/*
    WebGPU Example (Minimal Working Demo - Color Triangle) - 50 lines
*/
let canvas = document.createElement('canvas');
document.body.appendChild( canvas ); canvas.height=canvas.width=512;

const context = canvas.getContext('webgpu');
const adapter = await navigator.gpu.requestAdapter();
const device  = await adapter.requestDevice();
const presentationFormat = navigator.gpu.getPreferredCanvasFormat(); // context.getPreferredFormat(adapter); - no longer supported - no longer supported
context.configure({ device: device, format: presentationFormat  });

let shaderWGSL = `
@vertex fn vsmain(@builtin(vertex_index) VertexIndex : u32) -> @builtin(position) vec4<f32> 
{ // build the triangle here (based on the 'index')
  var pos = array<vec2<f32>, 3>(vec2<f32>( 0.0,  1.0),
                                vec2<f32>(-1.0, -1.0),
                                vec2<f32>( 1.0, -1.0));
  return vec4<f32>(pos[VertexIndex], 0.0, 1.0);
}
@fragment fn psmain() -> @location(0) vec4<f32> {
  return vec4<f32>(1.0, 0.5, 0.5, 1.0);
}`;

const shaderModule = device.createShaderModule({ code : shaderWGSL });
const pipeline = device.createRenderPipeline({
  layout : "auto",
  vertex:      {   module: shaderModule, entryPoint: 'vsmain', },
  fragment:    {   module: shaderModule, entryPoint: 'psmain',
                   targets: [ { format: presentationFormat } ]
               }, 
  primitive:   {   topology: 'triangle-list' },
});

function frame() 
{
  const commandEncoder = device.createCommandEncoder();
  const renderPassDescriptor =                                       { // GPURenderPassDescriptor 
             colorAttachments: [ { view       : context.getCurrentTexture().createView(),
                                   loadOp     : "clear", 
                                   loadOp:"clear", clearValue: [0, 0.5, 0.5, 1], // clear screen to green
                                   //clearValue : { r: 0.1, g: 1.0, b: 1.0, a: 1.0 },
                                   storeOp   : 'store' } ]           };
  const passEncoder = commandEncoder.beginRenderPass(renderPassDescriptor);
  passEncoder.setPipeline(pipeline);
  passEncoder.draw(3, 1, 0, 0);
  passEncoder.end();
  device.queue.submit([commandEncoder.finish()]);
  requestAnimationFrame(frame);
}
frame();
console.log('done...');