(function() {
  var distance, margin, max_depth, rand_tree, width;

  rand_tree = function(d, MAX_D, MAX_N, P, index) {
    /* return a tree with maximum depth MAX_D that branches with probability P at most N times for each internal node
    */
    var child_i, children, i, n;
    if (d === MAX_D) {
      return {
        index: Infinity
      };
    }
    /* if the tree branches, at least one branch is made
    */
    n = Math.floor(Math.random() * MAX_N) + 1;
    child_i = 0;
    children = [];
    for (i = 0; 0 <= n ? i < n : i > n; 0 <= n ? i++ : i--) {
      if (P >= Math.random()) {
        child_i += 1;
        children.push(rand_tree(d + 1, MAX_D, MAX_N, P, child_i));
      } else {
        children.push({
          index: Infinity
        });
      }
    }
    children.sort(function(a, b) {
      return a.index - b.index;
    });
    return {
      index: index,
      children: children
    };
  };

  width = 960;

  distance = 14;

  margin = 40;

  max_depth = 8;

  d3.select(self.frameElement).style('height', "" + (2 * margin) + "px");

  window.main = function() {
    /* create the tree
    */
    var diagonal, height, link, links, node, nodes, root, tree, vis;
    root = rand_tree(1, max_depth, 4, 0.5, 0);
    root.index = '';
    /* initialize the layout
    */
    tree = d3.layout.tree().size([0, 0]);
    nodes = tree.nodes(root);
    links = tree.links(nodes);
    height = 0;
    /* force the layout to display nodes in fixed rows and columns
    */
    nodes.forEach(function(n) {
      if ((n.parent != null) && n.parent.children[0] !== n) height += distance;
      n.x = height;
      return n.y = n.depth * (width / max_depth);
    });
    /* define a method for computing an internal node's prefix
    */
    nodes.filter(function(d) {
      return d.children;
    }).forEach(function(n, i) {
      return n.prefix = function() {
        return (n.parent != null ? n.parent.prefix() : '') + n.index;
      };
    });
    /* draw the vis
    */
    diagonal = d3.svg.diagonal().projection(function(d) {
      return [d.y, d.x];
    });
    vis = d3.select('body').append('svg').attr('width', width).attr('height', height + 2 * margin).append('g').attr('transform', "translate(" + margin + "," + margin + ")");
    link = vis.selectAll('path.link').data(links).enter().append('path').attr('class', 'link').attr('d', diagonal);
    node = vis.selectAll('g.node').data(nodes).enter().append('g').attr('class', 'node').attr('transform', function(d) {
      return "translate(" + d.y + "," + d.x + ")";
    });
    node.append('circle').attr('r', 4).attr('fill', function(d) {
      if (d.children) {
        return 'white';
      } else {
        return 'gray';
      }
    });
    node.filter(function(d) {
      return d.children;
    }).append('text').attr('dx', function(d) {
      if (d.children) {
        return -8;
      } else {
        return 8;
      }
    }).attr('dy', 3).attr('text-anchor', function(d) {
      if (d.children) {
        return 'end';
      } else {
        return 'start';
      }
    }).text(function(d) {
      return d.prefix();
    });
    /* adapt bl.ocks.org frame to the tree
    */
    return d3.select(self.frameElement).transition().duration(500).style('height', "" + (height + 2 * margin) + "px");
  };

}).call(this);