(function() {
  var global, mousemoved;

  global = {
    area: 1
  };

  /* whenever the mouse moves, compute a new area parameter for the simplification, then draw again the regions
  */

  mousemoved = function() {
    global.area = global.mouse_scale.invert(d3.mouse(this)[0]);
    return global.svg.selectAll('.region, .boundary').attr('d', global.path_generator);
  };

  window.main = function() {
    var colorify, dx, dy, height, radius, vis, width;
    width = 960;
    height = 500;
    /* prepare a scale for the mouse input
    */
    global.mouse_scale = d3.scale.sqrt().domain([0, 1e4]).range([0, width]);
    global.svg = d3.select('body').append('svg').attr('width', width).attr('height', height).on('mousemove', mousemoved);
    vis = global.svg.append('g').attr('transform', 'translate(640, 120)');
    /* custom projection to make hexagons appear regular (y axis is also flipped)
    */
    /* it also applies the Visvalingam simplification
    */
    radius = 0.6;
    dx = radius * 2 * Math.sin(Math.PI / 3);
    dy = radius * 1.5;
    global.path_generator = d3.geo.path().projection(d3.geo.transform({
      point: function(x, y, z) {
        /* draw only nodes that are "important" enough
        */        if (z >= global.area) {
          return this.stream.point(x * dx / 2, -(y - (2 - (y & 1)) / 3) * dy / 2);
        }
      }
    }));
    /* define a color scale (Colorbrewer's Set3)
    */
    colorify = d3.scale.ordinal().domain(['A', 'B', 'C', 'D']).range(["#8dd3c7", "#ffffb3", "#bebada", "#fb8072"]);
    /* load topoJSON data
    */
    return d3.json('readme.regions.topo.json', function(error, data) {
      /* presimplify the topology (compute the effective area (z) of each point)
      */      topojson.presimplify(data);
      /* draw the cells
      */
      vis.selectAll('.region').data(topojson.feature(data, data.objects.regions).features).enter().append('path').attr('class', 'region').attr('d', global.path_generator).attr('fill', function(d) {
        return colorify(d.properties['class']);
      });
      /* draw the boundaries
      */
      vis.append('path').datum(topojson.mesh(data, data.objects.regions, function(a, b) {
        return a === b;
      })).attr('d', global.path_generator).attr('class', 'outer boundary');
      return vis.append('path').datum(topojson.mesh(data, data.objects.regions, function(a, b) {
        return a !== b;
      })).attr('d', global.path_generator).attr('class', 'boundary');
    });
  };

}).call(this);