/**
 * Javascript wrapper for the Google Chart API. Enables users
 * to render charts from the API with a small piece of javascript.
 * This is software is still in development.
 * @author b.wenneker <b.wenneker@gmail.com>
 * @website <http://www.solutoire.com>
 * @date 12-6-2007 
 * @version 0.1 alpha.
 */
GChart = function(){
	var extend = function(){
		var args = arguments;
		if (!args[1]) args = [this, args[0]];
		for (var property in args[1]) args[0][property] = args[1][property];
		return args[0];
	};
	
	var get = function(e){		
		return (typeof e == 'string') ? document.getElementById(e) : (e || false);		
	};
		
	var urlhelper = function(o, type, key, ch){
		o = GChart.options[o];
		return (o && typeof o === type) ? '&ch' + key + '=' + ((type == 'object') ? o.join(ch || ',') : o) : '';
	};
	
	return {
		/**
		 * Sets the options for the GChart object. The options are evaluated
		 * in getUrl() using the private urlhelper().
		 * @since 0.1 alpha
		 * @param {Object} o Options object.
		 * @return void
		 */
		setOptions : function(o){
			this.options = extend({
				/**
				 * @type {String, Element} renderTo The id of the node or a DOM node that will be the container to render the chart into.
				 */
				renderTo: false,
				/**
				 * @type {String, Element} applyTo The id of the node or a DOM node corresponding to an IMG that is already present.
				 */
				applyTo: false,
				/**
				 * @type {String} size Specifies the size of the chart like <width in pixels>x<height in pixels> (defaults to 300x200).
				 */
				size: '300x200',
				/**
				 * @type {String} type Specifies the type of the chart (defaults to 'lc').
				 */
				type: 'lc',
				/**
				 * @type {String} encoding Specifies the chart encoding, can be 'simple' or 's', 'text' or 't' and 'extended' or 'e' (defaults to 's').
				 */
				encoding: 's',
				/**
				 * @type {String, Array} data Dataset(s) for the chart, can be a multidimensional array or a encoded string (defaults to []).
				 */
				data: [],
				/**
				 * @type {Integer} max Specifies the max value of a dataset, read <http://code.google.com/apis/chart/#encoding_data> maxValue (defaults to false).
				 */
				max: false,
				/**
				 * @type {String} alt Image alt attribute (defaults to '').
				 */
				alt: '',
				/**
				 * @type {String} title Chart title (defaults to null).
				 */
				title: null,
				/**
				 * @type {String, Array} titlestyle Title style, can be an Array (['color','fontsize']) or a formatted string '<color>,<font-size>' (defaults to null).
				 */
				titlestyle: null,
				/**
				 * @type {String, Array} legend Legend, can be an array or a formatted string (defaults to null).
				 */
				legend: null,
				/**
				 * @type {String} axistype Axis type.
				 */
				axistype: 'x,y',
				/**
				 * @todo
				 */
				labels: null,
				labelpositions: null,
				axisrange: null,
				axisstyle: null,	
				/**
				 * @type {String, Array} colors Colorset, can be an array (['color1','color2','colorn']) or String ('<color1>,<color2,<colorn>') (defaults to null).
				 */
				colors: null,
				/**
				 * @type {String, Array} fill Fill options, see <http://code.google.com/apis/chart/#chart_or_background_fill> (defaults to null).
				 */
				fill: null,
				/**
				 * @todo
				 */
				pielabels: null,
				linestyles: null,
				grid: null,
				shapemarkers: null,
				hormarkers: null,
				vertmarkers: null
			}, o || {});
			this.options.encoding = this.options.encoding.charAt(0);
			return this.options;
		},
		/**
		 * Function translates the passed object or this.options.data to a encoded string. This
		 * function handles the three encoding type specified by the Google Chart API: 'simple',
		 * 'text' and 'extended'. Read more about the encoding types on the Google Chart API Project page.
		 * @since 0.1 alpha
		 * @param {Object} d Encodes the data according to the encoding type specified in this.options.
		 * @return {String} Returns passed data in encoded format.
		 */
		getEncodedData : function(d){
			var d = d || this.options.data;						
			var str = '';	
			switch(this.options.encoding){
				default: case 'e': case 's':					
					if(d.length && typeof d[0] == 'object'){
						for(var i = 0, dln = d.length; i < dln; i++){
							str += ',' + this.getEncodedData(d[i]);
						}
						return str.substring(1);
					}else{
						if(typeof d == 'string') return d;
						var encoding = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
						if(this.options.encoding == 'e') encoding += '-.';			
						var constant = (encoding.length - 1) / (this.options.max || (encoding.length - 1));					
						for(var i = 0, dln = d.length; i < dln; i++){							
							if(this.options.encoding == 's'){
								str += ((!isNaN(d[i]) && d[i] >= 0) ? encoding.charAt(Math.round(constant * d[i])) : '_');
							}else if (this.options.encoding == 'e'){
								str += ((!isNaN(d[i]) && d[i] >= 0) ? encoding.charAt(Math.round(Math.floor(constant * d[i] / 64))) + encoding.charAt(Math.round(constant * (d[i] % 64))) : '__');
							}
						}
						return str;
					}
					break;
				case 't':
					if(typeof d == 'string') return d;
					if (d.length && typeof d[0] == 'object') {
						for(var i = 0, dln = d.length; i < dln; i++){
							str += '|' + (d[i]).join(',');
						}
						return str.substring(1);
					}
					return d.join(',');
			}			
		},
		
		getUrl : function(){
			var url = 'http://chart.apis.google.com/chart?';
			url += 'chs=' + this.options.size;
			url += '&chd=' + this.options.encoding + ':' + this.getEncodedData(this.options.data);
			url += '&cht=' + this.options.type;
			url += urlhelper('title', 'string', 'tt');
			url += urlhelper('legend', 'object', 'dl', '|');
			url += urlhelper('labels', 'object', 'l', '|');
			url += urlhelper('axistype', 'string', 'xt');
			url += urlhelper('colors', 'object', 'co');
			return url.replace(' ', '+');
		},
		
		render : function(o){
			o = this.setOptions(o);
			var url = this.getUrl();			
			if((img = get(o.applyTo))){
				img.src = url;
			}else{
				var img = document.createElement('img');
				img.src = url;
				img.alt = o.alt;
				if(o.renderTo !== false){				
					(get(o.renderTo)).appendChild(img);					
				}
				return img;								
			}
		}
	};
}();