Introduce AllDownloadEventNotifier to listen to all download events

AllDownloadEventNotifier will listen to SimpleDownloadManagerCoordinate.
And report all the download events to its observers.

BUG=942770

Change-Id: I29b1e573d9c1f0e8b05002499410f296b6873765
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1560446Reviewed-by: Shakti Sahu <shaktisahu@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Min Qin <qinmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#649719}

components/download/internal/common/BUILD.gn

@@ -18,6 +18,7 @@ source_set("internal") {
   ]
 
   sources = [
+    "all_download_event_notifier.cc",
     "base_file.cc",
     "base_file_win.cc",
     "download_create_info.cc",

components/download/internal/common/all_download_event_notifier.cc

+// Copyright 2019 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/download/public/common/all_download_event_notifier.h"
+
+namespace download {
+
+AllDownloadEventNotifier::AllDownloadEventNotifier(
+    SimpleDownloadManagerCoordinator* simple_download_manager_coordinator)
+    : simple_download_manager_coordinator_(simple_download_manager_coordinator),
+      download_initialized_(false) {
+  simple_download_manager_coordinator_->AddObserver(this);
+  std::vector<DownloadItem*> downloads;
+  simple_download_manager_coordinator_->GetAllDownloads(&downloads);
+  for (auto* download : downloads) {
+    download->AddObserver(this);
+    observing_.insert(download);
+  }
+}
+
+AllDownloadEventNotifier::~AllDownloadEventNotifier() {
+  if (simple_download_manager_coordinator_)
+    simple_download_manager_coordinator_->RemoveObserver(this);
+  for (auto it = observing_.begin(); it != observing_.end(); ++it) {
+    (*it)->RemoveObserver(this);
+  }
+  observing_.clear();
+}
+
+void AllDownloadEventNotifier::AddObserver(Observer* observer) {
+  observers_.AddObserver(observer);
+  if (download_initialized_) {
+    observer->OnDownloadsInitialized(
+        simple_download_manager_coordinator_,
+        !simple_download_manager_coordinator_->has_all_history_downloads());
+  }
+}
+
+void AllDownloadEventNotifier::RemoveObserver(Observer* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+void AllDownloadEventNotifier::OnDownloadsInitialized(
+    bool active_downloads_only) {
+  download_initialized_ = true;
+  for (auto& observer : observers_)
+    observer.OnDownloadsInitialized(simple_download_manager_coordinator_,
+                                    active_downloads_only);
+}
+
+void AllDownloadEventNotifier::OnManagerGoingDown() {
+  for (auto& observer : observers_)
+    observer.OnManagerGoingDown(simple_download_manager_coordinator_);
+  simple_download_manager_coordinator_->RemoveObserver(this);
+  simple_download_manager_coordinator_ = nullptr;
+}
+
+void AllDownloadEventNotifier::OnDownloadCreated(DownloadItem* item) {
+  if (observing_.find(item) != observing_.end())
+    return;
+  item->AddObserver(this);
+  observing_.insert(item);
+  for (auto& observer : observers_)
+    observer.OnDownloadCreated(simple_download_manager_coordinator_, item);
+}
+
+void AllDownloadEventNotifier::OnDownloadUpdated(DownloadItem* item) {
+  for (auto& observer : observers_)
+    observer.OnDownloadUpdated(simple_download_manager_coordinator_, item);
+}
+
+void AllDownloadEventNotifier::OnDownloadOpened(DownloadItem* item) {
+  for (auto& observer : observers_)
+    observer.OnDownloadOpened(simple_download_manager_coordinator_, item);
+}
+
+void AllDownloadEventNotifier::OnDownloadRemoved(DownloadItem* item) {
+  for (auto& observer : observers_)
+    observer.OnDownloadRemoved(simple_download_manager_coordinator_, item);
+}
+
+void AllDownloadEventNotifier::OnDownloadDestroyed(DownloadItem* item) {
+  item->RemoveObserver(this);
+  observing_.erase(item);
+}
+
+}  // namespace download

components/download/internal/common/simple_download_manager_coordinator.cc

@@ -6,6 +6,7 @@
 
 #include <utility>
 
+#include "components/download/public/common/all_download_event_notifier.h"
 #include "components/download/public/common/download_item.h"
 #include "components/download/public/common/simple_download_manager.h"
 
@@ -82,4 +83,10 @@ void SimpleDownloadManagerCoordinator::OnDownloadCreated(DownloadItem* item) {
     observer.OnDownloadCreated(item);
 }
 
