var c = document.getElementById("stage");
var ctx = c.getContext("2d");

var centerX = c.width / 2;
var centerY = c.height / 2;
var radius = 10;
var numCircles = 8;
var numParticles = 256;

var pct = 0.0;
var animLength = 7;
var lineLength = 16;

var stop = false;
var frameCount = 0;
//var $results=$("#results");
var fps, fpsInterval, startTime, now, then, elapsed;

// initialize the timer variables and start the animation
startAnimating(60);

function startAnimating(fps) {
    fpsInterval = 1000 / fps;
    then = Date.now();
    startTime = then;
    animate();
}

function Orb() {
  this.r = 0;  
  this.p = {};
    this.v = {};
    this.a = {
        x: 0,
        y: 0
    };
    this.tail = [];
    this.ageo = 0;
  this.id = -1;
}

Orb.prototype.init = function(_x, _y) {
    this.p.x = _x;
    this.p.y = _y;

    var f = Math.random() * 4;

    var angle = Math.random() * Math.PI * 2;

    //this.v.x = Math.cos(angle) * f;
    //this.v.y = Math.sin(angle) * f;
  this.v.x = this.v.y = 0;
    this.age = 0;
}
Orb.prototype.update = function() {

    this.age++;

    this.v.x += this.a.x;
    this.v.y += this.a.y;

    var maxSpeed = 3.0;
    var direction = Math.atan2(this.v.y, this.v.x);

    var fwdSpeed = Math.sqrt(this.v.x * this.v.x + this.v.y * this.v.y);
    if (fwdSpeed > maxSpeed || fwdSpeed < -1 * maxSpeed) {
        var modifier = fwdSpeed / maxSpeed;
        this.v.x /= modifier;
        this.v.y /= modifier;

    }

    this.p.x += this.v.x;
    this.p.y += this.v.y;
    // floor
    if (this.p.y > c.height) {
        this.p.y -= this.v.y;
        this.v.y *= -Math.random();
        this.v.x *= Math.random() / 2 + 0.5;
    }
   // ceiling
    if (this.p.y < 0) {
        this.p.y -= this.v.y;
        this.v.y *= -Math.random();
        this.v.x *= Math.random() / 2 + 0.5;
    }
      // right wall
    if (this.p.x > c.width) {
        this.p.x -= this.v.x;
        this.v.x *= -Math.random();
        this.v.y *= Math.random() / 2 + 0.5;
    }
   // left wall
    if (this.p.x < 0) {
        this.p.x -= this.v.x;
        this.v.x *= -Math.random();
        this.v.y *= Math.random() / 2 + 0.5;
    }

    this.v.x *= 0.99;
    this.v.y *= 0.99;
  
  this.r = Math.atan2(this.v.y,this.v.x);
  
}
Orb.prototype.draw = function() {
    ctx.beginPath();
    ctx.arc(this.p.x, this.p.y, 2, 0, 2 * Math.PI, false);
  var c = 0;
  var c2 = 0;  
  //var c = Math.min(255-this.age * 8, 255);
    //var c2 = Math.min(255-this.age * 16, 255);
  //  ctx.fillStyle = "rgba(" + c + "," + c + "," + c + ",0.5)";
  //ctx.fillStyle = "rgba(0,0,0,1.0)";  
  ctx.fill();
    ctx.beginPath();
    ctx.moveTo(this.p.x, this.p.y);
  ctx.lineTo(this.p.x+Math.cos(this.r)*5,this.p.y+Math.sin(this.r)*5);
    for (var j = 1; j < this.tail.length; j++) {

        ctx.lineTo(this.tail[j].x, this.tail[j].y);

    }
    ctx.lineWidth = 1;
    ctx.strokeStyle = "rgba(" + c2 + "," + c2 + "," + c2 + ",1.0)";
    ctx.stroke();
    this.tail.unshift({
        x: this.p.x,
        y: this.p.y
    });
    if (this.tail.length > lineLength) this.tail.pop();

