var w = 960,

    h = 700,

    r = Math.min(w, h) / 2,

    color = d3.scale.category20c();

var vis = d3.select("#chart").append("svg:svg")

    .attr("width", w)

    .attr("height", h)

  .append("svg:g")

    .attr("transform", "translate(" + w / 2 + "," + h / 2 + ")");

var partition = d3.layout.partition()

    .sort(null)

    .size([2 * Math.PI, r * r])

    .value(function(d) { return 1; });

var arc = d3.svg.arc()

    .startAngle(function(d) { return d.x; })

    .endAngle(function(d) { return d.x + d.dx; })

    .innerRadius(function(d) { return Math.sqrt(d.y); })

    .outerRadius(function(d) { return Math.sqrt(d.y + d.dy); });

d3.json("../data/flare.json", function(json) {

  var path = vis.data([json]).selectAll("path")

      .data(partition.nodes)

    .enter().append("svg:path")

      .attr("display", function(d) { return d.depth ? null : "none"; }) // hide inner ring

      .attr("d", arc)

      .attr("fill-rule", "evenodd")

      .style("stroke", "#fff")

      .style("fill", function(d) { return color((d.children ? d : d.parent).name); })

      .each(stash);

  d3.select("#size").on("click", function() {

    path

        .data(partition.value(function(d) { return d.size; }))

      .transition()

        .duration(1500)

        .attrTween("d", arcTween);

    d3.select("#size").classed("active", true);

    d3.select("#count").classed("active", false);

  });

  d3.select("#count").on("click", function() {

    path

        .data(partition.value(function(d) { return 1; }))

      .transition()

        .duration(1500)

        .attrTween("d", arcTween);

    d3.select("#size").classed("active", false);

    d3.select("#count").classed("active", true);

  });

});

// Stash the old values for transition.

function stash(d) {

  d.x0 = d.x;

  d.dx0 = d.dx;

}

// Interpolate the arcs in data space.

function arcTween(a) {

  var i = d3.interpolate({x: a.x0, dx: a.dx0}, a);

  return function(t) {

    var b = i(t);

    a.x0 = b.x;

    a.dx0 = b.dx;

    return arc(b);

  };

}