Docserver: Consolidate features caching and access.

chrome/common/extensions/docs/server2/features_bundle.py

Index: chrome/common/extensions/docs/server2/features_bundle.py
diff --git a/chrome/common/extensions/docs/server2/features_bundle.py b/chrome/common/extensions/docs/server2/features_bundle.py
new file mode 100644
index 0000000000000000000000000000000000000000..39abf408fe8a5e65434eb559b4bb1875bcf23cc0
--- /dev/null
+++ b/chrome/common/extensions/docs/server2/features_bundle.py
@@ -0,0 +1,91 @@
+# Copyright 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import features_utility
+import svn_constants
+from third_party.json_schema_compiler.json_parse import Parse
+
+
+def _AddPlatformsFromDependencies(feature, features_bundle):
+  features_map = {
+    'api': features_bundle.GetAPIFeatures(),
+    'manifest': features_bundle.GetManifestFeatures(),
+    'permission': features_bundle.GetPermissionFeatures()
+  }
+  dependencies = feature.get('dependencies')
+  if dependencies is None:
+    return ['apps', 'extensions']
+  platforms = set()
+  for dependency in dependencies:
+    dep_type, dep_name = dependency.split(':')
+    dependency_features = features_map[dep_type]
+    dependency_feature = dependency_features.get(dep_name)
+    # If the dependency can't be resolved, it is inaccessible and therefore
+    # so is this feature.
+    if dependency_feature is None:
+      return []
+    platforms = platforms.union(dependency_feature['platforms'])
+  feature['platforms'] = list(platforms)
+
+
+class _FeaturesCache(object):
+  def __init__(self, file_system, compiled_fs_factory, *json_paths):
+    self._file_system = file_system
+    self._cache = compiled_fs_factory.Create(self._CreateCache, type(self))
+    self._json_path = json_paths[0]
+    self._extra_paths = json_paths[1:]
+
+  def _CreateCache(self, _, features_json):
+    features = features_utility.Parse(Parse(features_json))
+    for path in self._extra_paths:
+      extra_json = self._file_system.ReadSingle(path)
+      features = features_utility.MergedWith(
+          features_utility.Parse(Parse(extra_json)), features)
+    return features
+
+  def GetFeatures(self):
+    if self._json_path is None:
+      return {}
+    return self._cache.GetFromFile(self._json_path)
+
+
+class FeaturesBundle(object):
+  '''Provides access to properties of API, Manifest, and Permission features.
+  '''
+  def __init__(self, file_system, compiled_fs_factory, object_store_creator):
+    self._api_cache = _FeaturesCache(
+        file_system,
+        compiled_fs_factory,
+        svn_constants.API_FEATURES_PATH)
+    self._manifest_cache = _FeaturesCache(
+        file_system,
+        compiled_fs_factory,
+        svn_constants.MANIFEST_FEATURES_PATH,
+        svn_constants.MANIFEST_JSON_PATH)
+    self._permission_cache = _FeaturesCache(
+        file_system,
+        compiled_fs_factory,
+        svn_constants.PERMISSION_FEATURES_PATH,
+        svn_constants.PERMISSIONS_JSON_PATH)
+    self._object_store = object_store_creator.Create(_FeaturesCache, 'features')
+
+  def GetPermissionFeatures(self):
+    return self._permission_cache.GetFeatures()
+
+  def GetManifestFeatures(self):
+    return self._manifest_cache.GetFeatures()
+
+  def GetAPIFeatures(self):
+    api_features = self._object_store.Get('api_features').Get()
+    if api_features is None:
+      api_features = self._api_cache.GetFeatures()
+      # TODO(rockot): Handle inter-API dependencies more gracefully.
+      # Not yet a problem because there is only one such case (windows -> tabs).
+      # If we don't store this value before annotating platforms, inter-API
+      # dependencies will lead to infinite recursion.
+      self._object_store.Set('api_features', api_features)
+      for feature in api_features.itervalues():
+        _AddPlatformsFromDependencies(feature, self)
+      self._object_store.Set('api_features', api_features)
+    return api_features