[CrOS Tether] Create HostScanCache, which caches scan results and inserts them into the network sta…

chromeos/components/tether/host_scan_cache.cc

Index: chromeos/components/tether/host_scan_cache.cc
diff --git a/chromeos/components/tether/host_scan_cache.cc b/chromeos/components/tether/host_scan_cache.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b34326e6227a77e0ea2ad7bd419a9bf2218e334d
--- /dev/null
+++ b/chromeos/components/tether/host_scan_cache.cc
@@ -0,0 +1,235 @@
+// 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 "chromeos/components/tether/host_scan_cache.h"
+
+#include <algorithm>
+
+#include "base/bind.h"
+#include "base/memory/ptr_util.h"
+#include "chromeos/components/tether/active_host.h"
+#include "chromeos/components/tether/device_id_tether_network_guid_map.h"
+#include "chromeos/components/tether/tether_host_response_recorder.h"
+#include "chromeos/network/network_state_handler.h"
+#include "components/proximity_auth/logging/logging.h"
+
+namespace chromeos {
+
+namespace tether {
+
+HostScanCache::TimerFactoryImpl::TimerFactoryImpl() {}
+
+HostScanCache::TimerFactoryImpl::~TimerFactoryImpl() {}
+
+std::unique_ptr<base::Timer>
+HostScanCache::TimerFactoryImpl::CreateOneShotTimer(
+    const std::string& tether_network_guid) {
+  // Note: |tether_network_guid| is ignored and is only used in the
+  // HostScanCacheTestst.
+  return base::MakeUnique<base::OneShotTimer>();
+}
+
+HostScanCache::HostScanCache(
+    NetworkStateHandler* network_state_handler,
+    ActiveHost* active_host,
+    TetherHostResponseRecorder* tether_host_response_recorder,
+    DeviceIdTetherNetworkGuidMap* device_id_tether_network_guid_map)
+    : HostScanCache(base::MakeUnique<TimerFactoryImpl>(),
+                    network_state_handler,
+                    active_host,
+                    tether_host_response_recorder,
+                    device_id_tether_network_guid_map) {}
+
+HostScanCache::HostScanCache(
+    std::unique_ptr<TimerFactory> timer_factory,
+    NetworkStateHandler* network_state_handler,
+    ActiveHost* active_host,
+    TetherHostResponseRecorder* tether_host_response_recorder,
+    DeviceIdTetherNetworkGuidMap* device_id_tether_network_guid_map)
+    : timer_factory_(std::move(timer_factory)),
+      network_state_handler_(network_state_handler),
+      active_host_(active_host),
+      tether_host_response_recorder_(tether_host_response_recorder),
+      device_id_tether_network_guid_map_(device_id_tether_network_guid_map),
+      weak_ptr_factory_(this) {
+  tether_host_response_recorder_->AddObserver(this);
+}
+
+HostScanCache::~HostScanCache() {
+  tether_host_response_recorder_->RemoveObserver(this);
+}
+
+void HostScanCache::SetHostScanResult(const std::string& tether_network_guid,
+                                      const std::string& device_name,
+                                      const std::string& carrier,
+                                      int battery_percentage,
+                                      int signal_strength) {
+  DCHECK(!tether_network_guid.empty());
+
+  bool not_in_map = tether_guid_to_timer_map_.find(tether_network_guid) ==
+                    tether_guid_to_timer_map_.end();
+
+  if (not_in_map) {
+    // Add the Tether network to NetworkStateHandler and create an associated
+    // Timer.
+    network_state_handler_->AddTetherNetworkState(
+        tether_network_guid, device_name, carrier, battery_percentage,
+        signal_strength, HasConnectedToHost(tether_network_guid));
+    tether_guid_to_timer_map_.emplace(

[Ryan Hansberry, 2017/04/28 22:31:04]

I think it would be clearer to do this in StartTimer.

[Kyle Horimoto, 2017/04/28 22:45:04]

StartTimer() is also called in the case where the timer is already in the map.
It's cleaner to have the preconditions to that function be the same in both
cases.

Plus, I don't like the idea of initializing a map entry with only a key and no
value.

