sync: Introduce classes for per-type counters

sync/sessions/directory_type_debug_info_emitter.h

Index: sync/sessions/directory_type_debug_info_emitter.h
diff --git a/sync/sessions/directory_type_debug_info_emitter.h b/sync/sessions/directory_type_debug_info_emitter.h
new file mode 100644
index 0000000000000000000000000000000000000000..62959da560959d96bf82310ea584e15285563475
--- /dev/null
+++ b/sync/sessions/directory_type_debug_info_emitter.h
@@ -0,0 +1,91 @@
+// Copyright 2014 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 SYNC_SESSIONS_DIRECTORY_TYPE_DEBUG_INFO_EMITTER_H_
+#define SYNC_SESSIONS_DIRECTORY_TYPE_DEBUG_INFO_EMITTER_H_
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/observer_list.h"
+#include "base/values.h"
+#include "sync/base/sync_export.h"
+#include "sync/internal_api/public/sessions/commit_counters.h"
+#include "sync/internal_api/public/sessions/update_counters.h"
+#include "sync/syncable/directory.h"
+
+namespace syncer {
+
+class DirectoryCommitContributor;
+class TypeDebugInfoObserver;
+
+// Supports various kinds of debugging requests for a certain directory type.
+//
+// The GetAllNodes() function is used to help export a snapshot of all current
+// nodes to its caller.  The complexity required to manage the request mostly
+// lives elsewhere.
+//
+// The Emit*() functions send updates to registered TypeDebugInfoObservers.
+// The DirectoryTypeDebugInfoEmitter does not directly own that list; it is
+// managed by the ModelTypeRegistry.
+//
+// For Update and Commit counters, the job of keeping the counters up to date
+// is delegated to the UpdateHandler and CommitContributors.  For the Stats
+// counters, the emitter will use its type_ and directory_ members to fetch all
+// the required information on demand.
+class SYNC_EXPORT_PRIVATE DirectoryTypeDebugInfoEmitter {
+ public:
+  DirectoryTypeDebugInfoEmitter(
+      syncable::Directory* directory,
+      syncer::ModelType type,
+      ObserverList<TypeDebugInfoObserver>* observers);

[tim (not reviewing), 2014/04/28 21:26:21]

Comment |observers| parameter, since e.g you can't unregister observers.

[rlarocque, 2014/04/28 21:59:59]

Comment added.

+
+  // A simple constructor for tests.  Should not be used in real code.
+  DirectoryTypeDebugInfoEmitter();
+
+  virtual ~DirectoryTypeDebugInfoEmitter();
+
+  // Returns a ListValue representation of all known nodes of this type.
+  scoped_ptr<base::ListValue> GetAllNodes();
+
+  // Returns a reference to the current commit counters.
+  const CommitCounters& GetCommitCounters() const;
+
+  // Allows others to mutate the commit counters.
+  CommitCounters* GetMutableCommitCounters();
+
+  // Triggerss a commit counters update to registered observers.
+  void EmitCommitCountersUpdate();
+
+  // Returns a reference to the current update counters.
+  const UpdateCounters& GetUpdateCounters() const;
+
+  // Allows others to mutate the update counters.
+  UpdateCounters* GetMutableUpdateCounters();
+
+  // Triggers an update counters update to registered observers.
+  void EmitUpdateCountersUpdate();
+
+  // Triggers a status counters update to registered observers.
+  void EmitStatusCountersUpdate();
+
+ private:
+  syncable::Directory* directory_;
+
+  const ModelType type_;
+
+  CommitCounters commit_counters_;
+  UpdateCounters update_counters_;
+
+  // Because there are so many emitters that come into and out of existence, it
+  // doesn't make sense to have them manage their own observer list.  They all
+  // share one observer list that is provided by their owner and which is
+  // guaranteed to outlive them.
+  ObserverList<TypeDebugInfoObserver>* type_debug_info_observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(DirectoryTypeDebugInfoEmitter);
+};
+
+}  // namespace syncer
+
+#endif  // SYNC_SESSIONS_DIRECTORY_TYPE_DEBUG_INFO_EMITTER_H_