/*
Parcycle: by Mr Speaker - www.mrspeaker.net
v: 1.0
license: MIT
Particle Emitter classes based on the code from 71squared.com iPhone tutorials
includes:
cParticle : class for individual particles
cParticleSystem : the controller for the particles
Vector : a vector helper object
*/

// Individual particle
function cParticle(){
this.position = Vector.create();
this.direction = Vector.create();
this.size = 0;
this.sizeSmall = 0;
this.timeToLive = 0;
this.colour = [];
this.drawColour = "";
this.deltaColour = [];
this.sharpness = 0;
}

// The particle emitter.
function cParticleSystem(){
this.maxParticles = 150;
this.particles = [];
this.active = true;

// Properties
this.position = Vector.create( 100, 100 );
this.positionRandom = Vector.create( 10, 10 );
this.size = 50;
this.sizeRandom = 15;
this.speed = 10;
this.speedRandom = 1.5;
this.lifeSpan = 15;
this.lifeSpanRandom = 7;
this.angle = 0;
this.angleRandom = 360;
this.gravity = Vector.create( 0.4, 0.2 );
this.startColour = [ 113, 44, 145, 1 ];
this.startColourRandom = [ 62, 60, 60, 0 ];
this.finishColour = [ 186, 133, 210, 0 ];
this.finishColourRandom = [ 60, 60, 60, 0 ];
this.sharpness = 20;
this.sharpnessRandom = 10;

this.particleCount = 0;
this.elapsedTime = 0;
this.duration = -1;
this.emissionRate = 2;
this.emitCounter = 4;
this.particleIndex = 2;

this.init = function(){
this.emissionRate = this.maxParticles / this.lifeSpan;
this.emitCounter = 0;
};

this.addParticle = function(){
if(this.particleCount == this.maxParticles) {
return false;
}

// Take the next particle out of the particle pool we have created and initialize it
var particle = new cParticle();
this.initParticle( particle );
this.particles[ this.particleCount ] = particle;
// Increment the particle count
this.particleCount++;

return true;
};

this.initParticle = function( particle ){
var RANDM1TO1 = function(){ return Math.random() * 2 - 1; };

particle.position.x = this.position.x + this.positionRandom.x * RANDM1TO1();
particle.position.y = this.position.y + this.positionRandom.y * RANDM1TO1();

var newAngle = (this.angle + this.angleRandom * RANDM1TO1() ) * ( Math.PI / 180 ); // convert to radians
var vector = Vector.create( Math.cos( newAngle ), Math.sin( newAngle ) ); // Could move to lookup for speed
var vectorSpeed = this.speed + this.speedRandom * RANDM1TO1();
particle.direction = Vector.multiply( vector, vectorSpeed );

particle.size = this.size + this.sizeRandom * RANDM1TO1();
particle.size = particle.size < 0 ? 0 : ~~particle.size;
particle.timeToLive = this.lifeSpan + this.lifeSpanRandom * RANDM1TO1();

particle.sharpness = this.sharpness + this.sharpnessRandom * RANDM1TO1();
particle.sharpness = particle.sharpness > 100 ? 100 : particle.sharpness < 0 ? 0 : particle.sharpness;
// internal circle gradient size - affects the sharpness of the radial gradient
particle.sizeSmall = ~~( ( particle.size / 200 ) * particle.sharpness ); //(size/2/100)

var start = [
this.startColour[ 0 ] + this.startColourRandom[ 0 ] * RANDM1TO1(),
this.startColour[ 1 ] + this.startColourRandom[ 1 ] * RANDM1TO1(),
this.startColour[ 2 ] + this.startColourRandom[ 2 ] * RANDM1TO1(),
this.startColour[ 3 ] + this.startColourRandom[ 3 ] * RANDM1TO1()
];

var end = [
this.finishColour[ 0 ] + this.finishColourRandom[ 0 ] * RANDM1TO1(),
this.finishColour[ 1 ] + this.finishColourRandom[ 1 ] * RANDM1TO1(),
this.finishColour[ 2 ] + this.finishColourRandom[ 2 ] * RANDM1TO1(),
this.finishColour[ 3 ] + this.finishColourRandom[ 3 ] * RANDM1TO1()
];

