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

  rand_tree = function(d, MAX_D, MAX_N) {
    /* return a tree with maximum depth MAX_D that branches with probability p at most N times for each internal node. p starts from 1 and decreases linearly with d, reaching zero at MAX_D
    */
    /* this still seems to be necessary to avoid infinte recursion (floating point precision?)
    */
    var children, i, n, p;
    if (d === MAX_D) {
      return {
        height: 0
      };
    }
    p = (MAX_D - d) / MAX_D;
    /* if the tree branches, at least one branch is made
    */
    n = Math.floor(Math.random() * MAX_N) + 1;
    children = [];
    for (i = 0; 0 <= n ? i < n : i > n; 0 <= n ? i++ : i--) {
      if (p >= Math.random()) {
        children.push(rand_tree(d + 1, MAX_D, MAX_N));
      } else {
        children.push({
          height: 0
        });
      }
    }
    children.sort(function(a, b) {
      return b.height - a.height;
    });
    return {
      height: d3.max(children, function(d) {
        return d.height;
      }) + 1,
      children: children
    };
  };

  width = 960;

  distance = 14;

  margin = 40;

  max_depth = 10;

  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, 3);
    /* 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);
    });
    /* 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 'steelblue';
      }
    });
    /* adapt bl.ocks.org frame to the tree
    */
    return d3.select(self.frameElement).transition().duration(500).style('height', "" + (height + 2 * margin) + "px");
  };

}).call(this);