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

class SnakeRenderer {
  createBuffers(device)
  {
    const boneCount = 100;
    const boneLength = 0.1;
    this.boneSystemAddress = this.module.instance.exports.bone_system__create(boneCount, boneLength);
    const mem = new DataView(this.module.memory.buffer);
    this.bonesAddress = mem.getUint32(this.boneSystemAddress, true);
    const configurationOffset = this.module.instance.exports.bone_system__configuration_offset();
    this.configurationAddress = this.boneSystemAddress + configurationOffset;
    this.bonesBufferSize = this.module.instance.exports.bone_system__bones_size(boneCount);
    this.configurationBufferSize = this.module.instance.exports.bone_system__configuration_size();

    this.frames = [];

    for (let i = 0; i < 2; i++) {
      const bonesBuffer = device.createBuffer({
        label: `bone buffer ${i}`,
        size: this.bonesBufferSize,
        usage: GPUBufferUsage.STORAGE | GPUBufferUsage.COPY_DST,
      });

      const configurationBuffer = device.createBuffer({
        label: `bone configuration buffer ${i}`,
        size: this.configurationBufferSize,
        usage: GPUBufferUsage.UNIFORM | GPUBufferUsage.COPY_DST,
      });

      const bindGroup = device.createBindGroup({
        label: `bone buffer bind group ${i}`,
        layout: this.bindGroupLayout.bone,
        entries: [{
          binding: 0,
          resource: { buffer: bonesBuffer },
        }, {
          binding: 1,
          resource: { buffer: configurationBuffer },
        }]
      });

      this.frames.push({
        bonesBuffer: bonesBuffer,
        configurationBuffer: configurationBuffer,
        bindGroup: bindGroup,
      });
    }
  }

  constructor(device, canvasFormat, viewUniformBuffer, wgsl, module)
  {
    const label = "bone";

    this.module = module;

    //////////////////////////////////////////////////////////////////////
    // shader module
    //////////////////////////////////////////////////////////////////////

    const shaderModule = device.createShaderModule({
      label: `${label} shader`,
      code: wgsl,
    });

    //////////////////////////////////////////////////////////////////////
    // index 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
    //////////////////////////////////////////////////////////////////////

    this.bindGroupLayout = {
      view: device.createBindGroupLayout({
        label: `${label} bind group layout view`,
        entries: [{
          binding: 0,
          visibility: GPUShaderStage.VERTEX,
          buffer: { type: "uniform" }
        }]
      }),
      bone: device.createBindGroupLayout({
        label: `${label} bind group layout particle`,
        entries: [{ // bones
          binding: 0,
          visibility: GPUShaderStage.FRAGMENT,
          buffer: { type: "read-only-storage" }
        }, { // configuration
          binding: 1,
          visibility: GPUShaderStage.FRAGMENT,
          buffer: { type: "uniform" }
        }]
      }),
    };

    const pipelineLayout = device.createPipelineLayout({
      label: `${label} pipeline layout`,
      bindGroupLayouts: [
        this.bindGroupLayout.view,
        this.bindGroupLayout.bone
      ],
    });

    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",
      },
    });

    //////////////////////////////////////////////////////////////////////
    // bones
    //////////////////////////////////////////////////////////////////////

    this.createBuffers(device);

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

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

  update(device, frameNumber, mousePosition, configuration)
  {
    this.module.instance.exports.bone_system__update_configuration(this.boneSystemAddress,
                                                                   configuration.boneCount,
                                                                   configuration.boneLength,
                                                                   configuration.velocityDamping,
                                                                   configuration.velocityAcceleration);

    this.module.instance.exports.bone_system__update(this.boneSystemAddress,
                                                     mousePosition[0], mousePosition[1], mousePosition[2]);

    device.queue.writeBuffer(this.frames[frameNumber].bonesBuffer, 0,
                             this.module.memory.buffer, this.bonesAddress, this.bonesBufferSize);

    device.queue.writeBuffer(this.frames[frameNumber].configurationBuffer, 0,
                             this.module.memory.buffer, this.configurationAddress, this.configurationBufferSize);
  }

  render(renderPass, frameNumber)
  {
    renderPass.setPipeline(this.renderPipeline);
    renderPass.setIndexBuffer(this.buffer, "uint16");
    renderPass.setBindGroup(0, this.viewBindGroup);
    renderPass.setBindGroup(1, this.frames[frameNumber].bindGroup);
    renderPass.drawIndexed(6);
  }
}

async function loadSnake(device, canvasFormat, viewUniformBuffer, module)
{
  const snakeWgsl = await getPath("snake.wgsl");

  const renderer = new SnakeRenderer(device, canvasFormat, viewUniformBuffer, snakeWgsl, module);
  return renderer;
}

export { loadSnake };