rooms-android/app/src/main/java/com/nextcloud/talk/webrtc/MagicAudioManager.java

/*
 * Nextcloud Talk application
 *
 * @author Mario Danic
 * Copyright (C) 2017 Mario Danic <mario@lovelyhq.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Original code:
 *
 *
 * Copyright 2014 The WebRTC Project Authors. All rights reserved.
 *
 * Use of this source code is governed by a BSD-style license
 * that can be found in the LICENSE file in the root of the source
 * tree. An additional intellectual property rights grant can be found
 * in the file PATENTS.  All contributing project authors may
 * be found in the AUTHORS file in the root of the source tree.
 */

package com.nextcloud.talk.webrtc;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.PackageManager;
import android.media.AudioDeviceInfo;
import android.media.AudioManager;
import android.os.Build;
import android.util.Log;
import com.nextcloud.talk.events.PeerConnectionEvent;
import com.nextcloud.talk.utils.power.PowerManagerUtils;
import org.greenrobot.eventbus.EventBus;
import org.webrtc.ThreadUtils;

import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

/**
 * MagicAudioManager manages all audio related parts of the AppRTC demo.
 */
public class MagicAudioManager {
    private static final String TAG = "MagicAudioManager";
    private static final String SPEAKERPHONE_AUTO = "auto";
    private static final String SPEAKERPHONE_FALSE = "false";
    private final Context magicContext;
    // Handles all tasks related to Bluetooth headset devices.
    private final MagicBluetoothManager bluetoothManager;
    // Contains speakerphone setting: auto, true or false
    private String useSpeakerphone;
    private AudioManager audioManager;
    private AudioManagerEvents audioManagerEvents;
    private AudioManagerState amState;
    private int savedAudioMode = AudioManager.MODE_INVALID;
    private boolean savedIsSpeakerPhoneOn = false;
    private boolean savedIsMicrophoneMute = false;
    private boolean hasWiredHeadset = false;
    // Default audio device; speaker phone for video calls or earpiece for audio
    // only calls.
    private AudioDevice defaultAudioDevice;
    // Contains the currently selected audio device.
    // This device is changed automatically using a certain scheme where e.g.
    // a wired headset "wins" over speaker phone. It is also possible for a
    // user to explicitly select a device (and overrid any predefined scheme).
    // See |userSelectedAudioDevice| for details.
    private AudioDevice selectedAudioDevice;
    // Contains the user-selected audio device which overrides the predefined
    // selection scheme.
    // TODO(henrika): always set to AudioDevice.NONE today. Add support for
    // explicit selection based on choice by userSelectedAudioDevice.
    private AudioDevice userSelectedAudioDevice;
    // Proximity sensor object. It measures the proximity of an object in cm
    // relative to the view screen of a device and can therefore be used to
    // assist device switching (close to ear <=> use headset earpiece if
    // available, far from ear <=> use speaker phone).
    private MagicProximitySensor proximitySensor = null;
    // Contains a list of available audio devices. A Set collection is used to
    // avoid duplicate elements.
    private Set<AudioDevice> audioDevices = new HashSet<>();
    // Broadcast receiver for wired headset intent broadcasts.
    private BroadcastReceiver wiredHeadsetReceiver;
    // Callback method for changes in audio focus.
    private AudioManager.OnAudioFocusChangeListener audioFocusChangeListener;

    private PowerManagerUtils powerManagerUtils;

    private MagicAudioManager(Context context, boolean useProximitySensor) {
        Log.d(TAG, "ctor");
        ThreadUtils.checkIsOnMainThread();
        magicContext = context;
        audioManager = ((AudioManager) context.getSystemService(Context.AUDIO_SERVICE));
        bluetoothManager = MagicBluetoothManager.create(context, this);
        wiredHeadsetReceiver = new WiredHeadsetReceiver();
        amState = AudioManagerState.UNINITIALIZED;

        powerManagerUtils = new PowerManagerUtils();
        powerManagerUtils.updatePhoneState(PowerManagerUtils.PhoneState.WITH_PROXIMITY_SENSOR_LOCK);

        if (useProximitySensor) {
            useSpeakerphone = SPEAKERPHONE_AUTO;
        } else {
            useSpeakerphone = SPEAKERPHONE_FALSE;
        }


        if (useSpeakerphone.equals(SPEAKERPHONE_FALSE)) {
            defaultAudioDevice = AudioDevice.EARPIECE;
        } else {
            defaultAudioDevice = AudioDevice.SPEAKER_PHONE;
        }

