// cannonjsのhelloWorld (https://github.com/schteppe/cannon.js)

var lastTime
var fixedTimeStep = 1.0 / 60.0; // seconds
var maxSubSteps = 3;
var world, sphereBody, groundBody
var loopFlag = false
var display = document.getElementById("display"),
    resetButton = document.getElementById("resetButton")

// シミレーション初期化のボタン設置
resetButton.addEventListener("click", function(){
  if(loopFlag) return
  initWorld() 
  simloop()
});

window.onload = function () {
  initWorld()
  simloop()
}

function initWorld() {
  // Setup our world
  world = new CANNON.World();
  world.gravity.set(0, 0, -9.82); // m/s²

  // Create a sphere
  var radius = 1; // m
  sphereBody = new CANNON.Body({
    mass: 5, // kg
    position: new CANNON.Vec3(0, 0, 10), // m
    shape: new CANNON.Sphere(radius)
  });
  world.addBody(sphereBody);

  // Create a plane
  groundBody = new CANNON.Body({
    mass: 0 // mass == 0 makes the body static
  });
  var groundShape = new CANNON.Plane();
  groundBody.addShape(groundShape);
  world.addBody(groundBody);
}

function simloop(time) {
  loopFlag = true
  var prePositionZ = sphereBody.position.z
  if (lastTime !== undefined) {
    var dt = (time - lastTime) / 1000;
    world.step(fixedTimeStep, dt, maxSubSteps);
  }
  console.log("Sphere z position: " + sphereBody.position.z);
  // コンソールだけだと寂しいので、hmtlに出してあげる
  display.innerHTML = "Sphere z position: " + sphereBody.position.z
  lastTime = time;
  
  // spher止まったらloopも止めちゃう
  if(sphereBody.position.z < 9 && sphereBody.position.z == prePositionZ){
    loopFlag = false
    return
  }
  
  requestAnimationFrame(simloop);
}