!function(){
	var gradPie={};
	
	var pie = d3.layout.pie().sort(null).value(function(d) {return d.value;});
			
	createGradients = function(defs, colors, r){	
		var gradient = defs.selectAll('.gradient')
			.data(colors).enter().append("radialGradient")
			.attr("id", function(d,i){return "gradient" + i;})
			.attr("gradientUnits", "userSpaceOnUse")
			.attr("cx", "0").attr("cy", "0").attr("r", r).attr("spreadMethod", "pad");
			
		gradient.append("stop").attr("offset", "0%").attr("stop-color", function(d){ return d;});

		gradient.append("stop").attr("offset", "30%")
			.attr("stop-color",function(d){ return d;})
			.attr("stop-opacity", 1);
			
		gradient.append("stop").attr("offset", "70%")
			.attr("stop-color",function(d){ return "black";})
			.attr("stop-opacity", 1);
	}
	
	gradPie.draw = function(id, data, cx, cy, r){
		var gPie = d3.select("#"+id).append("g")
			.attr("transform", "translate(" + cx + "," + cy + ")");
			
		createGradients(gPie.append("defs"), data.map(function(d){ return d.color; }), 2.5*r);

		gPie.selectAll("path").data(pie(data))
			.enter().append("path").attr("fill", function(d,i){ return "url(#gradient"+ i+")";})
			.attr("d", d3.svg.arc().outerRadius(r))
			.each(function(d) { this._current = d; });
	}
	
	gradPie.transition = function(id, data, r) {
		function arcTween(a) {
		  var i = d3.interpolate(this._current, a);
		  this._current = i(0);
		  return function(t) { return d3.svg.arc().outerRadius(r)(i(t));  };
		}
		
		d3.select("#"+id).selectAll("path").data(pie(data))
			.transition().duration(750).attrTween("d", arcTween); 
	}	
	
	this.gradPie = gradPie;
}();