        // Create and initialize the proximity sensor.
        // Tablet devices (e.g. Nexus 7) does not support proximity sensors.
        // Note that, the sensor will not be active until start() has been called.
        proximitySensor = MagicProximitySensor.create(context, new Runnable() {
            // This method will be called each time a state change is detected.
            // Example: user holds his hand over the device (closer than ~5 cm),
            // or removes his hand from the device.
            public void run() {
                onProximitySensorChangedState();
            }
        });

        Log.d(TAG, "defaultAudioDevice: " + defaultAudioDevice);
    }

    /**
     * Construction.
     */
    public static MagicAudioManager create(Context context, boolean useProximitySensor) {
        return new MagicAudioManager(context, useProximitySensor);
    }

    public void toggleUseSpeakerphone() {
        if (useSpeakerphone.equals(SPEAKERPHONE_FALSE)) {
            useSpeakerphone = SPEAKERPHONE_AUTO;
            setDefaultAudioDevice(AudioDevice.SPEAKER_PHONE);
        } else {
            useSpeakerphone = SPEAKERPHONE_FALSE;
            setDefaultAudioDevice(AudioDevice.EARPIECE);
        }

        updateAudioDeviceState();
    }

    public boolean isSpeakerphoneAutoOn() {
        return (useSpeakerphone.equals(SPEAKERPHONE_AUTO));
    }

    /**
     * This method is called when the proximity sensor reports a state change,
     * e.g. from "NEAR to FAR" or from "FAR to NEAR".
     */
    private void onProximitySensorChangedState() {

        if (!useSpeakerphone.equals(SPEAKERPHONE_AUTO)) {
            return;
        }

        // The proximity sensor should only be activated when there are exactly two
        // available audio devices.
        if (audioDevices.size() == 2 && audioDevices.contains(MagicAudioManager.AudioDevice.EARPIECE)
                && audioDevices.contains(MagicAudioManager.AudioDevice.SPEAKER_PHONE)) {
            if (proximitySensor.sensorReportsNearState()) {
                // Sensor reports that a "handset is being held up to a person's ear",
                // or "something is covering the light sensor".
                setAudioDeviceInternal(MagicAudioManager.AudioDevice.EARPIECE);

                EventBus.getDefault().post(new PeerConnectionEvent(PeerConnectionEvent.PeerConnectionEventType
                        .SENSOR_NEAR, null, null, null, null));

            } else {
                // Sensor reports that a "handset is removed from a person's ear", or
                // "the light sensor is no longer covered".
                setAudioDeviceInternal(MagicAudioManager.AudioDevice.SPEAKER_PHONE);

                EventBus.getDefault().post(new PeerConnectionEvent(PeerConnectionEvent.PeerConnectionEventType
                        .SENSOR_FAR, null, null, null, null));
            }
        }
    }

    public void start(AudioManagerEvents audioManagerEvents) {
        Log.d(TAG, "start");
        ThreadUtils.checkIsOnMainThread();
        if (amState == AudioManagerState.RUNNING) {
            Log.e(TAG, "AudioManager is already active");
            return;
        }
        // TODO(henrika): perhaps call new method called preInitAudio() here if UNINITIALIZED.

        Log.d(TAG, "AudioManager starts...");
        this.audioManagerEvents = audioManagerEvents;
        amState = AudioManagerState.RUNNING;

        // Store current audio state so we can restore it when stop() is called.
        savedAudioMode = audioManager.getMode();
        savedIsSpeakerPhoneOn = audioManager.isSpeakerphoneOn();
        savedIsMicrophoneMute = audioManager.isMicrophoneMute();
        hasWiredHeadset = hasWiredHeadset();

