import MetalKit
import UIKit

final class ViewController: UIViewController {
    private let mtkView = MTKView()
    private let renderer: Renderer?
    private let videoReader = VideoReader()
    private let sampleConverter: SampleConverter?

    init() {
        let device = MTLCreateSystemDefaultDevice()
        let pixelFormat = MTLPixelFormat.bgra8Unorm

        if let device = device {
            renderer = Renderer(device: device, pixelFormat: pixelFormat)
            sampleConverter = SampleConverter(device: device, pixelFormat: pixelFormat)
        } else {
            renderer = nil
            sampleConverter = nil
        }

        super.init(nibName: nil, bundle: nil)

        mtkView.delegate = renderer
        mtkView.device = device
        mtkView.clearColor = MTLClearColor(red: 1, green: 215 / 255, blue: 0, alpha: 1)
        mtkView.colorPixelFormat = pixelFormat
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .green

        view.addSubview(mtkView)

        startReadVideo()
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()

        mtkView.frame = CGRect(x: 0, y: view.safeAreaInsets.top, width: view.bounds.width, height: view.bounds.height - view.safeAreaInsets.top - view.safeAreaInsets.bottom)
    }

    private func startReadVideo() {
        guard
            let sampleConverter = sampleConverter,
            let videoReader = videoReader
        else { return }

        videoReader.sampleRead = { [weak self] sample in
            guard let texture = sampleConverter.convert(sample: sample) else { return }
            DispatchQueue.main.async { [weak self] in
                self?.renderer?.showTexture(texture)
            }
        }

        videoReader.readSamples()
    }
}