ViewController.swift

//
//  ViewController.swift
//  uipip
//
//  Created by Akihiro Urushihara on 2021/11/27.
//

import UIKit
import AVKit
import AVFoundation

class ViewController: UIViewController {

    private let _pipContent = VideoProvider()
    private var _pipController: AVPictureInPictureController?
    private let _bufferDisplayLayer = AVSampleBufferDisplayLayer()
    private var _pipPossibleObservation: NSKeyValueObservation?
    private var _observer: NSObjectProtocol?
    private let _startButton = UIButton()


    override func viewDidLoad() {
        super.viewDidLoad()
        let session = AVAudioSession.sharedInstance()
        try! session.setCategory(.playback, mode: .moviePlayback)
        try! session.setActive(true)

        let margin = ((view.bounds.width - 200) / 2)
        _startButton.frame = .init(x: margin, y: 80, width: 200, height: 30)
        _startButton.addTarget(self, action: #selector(ViewController.toggle), for: .touchUpInside)
        _startButton.setTitle("Start PiP", for: .normal)
        self.view.addSubview(_startButton)

        // 表示用の画面を作成
        let videoContainerView = UIView()
        videoContainerView.frame = .init(x: margin, y: 200, width: 200, height: 30)
        self.view.addSubview(videoContainerView)

        let bufferDisplayLayer = _pipContent.bufferDisplayLayer
        bufferDisplayLayer.frame = videoContainerView.bounds
        bufferDisplayLayer.videoGravity = .resizeAspect
        videoContainerView.layer.addSublayer(bufferDisplayLayer)

        _pipContent.start()

        DispatchQueue.main.async {
            self.start()
        }
    }

    func start() {

        // PinP をサポートしているデバイスかどうかを確認
        if AVPictureInPictureController.isPictureInPictureSupported() {

            // AVPictureInPictureController の生成
            _pipController = AVPictureInPictureController(
                contentSource: .init(
                    sampleBufferDisplayLayer:
                        _pipContent.bufferDisplayLayer,
                    playbackDelegate: self))
            _pipController?.delegate = self

            _pipPossibleObservation = _pipController?.observe(
                \AVPictureInPictureController.isPictureInPicturePossible,
                options: [.initial, .new]) { [weak self] _, change in
                guard let self = self else { return }

                // 再生可能になったら PinP ボタンを有効化
                if (change.newValue ?? false) {
                    self._startButton.isEnabled = (change.newValue ?? false)
                }
            }
        }
    }


    @objc func toggle() {
        guard let _pipController = _pipController else { return }
        if !_pipController.isPictureInPictureActive {
            _pipController.startPictureInPicture()
        } else {
            _pipController.stopPictureInPicture()
        }
    }
}


extension ViewController: AVPictureInPictureControllerDelegate {

    func pictureInPictureController(
        _ pictureInPictureController: AVPictureInPictureController,
        failedToStartPictureInPictureWithError error: Error
    ) {
        print("\(#function)")
        print("pip error: \(error)")
    }

    func pictureInPictureControllerWillStartPictureInPicture(
        _ pictureInPictureController: AVPictureInPictureController
    ) {
        print("\(#function)")
    }

    func pictureInPictureControllerWillStopPictureInPicture(
        _ pictureInPictureController: AVPictureInPictureController
    ) {
        print("\(#function)")
    }
}

extension ViewController: AVPictureInPictureSampleBufferPlaybackDelegate {

    func pictureInPictureController(
        _ pictureInPictureController: AVPictureInPictureController,
        setPlaying playing: Bool
    ) {
        print("\(#function)")
    }

    func pictureInPictureControllerTimeRangeForPlayback(
        _ pictureInPictureController: AVPictureInPictureController
    ) -> CMTimeRange {
        print("\(#function)")
        return CMTimeRange(start: .negativeInfinity, duration: .positiveInfinity)
    }

    func pictureInPictureControllerIsPlaybackPaused(
        _ pictureInPictureController: AVPictureInPictureController
    ) -> Bool {
        print("\(#function)")
        return false
    }

    func pictureInPictureController(
        _ pictureInPictureController: AVPictureInPictureController,
        didTransitionToRenderSize newRenderSize: CMVideoDimensions
    ) {
        print("\(#function)")
        print(newRenderSize)
    }

    func pictureInPictureController(
        _ pictureInPictureController: AVPictureInPictureController,
        skipByInterval skipInterval: CMTime,
        completion completionHandler: @escaping () -> Void
    ) {
        print("\(#function)")
        completionHandler()
    }
}