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

class FlatRenderer {
  constructor(device, canvasFormat, viewUniformBuffer, shaderModule)
  {
    const label = "flat";

    //////////////////////////////////////////////////////////////////////
    // buffer
    //////////////////////////////////////////////////////////////////////

    const array = new Uint16Array(6);
    array[0] = 0;
    array[1] = 1;
    array[2] = 2;
    array[3] = 0;
    array[4] = 3;
    array[5] = 1;

    this.buffer = device.createBuffer({
      label: `${label} renderer buffer`,
      size: array.byteLength,
      usage: GPUBufferUsage.INDEX | GPUBufferUsage.COPY_DST,
    });

    device.queue.writeBuffer(this.buffer, 0, array, 0, array.length);

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

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

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

    this.renderPipeline = device.createRenderPipeline({
      label: `${label} pipeline`,
      layout: pipelineLayout,
      vertex: {
        module: shaderModule,
        entryPoint: "vertexMain",
      },
      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.setIndexBuffer(this.buffer, "uint16");
    renderPass.setBindGroup(0, this.bindGroups[0]);
    renderPass.drawIndexed(6);
  }
}

async function loadFlat(device, canvasFormat, viewUniformBuffer)
{
  const flatWgsl = await getPath("flat.wgsl");
  const shaderModule = device.createShaderModule({
    label: "flag shader",
    code: flatWgsl,
  });

  const renderer = new FlatRenderer(device, canvasFormat, viewUniformBuffer, shaderModule);
  return renderer;
}

export { loadFlat };