Implement mediaGalleriesPrivate api to notify extensions about gallery changed events.

chrome/browser/extensions/api/media_galleries_private/gallery_watch_manager.cc

+// Copyright (c) 2012 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.
+//
+// GalleryWatchManager implementation.
+
+#include "chrome/browser/extensions/api/media_galleries_private/gallery_watch_manager.h"
+
+#include <list>
+#include <set>
+
+#include "base/bind.h"
+#include "base/compiler_specific.h"
+#include "base/files/file_path_watcher.h"
+#include "base/location.h"
+#include "base/memory/weak_ptr.h"
+#include "base/time.h"
+#include "chrome/browser/extensions/api/media_galleries_private/media_galleries_private_api.h"
+#include "chrome/browser/extensions/api/media_galleries_private/media_galleries_private_api_factory.h"
+#include "chrome/browser/extensions/api/media_galleries_private/media_galleries_private_event_router.h"
+#include "chrome/browser/profiles/profile.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace extensions {
+
+class GalleryWatchManager;
+
+namespace {
+
+using content::BrowserThread;
+
+// Map to keep track of profile specific GalleryWatchManager objects.
+// Key: Profile*.
+// Value: GalleryWatchManager*.
+// This map owns the GalleryWatchManager object.
+typedef std::map<const Profile*, extensions::GalleryWatchManager*>
+    WatchManagerMap;
+WatchManagerMap* g_gallery_watch_managers = NULL;
+
+// Dispatches the gallery changed event on the UI thread.
+void SendGalleryChangedEventOnUIThread(
+    const Profile* profile,
+    const std::string& gallery_id,
+    const std::set<std::string>& extension_ids) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK(profile);
+  MediaGalleriesPrivateEventRouter* router =
+      MediaGalleriesPrivateAPIFactory::GetForProfile(
+          const_cast<Profile*>(profile))->event_router();

[Lei Zhang, 2012/12/18 01:45:16]

GalleryWatchManager shouldn't promise to use a const Profile* and then cast away
its const-ness.

[kmadhusu, 2012/12/18 21:32:39]

Done.

+  if (!router)
+    return;
+  router->OnGalleryChanged(gallery_id, extension_ids);
+}
+
+}  // namespace
+
+///////////////////////////////////////////////////////////////////////////////
+//                       GalleryFilePathWatcher                              //
+///////////////////////////////////////////////////////////////////////////////
+
+// Gallery file path watcher delegate to handle the gallery change

[Lei Zhang, 2012/12/18 01:45:16]

From this comment, I still have trouble understanding what the exact
responsibility of this class is.

[kmadhusu, 2012/12/18 21:32:39]

How about this?
// This class does a recursive watch on the gallery file path and sends
notifications to the
// extensions about the gallery changed event. This class lives on the file
thread.

[Lei Zhang, 2012/12/19 01:03:47]

Your comment still does not answer the question of who are "the extensions"? How
about:

This class does a recursive watch on a gallery file path and holds a list of
extensions that are watching the gallery. When there is file system activity
within the gallery, GalleryFilePathWatcher notifies the interested extensions.

[kmadhusu, 2012/12/19 21:55:55]

sure. Done.

+// notifications. This class manages all the extension usage and forwards
+// the gallery change notifications to the extensions. This class lives on
+// the FILE thread. This class is instantiated per gallery watch path and does
+// recursive watches.
+class GalleryFilePathWatcher : public base::RefCounted<GalleryFilePathWatcher> {
+ public:
+  GalleryFilePathWatcher(const Profile* profile,
+                         const std::string& gallery_id,
+                         const FilePath& path,
+                         const std::string& extension_id);
+
+  // Adds the extension specified by the |extension_id| to the
+  // ExtensionWatchInfoMap and initiate the watch operation.

[Lei Zhang, 2012/12/18 01:45:16]

What does "initiate the watch operation" mean? How does it relate to "sets up
the watch operation" below?

[kmadhusu, 2012/12/18 21:32:39]

This function adds an extension reference to the watched gallery. Fixed the
comment.