        // Create an AudioManager.OnAudioFocusChangeListener instance.
        audioFocusChangeListener = new AudioManager.OnAudioFocusChangeListener() {
            // Called on the listener to notify if the audio focus for this listener has been changed.
            // The |focusChange| value indicates whether the focus was gained, whether the focus was lost,
            // and whether that loss is transient, or whether the new focus holder will hold it for an
            // unknown amount of time.
            // TODO(henrika): possibly extend support of handling audio-focus changes. Only contains
            // logging for now.
            @Override
            public void onAudioFocusChange(int focusChange) {
                String typeOfChange = "AUDIOFOCUS_NOT_DEFINED";
                switch (focusChange) {
                    case AudioManager.AUDIOFOCUS_GAIN:
                        typeOfChange = "AUDIOFOCUS_GAIN";
                        break;
                    case AudioManager.AUDIOFOCUS_GAIN_TRANSIENT:
                        typeOfChange = "AUDIOFOCUS_GAIN_TRANSIENT";
                        break;
                    case AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_EXCLUSIVE:
                        typeOfChange = "AUDIOFOCUS_GAIN_TRANSIENT_EXCLUSIVE";
                        break;
                    case AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK:
                        typeOfChange = "AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK";
                        break;
                    case AudioManager.AUDIOFOCUS_LOSS:
                        typeOfChange = "AUDIOFOCUS_LOSS";
                        break;
                    case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT:
                        typeOfChange = "AUDIOFOCUS_LOSS_TRANSIENT";
                        break;
                    case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK:
                        typeOfChange = "AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK";
                        break;
                    default:
                        typeOfChange = "AUDIOFOCUS_INVALID";
                        break;
                }
                Log.d(TAG, "onAudioFocusChange: " + typeOfChange);
            }
        };

        // Request audio playout focus (without ducking) and install listener for changes in focus.
        int result = audioManager.requestAudioFocus(audioFocusChangeListener,
                AudioManager.STREAM_VOICE_CALL, AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);
        if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
            Log.d(TAG, "Audio focus request granted for VOICE_CALL streams");
        } else {
            Log.e(TAG, "Audio focus request failed");
        }

        // Start by setting MODE_IN_COMMUNICATION as default audio mode. It is
        // required to be in this mode when playout and/or recording starts for
        // best possible VoIP performance.
        audioManager.setMode(AudioManager.MODE_IN_COMMUNICATION);

        // Always disable microphone mute during a WebRTC call.
        setMicrophoneMute(false);

        // Set initial device states.
        userSelectedAudioDevice = AudioDevice.NONE;
        selectedAudioDevice = AudioDevice.NONE;
        audioDevices.clear();

        // Initialize and start Bluetooth if a BT device is available or initiate
        // detection of new (enabled) BT devices.
        bluetoothManager.start();

        // Do initial selection of audio device. This setting can later be changed
        // either by adding/removing a BT or wired headset or by covering/uncovering
        // the proximity sensor.
        updateAudioDeviceState();

        proximitySensor.start();
        // Register receiver for broadcast intents related to adding/removing a
        // wired headset.
        registerReceiver(wiredHeadsetReceiver, new IntentFilter(Intent.ACTION_HEADSET_PLUG));
        Log.d(TAG, "AudioManager started");
    }

    public void stop() {
        Log.d(TAG, "stop");
        ThreadUtils.checkIsOnMainThread();
        if (amState != AudioManagerState.RUNNING) {
            Log.e(TAG, "Trying to stop AudioManager in incorrect state: " + amState);
            return;
        }
        amState = AudioManagerState.UNINITIALIZED;

        unregisterReceiver(wiredHeadsetReceiver);

        bluetoothManager.stop();

        // Restore previously stored audio states.
        setSpeakerphoneOn(savedIsSpeakerPhoneOn);
        setMicrophoneMute(savedIsMicrophoneMute);
        audioManager.setMode(savedAudioMode);

        // Abandon audio focus. Gives the previous focus owner, if any, focus.
        audioManager.abandonAudioFocus(audioFocusChangeListener);
        audioFocusChangeListener = null;
        Log.d(TAG, "Abandoned audio focus for VOICE_CALL streams");

        if (proximitySensor != null) {
            proximitySensor.stop();
            proximitySensor = null;
        }

        powerManagerUtils.updatePhoneState(PowerManagerUtils.PhoneState.IDLE);

        audioManagerEvents = null;
        Log.d(TAG, "AudioManager stopped");
    }

    ;

