/**
 * Creating the <Array>.random function, which return a random
 * element from any array.
 **/
Array.prototype.random = function () {
	return this[ Math.floor( Math.random() * this.length ) ];
}

/**
 * Global variables for fading process.
 **/
var lastColor;
var nextColor = bgColors.random();

/**
 * Call this to initiate the first fade. It will override the
 * background color of the body tag and call nextFade() -- there
 * will be a delay of <fadeGap> seconds before the first fade.
 *
 * NOTE: The function will do nothing if the browser doesn't
 *       understand document.getElementsByTageName(),
 **/
function initiateFade() {
	if (body = document.getElementsByTagName('body')) {
		body[0].style.backgroundColor = nextColor;
		body[0].id = 'Body';
		// We don't want fading untill fixed!
		//nextFade();
	}
}

/**
 * Queues the next fade. There will be a delay of <fadeGap>
 * seconds between the just completed and the next fade.
 **/
function nextFade() {
	lastColor = nextColor;
	nextColor = bgColors.random();
	window.setTimeout('doFade()', fadeGap * 1000);
}

/**
 * Wrapper function for fading of background of body tag.
 **/
function doFade() {
	fadeColor('Body', lastColor, nextColor, fadeStepping, fadeWait, 'b');
	nextFade();
}

/**
 * Convert a hex value to its decimal value - the inputed hex must be in the
 * format of a hex triplet - the kind we use for HTML colours. The function
 * will return an array with three values.
 **/
function hex2num(hex) {
	if(hex.charAt(0) == "#") { 
		hex = hex.slice(1);
	}
	hex = hex.toUpperCase();
	var hex_alphabets = "0123456789ABCDEF";
	var value = new Array(3);
	var k = 0;
	var int1,int2;
	for(var i=0;i<6;i+=2) {
		int1 = hex_alphabets.indexOf(hex.charAt(i));
		int2 = hex_alphabets.indexOf(hex.charAt(i+1));
		value[k] = (int1 * 16) + int2;
		k++;
	}
	return(value);
}

/**
 * Give a array with three values as the argument and the function will return
 * the corresponding hex triplet.
 **/
function num2hex(triplet) {
	var hex_alphabets = "0123456789ABCDEF";
	var hex = "#";
	var int1,int2;
	for(var i=0;i<3;i++) {
		int1 = triplet[i] / 16;
		int2 = triplet[i] % 16;

		hex += hex_alphabets.charAt(int1) + hex_alphabets.charAt(int2);
	}
	return(hex);
}


/**
 * Function that fades the color.
 *
 * id  - ID of the element whose colour must be faded.
 * start_hex - The initial color of the element.
 * stop_hex - The final color. The element will fade from the initial color to the final color.
 * difference- The colour values will be incremented by this number
 * delay  - The speed of the the effect - higher delay means slower effect.
 * color_background- The fade must be for the color of the element or for its background.
 * 
 * Allowed values are 'c'(Color of element) and 'b'(Background)
 **/
function fadeColor(id,start_hex,stop_hex,difference,delay,color_background) {
	//Default values...
	if(!difference) difference = 20;
	if(!delay) delay = 100;
	if(!start_hex) start_hex = "#FFFFFF";
	if(!stop_hex) stop_hex = "#000000";
	if(!color_background) color_background = "c";
                                       
	var ele = document.getElementById(id);
	if(!ele) return;
	var start= hex2num(start_hex);
	var stop = hex2num(stop_hex);
                                            
	//Make it numbers rather than strings.
	for(var i=0;i<3;i++) {
	start[i] = Number(start[i]);
	stop[i] = Number(stop[i]);
	}

	//Morph one colour to the other. If the start color is greater than the stop colour, start color will
	// be decremented till it reaches the stop color. If it is lower, it will incremented.
	for(var i=0;i<3;i++) {
		if (start[i] < stop[i]) {
			start[i] += difference;
			if(start[i] > stop[i]) start[i] = stop[i];//If we have overshot our target, make it equal - or it won't stop.
		}
		else if(start[i] > stop[i]) {
			start[i] -= difference;
			if(start[i] < stop[i]) start[i] = stop[i];
		}
	}

	//Change the color(or the background color).
	var color = "rgb("+start[0]+","+start[1]+","+start[2]+")";
	if(color_background == "b") {
		ele.style.backgroundColor = color;
	} else {
		ele.style.color = color;
	}

	//Stop if we have reached the target.
	if((start[0] == stop[0]) && (start[1] == stop[1]) && (start[2] == stop[2])) return;
	start_hex = num2hex(start);

	//Keep calling this function
	window.setTimeout("fadeColor('"+id+"','"+start_hex+"','"+stop_hex+"',"+difference+","+delay+",'"+color_background+"')",delay);
}