//
//  Created by Chiharu Nameki @Ridwy on 2021/07/30.
//

import UIKit
import AVFoundation

/*
 Using MTAudioProcessingTap, you can touch raw audio samples playing with AVPlayer.
 This sample code shows how to use MTAudioProcessingTap in Swift 5.
 */
class ViewController: UIViewController {
    // MTAudioProcessingTap works loacal and remote files, but not support streaming.
    private let player = AVPlayer(url: Bundle.main.url(forResource: "sample", withExtension: "mp3")!)

    override func viewDidLoad() {
        super.viewDidLoad()

        guard let track = player.currentItem?.asset.tracks(withMediaType: .audio).first else {
            return
        }

        let audioMix = AVMutableAudioMix()
        let params = AVMutableAudioMixInputParameters(track: track)
        var callbacks = MTAudioProcessingTapCallbacks(version: kMTAudioProcessingTapCallbacksVersion_0, clientInfo: nil)
        { tap, _, tapStorageOut in
            // initialize
        } finalize: { tap in
            // clean up
        } prepare: { tap, maxFrames, processingFormat in
            // allocate memory for sound processing
        } unprepare: { tap in
            // deallocate memory for sound processing
        } process: { tap, numberFrames, flags, bufferListInOut, numberFramesOut, flagsOut in
            guard noErr == MTAudioProcessingTapGetSourceAudio(tap, numberFrames, bufferListInOut, flagsOut, nil, numberFramesOut) else {
                return
            }

            // retrieve AudioBuffer using UnsafeMutableAudioBufferListPointer
            for buffer in UnsafeMutableAudioBufferListPointer(bufferListInOut) {
                // process audio samples here
                //memset(buffer.mData, 0, Int(buffer.mDataByteSize))
            }
        }

        var tap: Unmanaged<MTAudioProcessingTap>?
        let error = MTAudioProcessingTapCreate(kCFAllocatorDefault, &callbacks, kMTAudioProcessingTapCreationFlag_PreEffects, &tap)
        assert(error == noErr)

        params.audioTapProcessor = tap?.takeUnretainedValue()
        tap?.release()

        audioMix.inputParameters = [params]
        player.currentItem?.audioMix = audioMix

        player.play()
    }
}