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<Profile*, extensions::GalleryWatchManager*>
+    WatchManagerMap;
+WatchManagerMap* g_gallery_watch_managers = NULL;
+
+// Dispatches the gallery changed event on the UI thread.
+void SendGalleryChangedEventOnUIThread(
+    Profile* profile,
+    uint64 gallery_id,
+    const std::set<std::string>& extension_ids) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK(profile);
+  MediaGalleriesPrivateEventRouter* router =
+      MediaGalleriesPrivateAPIFactory::GetForProfile(profile)->event_router();
+  if (!router)
+    return;
+  router->OnGalleryChanged(gallery_id, extension_ids);
+}
+
+}  // namespace
+
+///////////////////////////////////////////////////////////////////////////////
+//                       GalleryFilePathWatcher                              //
+///////////////////////////////////////////////////////////////////////////////
+
+// 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.
+class GalleryFilePathWatcher : public base::RefCounted<GalleryFilePathWatcher> {
+ public:
+  GalleryFilePathWatcher(Profile* profile,
+                         uint64 gallery_id,
+                         const FilePath& path,
+                         const std::string& extension_id);
+
+  // Adds the extension reference to the watched gallery.
+  void AddExtension(const std::string& extension_id);
+
+  // Removes the extension reference to the watched gallery.
+  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 {
+    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;

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

So if you can have multiple instances of an extension, then doesn't each
instance need its own |last_gallery_changed_event| ?

You may want to replace ExtensionWatchInfoMap with a std::multi_map<std::string,
base::Time>.

[Lei Zhang, 2012/12/19 01:13:25]

Come to think of it, this is a very weird case. Even with a multimap, you know
there's some instance of the extension that needs the event notification, but
there's no way to send the event to only that instance.

[kmadhusu, 2012/12/19 23:13:17]

The chances of hitting this use case is very less. Lets use the counting method
now. If we find more corner cases, we will use a multi-map or find some other
way to distinguish multiple instances of the same extension.

+  };
+
+  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.
+  Profile* profile_;
+
+  // The gallery identifier, e.g "1".
+  uint64 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(Profile* profile,
+                                               uint64 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) {
+}
+
+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(
+    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(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(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()) {

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

Put this in DeleteAllWatchers().

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

Done.

+    // User closed the extension/browser without stoping the gallery watchers.

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

I don't find this comment useful. No user will ever think about removing gallery
watchers before closing their browser.

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

Removed.

+    DeleteAllWatchers();
+  }
+  DCHECK(gallery_watchers_.empty());
+}
+
+bool GalleryWatchManager::StartGalleryWatch(
+    uint64 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()) {

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

HasOneRef() is rarely used in our code base. I think this is just more manual
refcounting. WatcherMap probably should have a raw pointer and the watchers it
hold can have a callback to GalleryWatchManager when they get destroyed.

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

Done.

+      // 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(Profile* profile)
+    : profile_(profile) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  DCHECK(profile_);
+}
+
+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