Modified Audio Interruption Monitor with delegate pattern

AudioInterruptionMonitor.swift

//
//  AudioInterruptionMonitor.swift
//  JWPlayerDemo
//
//  Created by Amitai Blickstein
//  Copyright © 2019. All rights reserved.
//
// Credit: Code modified from Mohamed Afifi ->
// https://github.com/quran/quran-ios/blob/master/QueuePlayer/AudioInterruptionMonitor.swift

import AVFoundation

// MARK: Usage
/*
extension SwiftViewController: AudioInterruptionMonitorDelegate {
    func onAudioInterruption(type: AudioInterruptionType) {
        switch type {
            case .began:                player?.pause()
            case .endedShouldResume:    player?.play()
            case .endedShouldNotResume: player?.stop()
        }
    }
}
*/

// MARK: Type Safety
enum AudioInterruptionType {
    case began
    case endedShouldResume
    case endedShouldNotResume
}

protocol AudioInterruptionMonitorDelegate: AnyObject {
    func onAudioInterruption(type: AudioInterruptionType)
}

class AudioInterruptionMonitor {
    weak var delegate: AudioInterruptionMonitorDelegate?
    
    init() {
        NotificationCenter.default
            .addObserver(self,
                         selector: #selector(onInterruption(_:)),
                         name: .audioInterruption,
                         object: nil)
    }
    
    deinit {
        NotificationCenter.default
            .removeObserver(self,
                            name: .audioInterruption,
                            object: nil)
    }
    
    @objc private func onInterruption(_ notification: Notification) {
        guard let type = typeFrom(notification) else { return }
        
        switch type {
        case .began:
            delegate?.onAudioInterruption(type: .began)
        case .ended:
            guard let playerShouldResume = optionsFrom(notification)?.contains(.shouldResume)
            else { return }
            
            let endedType: AudioInterruptionType = playerShouldResume ?
                .endedShouldResume : .endedShouldNotResume
            
            delegate?.onAudioInterruption(type: endedType)
            @unknown default:
                fatalError("'@unknown default' in switch, line \(#line).")
        }
    }

    
    // MARK: Helpers
    
    func typeFrom(_ notification: Notification) -> AVAudioSession.InterruptionType? {
        guard
            let info    = notification.userInfo,
            let rawType = info[AVAudioSessionInterruptionTypeKey] as? UInt
            else { return nil }
            
        return AVAudioSession.InterruptionType(rawValue: rawType)
    }
    
    func optionsFrom(_ notification: Notification) -> AVAudioSession.InterruptionOptions? {
        guard
            let info    = notification.userInfo,
            let rawOptions = info[AVAudioSessionInterruptionOptionKey] as? UInt
        else { return nil }
            
        return AVAudioSession.InterruptionOptions(rawValue: rawOptions)
    }
}

// Makes the code above more readable
extension Notification.Name {
    static var audioInterruption: Self { AVAudioSession.interruptionNotification }
}