// Targeted Lightning, a lightning which will try to go to the specified target position, but has a random factor to define where it actually jumps to.
//Made by Boomer Shin

/*
  Color functions, forked from some animation which was forked from http://andreasstorm.com/ once, long ago. 
  Those are very handy for random colors, you know? 
*/
function Color(min) {
  min = min || 0;
  this.r = colorValue(min);
  this.g = colorValue(min);
  this.b = colorValue(min);
  this.style = createColorStyle(this.r, this.g, this.b);
};

function colorValue(min) {
  return Math.floor(Math.random() * 255 + min);
};

function createColorStyle(r,g,b) {
  return 'rgba(' + r + ',' + g + ',' + b + ', 0.8)';
};

/*
  Other utility functions
*/

function distance2dPositions(dx, dy){
  return Math.sqrt(dx*dx + dy*dy);
  
};

function distance2dCoordinates(x1, x2, y1, y2){
  var dx = x2 - x1;
  var dy = y2 - y1;
  var dist = Math.sqrt( dx*dx + dy*dy );
  return dist;
};

/*
  Config
*/


var minX = 0;
var maxX = window.innerWidth;
var minY = 0;
var maxY = window.innerHeight;

/*
  Proper Lightning
*/

function TargetedLightning(trailSize, target){
  var self = this;
  self.px = 0;
  self.py = 0;
  self.color = new Color(128);
  
  self.target = target;
  self.trailSize = trailSize;
  self.trail = [];
  for(var i = 0; i < self.trailSize; i++){
    self.trail.push({px: self.px, py: self.py});
  }
  
  self.jumpLength = 15;
  self.deltaJumpLength = 15;
  self.disturbLength = self.jumpLength * 2/ 3;
  self.deltaDisturbLength = self.deltaJumpLength * 2 / 3;
  
  // Anything with a px and py values
  self.setTarget = function(target){
    self.target = target;
  };
  
  self.update = function(){
    var dxTarget = self.target.px - self.px;
    var dyTarget = self.target.py - self.py;
    var dist = distance2dPositions(dxTarget, dyTarget);

    var randomAngle = Math.random() * Math.PI;
    var disturbLength = self.disturbLength + Math.random() * self.deltaDisturbLength;
    var jumpLength = self.jumpLength + self.deltaJumpLength * Math.random();
    // if close enough, goes exatly to the target. No disturbances!
    if(dist < (self.jumpLength + self.deltaJumpLength)){
      disturbLength = 0;
      jumpLength = dist;
      self.reachTarget();
    }
    
    

    var finalDx = ((dxTarget / dist) * jumpLength ) + disturbLength * Math.cos(randomAngle);
    var finalDy = ((dyTarget / dist) * jumpLength ) + disturbLength * Math.sin(randomAngle);

    self.px += finalDx;
    self.py += finalDy;
    self.trail.pop();
    self.trail.unshift({px: self.px, py: self.py});
  };
  

  self.draw = function(ctx){
      ctx.beginPath();
      ctx.moveTo(self.px, self.py);
      for(var i = 0; i < self.trail.length; i++){
        ctx.lineTo(self.trail[i].px, self.trail[i].py);
      }
      ctx.strokeStyle = self.color.style;
      ctx.lineWidth = 3;
      ctx.stroke();
    
      ctx.beginPath();
      //ctx.moveTo(self.target.px, self.target.py);
      ctx.arc(self.target.px, self.target.py, 10, 0, Math.PI * 2, false);
      ctx.strokeStyle = this.color.style;
      ctx.stroke();
  };

  // Selects a new target position
  self.reachTarget = function(){
    var newTarget = {
      px: Math.random() * maxX,
      py: Math.random() * maxY
    };
    self.setTarget(newTarget);
  }
  
};

$(function(){
  var self = this;
  self.canvas = document.querySelector('canvas');
  self.ctx = self.canvas.getContext('2d');
  self.canvas.width = window.innerWidth;
  self.canvas.height = window.innerHeight;

  self.lightnings = [];

  self.updateAll = function(){
    for(var i = 0; i < self.lightnings.length; i++){
      self.lightnings[i].update();
    }
  };

  self.drawAll = function(){
    for(var i = 0; i < self.lightnings.length; i++){
      self.lightnings[i].draw(self.ctx);
    }
  };

  self.animationCycle = function(){
    self.ctx.clearRect(0, 0, self.canvas.width, self.canvas.height);
    self.updateAll();
    self.drawAll();

    requestAnimationFrame(self.animationCycle);
  };

  self.initApp = function(){
    for(var i = 0; i < 2; i++){
    	self.lightnings.push(new TargetedLightning(15, {px: self.canvas.width / 2, py: self.canvas.height / 2}));
  	}
  };

  self.initApp();
  requestAnimationFrame(self.animationCycle);
  
});