main();

function main() {
  const canvas = document.querySelector('#glcanvas');
  const gl = canvas.getContext('webgl');


  if (!gl) {
    alert('Unable to initialize WebGL. Your browser or machine may not support it.');
    return;
  }


  const shaderProgramFactory = new ShaderProgramFactory(gl);
  const shaderProgram = shaderProgramFactory.createShaderProgram();

  // Collect all the info needed to use the shader program.
  // Look up which attributes our shader program is using
  // for aVertexPosition, aVertexNormal, aTextureCoord,
  // and look up uniform locations.
  const programInfo = {
    program: shaderProgram,
    attribLocations: {
      vertexPosition: gl.getAttribLocation(shaderProgram, 'aVertexPosition'),
      vertexNormal: gl.getAttribLocation(shaderProgram, 'aVertexNormal'),
      textureCoord: gl.getAttribLocation(shaderProgram, 'aTextureCoord'),
    },
    uniformLocations: {
      projectionMatrix: gl.getUniformLocation(shaderProgram, 'uProjectionMatrix'),
      modelViewMatrix: gl.getUniformLocation(shaderProgram, 'uModelViewMatrix'),
      normalMatrix: gl.getUniformLocation(shaderProgram, 'uNormalMatrix'),
      uSampler: gl.getUniformLocation(shaderProgram, 'uSampler'),
    },
  };


  const cubeBuffer = new CubeBuffer(gl);
  const buffers = cubeBuffer.startBuffer();

  const imageLoader = new ImageLoader(gl);
  const texture = imageLoader.loadImageIntoTexture( 'cubetexture.png');

  var then = 0;

  // Draw the scene repeatedly
  function render(now) {
    now *= 0.001;  // convert to seconds
    const deltaTime = now - then;
    then = now;

    drawScene(gl, programInfo, buffers, texture, deltaTime);

    requestAnimationFrame(render);
  }
  requestAnimationFrame(render);
}