particle.colour = start;
particle.deltaColour[ 0 ] = ( end[ 0 ] - start[ 0 ] ) / particle.timeToLive;
particle.deltaColour[ 1 ] = ( end[ 1 ] - start[ 1 ] ) / particle.timeToLive;
particle.deltaColour[ 2 ] = ( end[ 2 ] - start[ 2 ] ) / particle.timeToLive;
particle.deltaColour[ 3 ] = ( end[ 3 ] - start[ 3 ] ) / particle.timeToLive;
};

this.update = function( delta ){
if( this.active && this.emissionRate > 0 ){
var rate = 1 / this.emissionRate;
this.emitCounter += delta;
while( this.particleCount < this.maxParticles && this.emitCounter > rate ){
this.addParticle();
this.emitCounter -= rate;
}
this.elapsedTime += delta;
if( this.duration != -1 && this.duration < this.elapsedTime ){
this.stop();
}
}

this.particleIndex = 0;
while( this.particleIndex < this.particleCount ) {

var currentParticle = this.particles[ this.particleIndex ];

// If the current particle is alive then update it
if( currentParticle.timeToLive > 0 ){

// Calculate the new direction based on gravity
currentParticle.direction = Vector.add( currentParticle.direction, this.gravity );
currentParticle.position = Vector.add( currentParticle.position, currentParticle.direction );
currentParticle.timeToLive -= delta;

// Update colours based on delta
var r = currentParticle.colour[ 0 ] += ( currentParticle.deltaColour[ 0 ] * delta );
var g = currentParticle.colour[ 1 ] += ( currentParticle.deltaColour[ 1 ] * delta );
var b = currentParticle.colour[ 2 ] += ( currentParticle.deltaColour[ 2 ] * delta );
var a = currentParticle.colour[ 3 ] += ( currentParticle.deltaColour[ 3 ] * delta );

// Calculate the rgba string to draw.
var draw = [];
draw.push("rgba(" + ( r > 255 ? 255 : r < 0 ? 0 : ~~r ) );
draw.push( g > 255 ? 255 : g < 0 ? 0 : ~~g );
draw.push( b > 255 ? 255 : b < 0 ? 0 : ~~b );
draw.push( (a > 1 ? 1 : a < 0 ? 0 : a.toFixed( 2 ) ) + ")");
currentParticle.drawColour = draw.join( "," );

this.particleIndex++;
} else {
// Replace particle with the last active
if( this.particleIndex != this.particleCount - 1 ){
this.particles[ this.particleIndex ] = this.particles[ this.particleCount-1 ];
}
this.particleCount--;
}
}
};

this.stop = function(){
this.active = false;
this.elapsedTime = 0;
this.emitCounter = 0;
};

this.render = function( context ){
for( var i = 0, j = this.particleCount; i < j; i++ ){
var particle = this.particles[ i ];
var size = particle.size;
var halfSize = size >> 1;
var x = ~~particle.position.x;
var y = ~~particle.position.y;

var radgrad = context.createRadialGradient( x + halfSize, y + halfSize, particle.sizeSmall, x + halfSize, y + halfSize, halfSize);
radgrad.addColorStop( 0, particle.drawColour );
radgrad.addColorStop( 1, 'rgba(0,0,0,0)' ); //Super cool if you change these values (and add more colour stops)
context.fillStyle = radgrad;
context.fillRect( x, y, size, size );
}
};
}

/* Vector Helper */
var Vector = {
create : function( x, y ){
return {
"x" : x || -1,
"y" : y || -1
};
},
multiply : function( vector, scaleFactor ){
vector.x *= scaleFactor;
vector.y *= scaleFactor;
return vector;
},
add : function( vector1, vector2 ){
vector1.x += vector2.x;
vector1.y += vector2.y;
return vector1;
}
};