/*

    Copyright (C) 2016 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Playground version of MetalBasicTessellation.

 */

import Cocoa

import Metal

import MetalKit

import PlaygroundSupport

// Setup Metal

let device = MTLCreateSystemDefaultDevice()!

let commandQueue = device.makeCommandQueue()

let mtkView = MTKView(frame: CGRect(x: 0, y: 0, width: 512, height: 512), device: device)

var library: MTLLibrary?

do {

    let path = Bundle.main.path(forResource: "TessellationFunctions", ofType: "metal")

    let source = try String(contentsOfFile: path!, encoding: .utf8)

    library = try device.makeLibrary(source: source, options: nil)

} catch let error as NSError {

    print("library error: " + error.description)

}

// Setup Compute Pipeline

let kernelFunction = library?.makeFunction(name: "tessellation_kernel_triangle")

var computePipeline: MTLComputePipelineState?

do {

    computePipeline = try device.makeComputePipelineState(function: kernelFunction!)

} catch let error as NSError {

    print("compute pipeline error: " + error.description)

}

// Setup Vertex Descriptor

let vertexDescriptor = MTLVertexDescriptor()

vertexDescriptor.attributes[0].format = .float4;

vertexDescriptor.attributes[0].offset = 0;

vertexDescriptor.attributes[0].bufferIndex = 0;

vertexDescriptor.layouts[0].stepFunction = .perPatchControlPoint;

vertexDescriptor.layouts[0].stepRate = 1;

vertexDescriptor.layouts[0].stride = 4*MemoryLayout<Float>.size;

// Setup Render Pipeline

let renderPipelineDescriptor = MTLRenderPipelineDescriptor()

renderPipelineDescriptor.vertexDescriptor = vertexDescriptor

renderPipelineDescriptor.colorAttachments[0].pixelFormat = mtkView.colorPixelFormat

renderPipelineDescriptor.fragmentFunction = library?.makeFunction(name: "tessellation_fragment")

renderPipelineDescriptor.isTessellationFactorScaleEnabled = false

renderPipelineDescriptor.tessellationFactorFormat = .half

renderPipelineDescriptor.tessellationControlPointIndexType = .none

renderPipelineDescriptor.tessellationFactorStepFunction = .constant

renderPipelineDescriptor.tessellationOutputWindingOrder = .clockwise

renderPipelineDescriptor.tessellationPartitionMode = .fractionalEven

renderPipelineDescriptor.maxTessellationFactor = 64;

renderPipelineDescriptor.vertexFunction = library?.makeFunction(name: "tessellation_vertex_triangle")

var renderPipeline: MTLRenderPipelineState?

do {

    renderPipeline = try device.makeRenderPipelineState(descriptor: renderPipelineDescriptor)

} catch let error as NSError {

    print("render pipeline error: " + error.description)

}

// Setup Buffers

let tessellationFactorsBuffer = device.makeBuffer(length: 256, options: MTLResourceOptions.storageModePrivate)

let controlPointPositions: [Float] = [

    -0.8, -0.8, 0.0, 1.0,   // lower-left

     0.0,  0.8, 0.0, 1.0,   // upper-middle

     0.8, -0.8, 0.0, 1.0,   // lower-right

]

let controlPointsBuffer = device.makeBuffer(bytes: controlPointPositions, length:256 , options: [])

// Tessellation Pass

let commandBuffer = commandQueue.makeCommandBuffer()

let computeCommandEncoder = commandBuffer.makeComputeCommandEncoder()

computeCommandEncoder.setComputePipelineState(computePipeline!)

let edgeFactor: [Float] = [16.0]

let insideFactor: [Float] = [8.0]

computeCommandEncoder.setBytes(edgeFactor, length: MemoryLayout<Float>.size, at: 0)

computeCommandEncoder.setBytes(insideFactor, length: MemoryLayout<Float>.size, at: 1)

computeCommandEncoder.setBuffer(tessellationFactorsBuffer, offset: 0, at: 2)

computeCommandEncoder.dispatchThreadgroups(MTLSizeMake(1, 1, 1), threadsPerThreadgroup: MTLSizeMake(1, 1, 1))

computeCommandEncoder.endEncoding()

let renderPassDescriptor = mtkView.currentRenderPassDescriptor

let renderCommandEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: renderPassDescriptor!)

renderCommandEncoder.setRenderPipelineState(renderPipeline!)

renderCommandEncoder.setVertexBuffer(controlPointsBuffer, offset: 0, at: 0)

renderCommandEncoder.setTriangleFillMode(.lines)

renderCommandEncoder.setTessellationFactorBuffer(tessellationFactorsBuffer, offset: 0, instanceStride: 0)

renderCommandEncoder.drawPatches(numberOfPatchControlPoints: 3, patchStart: 0, patchCount: 1, patchIndexBuffer: nil, patchIndexBufferOffset: 0, instanceCount: 1, baseInstance: 0)

renderCommandEncoder.endEncoding()

commandBuffer.present(mtkView.currentDrawable!)

commandBuffer.commit()

commandBuffer.waitUntilCompleted()

// Display Tessellated Content

PlaygroundPage.current.liveView = mtkView