Add a throttle wrapper to OfflineContentProvider

components/offline_items_collection/core/throttled_offline_content_provider.cc

Index: components/offline_items_collection/core/throttled_offline_content_provider.cc
diff --git a/components/offline_items_collection/core/throttled_offline_content_provider.cc b/components/offline_items_collection/core/throttled_offline_content_provider.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1b534c84b871cbc411cb1dd0cd8e58d62ea96c19
--- /dev/null
+++ b/components/offline_items_collection/core/throttled_offline_content_provider.cc
@@ -0,0 +1,154 @@
+// Copyright 2017 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.
+
+#include "components/offline_items_collection/core/throttled_offline_content_provider.h"
+
+#include <utility>
+
+#include "base/bind.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "base/time/time.h"
+#include "components/offline_items_collection/core/offline_item.h"
+
+namespace offline_items_collection {
+namespace {
+const int kDelayBetweenUpdatesMs = 1000;
+}  // namespace
+
+ThrottledOfflineContentProvider::ThrottledOfflineContentProvider(
+    OfflineContentProvider* provider)
+    : ThrottledOfflineContentProvider(
+          base::TimeDelta::FromMilliseconds(kDelayBetweenUpdatesMs),
+          provider) {}
+
+ThrottledOfflineContentProvider::ThrottledOfflineContentProvider(
+    const base::TimeDelta& delay_between_updates,
+    OfflineContentProvider* provider)
+    : delay_between_updates_(delay_between_updates),
+      update_queued_(false),
+      wrapped_provider_(provider),
+      weak_ptr_factory_(this) {
+  DCHECK(wrapped_provider_);
+  wrapped_provider_->AddObserver(this);
+}
+
+ThrottledOfflineContentProvider::~ThrottledOfflineContentProvider() {
+  wrapped_provider_->RemoveObserver(this);
+}
+
+bool ThrottledOfflineContentProvider::AreItemsAvailable() {
+  return wrapped_provider_->AreItemsAvailable();
+}
+
+void ThrottledOfflineContentProvider::OpenItem(const ContentId& id) {
+  wrapped_provider_->OpenItem(id);
+}
+
+void ThrottledOfflineContentProvider::RemoveItem(const ContentId& id) {
+  wrapped_provider_->RemoveItem(id);
+}
+
+void ThrottledOfflineContentProvider::CancelDownload(const ContentId& id) {
+  wrapped_provider_->CancelDownload(id);
+}
+
+void ThrottledOfflineContentProvider::PauseDownload(const ContentId& id) {
+  wrapped_provider_->PauseDownload(id);
+}
+
+void ThrottledOfflineContentProvider::ResumeDownload(const ContentId& id) {
+  wrapped_provider_->ResumeDownload(id);
+}
+
+const OfflineItem* ThrottledOfflineContentProvider::GetItemById(
+    const ContentId& id) {
+  const OfflineItem* item = wrapped_provider_->GetItemById(id);
+  if (item)
+    UpdateItemIfPresent(*item);
+  return item;
+}
+
+OfflineContentProvider::OfflineItemList
+ThrottledOfflineContentProvider::GetAllItems() {
+  OfflineItemList items = wrapped_provider_->GetAllItems();
+  for (auto item : items)
+    UpdateItemIfPresent(item);
+  return items;
+}
+
+void ThrottledOfflineContentProvider::AddObserver(
+    OfflineContentProvider::Observer* observer) {
+  DCHECK(observer);
+  observers_.AddObserver(observer);
+  if (!wrapped_provider_->AreItemsAvailable())
+    return;
+
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE,
+      base::Bind(&ThrottledOfflineContentProvider::NotifyItemsAvailable,
+                 weak_ptr_factory_.GetWeakPtr(), base::Unretained(observer)));
+}
+
+void ThrottledOfflineContentProvider::RemoveObserver(
+    OfflineContentProvider::Observer* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+void ThrottledOfflineContentProvider::OnItemsAvailable(
+    OfflineContentProvider* provider) {
+  DCHECK_EQ(provider, wrapped_provider_);
+  for (auto& observer : observers_)
+    observer.OnItemsAvailable(this);
+}
+
+void ThrottledOfflineContentProvider::OnItemsAdded(
+    const OfflineItemList& items) {
+  for (auto& observer : observers_)
+    observer.OnItemsAdded(items);
+}
+
+void ThrottledOfflineContentProvider::OnItemRemoved(const ContentId& id) {
+  updates_.erase(id);
+  for (auto& observer : observers_)
+    observer.OnItemRemoved(id);
+}
+
+void ThrottledOfflineContentProvider::OnItemUpdated(const OfflineItem& item) {
+  updates_[item.id] = item;
+  if (update_queued_)
+    return;
+
+  update_queued_ = true;
+  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&ThrottledOfflineContentProvider::FlushUpdates,
+                 weak_ptr_factory_.GetWeakPtr()),
+      delay_between_updates_);
+}
+
+void ThrottledOfflineContentProvider::NotifyItemsAvailable(
+    OfflineContentProvider::Observer* observer) {
+  if (!observers_.HasObserver(observer))
+    return;
+  observer->OnItemsAvailable(this);
+}
+
+void ThrottledOfflineContentProvider::UpdateItemIfPresent(
+    const OfflineItem& item) {
+  OfflineItemMap::iterator it = updates_.find(item.id);
+  if (it != updates_.end())
+    it->second = item;
+}
+
+void ThrottledOfflineContentProvider::FlushUpdates() {
+  update_queued_ = false;
+
+  OfflineItemMap updates = std::move(updates_);
+  for (auto item_pair : updates) {
+    for (auto& observer : observers_)
+      observer.OnItemUpdated(item_pair.second);
+  }
+}
+
+}  // namespace offline_items_collection