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

chromeos/components/tether/tether_host_response_recorder.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_TETHER_HOST_RESPONSE_RECORDER_H_
 #define CHROMEOS_COMPONENTS_TETHER_TETHER_HOST_RESPONSE_RECORDER_H_
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
+#include "base/observer_list.h"
 #include "components/cryptauth/remote_device.h"
 
 class PrefService;
 class PrefRegistrySimple;
 
 namespace chromeos {
 
 namespace tether {
 
 // Records responses from tether hosts in user prefs, which persists these
 // responses between reboots of the device. When a TetherAvailabilityResponse or
 // ConnectTetheringResponse is received, it should be recorded using this class.
 // Responses can be retrieved at a later time via getter methods.
 class TetherHostResponseRecorder {
  public:
-  // Note: The PrefService* passed here must be created using the same registry
-  // passed to RegisterPrefs().
-  TetherHostResponseRecorder(PrefService* pref_service);
-  virtual ~TetherHostResponseRecorder();
+  class Observer {
+   public:
+    virtual void OnPreviouslyConnectedHostIdsChanged() = 0;
+  };
 
   // Registers the prefs used by this class to |registry|. Must be called before
   // this class is utilized.
   static void RegisterPrefs(PrefRegistrySimple* registry);
 
+  // Note: The PrefService* passed here must be created using the same registry
+  // passed to RegisterPrefs().
+  explicit TetherHostResponseRecorder(PrefService* pref_service);
+  virtual ~TetherHostResponseRecorder();
+
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
   // 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.
   virtual void RecordSuccessfulTetherAvailabilityResponse(
       const cryptauth::RemoteDevice& remote_device);
 
   // Gets device IDs corresponding to hosts which have sent
   // TetherAvailabilityResponses with a response code indicating that tethering
   // is available. The list is sorted; the IDs of the devices which have
   // responded most recently are at the front of the list and the IDs of the
   // devices which have responded least recently are at the end of the list.
   virtual std::vector<std::string> GetPreviouslyAvailableHostIds() const;
 
   // Records a ConnectTetheringResponse. This function should be called each
   // time that a response is received from a host.
   virtual void RecordSuccessfulConnectTetheringResponse(
       const cryptauth::RemoteDevice& remote_device);
 
   // Gets device IDs corresponding to hosts which have sent
   // ConnectTetheringResponses with a response code indicating that they have
   // successfully turned on their Wi-Fi hotspots. The list is sorted; the IDs of
   // the devices which have responded most recently are at the front of the list
   // and the IDs of the devices which have responded least recently are at the
   // end of the list.
   virtual std::vector<std::string> GetPreviouslyConnectedHostIds() const;
 
  private:
-  void AddRecentResponse(const std::string& device_id,
+  friend class HostScanCacheTest;
+
+  void NotifyObserversPreviouslyConnectedHostIdsChanged();
+
+  // Returns whether the list was changed due to adding the response.
+  bool AddRecentResponse(const std::string& device_id,
                          const std::string& pref_name);
   std::vector<std::string> GetDeviceIdsForPref(
       const std::string& pref_name) const;
 
   PrefService* pref_service_;
+  base::ObserverList<Observer> observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(TetherHostResponseRecorder);
 };
 
 }  // namespace tether
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_COMPONENTS_TETHER_TETHER_HOST_RESPONSE_RECORDER_H_