+        tether_network_guid,
+        timer_factory_->CreateOneShotTimer(tether_network_guid));
+
+    PA_LOG(INFO) << "Added scan result for Tether network with GUID "
+                 << tether_network_guid << ". Device name: " << device_name
+                 << ", carrier: " << carrier
+                 << ", battery percentage: " << battery_percentage
+                 << ", signal strength: " << signal_strength;
+  } else {
+    // Update the existing network and stop the associated Timer.
+    network_state_handler_->UpdateTetherNetworkProperties(
+        tether_network_guid, carrier, battery_percentage, signal_strength);
+    tether_guid_to_timer_map_[tether_network_guid]->Stop();
+
+    PA_LOG(INFO) << "Updated scan result for Tether network with GUID "
+                 << tether_network_guid << ". New carrier: " << carrier << ", "
+                 << "new battery percentage: " << battery_percentage << ", "
+                 << "new signal strength: " << signal_strength;
+  }
+
+  StartTimer(tether_network_guid);
+}
+
+bool HostScanCache::RemoveHostScanResult(
+    const std::string& tether_network_guid) {
+  DCHECK(!tether_network_guid.empty());
+
+  auto it = tether_guid_to_timer_map_.find(tether_network_guid);
+  if (it == tether_guid_to_timer_map_.end()) {
+    PA_LOG(ERROR) << "Attempted to remove a host scan result which does not "
+                  << "exist in the cache. GUID: " << tether_network_guid;
+    return false;
+  }
+
+  if (active_host_->GetTetherNetworkGuid() == tether_network_guid) {
+    PA_LOG(ERROR) << "RemoveHostScanResult() called for Tether network with "
+                  << "GUID " << tether_network_guid << ", but the "
+                  << "corresponding device is the active host. Not removing "
+                  << "this scan result from the cache.";
+    return false;
+  }
+
+  tether_guid_to_timer_map_.erase(it);
+  return network_state_handler_->RemoveTetherNetworkState(tether_network_guid);
+}
+
+void HostScanCache::ClearCacheExceptForActiveHost() {
+  // Create a list of all Tether network GUIDs serving as keys to
+  // |tether_guid_to_timer_map_|.
+  std::vector<std::string> tether_network_guids;
+  tether_network_guids.reserve(tether_guid_to_timer_map_.size());
+  for (auto& it : tether_guid_to_timer_map_)
+    tether_network_guids.push_back(it.first);
+
+  std::string active_host_tether_guid = active_host_->GetTetherNetworkGuid();
+  if (!active_host_tether_guid.empty()) {
+    PA_LOG(INFO) << "Clearing all " << tether_guid_to_timer_map_.size()
+                 << "entries from the cache.";
+  } else {
+    PA_LOG(INFO) << "Clearing " << (tether_guid_to_timer_map_.size() - 1) << " "
+                 << "of the " << tether_guid_to_timer_map_.size() << " "
+                 << "entries from the cache. Not removing the entry "
+                 << "corresponding to the Tether network with GUID "
+                 << active_host_tether_guid << " because it represents the "
+                 << "active host.";
+  }
+
+  // Iterate through the keys, removing all scan results not corresponding to
+  // the active host. Iteration is done via a list of pre-computed keys instead
+  // if iterating through the map because RemoteHostScanResult() will remove
+  // key/value pairs from the map, which would invalidate the map iterator.
+  for (auto& tether_network_guid : tether_network_guids) {
+    if (active_host_->GetTetherNetworkGuid() == tether_network_guid) {
+      // Do not remove the active host from the cache.
+      continue;
+    }
+
+    RemoveHostScanResult(tether_network_guid);
+  }
+}
+
+void HostScanCache::OnPreviouslyConnectedHostIdsChanged() {
+  for (auto& map_entry : tether_guid_to_timer_map_) {
+    const std::string& tether_network_guid = map_entry.first;
+    if (HasConnectedToHost(tether_network_guid)) {
+      // If a the current device has connected to the Tether network with GUID
+      // |tether_network_guid|, alert |network_state_handler_|. Note that this
+      // function is a no-op if it is called on a network which already has its
+      // HasConnectedToHost property set to true.
+      bool update_successful =
+          network_state_handler_->SetTetherNetworkHasConnectedToHost(
+              tether_network_guid);
+
+      if (update_successful) {
+        PA_LOG(INFO) << "Successfully set the HasConnectedToHost property of "
+                     << "the Tether network with GUID " << tether_network_guid
+                     << " to true.";
+      }
+    }
+  }
+}
+
+bool HostScanCache::HasConnectedToHost(const std::string& tether_network_guid) {
+  std::string device_id =
+      device_id_tether_network_guid_map_->GetDeviceIdForTetherNetworkGuid(
+          tether_network_guid);
+  std::vector<std::string> connected_device_ids =
+      tether_host_response_recorder_->GetPreviouslyConnectedHostIds();
+  return std::find(connected_device_ids.begin(), connected_device_ids.end(),
+                   device_id) != connected_device_ids.end();
+}
+
+void HostScanCache::StartTimer(const std::string& tether_network_guid) {
+  // Check that a Timer exists in |tether_guid_to_timer_map_| and that it is not

[Ryan Hansberry, 2017/04/28 22:31:04]

nit: This comment isn't really needed.

[Kyle Horimoto, 2017/04/28 22:45:04]

Done.

+  // currently running.
+  DCHECK(!tether_guid_to_timer_map_.find(tether_network_guid)
+              ->second->IsRunning());
+
+  PA_LOG(INFO) << "Starting host scan cache timer for Tether network with GUID "
+               << tether_network_guid << ". Will fire in "
+               << kNumMinutesBeforeCacheEntryExpires << " minutes.";
+
+  tether_guid_to_timer_map_[tether_network_guid]->Start(
+      FROM_HERE,
+      base::TimeDelta::FromMinutes(kNumMinutesBeforeCacheEntryExpires),
+      base::Bind(&HostScanCache::OnTimerFired, weak_ptr_factory_.GetWeakPtr(),
+                 tether_network_guid));
+}
+
+void HostScanCache::OnTimerFired(const std::string& tether_network_guid) {
+  if (active_host_->GetTetherNetworkGuid() == tether_network_guid) {
+    // Log as a warning. This situation should be uncommon in practice since
+    // KeepAliveScheduler should schedule a new keep-alive status update every
+    // 4 minutes.
+    PA_LOG(WARNING) << "Timer fired for Tether network GUID "
+                    << tether_network_guid << ", but the corresponding device "
+                    << "is the active host. Restarting timer.";
+
+    // If the Timer which fired corresponds to the active host, do not remove
+    // the cache entry. The active host must always remain in the cache so that
+    // the UI can reflect that it is the connecting/connected network. In this
+    // case, just restart the timer.
+    StartTimer(tether_network_guid);
+    return;
+  }
+
+  PA_LOG(INFO) << "Timer fired for Tether network GUID " << tether_network_guid
+               << ". Removing stale scan result.";
+
+  // Otherwise, the scan resulst are stale. Remove them.
+  RemoveHostScanResult(tether_network_guid);
+}
+
+}  // namespace tether
+
+}  // namespace chromeos