/**
 * Copyright (c) 2019 Razeware LLC
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * Notwithstanding the foregoing, you may not use, copy, modify, merge, publish,
 * distribute, sublicense, create a derivative work, and/or sell copies of the
 * Software in any work that is designed, intended, or marketed for pedagogical or
 * instructional purposes related to programming, coding, application development,
 * or information technology.  Permission for such use, copying, modification,
 * merger, publication, distribution, sublicensing, creation of derivative works,
 * or sale is expressly withheld.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

import PlaygroundSupport
import MetalKit

guard let device = MTLCreateSystemDefaultDevice() else {
  fatalError("GPU is not supported")
}

let frame = CGRect(x: 0, y: 0, width: 600, height: 600)
let view = MTKView(frame: frame, device: device)
view.clearColor = MTLClearColor(red: 1, green: 1, blue: 0.8, alpha: 1)

let allocator = MTKMeshBufferAllocator(device: device)
let mdlMesh = MDLMesh(sphereWithExtent: [0.2, 0.75, 0.2],
                      segments: [100, 100],
                      inwardNormals: false,
                      geometryType: .triangles,
                      allocator: allocator)
let mesh = try MTKMesh(mesh: mdlMesh, device: device)

guard let commandQueue = device.makeCommandQueue() else {
  fatalError("Could not create a command queue")
}

let shader = """
#include <metal_stdlib>
using namespace metal;
struct VertexIn {
  float4 position [[ attribute(0) ]];
};
vertex float4 vertex_main(const VertexIn vertex_in [[ stage_in ]]) {
  return vertex_in.position;
}
fragment float4 fragment_main() {
  return float4(0, 0.4, 0.21, 1);
}
"""

let library = try device.makeLibrary(source: shader, options: nil)
let vertexFunction = library.makeFunction(name: "vertex_main")
let fragmentFunction = library.makeFunction(name: "fragment_main")

let pipelineDescriptor = MTLRenderPipelineDescriptor()
pipelineDescriptor.colorAttachments[0].pixelFormat = .bgra8Unorm
pipelineDescriptor.vertexFunction = vertexFunction
pipelineDescriptor.fragmentFunction = fragmentFunction

pipelineDescriptor.vertexDescriptor =
  MTKMetalVertexDescriptorFromModelIO(mesh.vertexDescriptor)

let pipelineState =
  try device.makeRenderPipelineState(descriptor: pipelineDescriptor)

guard let commandBuffer = commandQueue.makeCommandBuffer(),
  let renderPassDescriptor = view.currentRenderPassDescriptor,
  let renderEncoder =
  commandBuffer.makeRenderCommandEncoder(descriptor: renderPassDescriptor)
  else {  fatalError() }

renderEncoder.setRenderPipelineState(pipelineState)

renderEncoder.setVertexBuffer(mesh.vertexBuffers[0].buffer,
                              offset: 0, index: 0)

guard let submesh = mesh.submeshes.first else {
  fatalError()
}

renderEncoder.drawIndexedPrimitives(type: .triangle,
                                    indexCount: submesh.indexCount,
                                    indexType: submesh.indexType,
                                    indexBuffer: submesh.indexBuffer.buffer,
                                    indexBufferOffset: 0)
renderEncoder.endEncoding()
guard let drawable = view.currentDrawable else {
  fatalError()
}
commandBuffer.present(drawable)
commandBuffer.commit()

PlaygroundPage.current.liveView = view