    /**
     * Changes selection of the currently active audio device.
     */
    private void setAudioDeviceInternal(AudioDevice device) {
        Log.d(TAG, "setAudioDeviceInternal(device=" + device + ")");

        if (audioDevices.contains(device)) {

            switch (device) {
                case SPEAKER_PHONE:
                    setSpeakerphoneOn(true);
                    break;
                case EARPIECE:
                    setSpeakerphoneOn(false);
                    break;
                case WIRED_HEADSET:
                    setSpeakerphoneOn(false);
                    break;
                case BLUETOOTH:
                    setSpeakerphoneOn(false);
                    break;
                default:
                    Log.e(TAG, "Invalid audio device selection");
                    break;
            }
            selectedAudioDevice = device;
        }
    }

    /**
     * Changes default audio device.
     * TODO(henrika): add usage of this method in the AppRTCMobile client.
     */
    public void setDefaultAudioDevice(AudioDevice defaultDevice) {
        ThreadUtils.checkIsOnMainThread();
        switch (defaultDevice) {
            case SPEAKER_PHONE:
                defaultAudioDevice = defaultDevice;
                break;
            case EARPIECE:
                if (hasEarpiece()) {
                    defaultAudioDevice = defaultDevice;
                } else {
                    defaultAudioDevice = AudioDevice.SPEAKER_PHONE;
                }
                break;
            default:
                Log.e(TAG, "Invalid default audio device selection");
                break;
        }
        Log.d(TAG, "setDefaultAudioDevice(device=" + defaultAudioDevice + ")");
        updateAudioDeviceState();
    }

    /**
     * Changes selection of the currently active audio device.
     */
    public void selectAudioDevice(AudioDevice device) {
        ThreadUtils.checkIsOnMainThread();
        if (!audioDevices.contains(device)) {
            Log.e(TAG, "Can not select " + device + " from available " + audioDevices);
        }
        userSelectedAudioDevice = device;
        updateAudioDeviceState();
    }

    /**
     * Returns current set of available/selectable audio devices.
     */
    public Set<AudioDevice> getAudioDevices() {
        ThreadUtils.checkIsOnMainThread();
        return Collections.unmodifiableSet(new HashSet<AudioDevice>(audioDevices));
    }

    /**
     * Returns the currently selected audio device.
     */
    public AudioDevice getSelectedAudioDevice() {
        ThreadUtils.checkIsOnMainThread();
        return selectedAudioDevice;
    }

    /**
     * Helper method for receiver registration.
     */
    private void registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
        magicContext.registerReceiver(receiver, filter);
    }

    /**
     * Helper method for unregistration of an existing receiver.
     */
    private void unregisterReceiver(BroadcastReceiver receiver) {
        magicContext.unregisterReceiver(receiver);
    }

    /**
     * Sets the speaker phone mode.
     */
    private void setSpeakerphoneOn(boolean on) {
        boolean wasOn = audioManager.isSpeakerphoneOn();
        if (wasOn == on) {
            return;
        }
        audioManager.setSpeakerphoneOn(on);
    }

    /**
     * Sets the microphone mute state.
     */
    private void setMicrophoneMute(boolean on) {
        boolean wasMuted = audioManager.isMicrophoneMute();
        if (wasMuted == on) {
            return;
        }
        audioManager.setMicrophoneMute(on);
    }

    /**
     * Gets the current earpiece state.
     */
    private boolean hasEarpiece() {
        return magicContext.getPackageManager().hasSystemFeature(PackageManager.FEATURE_TELEPHONY);
    }

    /**
     * Checks whether a wired headset is connected or not.
     * This is not a valid indication that audio playback is actually over
     * the wired headset as audio routing depends on other conditions. We
     * only use it as an early indicator (during initialization) of an attached
     * wired headset.
     */
    @Deprecated
    private boolean hasWiredHeadset() {
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
            return audioManager.isWiredHeadsetOn();
        } else {
            final AudioDeviceInfo[] devices = audioManager.getDevices(AudioManager.GET_DEVICES_ALL);
            for (AudioDeviceInfo device : devices) {
                final int type = device.getType();
                if (type == AudioDeviceInfo.TYPE_WIRED_HEADSET) {
                    Log.d(TAG, "hasWiredHeadset: found wired headset");
                    return true;
                } else if (type == AudioDeviceInfo.TYPE_USB_DEVICE) {
                    Log.d(TAG, "hasWiredHeadset: found USB audio device");
                    return true;
                }
            }
            return false;
        }
    }

