UpdateAudioDeviceState.kt

fun updateAudioDeviceState() {

    // Check if any Bluetooth headset is connected. The internal BT state will
    // change accordingly.
    if (bluetoothManager.state == State.HEADSET_AVAILABLE || bluetoothManager.state == State.HEADSET_UNAVAILABLE || bluetoothManager.state == State.SCO_DISCONNECTING) {
        bluetoothManager.updateDevice()
    }
    // Update the set of available audio devices.
    val newAudioDevices: MutableSet<AudioDevice> =
        HashSet()
    if (bluetoothManager.state == State.SCO_CONNECTED || bluetoothManager.state == State.SCO_CONNECTING || bluetoothManager.state == 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.
    var audioDeviceSetUpdated = audioDevices != newAudioDevices
    // Update the existing audio device set.
    audioDevices = newAudioDevices
    // Correct user selected audio devices if needed.
    if (bluetoothManager.state == State.HEADSET_UNAVAILABLE
        && userSelectedAudioDevice == AudioDevice.BLUETOOTH
    ) { // If BT is not available, it can't be the user selection.
        userSelectedAudioDevice = AudioDevice.NONE
    }
    // If user selected speaker phone, but then plugged wired headset then make
    // wired headset as user selected device.
    if (hasWiredHeadset && userSelectedAudioDevice == AudioDevice.SPEAKER_PHONE) {
        userSelectedAudioDevice = AudioDevice.WIRED_HEADSET
    }
    // If user selected wired headset, but then unplugged wired headset then make
    // speaker phone as user selected device.
    if (!hasWiredHeadset && userSelectedAudioDevice == AudioDevice.WIRED_HEADSET) {
        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.
    val needBluetoothAudioStart =
        (bluetoothManager.state == 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.
    val needBluetoothAudioStop =
        ((bluetoothManager.state == State.SCO_CONNECTED
                || bluetoothManager.state == State.SCO_CONNECTING)
                && (userSelectedAudioDevice != AudioDevice.NONE
                && userSelectedAudioDevice != AudioDevice.BLUETOOTH))
    // Start or stop Bluetooth SCO connection given states set earlier.
    if (needBluetoothAudioStop) {
        bluetoothManager.stopScoAudio()
        bluetoothManager.updateDevice()
    }
    if (needBluetoothAudioStart && !needBluetoothAudioStop) { // Attempt to start Bluetooth SCO audio (takes a few second to start).
        if (!bluetoothManager.startScoAudio()) { // Remove BLUETOOTH from list of available devices since SCO failed.
            audioDevices.remove(AudioDevice.BLUETOOTH)
            audioDeviceSetUpdated = true
        }
    }
    // Update selected audio device.
    val newAudioDevice = when {
        // 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.
        bluetoothManager.state == State.SCO_CONNECTED -> {
            AudioDevice.BLUETOOTH
        }
        // If a wired headset is connected, but Bluetooth is not, then wired headset is used as
        // audio device.
        hasWiredHeadset -> {
            AudioDevice.WIRED_HEADSET
        }
        // 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.
        else -> {
            defaultAudioDevice
        }
    }
    // Switch to new device but only if there has been any changes.
    if (newAudioDevice != selectedAudioDevice || audioDeviceSetUpdated) { // Do the required device switch.
        setAudioDeviceInternal(newAudioDevice)
        onAudioDeviceChanged?.invoke(selectedAudioDevice, audioDevices)
    }
}