components/proximity_auth/proximity_monitor_impl.cc

// Copyright 2015 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 "components/proximity_auth/proximity_monitor_impl.h"

#include <math.h>
#include <utility>

#include "base/bind.h"
#include "base/location.h"
#include "base/threading/thread_task_runner_handle.h"
#include "base/time/tick_clock.h"
#include "base/time/time.h"
#include "components/proximity_auth/logging/logging.h"
#include "components/proximity_auth/metrics.h"
#include "components/proximity_auth/proximity_auth_pref_manager.h"
#include "components/proximity_auth/proximity_monitor_observer.h"
#include "device/bluetooth/bluetooth_adapter.h"
#include "device/bluetooth/bluetooth_adapter_factory.h"

using device::BluetoothDevice;

namespace proximity_auth {

// The time to wait, in milliseconds, between proximity polling iterations.
const int kPollingTimeoutMs = 250;

// The weight of the most recent RSSI sample.
const double kRssiSampleWeight = 0.3;

// The default RSSI threshold.
const int kDefaultRssiThreshold = -70;

ProximityMonitorImpl::ProximityMonitorImpl(
    cryptauth::Connection* connection,
    ProximityAuthPrefManager* pref_manager)
    : connection_(connection),
      remote_device_is_in_proximity_(false),
      is_active_(false),
      rssi_threshold_(kDefaultRssiThreshold),
      pref_manager_(pref_manager),
      polling_weak_ptr_factory_(this),
      weak_ptr_factory_(this) {
  if (device::BluetoothAdapterFactory::IsBluetoothSupported()) {
    device::BluetoothAdapterFactory::GetAdapter(
        base::Bind(&ProximityMonitorImpl::OnAdapterInitialized,
                   weak_ptr_factory_.GetWeakPtr()));
  } else {
    PA_LOG(ERROR) << "[Proximity] Proximity monitoring unavailable: "
                  << "Bluetooth is unsupported on this platform.";
  }
}

ProximityMonitorImpl::~ProximityMonitorImpl() {
}

void ProximityMonitorImpl::Start() {
  is_active_ = true;
  GetRssiThresholdFromPrefs();
  UpdatePollingState();
}

void ProximityMonitorImpl::Stop() {
  is_active_ = false;
  ClearProximityState();
  UpdatePollingState();
}

bool ProximityMonitorImpl::IsUnlockAllowed() const {
  return remote_device_is_in_proximity_;
}

void ProximityMonitorImpl::RecordProximityMetricsOnAuthSuccess() {
  double rssi_rolling_average = rssi_rolling_average_
                                    ? *rssi_rolling_average_
                                    : metrics::kUnknownProximityValue;

  std::string remote_device_model = metrics::kUnknownDeviceModel;
  cryptauth::RemoteDevice remote_device = connection_->remote_device();
  if (!remote_device.name.empty())
    remote_device_model = remote_device.name;

  metrics::RecordAuthProximityRollingRssi(round(rssi_rolling_average));
  metrics::RecordAuthProximityRemoteDeviceModelHash(remote_device_model);
}

void ProximityMonitorImpl::AddObserver(ProximityMonitorObserver* observer) {
  observers_.AddObserver(observer);
}

void ProximityMonitorImpl::RemoveObserver(ProximityMonitorObserver* observer) {
  observers_.RemoveObserver(observer);
}

void ProximityMonitorImpl::OnAdapterInitialized(
    scoped_refptr<device::BluetoothAdapter> adapter) {
  bluetooth_adapter_ = adapter;
  UpdatePollingState();
}

void ProximityMonitorImpl::UpdatePollingState() {
  if (ShouldPoll()) {
    // If there is a polling iteration already scheduled, wait for it.
    if (polling_weak_ptr_factory_.HasWeakPtrs())
      return;