    /**
     * Updates list of possible audio devices and make new device selection.
     * TODO(henrika): add unit test to verify all state transitions.
     */
    public void updateAudioDeviceState() {
        ThreadUtils.checkIsOnMainThread();
        Log.d(TAG, "--- updateAudioDeviceState: "
                + "wired headset=" + hasWiredHeadset + ", "
                + "BT state=" + bluetoothManager.getState());
        Log.d(TAG, "Device status: "
                + "available=" + audioDevices + ", "
                + "selected=" + selectedAudioDevice + ", "
                + "user selected=" + userSelectedAudioDevice);

        // Check if any Bluetooth headset is connected. The internal BT state will
        // change accordingly.
        // TODO(henrika): perhaps wrap required state into BT manager.
        if (bluetoothManager.getState() == MagicBluetoothManager.State.HEADSET_AVAILABLE
                || bluetoothManager.getState() == MagicBluetoothManager.State.HEADSET_UNAVAILABLE
                || bluetoothManager.getState() == MagicBluetoothManager.State.SCO_DISCONNECTING) {
            bluetoothManager.updateDevice();
        }

        // Update the set of available audio devices.
        Set<AudioDevice> newAudioDevices = new HashSet<>();

        if (bluetoothManager.getState() == MagicBluetoothManager.State.SCO_CONNECTED
                || bluetoothManager.getState() == MagicBluetoothManager.State.SCO_CONNECTING
                || bluetoothManager.getState() == MagicBluetoothManager.State.HEADSET_AVAILABLE) {
            newAudioDevices.add(AudioDevice.BLUETOOTH);
        }

        if (hasWiredHeadset) {
            // If a wired headset is connected, then it is the only possible option.
            newAudioDevices.add(AudioDevice.WIRED_HEADSET);
        } else {
            // No wired headset, hence the audio-device list can contain speaker
            // phone (on a tablet), or speaker phone and earpiece (on mobile phone).
            newAudioDevices.add(AudioDevice.SPEAKER_PHONE);
            if (hasEarpiece()) {
                newAudioDevices.add(AudioDevice.EARPIECE);
            }
        }
        // Store state which is set to true if the device list has changed.
        boolean audioDeviceSetUpdated = !audioDevices.equals(newAudioDevices);
        // Update the existing audio device set.
        audioDevices = newAudioDevices;
        // Correct user selected audio devices if needed.
        if (bluetoothManager.getState() == MagicBluetoothManager.State.HEADSET_UNAVAILABLE
                && userSelectedAudioDevice == AudioDevice.BLUETOOTH) {
            // If BT is not available, it can't be the user selection.
            userSelectedAudioDevice = AudioDevice.NONE;
        }
        if (hasWiredHeadset && userSelectedAudioDevice == AudioDevice.SPEAKER_PHONE) {
            // If user selected speaker phone, but then plugged wired headset then make
            // wired headset as user selected device.
            userSelectedAudioDevice = AudioDevice.WIRED_HEADSET;
        }
        if (!hasWiredHeadset && userSelectedAudioDevice == AudioDevice.WIRED_HEADSET) {
            // If user selected wired headset, but then unplugged wired headset then make
            // speaker phone as user selected device.
            userSelectedAudioDevice = AudioDevice.SPEAKER_PHONE;
        }

        // Need to start Bluetooth if it is available and user either selected it explicitly or
        // user did not select any output device.
        boolean needBluetoothAudioStart =
                bluetoothManager.getState() == MagicBluetoothManager.State.HEADSET_AVAILABLE
                        && (userSelectedAudioDevice == AudioDevice.NONE
                        || userSelectedAudioDevice == AudioDevice.BLUETOOTH);