+AllDownloadEventNotifier* SimpleDownloadManagerCoordinator::GetNotifier() {
+  if (!notifier_)
+    notifier_ = std::make_unique<AllDownloadEventNotifier>(this);
+  return notifier_.get();
+}
+
 }  // namespace download

components/download/public/common/BUILD.gn

@@ -15,6 +15,7 @@ config("components_download_implementation") {
 
 component("public") {
   sources = [
+    "all_download_event_notifier.h",
     "auto_resumption_handler.cc",
     "auto_resumption_handler.h",
     "base_file.h",

components/download/public/common/all_download_event_notifier.h

+// Copyright 2019 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 COMPONENTS_DOWNLOAD_PUBLIC_COMMON_ALL_DOWNLOAD_EVENT_NOTIFIER_H_
+#define COMPONENTS_DOWNLOAD_PUBLIC_COMMON_ALL_DOWNLOAD_EVENT_NOTIFIER_H_
+
+#include <set>
+
+#include "base/macros.h"
+#include "base/observer_list.h"
+#include "components/download/public/common/download_item.h"
+#include "components/download/public/common/simple_download_manager_coordinator.h"
+
+namespace download {
+
+// Observes all the download events from a single
+// SimpleDownloadManagerCoordinator.
+class AllDownloadEventNotifier
+    : public SimpleDownloadManagerCoordinator::Observer,
+      public DownloadItem::Observer {
+ public:
+  // All of the methods take the SimpleDownloadManagerCoordinator so that
+  // subclasses can observe multiple managers at once and easily distinguish
+  // which manager a given item belongs to.
+  class Observer {
+   public:
+    Observer() = default;
+    virtual ~Observer() = default;
+
+    virtual void OnDownloadsInitialized(
+        SimpleDownloadManagerCoordinator* coordinator,
+        bool active_downloads_only) {}
+    virtual void OnManagerGoingDown(
+        SimpleDownloadManagerCoordinator* coordinator) {}
+    virtual void OnDownloadCreated(SimpleDownloadManagerCoordinator* manager,
+                                   DownloadItem* item) {}
+    virtual void OnDownloadUpdated(SimpleDownloadManagerCoordinator* manager,
+                                   DownloadItem* item) {}
+    virtual void OnDownloadOpened(SimpleDownloadManagerCoordinator* manager,
+                                  DownloadItem* item) {}
+    virtual void OnDownloadRemoved(SimpleDownloadManagerCoordinator* manager,
+                                   DownloadItem* item) {}
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(Observer);
+  };
+
+  explicit AllDownloadEventNotifier(SimpleDownloadManagerCoordinator* manager);
+  ~AllDownloadEventNotifier() override;
+
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+ private:
+  // SimpleDownloadManagerCoordinator::Observer
+  void OnDownloadsInitialized(bool active_downloads_only) override;
+  void OnManagerGoingDown() override;
+  void OnDownloadCreated(DownloadItem* item) override;
+
+  // DownloadItem::Observer
+  void OnDownloadUpdated(DownloadItem* item) override;
+  void OnDownloadOpened(DownloadItem* item) override;
+  void OnDownloadRemoved(DownloadItem* item) override;
+  void OnDownloadDestroyed(DownloadItem* item) override;
+
+  SimpleDownloadManagerCoordinator* simple_download_manager_coordinator_;
+  std::set<DownloadItem*> observing_;
+
+  bool download_initialized_;
+
+  // Observers that want to be notified of download events.
+  base::ObserverList<Observer>::Unchecked observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(AllDownloadEventNotifier);
+};
+
+}  // namespace download
+
+#endif  // COMPONENTS_DOWNLOAD_PUBLIC_COMMON_ALL_DOWNLOAD_EVENT_NOTIFIER_H_

components/download/public/common/simple_download_manager_coordinator.h

@@ -18,6 +18,7 @@
 
 namespace download {
 
+class AllDownloadEventNotifier;
 class DownloadItem;
 
 // This object allows swapping between different SimppleDownloadManager
@@ -65,6 +66,9 @@ class COMPONENTS_DOWNLOAD_EXPORT SimpleDownloadManagerCoordinator
   // Return whether this object has download manager set.
   bool HasSetDownloadManager();
 
+  // Returns a non-empty notifier to be used for observing download events.
+  AllDownloadEventNotifier* GetNotifier();
+
   bool has_all_history_downloads() const { return has_all_history_downloads_; }
 
  private:
@@ -77,6 +81,9 @@ class COMPONENTS_DOWNLOAD_EXPORT SimpleDownloadManagerCoordinator
 
   SimpleDownloadManager* simple_download_manager_;
 
+  // Object for notifying others about various download events.
+  std::unique_ptr<AllDownloadEventNotifier> notifier_;
+
   // Whether all the history downloads are ready.
   bool has_all_history_downloads_;