if (!navigator.gpu) {
  throw new Error("WebGPU not supported on this browser.");
}

const adapter = await navigator.gpu.requestAdapter();
if (!adapter) {
  throw new Error("No WebGPU adapter");
}

const device = await adapter.requestDevice();

const canvas = document.querySelector("canvas");
canvas.width = canvas.clientWidth
canvas.height = canvas.clientHeight

const context = canvas.getContext("webgpu");
const canvasFormat = navigator.gpu.getPreferredCanvasFormat();
context.configure({
  device: device,
  format: canvasFormat,
});

const encoder = device.createCommandEncoder();

const renderPass = encoder.beginRenderPass({
  colorAttachments: [{
    view: context.getCurrentTexture().createView(),
    loadOp: "clear",
    clearValue: { r: 0.9, g: 0.5, b: 0.2, a: 1 },
    storeOp: "store",
  }]
});
renderPass.end();

const commandBuffer = encoder.finish();
device.queue.submit([commandBuffer]);


const cubeResponse = await fetch("obj/cube.bin");
const cubeObj = await cubeResponse.arrayBuffer();

const cubeView = new DataView(cubeObj);
const indexCount = cubeView.getUint32(0, true);
const indexBufferOffset = cubeView.getUint32(4, true);
const indexBufferSize = cubeView.getUint32(8, true);
const vertexBufferOffset = cubeView.getUint32(12, true);
const vertexBufferSize = cubeView.getUint32(16, true);
console.log(`indexBufferOffset ${indexBufferOffset} indexBufferSize ${indexBufferSize}`);
console.log(`vertexBufferOffset ${vertexBufferOffset} vertexBufferSize ${vertexBufferSize}`);
const cubeIndexCount = indexBufferSize / 2;

const cubeVerticesStride = 36;

const indexVertexBuffer = device.createBuffer({
  label: "cell vertices",
  size: indexBufferSize + vertexBufferSize,
  usage: GPUBufferUsage.INDEX | GPUBufferUsage.VERTEX | GPUBufferUsage.COPY_DST,
});
device.queue.writeBuffer(indexVertexBuffer, 0, cubeObj, indexBufferOffset, indexBufferSize);
device.queue.writeBuffer(indexVertexBuffer, indexBufferSize, cubeObj, vertexBufferOffset, vertexBufferSize);

const vertexBufferLayout = {
  arrayStride: cubeVerticesStride,
  attributes: [{
    format: "float32x3",
    offset: 0,
    shaderLocation: 0,
  }, {
    format: "float32x2",
    offset: 12,
    shaderLocation: 1,
  }, {
    format: "float16x4",
    offset: 20,
    shaderLocation: 2,
  }, {
    format: "float16x4",
    offset: 28,
    shaderLocation: 3,
  }],
  stepMode: "vertex",
};

function getPath(path)
{
  return fetch(path).then((response) => {
    if (!response.ok) {
      throw new Error(`${path}: ${response.status}`)
    }
    return response.blob()
  }).then((blob) => { return blob.text() })
}

const cellShaderModule = device.createShaderModule({
  label: "cell shader",
  code: await getPath("index.wgsl")
});

const bindGroupLayout = device.createBindGroupLayout({
  label: "bind group layout",
  entries: [{
    binding: 0,
    visibility: GPUShaderStage.VERTEX | GPUShaderStage.COMPUTE,
    buffer: { type: "uniform" }
  }, {
    binding: 1,
    visibility: GPUShaderStage.VERTEX | GPUShaderStage.COMPUTE,
    buffer: { type: "read-only-storage" }
  }, {
    binding: 2,
    visibility: GPUShaderStage.COMPUTE,
    buffer: { type: "storage" }
  }]
});

const pipelineLayout = device.createPipelineLayout({
  label: "pipeline layout",
  bindGroupLayouts: [ bindGroupLayout ],
});

const cellPipeline = device.createRenderPipeline({
  label: "cell pipeline",
  layout: pipelineLayout,
  vertex: {
    module: cellShaderModule,
    entryPoint: "vertexMain",
    buffers: [vertexBufferLayout],
  },
  fragment: {
    module: cellShaderModule,
    entryPoint: "fragmentMain",
    targets: [{
      format: canvasFormat,
    }]
  },
  primitive: {
    topology: 'triangle-list',
  },
  depthStencil: {
    depthWriteEnabled: true,
    depthCompare: 'less',
    format: 'depth24plus',
  },
});

const computeShaderModule = device.createShaderModule({
  label: "compute shader",
  code: await getPath("compute.wgsl")
});

const computePipeline = device.createComputePipeline({
  label: "compute pipeline",
  layout: pipelineLayout,
  compute: {
    module: computeShaderModule,
    entryPoint: "computeMain",
  },
});

const gridSize = 32;
const workGroupSize = 16;

