Switch between online and offline version per network connection

chrome/browser/android/offline_pages/offline_page_tab_helper.cc

+// Copyright 2016 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 "chrome/browser/android/offline_pages/offline_page_tab_helper.h"
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "base/metrics/histogram.h"
+#include "base/thread_task_runner_handle.h"
+#include "chrome/browser/android/offline_pages/offline_page_utils.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/navigation_controller.h"
+#include "content/public/browser/render_frame_host.h"
+#include "content/public/browser/web_contents.h"
+#include "net/base/net_errors.h"
+#include "net/base/network_change_notifier.h"
+
+DEFINE_WEB_CONTENTS_USER_DATA_KEY(offline_pages::OfflinePageTabHelper);
+
+namespace offline_pages {
+
+OfflinePageTabHelper::OfflinePageTabHelper(content::WebContents* web_contents)
+    : content::WebContentsObserver(web_contents),
+      weak_ptr_factory_(this) {
+  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+}
+
+OfflinePageTabHelper::~OfflinePageTabHelper() {}
+
+void OfflinePageTabHelper::DidStartProvisionalLoadForFrame(
+    content::RenderFrameHost* render_frame_host,
+    const GURL& validated_url,
+    bool is_error_page,
+    bool is_iframe_srcdoc) {
+  GURL last_redirect_from_url_copy = last_redirect_from_url_;
+  last_redirect_from_url_ = GURL();
+
+  // Skips non-main frame.
+  if (render_frame_host->GetParent() != nullptr)
+    return;
+
+  // Redirecting to online version will only take effect when there is network
+  // connection.
+  if (net::NetworkChangeNotifier::GetConnectionType() ==
+          net::NetworkChangeNotifier::CONNECTION_NONE) {

[Pete Williamson, 2016/02/25 18:05:30]

Why not use if (!NetworkChangeNotifier::IsOnline()) here instead?  That would
keep us from also depending on the CONNECTION_NONE constant.

[jianli, 2016/02/25 21:34:52]

Changed to call IsOffline.

+    return;
+  }
+
+  // Skips if not loading an offline copy of saved page.
+  GURL online_url = offline_pages::OfflinePageUtils::GetOnlineURLForOfflineURL(
+      web_contents()->GetBrowserContext(), validated_url);
+  if (!online_url.is_valid())
+    return;
+
+  // Avoids loop between online and offline redirections.
+  if (last_redirect_from_url_copy == online_url)

[Pete Williamson, 2016/02/25 18:05:31]

What if our last succesful transfer just happened to be the same page we are
loading now?  Will last_redirect_from_url_copy get cleared between uses?

[jianli, 2016/02/25 21:34:52]

last_redirect_from_url_copy is just a saved value before last_redirect_from_url_
is cleared (see line 36-37).

+    return;
+  last_redirect_from_url_ = validated_url;
+
+  base::ThreadTaskRunnerHandle::Get()->PostTask(

[Pete Williamson, 2016/02/25 18:05:31]

So if we delay the redirect, it lets the existing page load attempt get further.
 Is that a problem?  (I suspect not, I just wanted to double check).

[jianli, 2016/02/25 21:34:52]

This is to let other observers finish their work.

+      FROM_HERE,
+      base::Bind(&OfflinePageTabHelper::RedirectFromOfflineToOnline,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 online_url));
+}
+
+void OfflinePageTabHelper::DidFailProvisionalLoad(
+    content::RenderFrameHost* render_frame_host,
+    const GURL& validated_url,
+    int error_code,
+    const base::string16& error_description,
+    bool was_ignored_by_handler) {
+  GURL last_redirect_from_url_copy = last_redirect_from_url_;
+  last_redirect_from_url_ = GURL();
+
+  // Skips non-main frame or load failure other than no network.
+  if (error_code != net::ERR_INTERNET_DISCONNECTED ||
+      render_frame_host->GetParent() != nullptr) {
+    return;
+  }
+
+  // Redirecting to offline version will only take effect when there is no
+  // network connection.
+  if (net::NetworkChangeNotifier::GetConnectionType() !=
+          net::NetworkChangeNotifier::CONNECTION_NONE) {

[Pete Williamson, 2016/02/25 18:05:30]

NetworkChangeNotifier::IsOnline() ?

[jianli, 2016/02/25 21:34:52]

Changed to call IsOffline.

+    return;
+  }
+
+  // Skips if not loading an online version of saved page.
+  GURL offline_url = offline_pages::OfflinePageUtils::GetOfflineURLForOnlineURL(
+      web_contents()->GetBrowserContext(), validated_url);
+  if (!offline_url.is_valid())
+    return;
+
+  // Avoids loop between online and offline redirections.
+  if (last_redirect_from_url_ == offline_url)
+    return;
+  last_redirect_from_url_ = validated_url;
+
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE,
+      base::Bind(&OfflinePageTabHelper::RedirectFromOnlineToOffline,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 offline_url));
+}
+
+void OfflinePageTabHelper::RedirectFromOfflineToOnline(const GURL& online_url) {
+  UMA_HISTOGRAM_COUNTS("OfflinePages.RedirectToOnlineCount", 1);
+  content::NavigationController::LoadURLParams load_params(online_url);
+  load_params.transition_type = ui::PAGE_TRANSITION_CLIENT_REDIRECT;
+  web_contents()->GetController().LoadURLWithParams(load_params);
+}
+
+void OfflinePageTabHelper::RedirectFromOnlineToOffline(
+    const GURL& offline_url) {
+  UMA_HISTOGRAM_COUNTS("OfflinePages.RedirectToOfflineCount", 1);
+  content::NavigationController::LoadURLParams load_params(offline_url);
+  load_params.transition_type = ui::PAGE_TRANSITION_CLIENT_REDIRECT;
+  web_contents()->GetController().LoadURLWithParams(load_params);
+}
+
+}  // namespace offline_pages