}
function steer(){
  var steerCount = 0;
  var steerVec = {
    x:0,
                      y:0
  };
  for(var i=0;i<numParticles;i++){
    for(var j=0;j<i;j++){
      var theDist = lineDistance(orbs[i].p,orbs[j].p);
      if(theDist<15){

      steerCount++;
      steerVec.x += orbs[j].v.x;
      steerVec.y += orbs[j].v.y;
                                                              
                                                              
       
        


        
        
        
      }
          if(steerCount>0){
        orbs[i].v.x += steerVec.x/steerCount*0.0008;
        orbs[i].v.y += steerVec.y/steerCount*0.0008;
        }
    }
  }
}
function avoid(){
  
  for(var i=0;i<numParticles;i++){
    for(var j=0;j<i;j++){
      var theDist = lineDistance(orbs[i].p,orbs[j].p);
      if(theDist<10){
      var theAngle = Math.atan2(orbs[j].p.y-orbs[i].p.y,orbs[j].p.x-orbs[i].p.x);
        var xa = Math.cos(theAngle);
        var ya = Math.sin(theAngle);
        
        orbs[i].v.x -= xa*5/(theDist*theDist);
        orbs[i].v.y -= ya*5/(theDist*theDist);
        orbs[j].v.x += xa*5/(theDist*theDist);
        orbs[j].v.y += ya*5/(theDist*theDist);
        
        
        
      }
    }
  }
  
}

function cohesion(){
  for(var i=0;i<numParticles;i++){
    for(var j=0;j<i;j++){
      var theDist = lineDistance(orbs[i].p,orbs[j].p);
      if(theDist<50){
      var theAngle = Math.atan2(orbs[j].p.y-orbs[i].p.y,orbs[j].p.x-orbs[i].p.x);
        var xa = Math.cos(theAngle);
        var ya = Math.sin(theAngle);
        
        orbs[i].v.x += xa*40/(theDist*theDist);
        orbs[i].v.y += ya*40/(theDist*theDist);
        orbs[j].v.x -= xa*40/(theDist*theDist);
        orbs[j].v.y -= ya*40/(theDist*theDist);
        
        
        
      }
    }
  }
}

function getMousePos(canvas, evt) {
    var rect = canvas.getBoundingClientRect();
    return {
        x: evt.clientX - rect.left,
        y: evt.clientY - rect.top
    };
}

var orbs;

function init(_x, _y) {
    orbs = [];
    for (var i = 0; i < numParticles; i++) {
        var o = new Orb();
        o.init(_x+Math.random()*10, _y+Math.random()*10);
      o.id = i;
        orbs.push(o);
    }
}
init(c.width / 2, c.height / 2);

c.addEventListener('mousedown', function(evt) {
    var mousePos = getMousePos(c, evt);

    init(mousePos.x, mousePos.y);
});

function animate() {

    // stop
    if (stop) {
        return;
    }

    // request another frame

    requestAnimationFrame(animate);

    // calc elapsed time since last loop

    now = Date.now();
    elapsed = now - then;

    // if enough time has elapsed, draw the next frame

    if (elapsed > fpsInterval) {

        // Get ready for next frame by setting then=now, but...
        // Also, adjust for fpsInterval not being multiple of 16.67
        then = now - (elapsed % fpsInterval);
        frameCount++;
        // draw stuff here
        drawStuff();

    }
}

function drawStuff() {

    ctx.clearRect(0, 0, c.width, c.height);

  avoid();
  steer();
  
    for (var i = 0; i < numParticles; i++) {
        var o = orbs[i];



       // o.a.x += Math.cos(Math.atan2(a.p.y - o.p.y, a.p.x - o.p.x)) * accel;
        //o.a.y += Math.sin(Math.atan2(a.p.y - o.p.y, a.p.x - o.p.x)) * accel;

        o.update();
    }

    for (var i = 0; i < numParticles; i++) {
        var o = orbs[i];
        o.draw();

    }

}


function lineDistance( point1, point2 )
{
  var xs = 0;
  var ys = 0;
 
  xs = point2.x - point1.x;
  xs = xs * xs;
 
  ys = point2.y - point1.y;
  ys = ys * ys;
 
  return Math.sqrt( xs + ys );
}