[CrOS Tether] Create HostScanDevicePrioritizer, a class which prioritizes the order of connection a…

chromeos/components/tether/host_scan_device_prioritizer.h

+// 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.
+
+#ifndef CHROMEOS_COMPONENTS_TETHER_HOST_SCAN_DEVICE_PRIORITIZER_H_
+#define CHROMEOS_COMPONENTS_TETHER_HOST_SCAN_DEVICE_PRIORITIZER_H_
+
+#include "base/macros.h"
+#include "components/cryptauth/remote_device.h"
+
+class PrefService;
+class PrefRegistrySimple;
+
+namespace chromeos {
+
+namespace tether {
+
+// Prioritizes the order of devices when performing a host scan. To optimize for
+// the most common tethering operations, this class uses the following rules:
+//   * The device which has most recently sent a successful
+//     ConnectTetheringResponse is always at the front of the queue.
+//   * Devices which have most recently sent a successful
+//     TetherAvailabilityResponse are next in the order, as long as they do not
+//     violate the first rule.
+//   * All other devices are left in the order they are passed.
+class HostScanDevicePrioritizer {
+ public:
+  // Note: The PrefService* passed here must be created using the same registry
+  // passed to RegisterPrefs().
+  HostScanDevicePrioritizer(PrefService* pref_service);
+  ~HostScanDevicePrioritizer();
+
+  // Registers the prefs used by this class to |registry|. Must be called before
+  // this class is utilized.
+  static void RegisterPrefs(PrefRegistrySimple* registry);
+
+  // Records a TetherAvailabilityResponse. This function should be called each
+  // time that a response is received from a potential host, even if a
+  // connection is not started.
+  void RecordSuccessfulTetherAvailabilityResponse(
+      const cryptauth::RemoteDevice& remote_device);
+
+  // Records a ConnectTetheringResponse. This function should be called each
+  // time that a response is received from a host.
+  void RecordSuccessfulConnectTetheringResponse(
+      const cryptauth::RemoteDevice& remote_device);
+
+  // Prioritizes |remote_devices| using the rules described above.
+  void PrioritizeHostScanDeviceOrder(
+      std::vector<cryptauth::RemoteDevice>& remote_devices) const;

[Tim Song, 2017/02/24 18:57:40]

According to the Google style guide, all arguments passed by reference must be
const:
https://google.github.io/styleguide/cppguide.html#Reference_Arguments

I would make this a pointer instead, and perhaps name the function something
like SortByHostScanOrder() to really emphasize that the vector will be mutated.

[Kyle Horimoto, 2017/02/24 19:21:30]

Done.

+
+ private:
+  PrefService* pref_service_;
+
+  DISALLOW_COPY_AND_ASSIGN(HostScanDevicePrioritizer);
+};
+
+}  // namespace tether
+
+}  // namespace chromeos
+
+#endif  // CHROMEOS_COMPONENTS_TETHER_HOST_SCAN_DEVICE_PRIORITIZER_H_