import Foundation
import MetalKit

final class Renderer: NSObject {
    private let queue: MTLCommandQueue?

    private var time: Float = 0
    private var animatedBy: Float = 0
    private var constants = Constants()

    private let triangleModel: TriangleModel?
    private let rectangleModel: RectangleModel?
    private let textureModel: TextureModel?

    init?(device: MTLDevice, pixelFormat: MTLPixelFormat) {
        queue = device.makeCommandQueue()
        guard let library = device.makeDefaultLibrary() else { return nil }

        triangleModel = TriangleModel(device: device, library: library, pixelFormat: pixelFormat)
        rectangleModel = RectangleModel(device: device, library: library, pixelFormat: pixelFormat)
        textureModel = TextureModel(device: device, library: library, pixelFormat: pixelFormat)

        super.init()
    }

    func showTexture(_ texture: MTLTexture) {
        textureModel?.updateTexture(texture)
    }
}

extension Renderer: MTKViewDelegate {
    func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {
        print(#function, size)
    }

    func draw(in view: MTKView) {
        time += 1 / Float(view.preferredFramesPerSecond)
        animatedBy = abs(sin(time) / 2 + 0.5)
        constants.animatedBy = animatedBy

        guard
            let drawable = view.currentDrawable,
            let descriptor = view.currentRenderPassDescriptor,
            let commandBuffer = queue?.makeCommandBuffer(),
            let parallelRenderCommandEncoder = commandBuffer.makeParallelRenderCommandEncoder(descriptor: descriptor)
        else { return }

        textureModel?.setupRenderCommandEncoder(parallelRenderCommandEncoder: parallelRenderCommandEncoder)
        rectangleModel?.setupRenderCommandEncoder(parallelRenderCommandEncoder: parallelRenderCommandEncoder, constants: constants, animatedBy: animatedBy)
        triangleModel?.setupRenderCommandEncoder(parallelRenderCommandEncoder: parallelRenderCommandEncoder, constants: constants)

        parallelRenderCommandEncoder.endEncoding()

        commandBuffer.present(drawable)
        commandBuffer.commit()
    }
}