// Galaxy background - moonlit terrain with floating stars
(function initGalaxy(){
  console.clear();

  var ww = window.innerWidth,
      wh = window.innerHeight;

  var renderer = new THREE.WebGLRenderer({
    antialias: true,
    canvas: document.querySelector('#galaxy-canvas')
  });
  renderer.setSize(ww, wh);
  renderer.setClearColor(0x001a2d);

  var scene = new THREE.Scene();
  scene.fog = new THREE.Fog(0x001a2d, 80, 140);

  var camera = new THREE.PerspectiveCamera(45, ww/wh, 0.1, 200);
  camera.position.x = 70;
  camera.position.y = 30;
  camera.position.z = 5;
  camera.lookAt(new THREE.Vector3());

  /* LIGHTS */
  var moonLight = new THREE.PointLight(0xffffff, 2, 150);
  scene.add(moonLight);

  var moon;
  function createMoon() {
    var geometry = new THREE.SphereGeometry(8, 32, 32);
    var material = new THREE.MeshPhongMaterial({
      color: 0x26fdd9,
      shininess: 15,
      emissive: 0x2bb2e6,
      emissiveIntensity: 0.8
    });
    moon = new THREE.Mesh(geometry, material);
    moon.position.x = -9;
    moon.position.z = -6.5;
    moon.position.y = 1;
    moon.rotation.y = -1;
    scene.add(moon);
    moonLight.position.copy(moon.position);
    moonLight.position.y += 4;
    var moonLight2 = new THREE.PointLight(0xffffff, 0.6, 150);
    scene.add(moonLight2);
    moonLight2.position.x += 20;
    moonLight2.position.y -= 20;
    moonLight2.position.z -= 25;
  }

  // Initialize simplex noise
  var noise = new SimplexNoise();

  function createTerrain() {
    var geometry = new THREE.PlaneGeometry(150, 150, 120, 120);
    var m = new THREE.Matrix4();
    m.makeRotationX(Math.PI * -0.5);
    geometry.applyMatrix4(m);
    
    var positions = geometry.attributes.position;
    for(var i = 0; i < positions.count; i++) {
      var x = positions.getX(i);
      var z = positions.getZ(i);
      var ratio = noise.noise3D(x * 0.03, z * 0.03, 0);
      positions.setY(i, ratio * 10);
    }
    positions.needsUpdate = true;
    geometry.computeVertexNormals();
    
    var material = new THREE.MeshPhongMaterial({
      color: 0x198257,
      emissive: 0x032f50
    });
    var plane = new THREE.Mesh(geometry, material);
    scene.add(plane);
  }

  var stars = new THREE.Group();
  scene.add(stars);
  var starsLights = new THREE.Group();
  scene.add(starsLights);
  var starsAmount = 20;
  
  function createStars() {
    var geometry = new THREE.SphereGeometry(0.3, 16, 16);
    var material = new THREE.MeshBasicMaterial({color: 0xffffff});
    for(var i = 0; i < starsAmount; i++) {
      var star = new THREE.Mesh(geometry, material);
      star.position.x = (Math.random() - 0.5) * 150;
      star.position.z = (Math.random() - 0.5) * 150;
      var ratio = noise.noise3D(star.position.x * 0.03, star.position.z * 0.03, 0);
      star.position.y = ratio * 10 + 0.3;
      stars.add(star);
      var velX = (Math.random() + 0.1) * 0.1 * (Math.random() < 0.5 ? -1 : 1);
      var velY = (Math.random() + 0.1) * 0.1 * (Math.random() < 0.5 ? -1 : 1);
      star.vel = new THREE.Vector2(velX, velY);
      var starLight = new THREE.PointLight(0xffffff, 0.8, 3);
      starLight.position.copy(star.position);
      starLight.position.y += 0.5;
      starsLights.add(starLight);
    }
  }

  function updateStar(star, index) {
    if(star.position.x < -75) {
      star.position.x = 75;
    }
    if(star.position.x > 75) {
      star.position.x = -75;
    }
    if(star.position.z < -75) {
      star.position.z = 75;
    }
    if(star.position.z > 75) {
      star.position.z = -75;
    }

    star.position.x += star.vel.x;
    star.position.z += star.vel.y;
    var ratio = noise.noise3D(star.position.x * 0.03, star.position.z * 0.03, 0);
    star.position.y = ratio * 10 + 0.3;

    starsLights.children[index].position.copy(star.position);
    starsLights.children[index].position.y += 0.5;
  }

  function render(a) {
    requestAnimationFrame(render);
    for(var i = 0; i < starsAmount; i++) {
      updateStar(stars.children[i], i);
    }
    renderer.render(scene, camera);
  }

  function onResize() {
    ww = window.innerWidth;
    wh = window.innerHeight;
    camera.aspect = ww / wh;
    camera.updateProjectionMatrix();
    renderer.setSize(ww, wh);
  }

  createMoon();
  createTerrain();
  createStars();
  requestAnimationFrame(render);
  window.addEventListener('resize', onResize);
})();