+  void AddExtension(const std::string& extension_id);
+
+  // Cancels the watch for the extension specified by the |extension_id|.
+  void RemoveExtension(const std::string& extension_id);
+
+  // Handles the extension unloaded/uninstalled/destroyed event.
+  void OnExtensionDestroyed(const std::string& extension_id);
+
+  // Sets up the watch operation for the specified |gallery_path_|. On
+  // success, returns true.
+  bool SetupWatch();
+
+  // Removes all the extension references when the browser profile is in
+  // shutdown mode.
+  void RemoveAllWatchReferences();
+
+ private:
+  friend class base::RefCounted<GalleryFilePathWatcher>;
+
+  // Keeps track of extension watch details.
+  struct ExtensionWatchInfo {

[Lei Zhang, 2012/12/18 01:45:16]

Are you keeping track of how many times a particular extension tries to add a
particular gallery watch? i.e. if extension foo calls AddGalleryWatch for /bar
twice, then it takes 2 remove AddGalleryWatch calls to stop watching /bar.

You shouldn't have to do this. If extension foo calls AddGallery() twice for a
particular gallery, the second call is a no-op. Whether a given extension is
watching a given gallery should be an on/off state.

[kmadhusu, 2012/12/18 21:32:39]

Yes
When we have multiple instances of the same extension, we need to count the
total number of references.

(FYI) All the instances have the same extension id. We receive the extension
destroyed event only when the last instance of the extension is destroyed. 

+    ExtensionWatchInfo();
+
+    // Number of watches in this extension, e.g "3"
+    unsigned int watch_count;
+
+    // Used to manage the gallery changed events.
+    base::Time last_gallery_changed_event;
+  };
+
+  typedef std::map<std::string, ExtensionWatchInfo> ExtensionWatchInfoMap;
+
+  // Private because GalleryFilePathWatcher is ref-counted.
+  virtual ~GalleryFilePathWatcher();
+
+  // FilePathWatcher callback.
+  void OnFilePathChanged(const FilePath& path, bool error);
+
+  // Remove the watch references for the extension specified by the
+  // |extension_id|.
+  void RemoveExtensionReferences(const std::string& extension_id);
+
+  // Current profile.
+  const Profile* profile_;
+
+  // The gallery identifier, e.g "1".
+  const std::string gallery_id_;
+
+  // The gallery file path watcher.
+  base::files::FilePathWatcher file_watcher_;
+
+  // The gallery file path, e.g "C:\My Pictures".
+  FilePath gallery_path_;
+
+  // Map to keep track of the extension and its corresponding watch count.
+  // Key: Extension identifier, e.g "qoueruoweuroiwueroiwujkshdf".
+  // Value: Watch information.
+  ExtensionWatchInfoMap extension_watch_info_map_;
+
+  // Used to provide a weak pointer to FilePathWatcher callback.
+  base::WeakPtrFactory<GalleryFilePathWatcher> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(GalleryFilePathWatcher);
+};
+
+GalleryFilePathWatcher::GalleryFilePathWatcher(const Profile* profile,
+                                               const std::string& gallery_id,
+                                               const FilePath& path,
+                                               const std::string& extension_id)
+    : profile_(profile),
+      gallery_id_(gallery_id),
+      weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  gallery_path_ = path;
+  AddExtension(extension_id);
+}
+
+void GalleryFilePathWatcher::AddExtension(const std::string& extension_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  ExtensionWatchInfoMap::iterator it =
+      extension_watch_info_map_.find(extension_id);
+  if (it != extension_watch_info_map_.end()) {
+    it->second.watch_count++;
+  } else {
+    extension_watch_info_map_.insert(
+        ExtensionWatchInfoMap::value_type(extension_id, ExtensionWatchInfo()));
+  }
+  AddRef();
+}
+
+void GalleryFilePathWatcher::RemoveExtension(const std::string& extension_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  ExtensionWatchInfoMap::iterator it =
+      extension_watch_info_map_.find(extension_id);
+  if (it == extension_watch_info_map_.end())
+    return;
+  // If entry found - decrease it's count and remove if necessary
+  it->second.watch_count--;
+  if (0 == it->second.watch_count)
+    extension_watch_info_map_.erase(it);
+  Release();
+}
+
+void GalleryFilePathWatcher::OnExtensionDestroyed(
+    const std::string& extension_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  RemoveExtensionReferences(extension_id);
+}
+
+bool GalleryFilePathWatcher::SetupWatch() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  return file_watcher_.Watch(
+      gallery_path_, true,
+      base::Bind(&GalleryFilePathWatcher::OnFilePathChanged,
+                 weak_ptr_factory_.GetWeakPtr()));
+}
+
+void GalleryFilePathWatcher::RemoveAllWatchReferences() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  std::set<std::string> extension_ids;
+  for (ExtensionWatchInfoMap::iterator iter = extension_watch_info_map_.begin();
+       iter != extension_watch_info_map_.end(); ++iter)
+    extension_ids.insert(iter->first);
+
+  for (std::set<std::string>::const_iterator it = extension_ids.begin();
+       it != extension_ids.end(); ++it)
+    RemoveExtensionReferences(*it);
+}
+
+GalleryFilePathWatcher::~GalleryFilePathWatcher() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+}
+
+GalleryFilePathWatcher::ExtensionWatchInfo::ExtensionWatchInfo()
+    : watch_count(1) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));

