WORK IN PROGRESS.

chrome/browser/extensions/syncable_extension_settings_storage.h

+// Copyright (c) 2011 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.
+
+#ifndef CHROME_BROWSER_EXTENSIONS_SYNCABLE_EXTENSION_SETTINGS_STORAGE_H_
+#define CHROME_BROWSER_EXTENSIONS_SYNCABLE_EXTENSION_SETTINGS_STORAGE_H_
+#pragma once
+
+#include "base/compiler_specific.h"
+#include "base/memory/weak_ptr.h"
+#include "base/values.h"
+#include "chrome/browser/extensions/extension_settings_storage.h"
+#include "chrome/browser/extensions/extension_settings_sync_data.h"
+#include "chrome/browser/sync/api/syncable_service.h"
+#include "chrome/browser/sync/api/sync_change.h"
+
+// XXX repro/investigate sqlite crash.
+// XXX rename Push to Send?
+// ... RemoveFromSyncCallback -> SendRemoveToSyncCallback?
+
+// Decorates an ExtensionSettingsStorage with sync behaviour.
+class SyncableExtensionSettingsStorage : public ExtensionSettingsStorage {
+ public:
+  // Bundles the sync dependencies for sync-related callbacks.  Since sync may
+  // be disabled at any time, and therefore the sync processor and synced keys
+  // made invalid, callbacks must only be passed weak references to them.
+  // Public for anonymous namespace access.
+  class SyncDeps : public base::SupportsWeakPtr<SyncDeps> {
+   public:
+    // Ownership of processor NOT taken.
+    explicit SyncDeps(SyncChangeProcessor* processor);
+    virtual ~SyncDeps();
+
+    SyncChangeProcessor* processor() { return processor_; }
+    std::set<std::string>* keys() { return &keys_; }
+
+   private:
+    // Sync's SyncChange handler.  All changes are pushed through this.
+    SyncChangeProcessor* processor_;
+
+    // Keys of settings that have been synced.  Track in order to correctly
+    // send an ACTION_ADD or ACTION_UPDATE to the processor on Set().
+    std::set<std::string> keys_;
+  };
+
+  explicit SyncableExtensionSettingsStorage(
+      std::string extension_id,
+      // Ownership taken.
+      ExtensionSettingsStorage* delegate);
+
+  // ExtensionSettingsStorage implementation.
+  virtual void Get(const std::string& key, Callback* callback) OVERRIDE;
+  virtual void Get(const ListValue& keys, Callback* callback) OVERRIDE;
+  virtual void Get(Callback* callback) OVERRIDE;
+  virtual void Set(
+      const std::string& key, const Value& value, Callback* callback) OVERRIDE;
+  virtual void Set(const DictionaryValue& values, Callback* callback) OVERRIDE;
+  virtual void Remove(const std::string& key, Callback* callback) OVERRIDE;
+  virtual void Remove(const ListValue& keys, Callback* callback) OVERRIDE;
+  virtual void Clear(Callback *callback) OVERRIDE;
+  virtual void DeleteSoon() OVERRIDE;
+
+  // Sync-related methods.
+  void StartSyncing(
+      const DictionaryValue& sync_state,
+      // Guaranteed non-NULL. Ownership NOT taken.
+      SyncChangeProcessor* sync_processor);
+  void StopSyncing();
+  void ProcessSyncChanges(const ExtensionSettingsSyncDataList& sync_changes);
+
+ private:
+  // Deleted from DeleteSoon().
+  virtual ~SyncableExtensionSettingsStorage();
+
+  // Id of the extension these settings are for.
+  std::string extension_id_;
+
+  // Decorated storage.  Deleted in DeleteSoon().
+  ExtensionSettingsStorage* delegate_;
+
+  // Weak sync dependencies.  Non-NULL while sync enabled (between calls to
+  // MergeDataAndStartSyncing and StopSyncing), NULL at other times.
+  SyncDeps* sync_deps_;
+
+  DISALLOW_COPY_AND_ASSIGN(SyncableExtensionSettingsStorage);
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_SYNCABLE_EXTENSION_SETTINGS_STORAGE_H_