        // Need to stop Bluetooth audio if user selected different device and
        // Bluetooth SCO connection is established or in the process.
        boolean needBluetoothAudioStop =
                (bluetoothManager.getState() == MagicBluetoothManager.State.SCO_CONNECTED
                        || bluetoothManager.getState() == MagicBluetoothManager.State.SCO_CONNECTING)
                        && (userSelectedAudioDevice != AudioDevice.NONE
                        && userSelectedAudioDevice != AudioDevice.BLUETOOTH);

        if (bluetoothManager.getState() == MagicBluetoothManager.State.HEADSET_AVAILABLE
                || bluetoothManager.getState() == MagicBluetoothManager.State.SCO_CONNECTING
                || bluetoothManager.getState() == MagicBluetoothManager.State.SCO_CONNECTED) {
            Log.d(TAG, "Need BT audio: start=" + needBluetoothAudioStart + ", "
                    + "stop=" + needBluetoothAudioStop + ", "
                    + "BT state=" + bluetoothManager.getState());
        }

        // Start or stop Bluetooth SCO connection given states set earlier.
        if (needBluetoothAudioStop) {
            bluetoothManager.stopScoAudio();
            bluetoothManager.updateDevice();
        }

        // Attempt to start Bluetooth SCO audio (takes a few second to start).
        if (needBluetoothAudioStart &&
                !needBluetoothAudioStop &&
                !bluetoothManager.startScoAudio()) {
            // Remove BLUETOOTH from list of available devices since SCO failed.
            audioDevices.remove(AudioDevice.BLUETOOTH);
            audioDeviceSetUpdated = true;
        }


        // Update selected audio device.
        AudioDevice newAudioDevice = selectedAudioDevice;

        if (bluetoothManager.getState() == MagicBluetoothManager.State.SCO_CONNECTED) {
            // If a Bluetooth is connected, then it should be used as output audio
            // device. Note that it is not sufficient that a headset is available;
            // an active SCO channel must also be up and running.
            newAudioDevice = AudioDevice.BLUETOOTH;
        } else if (hasWiredHeadset) {
            // If a wired headset is connected, but Bluetooth is not, then wired headset is used as
            // audio device.
            newAudioDevice = AudioDevice.WIRED_HEADSET;
        } else {
            // No wired headset and no Bluetooth, hence the audio-device list can contain speaker
            // phone (on a tablet), or speaker phone and earpiece (on mobile phone).
            // |defaultAudioDevice| contains either AudioDevice.SPEAKER_PHONE or AudioDevice.EARPIECE
            // depending on the user's selection.
            newAudioDevice = defaultAudioDevice;
        }
        // Switch to new device but only if there has been any changes.
        if (newAudioDevice != selectedAudioDevice || audioDeviceSetUpdated) {
            // Do the required device switch.
            setAudioDeviceInternal(newAudioDevice);
            Log.d(TAG, "New device status: "
                    + "available=" + audioDevices + ", "
                    + "selected=" + newAudioDevice);
            if (audioManagerEvents != null) {
                // Notify a listening client that audio device has been changed.
                audioManagerEvents.onAudioDeviceChanged(selectedAudioDevice, audioDevices);
            }
        }
        Log.d(TAG, "--- updateAudioDeviceState done");
    }

    /**
     * AudioDevice is the names of possible audio devices that we currently
     * support.
     */
    public enum AudioDevice {
        SPEAKER_PHONE, WIRED_HEADSET, EARPIECE, BLUETOOTH, NONE
    }

    /**
     * AudioManager state.
     */
    public enum AudioManagerState {
        UNINITIALIZED,
        PREINITIALIZED,
        RUNNING,
    }

    /**
     * Selected audio device change event.
     */
    public static interface AudioManagerEvents {
        // Callback fired once audio device is changed or list of available audio devices changed.
        void onAudioDeviceChanged(
                AudioDevice selectedAudioDevice, Set<AudioDevice> availableAudioDevices);
    }

    /* Receiver which handles changes in wired headset availability. */
    private class WiredHeadsetReceiver extends BroadcastReceiver {
        private static final int STATE_UNPLUGGED = 0;
        private static final int STATE_PLUGGED = 1;
        private static final int HAS_NO_MIC = 0;

        @Override
        public void onReceive(Context context, Intent intent) {
            int state = intent.getIntExtra("state", STATE_UNPLUGGED);
            // int microphone = intent.getIntExtra("microphone", HAS_NO_MIC);
            // String name = intent.getStringExtra("name");
            hasWiredHeadset = (state == STATE_PLUGGED);
            updateAudioDeviceState();
        }
    }
}