[Lei Zhang, 2012/12/18 01:45:16]

Structs should not do anything other can carry value.
http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Structs_vs._Cl...

[kmadhusu, 2012/12/18 21:32:39]

Done.

+}
+
+void GalleryFilePathWatcher::OnFilePathChanged(const FilePath& path,
+                                               bool error) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  if (error || (path != gallery_path_))
+    return;
+
+  std::set<std::string> extension_ids;
+  for (ExtensionWatchInfoMap::iterator iter = extension_watch_info_map_.begin();
+       iter != extension_watch_info_map_.end(); ++iter) {
+    if (!iter->second.last_gallery_changed_event.is_null()) {
+      // Ignore gallery change event if it is received too frequently.
+      // For example, when an user copies/deletes 1000 media files from a
+      // gallery, this callback is called 1000 times within a span of 10ms.
+      // GalleryWatchManager should not send 1000 gallery changed events to
+      // the watching extension.
+      const int kMinSecondsToIgnoreGalleryChangedEvent = 3;
+      base::TimeDelta diff =
+          base::Time::Now() - iter->second.last_gallery_changed_event;
+      if (diff.InSeconds() < kMinSecondsToIgnoreGalleryChangedEvent)
+        continue;
+    }
+    iter->second.last_gallery_changed_event = base::Time::Now();
+    extension_ids.insert(iter->first);
+  }
+  if (!extension_ids.empty()) {
+    content::BrowserThread::PostTask(
+        content::BrowserThread::UI, FROM_HERE,
+        base::Bind(SendGalleryChangedEventOnUIThread, profile_, gallery_id_,
+                   extension_ids));
+  }
+}
+
+void GalleryFilePathWatcher::RemoveExtensionReferences(
+    const std::string& extension_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  ExtensionWatchInfoMap::iterator it =
+      extension_watch_info_map_.find(extension_id);
+  if (it == extension_watch_info_map_.end())
+    return;
+  const ExtensionWatchInfo watch_info = it->second;
+  for (unsigned int i = 0; i < watch_info.watch_count; ++i)
+    Release();
+  extension_watch_info_map_.erase(it);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//                       GalleryWatchManager                                 //
+///////////////////////////////////////////////////////////////////////////////
+
+// static
+GalleryWatchManager* GalleryWatchManager::GetForProfile(
+    const Profile* profile) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  DCHECK(profile);
+  bool has_watch_manager = (g_gallery_watch_managers &&
+                            GalleryWatchManager::HasForProfile(profile));
+  if (!g_gallery_watch_managers)
+    g_gallery_watch_managers = new WatchManagerMap;
+  if (!has_watch_manager)
+    (*g_gallery_watch_managers)[profile] = new GalleryWatchManager(profile);
+  return (*g_gallery_watch_managers)[profile];
+}
+
+// static
+bool GalleryWatchManager::HasForProfile(const Profile* profile) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  DCHECK(profile);
+  if (!g_gallery_watch_managers)
+    return false;
+  WatchManagerMap::const_iterator it = g_gallery_watch_managers->find(profile);
+  return (it != g_gallery_watch_managers->end());
+}
+
+// static
+void GalleryWatchManager::OnProfileShutdown(const Profile* profile) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  DCHECK(profile);
+  if (!g_gallery_watch_managers || g_gallery_watch_managers->empty())
+    return;
+  WatchManagerMap::iterator it = g_gallery_watch_managers->find(profile);
+  if (it == g_gallery_watch_managers->end())
+    return;
