App to map next track button to input mute toggle

main.swift

//
//  main.swift
//  mediakeymute
//
//  Created by Adam Malcontenti-Wilson on 16/6/20.
//  Copyright © 2020 Adam Malcontenti-Wilson.
//
//  Permission is hereby granted, free of charge, to any person obtaining a 
//  copy of this software and associated documentation files (the "Software"), 
//  to deal in the Software without restriction, including without limitation 
//  the rights to use, copy, modify, merge, publish, distribute, sublicense, 
//  and/or sell copies of the Software, and to permit persons to whom the 
//  Software is furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in 
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 
//  OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
//  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
//  DEALINGS IN THE SOFTWARE.

import Foundation
import AVFoundation
import MediaPlayer
import CoreAudio

func getDefaultInputDevice() -> AudioObjectID? {
    var propertyAddress = AudioObjectPropertyAddress(mSelector: kAudioHardwarePropertyDefaultInputDevice,
                                                     mScope: kAudioObjectPropertyScopeGlobal,
                                                     mElement: kAudioObjectPropertyElementMaster)
    var deviceID:AudioObjectID = AudioObjectID(0)
    var size:UInt32 = UInt32(MemoryLayout<AudioObjectID>.size)
    let err = AudioObjectGetPropertyData(AudioObjectID(kAudioObjectSystemObject), &propertyAddress, 0, nil, &size, &deviceID)
    
    if err == noErr {
        return deviceID
    } else {
        return nil
    }
}

func getDeviceName(deviceID: AudioObjectID) -> String {
    var propertyAddress = AudioObjectPropertyAddress(mSelector: kAudioDevicePropertyDeviceName,
                                                     mScope: kAudioObjectPropertyScopeGlobal,
                                                     mElement: kAudioObjectPropertyElementMaster)
    var deviceName = [CChar](repeating:0, count: 64)
    var size = UInt32(MemoryLayout<CChar>.size * 64)
    let err = AudioObjectGetPropertyData(deviceID, &propertyAddress, 0, nil, &size, &deviceName)
    // TODO: handle err
    return String.init(cString: deviceName)
}

func getInputMute(deviceID: AudioObjectID) -> Bool {
    var propertyAddress = AudioObjectPropertyAddress(mSelector: kAudioDevicePropertyMute,
                                                     mScope: kAudioDevicePropertyScopeInput,
                                                     mElement: kAudioObjectPropertyElementMaster)
    var muteVal = UInt32(0)
    var size = UInt32(MemoryLayout<UInt32>.size)
    let err = AudioObjectGetPropertyData(deviceID, &propertyAddress, 0, nil, &size, &muteVal)
    // TODO: handle err
    return muteVal != 0
}

func setInputMute(deviceID: AudioObjectID, mute: Bool) {
    var propertyAddress = AudioObjectPropertyAddress(mSelector: kAudioDevicePropertyMute,
                                                     mScope: kAudioDevicePropertyScopeInput,
                                                     mElement: kAudioObjectPropertyElementMaster)
    var muteVal = UInt32(mute ? 1 : 0)
    let size = UInt32(MemoryLayout<UInt32>.size)
    let err = AudioObjectSetPropertyData(deviceID, &propertyAddress, 0, nil, size, &muteVal)
    // TODO: handle err
}

print("Hello, World!")

let deviceID = getDefaultInputDevice()
let deviceName = getDeviceName(deviceID: deviceID!)
print("Controlling device: \(deviceName)")

var mute = getInputMute(deviceID: deviceID!)

var onSoundID = SystemSoundID()
var offSoundID = SystemSoundID()
AudioServicesCreateSystemSoundID(URL.init(fileURLWithPath: "/System/Library/Sounds/Bottle.aiff") as CFURL, &onSoundID)
AudioServicesCreateSystemSoundID(URL.init(fileURLWithPath: "/System/Library/Sounds/Submarine.aiff") as CFURL, &offSoundID)


let commandCenter = MPRemoteCommandCenter.shared()
commandCenter.nextTrackCommand.isEnabled = true;
commandCenter.nextTrackCommand.addTarget(handler: { (e: MPRemoteCommandEvent) -> MPRemoteCommandHandlerStatus in
    print("Toggling mute \(mute) -> \(!mute)")
    mute = !mute
    if mute {
        AudioServicesPlayAlertSound(offSoundID)
    } else {
        AudioServicesPlayAlertSound(onSoundID)
    }
    setInputMute(deviceID: deviceID!, mute: mute)
    return .success
} )

// required to tell macOS we're playing to be able to get commands
MPNowPlayingInfoCenter.default().playbackState = .playing

CFRunLoopRun()