//
//  AudioEngine.swift
//  TPI
//
//  Created by Stephen Radford on 29/05/2017.
//  Copyright © 2017 Cocoon Development Ltd. All rights reserved.
//

import Foundation
import AudioKit

class AudioEngine {

    static let shared = AudioEngine()

    var mic: AKMicrophone!
    var booster: AKBooster!
    var tracker: AKFrequencyTracker!
    var silence: AKBooster!
    var tap: AKFFTTap?
    var mixer: AKMixer

    private init() {
        AKSettings.audioInputEnabled = true

        // Shared by SPL + RTA
        mic = AKMicrophone()
        booster = AKBooster(mic)
        tracker = AKFrequencyTracker(booster)
        silence = AKBooster(tracker, gain: 0)

        // Tap for RTA
        tap = AKFFTTap(booster)
        mixer = AKMixer(silence, white, pink, sineOscillator, squareOscillator)

        AudioKit.output = mixer
        AudioKit.start()

        NotificationCenter.default.addObserver(self, selector: #selector(start), name: NSNotification.Name.UIApplicationDidBecomeActive, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(stop), name: NSNotification.Name.UIApplicationDidEnterBackground, object: nil)
    }

    deinit {
        NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIApplicationDidBecomeActive, object: nil)
        NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIApplicationDidEnterBackground, object: nil)
    }

    @objc private func stop() {
        AudioKit.stop()
    }

    @objc private func start() {
        AudioKit.start()
    }

}