// triangulation using https://github.com/ironwallaby/delaunay

// For more check out zachsaucier.com

const TWO_PI = Math.PI * 2;

var images = [], 
    imageIndex = 0;

var image,
    imageWidth = 768,
    imageHeight = 485;
 
var vertices = [],
    indices = [],
    prevfrag = [],
    fragments = [];

var margin = 50;

var container = document.getElementById('container');

var clickPosition = [imageWidth * 0.5, imageHeight * 0.5];

window.onload = function() {
    TweenMax.set(container, {perspective:500});

    // images from http://www.hdwallpapers.in
    var urls = [
            'http://i.imgur.com/QddsEpk.jpg',
            'http://i.imgur.com/OeDykaH.jpg',
            'http://i.imgur.com/lLHspCj.jpg',
            'http://i.imgur.com/tCz9GQS.jpg'
        ],
        image,
        loaded = 0;
    // very quick and dirty hack to load and display the first image asap
    images[0] = image = new Image();
        image.onload = function() {
            if (++loaded === 1) {
                
                for (var i = 1; i < 4; i++) {
                    images[i] = image = new Image();

                    image.src = urls[i];
                } 
                placeImage();
            }
        };
        image.src = urls[0]; 
};

function placeImage(transitionIn) {
    image = images[imageIndex];

    if (++imageIndex === images.length) imageIndex = 0;
  
    var num = Math.random();
    if(num < .25) {
      image.direction = "left";
    } else if(num < .5) {
      image.direction = "top";
    } else if(num < .75) {
      image.direction = "bottom";
    } else {
      image.direction = "right";
    }

    container.appendChild(image);
    image.style.opacity = 0;
  
    if (transitionIn !== false) {
        triangulateIn();
    }
}

function triangulateIn(event) {
    var box = image.getBoundingClientRect(),
        top = box.top,
        left = box.left;
  
    if(image.direction == "left") {
      clickPosition[0] = 0; 
      clickPosition[1] = imageHeight / 2;
    } else if(image.direction == "top") {
      clickPosition[0] = imageWidth / 2;
      clickPosition[1] = 0;
    } else if(image.direction == "bottom") {
      clickPosition[0] = imageWidth / 2;
      clickPosition[1] = imageHeight;
    } else if(image.direction == "right") {
      clickPosition[0] = imageWidth;
      clickPosition[1] = imageHeight / 2;
    } 
    

    triangulate();
    build();
}

function triangulate() {
    for(var i = 0; i < 40; i++) {      
      x = -margin + Math.random() * (imageWidth + margin * 2);
      y = -margin + Math.random() * (imageHeight + margin * 2);
      vertices.push([x, y]);
    }
    vertices.push([0,0]);
    vertices.push([imageWidth,0]);
    vertices.push([imageWidth, imageHeight]);
    vertices.push([0, imageHeight]);
  
    vertices.forEach(function(v) {
        v[0] = clamp(v[0], 0, imageWidth);
        v[1] = clamp(v[1], 0, imageHeight);
    });
  
    indices = Delaunay.triangulate(vertices);
}

function build() {
    var p0, p1, p2,
        fragment;

    var tl0 = new TimelineMax({onComplete:buildCompleteHandler});

    for (var i = 0; i < indices.length; i += 3) {
        p0 = vertices[indices[i + 0]];
        p1 = vertices[indices[i + 1]];
        p2 = vertices[indices[i + 2]];

        fragment = new Fragment(p0, p1, p2);

        var dx = fragment.centroid[0] - clickPosition[0],
            dy = fragment.centroid[1] - clickPosition[1],
            d = Math.sqrt(dx * dx + dy * dy),
            rx = 30 * sign(dy),
            ry = 90 * -sign(dx),
            delay = d * 0.003 * randomRange(0.9, 1.1);
        fragment.canvas.style.zIndex = Math.floor(d).toString();

        var tl1 = new TimelineMax(); 

        if(image.direction == "left") {
          rx = Math.abs(rx); 
          ry = 0;          
        } else if(image.direction == "top") {
          rx = 0;
          ry = Math.abs(ry);
        } else if(image.direction == "bottom") {
          rx = 0;
          ry = - Math.abs(ry);
        } else if(image.direction == "right") {
          rx = - Math.abs(rx);
          ry = 0;
        } 
        
        tl1.from(fragment.canvas, 1, {
              z:-50,
              rotationX:rx,
              rotationY:ry,
              scaleX:0,
              scaleY:0,
              ease:Cubic.easeIn
         });
        tl1.from(fragment.canvas, 0.4,{alpha:0}, 0.6);
      
        tl0.insert(tl1, delay);

        fragments.push(fragment);
        container.appendChild(fragment.canvas);
    }
}

function buildCompleteHandler() {
    // add pooling?
    image.style.opacity = 1;
    image.addEventListener('transitionend', function catchTrans() {
      fragments.forEach(function(f) {
          container.removeChild(f.canvas);
      });

      fragments.length = 0;
      vertices.length = 0;
      indices.length = 0;

      placeImage();
      this.removeEventListener('transitionend',catchTrans,false);
    }, false);
    
}

//////////////
// MATH UTILS
//////////////

function randomRange(min, max) {
    return min + (max - min) * Math.random();
}

function clamp(x, min, max) {
    return x < min ? min : (x > max ? max : x);
}

function sign(x) {
    return x < 0 ? -1 : 1;
}

//////////////
// FRAGMENT
//////////////

Fragment = function(v0, v1, v2) {
    this.v0 = v0;
    this.v1 = v1;
    this.v2 = v2;

    this.computeBoundingBox();
    this.computeCentroid();
    this.createCanvas();
    this.clip();
};
Fragment.prototype = {
    computeBoundingBox:function() {
        var xMin = Math.min(this.v0[0], this.v1[0], this.v2[0]),
            xMax = Math.max(this.v0[0], this.v1[0], this.v2[0]),
            yMin = Math.min(this.v0[1], this.v1[1], this.v2[1]),
            yMax = Math.max(this.v0[1], this.v1[1], this.v2[1]);

         this.box = {
            x:Math.round(xMin),
            y:Math.round(yMin),
            w:Math.round(xMax - xMin),
            h:Math.round(yMax - yMin)
        };

    },
    computeCentroid:function() {
        var x = (this.v0[0] + this.v1[0] + this.v2[0]) / 3,
            y = (this.v0[1] + this.v1[1] + this.v2[1]) / 3;

        this.centroid = [x, y];
    },
    createCanvas:function() {
        this.canvas = document.createElement('canvas');
        this.canvas.width = this.box.w;
        this.canvas.height = this.box.h;
        this.canvas.style.width = this.box.w + 'px';
        this.canvas.style.height = this.box.h + 'px';
        this.canvas.style.left = this.box.x + 'px';
        this.canvas.style.top = this.box.y + 'px';
        this.ctx = this.canvas.getContext('2d');
    },
    clip:function() {
        this.ctx.save();
        this.ctx.translate(-this.box.x, -this.box.y);
        this.ctx.beginPath();
        this.ctx.moveTo(this.v0[0], this.v0[1]);
        this.ctx.lineTo(this.v1[0], this.v1[1]);
        this.ctx.lineTo(this.v2[0], this.v2[1]);
        this.ctx.closePath();
        this.ctx.clip();
        this.ctx.drawImage(image, 0, 0);
        this.ctx.restore();
    }
};