import AVFoundation
import MetalKit

final class SampleConverter {
    private var textureCache: CVMetalTextureCache?
    private let pixelFormat: MTLPixelFormat

    init?(device: MTLDevice, pixelFormat: MTLPixelFormat) {
        guard
            CVMetalTextureCacheCreate(nil, nil, device, nil, &textureCache) == kCVReturnSuccess,
            textureCache != nil
        else { return nil }

        self.pixelFormat = pixelFormat
    }

    func convert(sample: CMSampleBuffer) -> MTLTexture? {
        guard
            let cvImageBuffer = CMSampleBufferGetImageBuffer(sample),
            let textureCache = textureCache
        else {
            return nil
        }

        let width = CVPixelBufferGetWidth(cvImageBuffer)
        let height = CVPixelBufferGetHeight(cvImageBuffer)
        var textureOptional: CVMetalTexture?

        let createResult = CVMetalTextureCacheCreateTextureFromImage(kCFAllocatorDefault, textureCache, cvImageBuffer, nil, pixelFormat, width, height, 0, &textureOptional)

        guard
            createResult == kCVReturnSuccess,
            let texture = textureOptional,
            let resultTexture = CVMetalTextureGetTexture(texture)
        else {
            return nil
        }

        return resultTexture
    }
}