//const uniformArray2 = new Float32Array([gridSize, gridSize, 1, 1]);
const memory = new WebAssembly.Memory({ initial: 1 });
const uniformArray = new Float32Array(memory.buffer);
uniformArray[0] = gridSize;
uniformArray[1] = gridSize;
uniformArray[2] = 1;
uniformArray[3] = 1;
const uniformArraySize = 4 * 4 + 4 * 4 * 4;
const rotate = await WebAssembly.instantiateStreaming(fetch("rotate.wasm"), {
  env: { memory: memory }
});

const uniformBuffer = device.createBuffer({
  label: "grid uniform",
  size: uniformArraySize,
  usage: GPUBufferUsage.UNIFORM | GPUBufferUsage.COPY_DST,
});
device.queue.writeBuffer(uniformBuffer, 0, uniformArray, 0, uniformArraySize / 4);

const cellStateArray = new Uint32Array(gridSize * gridSize);

const cellStateStorage = [
  device.createBuffer({
    label: "cell state 0",
    size: cellStateArray.byteLength,
    usage: GPUBufferUsage.STORAGE | GPUBufferUsage.COPY_DST,
  }),
  device.createBuffer({
    label: "cell state 1",
    size: cellStateArray.byteLength,
    usage: GPUBufferUsage.STORAGE | GPUBufferUsage.COPY_DST,
  }),
];

for (let i = 0; i < cellStateArray.length; i += 1) {
  cellStateArray[i] = Math.random() > 0.6 ? 1 : 0;
}
device.queue.writeBuffer(cellStateStorage[0], 0, cellStateArray);
device.queue.writeBuffer(cellStateStorage[1], 0, cellStateArray);

const bindGroups = [
  device.createBindGroup({
    label: "cell bind group 0",
    layout: bindGroupLayout,
    entries: [{
      binding: 0,
      resource: { buffer: uniformBuffer },
    }, {
      binding: 1,
      resource: { buffer: cellStateStorage[0] },
    }, {
      binding: 2,
      resource: { buffer: cellStateStorage[1] },
    }],
  }),
  device.createBindGroup({
    label: "cell bind group 1",
    layout: bindGroupLayout,
    entries: [{
      binding: 0,
      resource: { buffer: uniformBuffer },
    }, {
      binding: 1,
      resource: { buffer: cellStateStorage[1] },
    }, {
      binding: 2,
      resource: { buffer: cellStateStorage[0] },
    }],
  })
];

let tick = 0;
let which = 0;

function createDepthTexture() {
  return device.createTexture({
    size: [canvas.width, canvas.height],
    format: 'depth24plus',
    usage: GPUTextureUsage.RENDER_ATTACHMENT,
  });
}

var depthTexture = undefined;

function render()
{
  if (canvas.clientWidth !== canvas.width || canvas.clientWidth !== canvas.height) {
    canvas.width = canvas.clientWidth;
    canvas.height = canvas.clientHeight;

    if (depthTexture !== undefined) {
      depthTexture.destroy();
    }
    depthTexture = createDepthTexture();
  }

  const encoder = device.createCommandEncoder();

  const computePass = encoder.beginComputePass();
  computePass.setPipeline(computePipeline);
  computePass.setBindGroup(0, bindGroups[which]);
  const workgroupCount = Math.ceil((gridSize * gridSize) / workGroupSize);
  computePass.dispatchWorkgroups(workgroupCount);
  computePass.end();

  const aspect = canvas.width / canvas.height;
  rotate.instance.exports.rotate(tick * 0.01, aspect, 4 * 4);

  tick += 1;
  if ((tick % 5) == 0) {
    which ^= 1;
  }

  if (canvas.width > canvas.height) {
    uniformArray[2] = aspect;
    uniformArray[3] = 1;
  } else {
    uniformArray[2] = 1;
    uniformArray[3] = 1 / aspect;
  }
  device.queue.writeBuffer(uniformBuffer, 0, uniformArray, 0, uniformArraySize / 4);

  const renderPass = encoder.beginRenderPass({
    colorAttachments: [{
      view: context.getCurrentTexture().createView(),
      loadOp: "clear",
      clearValue: { r: 0.2, g: 0.2, b: 0.4, a: 1 },
      storeOp: "store",
    }],
    depthStencilAttachment: {
      view: depthTexture.createView(),
      depthClearValue: 1.0,
      depthLoadOp: 'clear',
      depthStoreOp: 'store',
    },
  });

  renderPass.setPipeline(cellPipeline);
  const vertexOffset = indexBufferSize;
  renderPass.setVertexBuffer(0, indexVertexBuffer, vertexOffset, vertexBufferSize);
  renderPass.setIndexBuffer(indexVertexBuffer, "uint16", 0, indexBufferSize);
  renderPass.setBindGroup(0, bindGroups[which]);
  //renderPass.draw(cubeVerticesCount, gridSize * gridSize);
  renderPass.drawIndexed(cubeIndexCount, gridSize * gridSize);
  //renderPass.drawIndexed(cubeIndexCount);

  renderPass.end();

  const commandBuffer = encoder.finish();
  device.queue.submit([commandBuffer]);

  requestAnimationFrame(render)
}
requestAnimationFrame(render)