[CrOS Tether] Create TetherHostResponseRecorder, which records ConnectTetheringResponses and Tether…

chromeos/components/tether/host_scan_device_prioritizer.cc

Index: chromeos/components/tether/host_scan_device_prioritizer.cc
diff --git a/chromeos/components/tether/host_scan_device_prioritizer.cc b/chromeos/components/tether/host_scan_device_prioritizer.cc
index 13f2b506897ab6fe3e9fda9dcc590e3e4183ca00..e2bfb9ac421140fd86410557de6676b5d08e355f 100644
--- a/chromeos/components/tether/host_scan_device_prioritizer.cc
+++ b/chromeos/components/tether/host_scan_device_prioritizer.cc
@@ -7,6 +7,7 @@
 #include "base/memory/ptr_util.h"
 #include "base/values.h"
 #include "chromeos/components/tether/pref_names.h"
+#include "chromeos/components/tether/tether_host_response_recorder.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 
@@ -14,97 +15,43 @@ namespace chromeos {
 
 namespace tether {
 
-// static
-void HostScanDevicePrioritizer::RegisterPrefs(PrefRegistrySimple* registry) {
-  registry->RegisterListPref(prefs::kMostRecentTetherAvailablilityResponderIds);
-  registry->RegisterStringPref(prefs::kMostRecentConnectTetheringResponderId,
-                               "");
-}
-
-HostScanDevicePrioritizer::HostScanDevicePrioritizer(PrefService* pref_service)
-    : pref_service_(pref_service) {}
+HostScanDevicePrioritizer::HostScanDevicePrioritizer(
+    TetherHostResponseRecorder* tether_host_response_recorder)
+    : tether_host_response_recorder_(tether_host_response_recorder) {}
 
 HostScanDevicePrioritizer::~HostScanDevicePrioritizer() {}
 
-void HostScanDevicePrioritizer::RecordSuccessfulTetherAvailabilityResponse(
-    const cryptauth::RemoteDevice& remote_device) {
-  std::string device_id = remote_device.GetDeviceId();
-
-  const base::ListValue* ids =
-      pref_service_->GetList(prefs::kMostRecentTetherAvailablilityResponderIds);
-
-  // Create a mutable copy of the stored IDs, or create one if it has yet to be
-  // stored.
-  std::unique_ptr<base::ListValue> updated_ids =
-      ids ? ids->CreateDeepCopy() : base::MakeUnique<base::ListValue>();
-
-  // Remove the device ID if it was already present in the list.
-  std::unique_ptr<base::Value> device_id_value =
-      base::MakeUnique<base::Value>(device_id);
-  updated_ids->Remove(*device_id_value, nullptr);
-
-  // Add the device ID to the front of the queue.
-  updated_ids->Insert(0, std::move(device_id_value));
-
-  // Store the updated list back in |pref_service_|.
-  pref_service_->Set(prefs::kMostRecentTetherAvailablilityResponderIds,
-                     *updated_ids);
-}
-
-void HostScanDevicePrioritizer::RecordSuccessfulConnectTetheringResponse(
-    const cryptauth::RemoteDevice& remote_device) {
-  pref_service_->Set(prefs::kMostRecentConnectTetheringResponderId,
-                     base::Value(remote_device.GetDeviceId()));
-}
-
 void HostScanDevicePrioritizer::SortByHostScanOrder(
     std::vector<cryptauth::RemoteDevice>* remote_devices) const {
-  // Fetch the stored IDs associated with the devices which most recently sent
-  // TetherAvailabilityResponses.
-  const base::ListValue* tether_availability_ids =
-      pref_service_->GetList(prefs::kMostRecentTetherAvailablilityResponderIds);
-
-  // Create a mutable copy of the stored IDs, or create one if it has yet to be
-  // stored.
-  std::unique_ptr<base::ListValue> prioritized_ids =
-      tether_availability_ids ? tether_availability_ids->CreateDeepCopy()
-                              : base::MakeUnique<base::ListValue>();
-
-  // Now, fetch the ID associated with the device which most recently sent a
-  // ConnectTetheringRequest.
-  std::string connect_tethering_id =
-      pref_service_->GetString(prefs::kMostRecentConnectTetheringResponderId);
-
-  // If an ID exists, insert it at the front of |prioritized_ids|.
-  if (!connect_tethering_id.empty()) {
-    prioritized_ids->Insert(
-        0, base::MakeUnique<base::Value>(connect_tethering_id));
+  // First, fetch the hosts which have previously responded.
+  std::vector<std::string> prioritized_ids =
+      tether_host_response_recorder_->GetPreviouslyAvailableHostIds();
+
+  std::vector<std::string> previously_connectable_host_ids =
+      tether_host_response_recorder_->GetPreviouslyConnectedHostIds();
+  if (!previously_connectable_host_ids.empty()) {
+    // If there is a most-recently connectable host, insert it at the front of
+    // the list.
+    prioritized_ids.insert(prioritized_ids.begin(),
+                           previously_connectable_host_ids[0]);
   }
 
   // Iterate from the last stored ID to the first stored ID. This ensures that
   // the items at the front of the list end up in the front of the prioritized
   // |remote_devices| vector.
-  for (size_t i = prioritized_ids->GetSize(); i-- > 0;) {
-    base::Value* stored_id_value;
-    if (!prioritized_ids->Get(i, &stored_id_value)) {
-      continue;
-    }
-
-    std::string stored_id;
-    if (!stored_id_value->GetAsString(&stored_id)) {
-      continue;
-    }
-
+  for (auto prioritized_it = prioritized_ids.rbegin();
+       prioritized_it != prioritized_ids.rend(); ++prioritized_it) {
     // Iterate through |remote_devices| to see if a device exists with a
     // device ID of |stored_id|. If one exists, remove it from its previous
     // position in the list and add it at the front instead.
-    for (auto it = remote_devices->begin(); it != remote_devices->end(); ++it) {
-      if (it->GetDeviceId() != stored_id) {
+    for (auto remote_devices_it = remote_devices->begin();
+         remote_devices_it != remote_devices->end(); ++remote_devices_it) {
+      if (remote_devices_it->GetDeviceId() != *prioritized_it) {
         continue;
       }
 
-      cryptauth::RemoteDevice device_to_move = *it;
-      remote_devices->erase(it);
+      cryptauth::RemoteDevice device_to_move = *remote_devices_it;
+      remote_devices->erase(remote_devices_it);
       remote_devices->insert(remote_devices->begin(), device_to_move);
       break;
     }