatched,))
                unsaved = self.get_num_unsaved_files()
                if unsaved:
                    elems.append('%d*' % (unsaved,))
                ca_detailed = self.cover_art_description_detailed()
                if ca_detailed:
                    elems.append(ca_detailed)

                return '%s\u200E (%s)' % (title, '; '.join(elems))
            else:
                return title
        elif column == '~length':
            length = self.metadata.length
            if length:
                return format_time(length)
            else:
                return ''
        elif column == 'artist':
            return self.metadata['albumartist']
        elif column == 'tracknumber':
            return self.metadata['~totalalbumtracks']
        elif column == 'discnumber':
            return self.metadata['totaldiscs']
        elif column == 'covercount':
            return self.cover_art_description()
        else:
            return self.metadata[column]

    def switch_release_version(self, mbid):
        if mbid == self.id:
            return
        for file in list(self.iterfiles(True)):
            file.move(self.unmatched_files)
        album = self.tagger.albums.get(mbid)
        if album:
            album.match_files(self.unmatched_files.files)
            album.update()
            self.tagger.remove_album(self)
        else:
            del self.tagger.albums[self.id]
            self.release_group.loaded_albums.discard(self.id)
            self.id = mbid
            self.tagger.albums[mbid] = self
            self.load(priority=True, refresh=True)

    def update_metadata_images(self):
        if not self.update_metadata_images_enabled:
            return

        if update_metadata_images(self):
            self.update(False)
            self.metadata_images_changed.emit()

    def keep_original_images(self):
        self.enable_update_metadata_images(False)
        for track in self.tracks:
            track.keep_original_images()
        for file in list(self.unmatched_files.files):
            file.keep_original_images()
        self.enable_update_metadata_images(True)
        self.update_metadata_images()


class NatAlbum(Album):

    def __init__(self):
        super().__init__("NATS")
        self.loaded = True
        self.update()

    def update(self, update_tracks=True, update_selection=True):
        config = get_config()
        self.enable_update_metadata_images(False)
        old_album_title = self.metadata["album"]
        self.metadata["album"] = config.setting["nat_name"]
        for track in self.tracks:
            if old_album_title == track.metadata["album"]:
                track.metadata["album"] = self.metadata["album"]
            for file in track.files:
                track.update_file_metadata(file)
        self.enable_update_metadata_images(True)
        super().update(update_tracks, update_selection)

    def _finalize_loading(self, error):
        self.update()

    def can_refresh(self):
        return False

    def can_browser_lookup(self):
        return False

    def can_view_info(self):
        return False


_album_post_removal_processors = PluginFunctions(label='album_post_removal_processors')


def register_album_post_removal_processor(function, priority=PluginPriority.NORMAL):
    """Registers an album-removed processor.
    Args:
        function: function to call after album removal, it will be passed the album object
        priority: optional, PluginPriority.NORMAL by default
    Returns:
        None
    """
    _album_post_removal_processors.register(function.__module__, function, priority)


def run_album_post_removal_processors(album_object):
    _album_post_removal_processors.run(album_object)