+  delete it->second;
+  g_gallery_watch_managers->erase(it);
+  if (g_gallery_watch_managers->empty())
+    delete g_gallery_watch_managers;
+}
+
+GalleryWatchManager::~GalleryWatchManager() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  if (!gallery_watchers_.empty()) {
+    // User closed the extension/browser without stoping the gallery watchers.
+    DeleteAllWatchers();
+  }
+  DCHECK(gallery_watchers_.empty());
+}
+
+bool GalleryWatchManager::StartGalleryWatch(
+    const std::string& gallery_id,
+    const FilePath& watch_path,
+    const std::string& extension_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  WatcherMap::const_iterator iter = gallery_watchers_.find(watch_path);
+  if (iter != gallery_watchers_.end()) {
+    // Already watched.
+    iter->second->AddExtension(extension_id);
+    return true;
+  }
+
+  // Need to add a new watcher.
+  scoped_refptr<GalleryFilePathWatcher> watch(
+      new GalleryFilePathWatcher(profile_, gallery_id, watch_path,
+                                 extension_id));
+  if (!watch->SetupWatch())
+    return false;
+  gallery_watchers_[watch_path] = watch;
+  return true;
+}
+
+void GalleryWatchManager::StopGalleryWatch(
+    const FilePath& watch_path,
+    const std::string& extension_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  WatcherMap::iterator iter = gallery_watchers_.find(watch_path);
+  if (iter == gallery_watchers_.end())
+    return;
+  // Remove the renderer process for this watch.
+  iter->second->RemoveExtension(extension_id);
+  if (iter->second->HasOneRef()) {
+    // There are no references other than the one |gallery_watchers_| holds.
+    iter->second = NULL;
+    gallery_watchers_.erase(iter);
+  }
+}
+
+void GalleryWatchManager::OnExtensionDestroyed(
+    const std::string& extension_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  std::list<FilePath> watchers_to_erase;
+  for (WatcherMap::iterator iter = gallery_watchers_.begin();
+       iter != gallery_watchers_.end(); ++iter) {
+    // Remove the renderer process for this watch.
+    iter->second->OnExtensionDestroyed(extension_id);
+    if (iter->second->HasOneRef()) {
+      // There are no references other than the one |gallery_watchers_| holds.
+      watchers_to_erase.push_back(iter->first);
+    }
+  }
+
+  for (std::list<FilePath>::const_iterator path = watchers_to_erase.begin();
+       path != watchers_to_erase.end(); ++path) {
+    WatcherMap::iterator iter = gallery_watchers_.find(*path);
+    DCHECK(iter != gallery_watchers_.end());
+    iter->second = NULL;
+    gallery_watchers_.erase(iter);
+  }
+}
+
+GalleryWatchManager::GalleryWatchManager(const Profile* profile)
+    : profile_(profile) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+}
+
+void GalleryWatchManager::DeleteAllWatchers() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  std::list<FilePath> watchers_to_erase;
+  for (WatcherMap::iterator iter = gallery_watchers_.begin();
+       iter != gallery_watchers_.end(); ++iter) {
+    iter->second->RemoveAllWatchReferences();
+    // Verify that there are no references other than the one
+    // |gallery_watchers_| holds.
+    DCHECK(iter->second->HasOneRef());
+    watchers_to_erase.push_back(iter->first);
+  }
+
+  for (std::list<FilePath>::const_iterator path = watchers_to_erase.begin();
+       path != watchers_to_erase.end(); ++path) {
+    WatcherMap::iterator iter = gallery_watchers_.find(*path);
+    DCHECK(iter != gallery_watchers_.end());
+    iter->second = NULL;
+    gallery_watchers_.erase(iter);
+  }
+}
+
+}  // namespace extensions