local: Add new json based library

- Sets local-tagcache as disabled
- Implements new library that uses a gzip compressed json as storage.
- Thanks to reuse of existing serialization code this is a fairly small change.

mopidy/backends/local/json/__init__.py

@@ -0,0 +1,33 @@
+from __future__ import unicode_literals
+
+import os
+
+import mopidy
+from mopidy import config, ext
+
+
+class Extension(ext.Extension):
+
+    dist_name = 'Mopidy-Local-JSON'
+    ext_name = 'local-json'
+    version = mopidy.__version__
+
+    def get_default_config(self):
+        conf_file = os.path.join(os.path.dirname(__file__), 'ext.conf')
+        return config.read(conf_file)
+
+    def get_config_schema(self):
+        schema = super(Extension, self).get_config_schema()
+        schema['json_file'] = config.Path()
+        return schema
+
+    def validate_environment(self):
+        pass
+
+    def get_backend_classes(self):
+        from .actor import LocalJsonBackend
+        return [LocalJsonBackend]
+
+    def get_library_updaters(self):
+        from .library import LocalJsonLibraryUpdateProvider
+        return [LocalJsonLibraryUpdateProvider]

mopidy/backends/local/json/actor.py

@@ -0,0 +1,30 @@
+from __future__ import unicode_literals
+
+import logging
+
+import pykka
+
+from mopidy.backends import base
+from mopidy.utils import encoding, path
+
+from .library import LocalJsonLibraryProvider
+
+logger = logging.getLogger('mopidy.backends.local.json')
+
+
+class LocalJsonBackend(pykka.ThreadingActor, base.Backend):
+    def __init__(self, config, audio):
+        super(LocalJsonBackend, self).__init__()
+
+        self.config = config
+        self.check_dirs_and_files()
+        self.library = LocalJsonLibraryProvider(backend=self)
+        self.uri_schemes = ['local']
+
+    def check_dirs_and_files(self):
+        try:
+            path.get_or_create_file(self.config['local-json']['json_file'])
+        except EnvironmentError as error:
+            logger.warning(
+                'Could not create empty json file: %s',
+                encoding.locale_decode(error))

mopidy/backends/local/json/ext.conf

@@ -0,0 +1,3 @@
+[local-json]
+enabled = true
+json_file = $XDG_DATA_DIR/mopidy/local/library.json.gz

mopidy/backends/local/json/library.py

@@ -0,0 +1,106 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+import gzip
+import json
+import logging
+import os
+import tempfile
+
+import mopidy
+from mopidy import models
+from mopidy.backends import base
+from mopidy.backends.local import search
+
+logger = logging.getLogger('mopidy.backends.local.json')
+
+
+def _load_tracks(json_file):
+    try:
+        with gzip.open(json_file, 'rb') as fp:
+            result = json.load(fp, object_hook=models.model_json_decoder)
+    except IOError:
+        return []
+    return result.get('tracks', [])
+
+
+class LocalJsonLibraryProvider(base.BaseLibraryProvider):
+    def __init__(self, *args, **kwargs):
+        super(LocalJsonLibraryProvider, self).__init__(*args, **kwargs)
+        self._uri_mapping = {}
+        self._media_dir = self.backend.config['local']['media_dir']
+        self._json_file = self.backend.config['local-json']['json_file']
+        self.refresh()
+
+    def refresh(self, uri=None):
+        logger.debug(
+            'Loading local tracks from %s using %s',
+            self._media_dir, self._json_file)
+
+        tracks = _load_tracks(self._json_file)
+        uris_to_remove = set(self._uri_mapping)
+
+        for track in tracks:
+            self._uri_mapping[track.uri] = track
+            uris_to_remove.discard(track.uri)
+
+        for uri in uris_to_remove:
+            del self._uri_mapping[uri]
+
+        logger.info(
+            'Loaded %d local tracks from %s using %s',
+            len(tracks), self._media_dir, self._json_file)
+
+    def lookup(self, uri):
+        try:
+            return [self._uri_mapping[uri]]
+        except KeyError:
+            logger.debug('Failed to lookup %r', uri)
+            return []
+
+    def find_exact(self, query=None, uris=None):
+        tracks = self._uri_mapping.values()
+        return search.find_exact(tracks, query=query, uris=uris)
+
+    def search(self, query=None, uris=None):
+        tracks = self._uri_mapping.values()
+        return search.search(tracks, query=query, uris=uris)
+
+
+class LocalJsonLibraryUpdateProvider(base.BaseLibraryProvider):
+    uri_schemes = ['local']
+
+    def __init__(self, config):
+        self._tracks = {}
+        self._media_dir = config['local']['media_dir']
+        self._json_file = config['local-json']['json_file']
+
+    def load(self):
+        for track in _load_tracks(self._json_file):
+            self._tracks[track.uri] = track
+        return self._tracks.values()
+
+    def add(self, track):
+        self._tracks[track.uri] = track
+
+    def remove(self, uri):
+        if uri in self._tracks:
+            del self._tracks[uri]
+
+    def commit(self):
+        directory, basename = os.path.split(self._json_file)
+
+        # TODO: cleanup directory/basename.* files.
+        tmp = tempfile.NamedTemporaryFile(
+            prefix=basename + '.', dir=directory, delete=False)
+
+        try:
+            with gzip.GzipFile(fileobj=tmp, mode='wb') as fp:
+                data = {'version': mopidy.__version__,
+                        'tracks': self._tracks.values()}
+                json.dump(data, fp, cls=models.ModelJSONEncoder,
+                          indent=2, separators=(',', ': '))
+            os.rename(tmp.name, self._json_file)
+        finally:
+            if os.path.exists(tmp.name):
+                os.remove(tmp.name)

mopidy/backends/local/tagcache/ext.conf

@@ -1,2 +1,2 @@
 [local-tagcache]
-enabled = true
+enabled = false

setup.py

@@ -44,6 +44,7 @@ setup(
             'http = mopidy.frontends.http:Extension [http]',
             'local = mopidy.backends.local:Extension',
             'local-tagcache = mopidy.backends.local.tagcache:Extension',
+            'local-json = mopidy.backends.local.json:Extension',
             'mpd = mopidy.frontends.mpd:Extension',
             'stream = mopidy.backends.stream:Extension',
         ],