import { getPath } from "./common.js";

function parseHeader(buffer)
{
  const array = new Uint32Array(buffer);
  /*
    console.log("index count", icosphereU32[0]);
    console.log("index buffer offset", icosphereU32[1]);
    console.log("index buffer size", icosphereU32[2]);
    console.log("vertex buffer offset", icosphereU32[3]);
    console.log("vertex buffer size", icosphereU32[4]);
  */

  return {
    indexCount: array[0],
    indexOffset: array[1],
    indexSize: array[2],
    vertexOffset: array[3],
    vertexSize: array[4],
  };
}

class LightRenderer {
  constructor(device, canvasFormat, viewUniformBuffer,
              shaderModule, binBuffer, label)
  {
    //////////////////////////////////////////////////////////////////////
    // buffer
    //////////////////////////////////////////////////////////////////////

    const header = parseHeader(binBuffer);
    this.header = header;

    this.buffer = device.createBuffer({
      label: `${label} renderer buffer`,
      size: header.indexSize + header.vertexSize,
      usage: GPUBufferUsage.INDEX | GPUBufferUsage.VERTEX | GPUBufferUsage.COPY_DST,
    });
    this.indexOffset = 0;
    this.vertexOffset = header.indexSize;

    device.queue.writeBuffer(this.buffer, this.indexOffset,
                             binBuffer, header.indexOffset, header.indexSize);
    device.queue.writeBuffer(this.buffer, this.vertexOffset,
                             binBuffer, header.vertexOffset, header.vertexSize);

    //////////////////////////////////////////////////////////////////////
    // pipeline
    //////////////////////////////////////////////////////////////////////

    const bindGroupLayouts = [
      device.createBindGroupLayout({
        label: `${label} view matrix bind group layout`,
        entries: [{
          binding: 0,
          visibility: GPUShaderStage.VERTEX,
          buffer: { type: "uniform" }
        },/* {
          binding: 1,
          visibility: GPUShaderStage.VERTEX,
          buffer: { type: "read-only-storage" }
        }*/]
      }),
    ];

    const pipelineLayout = device.createPipelineLayout({
      label: `${label} pipeline layout`,
      bindGroupLayouts: bindGroupLayouts,
    });

    const vertexBufferLayouts = [{
      arrayStride: 36,
      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",
    }];

    this.renderPipeline = device.createRenderPipeline({
      label: `${label} pipeline`,
      layout: pipelineLayout,
      vertex: {
        module: shaderModule,
        entryPoint: "vertexMain",
        buffers: vertexBufferLayouts,
      },
      fragment: {
        module: shaderModule,
        entryPoint: "fragmentMain",
        targets: [{
          format: canvasFormat,
        }]
      },
      primitive: {
        topology: "triangle-list",
      },
      depthStencil: {
        depthWriteEnabled: true,
        depthCompare: "less",
        format: "depth24plus",
      },
    });

    //////////////////////////////////////////////////////////////////////
    // bind group
    //////////////////////////////////////////////////////////////////////

    this.bindGroups = [
      device.createBindGroup({
        label: `${label} bind group`,
        layout: bindGroupLayouts[0],
        entries: [{
          binding: 0,
          resource: { buffer: viewUniformBuffer },
        }],
      }),
    ];
  }

  render(renderPass)
  {
    renderPass.setPipeline(this.renderPipeline);
    renderPass.setVertexBuffer(0, this.buffer, this.vertexOffset, this.header.vertexSize);
    renderPass.setIndexBuffer(this.buffer, "uint16", this.indexOffset, this.header.indexSize);
    renderPass.setBindGroup(0, this.bindGroups[0]);
    renderPass.drawIndexed(this.header.indexCount);
  }
}

async function loadLight(device, canvasFormat, viewUniformBuffer)
{
  const lightWgsl = getPath("light.wgsl");
  const shaderModule = device.createShaderModule({
    label: "light shader",
    code: await lightWgsl,
  });

  const response = await fetch("obj/icosphere.bin");
  const binBuffer = await response.arrayBuffer();

  const renderer = new LightRenderer(device, canvasFormat, viewUniformBuffer,
                                     shaderModule, binBuffer, "light");
  return renderer;
}

export { loadLight };