Add DiscoveryNetworkMonitor implementation

chrome/browser/media/router/discovery/discovery_network_monitor.cc

+// Copyright (c) 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 "chrome/browser/media/router/discovery/discovery_network_monitor.h"
+
+#include <unordered_set>
+
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/sha1.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
+#include "chrome/browser/media/router/discovery/discovery_network_list.h"
+#include "net/base/network_interfaces.h"
+
+namespace {
+
+using content::BrowserThread;
+
+std::string ComputeNetworkId(
+    const std::vector<DiscoveryNetworkInfo>& network_info_list) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+
+  if (network_info_list.size() == 0) {

[mark a. foltz, 2017/06/05 21:28:43]

I slightly prefer omitting the { } for one-line if statements.  But remain
consistent with the style of surrounding code.

[btolsch, 2017/06/05 22:38:33]

Acknowledged.

+    return DiscoveryNetworkMonitor::kNetworkIdDisconnected;
+  }
+  bool has_nonempty_network_id = false;

[mark a. foltz, 2017/06/05 21:28:43]

This could be one liner with std::find_if, and slightly more efficient by loop
breaking, but I don't feel strongly.  (I like that the std:: algorithms denote a
specific loop structure, while others find the use of lambda expressions
annoying...)

[btolsch, 2017/06/05 22:38:33]

Done.

+  for (const auto& network_info : network_info_list) {
+    has_nonempty_network_id =
+        has_nonempty_network_id || network_info.network_id.size() > 0;
+  }
+  if (!has_nonempty_network_id) {
+    return DiscoveryNetworkMonitor::kNetworkIdUnknown;
+  }
+
+  std::string combined_ids;
+  for (const auto& network_info : network_info_list) {
+    combined_ids = combined_ids + "!" + network_info.network_id;
+  }
+
+  std::string hash = base::SHA1HashString(combined_ids);
+  return base::ToLowerASCII(base::HexEncode(hash.data(), hash.length()));
+}
+
+std::vector<DiscoveryNetworkInfo> GetNetworkInfo() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  return GetDiscoveryNetworkInfoList();
+}
+
+base::LazyInstance<DiscoveryNetworkMonitor>::Leaky g_discovery_monitor;
+
+}  // namespace
+
+// static
+constexpr char DiscoveryNetworkMonitor::kNetworkIdDisconnected[];

[imcheng, 2017/05/31 21:19:55]

Are these necessary since you've already defined them in the .h?

[btolsch, 2017/06/05 22:38:33]

Yes.  In short, any odr-use still requires a definition, e.g. line 26 above
which is essentially |return std::string(&kNetworkIdDisconnected[0]);|.

+// static
+constexpr char DiscoveryNetworkMonitor::kNetworkIdUnknown[];
+
+// static
+DiscoveryNetworkMonitor* DiscoveryNetworkMonitor::GetInstance() {
+  DiscoveryNetworkMonitor* monitor = g_discovery_monitor.Pointer();
+  if (!monitor->network_info_function_) {
+    monitor->network_info_function_ = &GetNetworkInfo;
+  }
+  return monitor;
+}
+
+void DiscoveryNetworkMonitor::RebindNetworkChangeObserverForTest() {
+  net::NetworkChangeNotifier::AddNetworkChangeObserver(this);
+}
+
+void DiscoveryNetworkMonitor::SetNetworkInfoFunctionForTest(
+    NetworkInfoFunction strategy) {
+  network_info_function_ = strategy;
+}
+
+void DiscoveryNetworkMonitor::AddObserver(Observer* const observer) {
+  observers_->AddObserver(observer);
+}
+
+void DiscoveryNetworkMonitor::RemoveObserver(Observer* const observer) {
+  observers_->RemoveObserver(observer);
+}
+
+void DiscoveryNetworkMonitor::Refresh(NetworkRefreshCompleteCallback callback) {
+  BrowserThread::PostTaskAndReply(
+      BrowserThread::IO, FROM_HERE,
+      base::BindOnce(&DiscoveryNetworkMonitor::UpdateNetworkInfo,
+                     base::Unretained(this)),
+      std::move(callback));
+}
+
+const std::string& DiscoveryNetworkMonitor::GetNetworkId() const {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  return network_id_;
+}
+
+DiscoveryNetworkMonitor::DiscoveryNetworkMonitor()
+    : network_id_(kNetworkIdDisconnected),
+      observers_(new base::ObserverListThreadSafe<Observer>(
+          base::ObserverListThreadSafe<
+              Observer>::NotificationType::NOTIFY_EXISTING_ONLY)) {

[imcheng, 2017/05/31 21:19:55]

Can we initialize network_info_function_ to &GetNetworkInfo here?

[btolsch, 2017/06/05 22:38:33]

Done.

+  net::NetworkChangeNotifier::AddNetworkChangeObserver(this);
+}
+
+DiscoveryNetworkMonitor::~DiscoveryNetworkMonitor() {
+  net::NetworkChangeNotifier::RemoveNetworkChangeObserver(this);
+}
+
+void DiscoveryNetworkMonitor::OnNetworkChanged(
+    net::NetworkChangeNotifier::ConnectionType) {
+  BrowserThread::PostTask(
+      BrowserThread::IO, FROM_HERE,
+      base::Bind(&DiscoveryNetworkMonitor::UpdateNetworkInfo,
+                 base::Unretained(this)));
+}
+
+void DiscoveryNetworkMonitor::UpdateNetworkInfo() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+
+  auto network_info_list = network_info_function_();
+  auto network_id = ComputeNetworkId(network_info_list);
+
+  network_id_.swap(network_id);
+
+  if (network_id_ != network_id) {
+    observers_->Notify(FROM_HERE, &Observer::OnNetworksChanged,
+                       base::ConstRef(*this));
+  }
+}