    // Polling can re-entrantly call back into this method, so make sure to
    // schedule the next polling iteration prior to executing the current one.
    base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
        FROM_HERE,
        base::Bind(&ProximityMonitorImpl::PerformScheduledUpdatePollingState,
                   polling_weak_ptr_factory_.GetWeakPtr()),
        base::TimeDelta::FromMilliseconds(kPollingTimeoutMs));
    Poll();
  } else {
    polling_weak_ptr_factory_.InvalidateWeakPtrs();
    remote_device_is_in_proximity_ = false;
  }
}

void ProximityMonitorImpl::PerformScheduledUpdatePollingState() {
  polling_weak_ptr_factory_.InvalidateWeakPtrs();
  UpdatePollingState();
}

bool ProximityMonitorImpl::ShouldPoll() const {
  return is_active_ && bluetooth_adapter_;
}

void ProximityMonitorImpl::Poll() {
  DCHECK(ShouldPoll());

  std::string address = connection_->GetDeviceAddress();
  BluetoothDevice* device = bluetooth_adapter_->GetDevice(address);

  if (!device) {
    PA_LOG(ERROR) << "Unknown Bluetooth device with address " << address;
    ClearProximityState();
    return;
  }
  if (!device->IsConnected()) {
    PA_LOG(ERROR) << "Bluetooth device with address " << address
                  << " is not connected.";
    ClearProximityState();
    return;
  }

  device->GetConnectionInfo(base::Bind(&ProximityMonitorImpl::OnConnectionInfo,
                                       weak_ptr_factory_.GetWeakPtr()));
}

void ProximityMonitorImpl::OnConnectionInfo(
    const BluetoothDevice::ConnectionInfo& connection_info) {
  if (!is_active_) {
    PA_LOG(INFO) << "[Proximity] Got connection info after stopping";
    return;
  }

  if (connection_info.rssi != BluetoothDevice::kUnknownPower) {
    AddSample(connection_info);
  } else {
    PA_LOG(WARNING) << "[Proximity] Unknown values received from API: "
                    << connection_info.rssi;
    rssi_rolling_average_.reset();
    CheckForProximityStateChange();
  }
}

void ProximityMonitorImpl::ClearProximityState() {
  if (is_active_ && remote_device_is_in_proximity_) {
    for (auto& observer : observers_)
      observer.OnProximityStateChanged();
  }

  remote_device_is_in_proximity_ = false;
  rssi_rolling_average_.reset();
}

void ProximityMonitorImpl::AddSample(
    const BluetoothDevice::ConnectionInfo& connection_info) {
  double weight = kRssiSampleWeight;
  if (!rssi_rolling_average_) {
    rssi_rolling_average_.reset(new double(connection_info.rssi));
  } else {
    *rssi_rolling_average_ =
        weight * connection_info.rssi + (1 - weight) * (*rssi_rolling_average_);
  }

  CheckForProximityStateChange();
}

void ProximityMonitorImpl::CheckForProximityStateChange() {
  bool is_now_in_proximity =
      rssi_rolling_average_ && *rssi_rolling_average_ > rssi_threshold_;

  if (rssi_rolling_average_)
    PA_LOG(INFO) << "  Rolling RSSI: " << *rssi_rolling_average_;

  if (remote_device_is_in_proximity_ != is_now_in_proximity) {
    PA_LOG(INFO) << "[Proximity] Updated proximity state: "
                 << (is_now_in_proximity ? "proximate" : "distant");
    remote_device_is_in_proximity_ = is_now_in_proximity;
    for (auto& observer : observers_)
      observer.OnProximityStateChanged();
  }
}

void ProximityMonitorImpl::GetRssiThresholdFromPrefs() {
  ProximityAuthPrefManager::ProximityThreshold threshold =
      pref_manager_->GetProximityThreshold();
  switch (threshold) {
    case ProximityAuthPrefManager::ProximityThreshold::kVeryClose:
      rssi_threshold_ = -45;
      return;
    case ProximityAuthPrefManager::ProximityThreshold::kClose:
      rssi_threshold_ = -60;
      return;
    case ProximityAuthPrefManager::ProximityThreshold::kFar:
      rssi_threshold_ = -70;
      return;
    case ProximityAuthPrefManager::ProximityThreshold::kVeryFar:
      rssi_threshold_ = -85;
      return;
  }
  NOTREACHED();
}

}  // namespace proximity_auth