import MetalKit

final class TextureModel {
    private struct VertexTexture {
        var position: simd_float3
        var texture: simd_float2
    }

    // texture
    private let samplerState: MTLSamplerState?
    private var texture: MTLTexture?
    private let pipelineTexture: MTLRenderPipelineState?
    private let vertexBufferTexture: MTLBuffer?

    // 1320 - 308 = 330 - 77
    private let verticesTexture: [VertexTexture] = [
        VertexTexture(position: simd_float3(-1, 0.1, 0), texture: simd_float2(0, 1)),
        VertexTexture(position: simd_float3(-1, -0.1, 0), texture: simd_float2(0, 0)),
        VertexTexture(position: simd_float3(1, -0.1, 0), texture: simd_float2(1, 0)),
        VertexTexture(position: simd_float3(1, 0.1, 0), texture: simd_float2(1, 1)),
    ]
    private let indicesBufferTexture: MTLBuffer?
    private let indicesTexture: [UInt16] = [
        0, 1, 2,
        2, 3, 0,
    ]

    init?(device: MTLDevice, library: MTLLibrary, pixelFormat: MTLPixelFormat) {
        guard
            let url = Bundle.main.url(forResource: "texture", withExtension: "png"),
            let vertexShader = library.makeFunction(name: "vertex_shader_texture"),
            let fragmentShader = library.makeFunction(name: "fragment_shader_texture")
        else {
            print("url or vertexShader or fragmentShader is nil")
            return nil
        }

        let textureLoader = MTKTextureLoader(device: device)
        let options: [MTKTextureLoader.Option: Any] = [MTKTextureLoader.Option.origin: MTKTextureLoader.Origin.bottomLeft.rawValue]
        do {
            texture = try textureLoader.newTexture(URL: url, options: options)
        } catch {
            print(#function, error)
            return nil
        }

        let descriptorTexture = MTLRenderPipelineDescriptor()
        descriptorTexture.colorAttachments[0].pixelFormat = pixelFormat

        descriptorTexture.vertexFunction = vertexShader
        descriptorTexture.fragmentFunction = fragmentShader

        let vertexDescriptorTexture = MTLVertexDescriptor()

        // position
        vertexDescriptorTexture.attributes[0].format = .float3
        vertexDescriptorTexture.attributes[0].offset = 0
        vertexDescriptorTexture.attributes[0].bufferIndex = 0

        // texture
        vertexDescriptorTexture.attributes[1].format = .float2
        vertexDescriptorTexture.attributes[1].offset = MemoryLayout<simd_float3>.size// + MemoryLayout<simd_float4>.stride
        vertexDescriptorTexture.attributes[1].bufferIndex = 0

        vertexDescriptorTexture.layouts[0].stride = MemoryLayout<VertexTexture>.stride

        descriptorTexture.vertexDescriptor = vertexDescriptorTexture

        do {
            pipelineTexture = try device.makeRenderPipelineState(descriptor: descriptorTexture)
        } catch {
            print(#function, error)
            return nil
        }

        let descriptor = MTLSamplerDescriptor()
        descriptor.minFilter = .linear
        descriptor.magFilter = .linear
        samplerState = device.makeSamplerState(descriptor: descriptor)

        vertexBufferTexture = device.makeBuffer(bytes: verticesTexture, length: verticesTexture.count * MemoryLayout<VertexTexture>.stride, options: [])
        indicesBufferTexture = device.makeBuffer(bytes: indicesTexture, length: indicesTexture.count * MemoryLayout<UInt16>.stride, options: [])
    }

    func updateTexture(_ texture: MTLTexture) {
        self.texture = texture
    }

    func setupRenderCommandEncoder(parallelRenderCommandEncoder: MTLParallelRenderCommandEncoder) {
        guard
            let pipeline = pipelineTexture,
            let renderCommandEncoder = parallelRenderCommandEncoder.makeRenderCommandEncoder(),
            let vertexBufferTexture = vertexBufferTexture,
            let indicesBufferTexture = indicesBufferTexture
        else { return }
        renderCommandEncoder.setRenderPipelineState(pipeline)
        renderCommandEncoder.setVertexBuffer(vertexBufferTexture, offset: 0, index: 0)
        renderCommandEncoder.setFragmentSamplerState(samplerState, index: 0)
        renderCommandEncoder.setFragmentTexture(texture, index: 0)
        renderCommandEncoder.drawIndexedPrimitives(type: .triangle, indexCount: indicesTexture.count, indexType: .uint16, indexBuffer: indicesBufferTexture, indexBufferOffset: 0)
        renderCommandEncoder.endEncoding()
    }
}