Initial python3 changes

Mostly just updating libraries, removing string encoding/decoding,
fixing some edge cases. No new functionality was added in this
commit.

lib/beetsplug/metasync/__init__.py

@@ -0,0 +1,138 @@
+# This file is part of beets.
+# Copyright 2016, Heinz Wiesinger.
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+
+"""Synchronize information from music player libraries
+"""
+
+
+from abc import abstractmethod, ABCMeta
+from importlib import import_module
+
+from confuse import ConfigValueError
+from beets import ui
+from beets.plugins import BeetsPlugin
+
+
+METASYNC_MODULE = 'beetsplug.metasync'
+
+# Dictionary to map the MODULE and the CLASS NAME of meta sources
+SOURCES = {
+    'amarok': 'Amarok',
+    'itunes': 'Itunes',
+}
+
+
+class MetaSource(metaclass=ABCMeta):
+    def __init__(self, config, log):
+        self.item_types = {}
+        self.config = config
+        self._log = log
+
+    @abstractmethod
+    def sync_from_source(self, item):
+        pass
+
+
+def load_meta_sources():
+    """ Returns a dictionary of all the MetaSources
+    E.g., {'itunes': Itunes} with isinstance(Itunes, MetaSource) true
+    """
+    meta_sources = {}
+
+    for module_path, class_name in SOURCES.items():
+        module = import_module(METASYNC_MODULE + '.' + module_path)
+        meta_sources[class_name.lower()] = getattr(module, class_name)
+
+    return meta_sources
+
+
+META_SOURCES = load_meta_sources()
+
+
+def load_item_types():
+    """ Returns a dictionary containing the item_types of all the MetaSources
+    """
+    item_types = {}
+    for meta_source in META_SOURCES.values():
+        item_types.update(meta_source.item_types)
+    return item_types
+
+
+class MetaSyncPlugin(BeetsPlugin):
+
+    item_types = load_item_types()
+
+    def __init__(self):
+        super().__init__()
+
+    def commands(self):
+        cmd = ui.Subcommand('metasync',
+                            help='update metadata from music player libraries')
+        cmd.parser.add_option('-p', '--pretend', action='store_true',
+                              help='show all changes but do nothing')
+        cmd.parser.add_option('-s', '--source', default=[],
+                              action='append', dest='sources',
+                              help='comma-separated list of sources to sync')
+        cmd.parser.add_format_option()
+        cmd.func = self.func
+        return [cmd]
+
+    def func(self, lib, opts, args):
+        """Command handler for the metasync function.
+        """
+        pretend = opts.pretend
+        query = ui.decargs(args)
+
+        sources = []
+        for source in opts.sources:
+            sources.extend(source.split(','))
+
+        sources = sources or self.config['source'].as_str_seq()
+
+        meta_source_instances = {}
+        items = lib.items(query)
+
+        # Avoid needlessly instantiating meta sources (can be expensive)
+        if not items:
+            self._log.info('No items found matching query')
+            return
+
+        # Instantiate the meta sources
+        for player in sources:
+            try:
+                cls = META_SOURCES[player]
+            except KeyError:
+                self._log.error('Unknown metadata source \'{}\''.format(
+                    player))
+
+            try:
+                meta_source_instances[player] = cls(self.config, self._log)
+            except (ImportError, ConfigValueError) as e:
+                self._log.error('Failed to instantiate metadata source '
+                                '\'{}\': {}'.format(player, e))
+
+        # Avoid needlessly iterating over items
+        if not meta_source_instances:
+            self._log.error('No valid metadata sources found')
+            return
+
+        # Sync the items with all of the meta sources
+        for item in items:
+            for meta_source in meta_source_instances.values():
+                meta_source.sync_from_source(item)
+
+            changed = ui.show_model_changes(item)
+
+            if changed and not pretend:
+                item.store()