
function sunburst(config) {

  var width = config.width,
    height = config.height,
    radius = width / 2,
    x = d3.scale.linear().range([0, 2 * Math.PI]),
    y = d3.scale.pow().exponent(1.3).domain([0, 1]).range([0, radius]),
    padding = 5,
    duration = 1000;

  var vis = d3.select(config.placeholder).append("svg")
    .attr("width", width + padding * 2)
    .attr("height", height + padding * 2)
    .append("g")
      .attr("transform", "translate(" + [radius + padding, radius + padding] + ")");

  var partition = d3.layout.partition()
    .sort(null)
    .value(function(d) { return 5.8 - d.depth; });

  var arc = d3.svg.arc()
    .startAngle(function(d) { return Math.max(0, Math.min(2 * Math.PI, x(d.x))); })
    .endAngle(function(d) { return Math.max(0, Math.min(2 * Math.PI, x(d.x + d.dx))); })
    .innerRadius(function(d) { return Math.max(0, d.y ? y(d.y) : d.y); })
    .outerRadius(function(d) { return Math.max(0, y(d.y + d.dy)); });

  d3.json(config.data_source, function(error, json) {
    var nodes = partition.nodes(json);

    var color = d3.scale.category20c();

    var path = vis.selectAll("path").data(nodes);
    path.enter().append("path")
      .attr("id", function(d, i) { return "path-" + i; })
      .attr("d", arc)
//      .attr("fill-rule", "evenodd")
      .style("fill", function(d) { return color((d.children ? d : d.parent).name); })
      .on("click", click);

    var text = vis.selectAll("text").data(nodes);
    var textEnter = text.enter().append("text")
      .style("fill-opacity", 1)
      .style("fill", function(d) {
      	return "#000";
        return brightness(d3.rgb(color(d))) < 125 ? "#eee" : "#000";
      })
      .attr("text-anchor", function(d) {
        return x(d.x + d.dx / 2) > Math.PI ? "end" : "start";
      })
      .attr("dy", ".2em")
      .attr("transform", function(d) {
        var multiline = (d.name || "").split(" ").length > 1,
            angle = x(d.x + d.dx / 2) * 180 / Math.PI - 90,
            rotate = angle + (multiline ? -.5 : 0);
        return "rotate(" + rotate + ")translate(" + (y(d.y) + padding) + ")rotate(" + (angle > 90 ? -180 : 0) + ")";
      })
      .on("click", click);
    textEnter.append("tspan")
      .attr("x", 0)
      .text(function(d) { return d.depth ? d.name.split(" ")[0] : ""; });
    textEnter.append("tspan")
      .attr("x", 0)
      .attr("dy", "1em")
      .text(function(d) { return d.depth ? d.name.split(" ")[1] || "" : ""; });

  function click(d) {
    path.transition()
      .duration(duration)
      .attrTween("d", arcTween(d));

    // Somewhat of a hack as we rely on arcTween updating the scales.
    text.style("visibility", function(e) {
          return isParentOf(d, e) ? null : d3.select(this).style("visibility");
        })
      .transition()
        .duration(duration)
        .attrTween("text-anchor", function(d) {
          return function() {
            return x(d.x + d.dx / 2) > Math.PI ? "end" : "start";
          };
        })
        .attrTween("transform", function(d) {
          var multiline = (d.name || "").split(" ").length > 1;
          return function() {
            var angle = x(d.x + d.dx / 2) * 180 / Math.PI - 90,
                rotate = angle + (multiline ? -.5 : 0);
            return "rotate(" + rotate + ")translate(" + (y(d.y) + padding) + ")rotate(" + (angle > 90 ? -180 : 0) + ")";
          };
        })
        .style("fill-opacity", function(e) { return isParentOf(d, e) ? 1 : 1e-6; })
        .each("end", function(e) {
          d3.select(this).style("visibility", isParentOf(d, e) ? null : "hidden");
        });
  }
});

function isParentOf(p, c) {
  if (p === c) return true;
  if (p.children) {
    return p.children.some(function(d) {
      return isParentOf(d, c);
    });
  }
  return false;
}

/*
function colour(d) {
  if (d.children) {
    // There is a maximum of two children!
    var colours = d.children.map(colour),
        a = d3.hsl(colours[0]),
        b = d3.hsl(colours[1]);
    // L*a*b* might be better here...
    return d3.hsl((a.h + b.h) / 2, a.s * 1.2, a.l / 1.2);
  }
  return d.colour || "#fff";
}
*/

  // Interpolate the scales!
  function arcTween(d) {
    var my = maxY(d),
      xd = d3.interpolate(x.domain(), [d.x, d.x + d.dx]),
      yd = d3.interpolate(y.domain(), [d.y, my]),
      yr = d3.interpolate(y.range(), [d.y ? 20 : 0, radius]);
    return function(d) {
      return function(t) { x.domain(xd(t)); y.domain(yd(t)).range(yr(t)); return arc(d); };
    };
  }

  function maxY(d) {
    return d.children ? Math.max.apply(Math, d.children.map(maxY)) : d.y + d.dy;
  }

  // http://www.w3.org/WAI/ER/WD-AERT/#color-contrast
  function brightness(rgb) {
    return rgb.r * .299 + rgb.g * .587 + rgb.b * .114;
  }

}
