/* compute a Lindenmayer system given an axiom, a number of steps and rules
*/

(function() {
  var curve, d, fractalize, height, svg, svg_path, transition, tweenDash, width;

  fractalize = function(config) {
    var char, i, input, output, _i, _len, _ref;
    input = config.axiom;
    for (i = 0, _ref = config.steps; 0 <= _ref ? i < _ref : i > _ref; 0 <= _ref ? i++ : i--) {
      output = '';
      for (_i = 0, _len = input.length; _i < _len; _i++) {
        char = input[_i];
        if (char in config.rules) {
          output += config.rules[char];
        } else {
          output += char;
        }
      }
      input = output;
    }
    return output;
  };

  /* convert a Lindenmayer string into an SVG path string
  */

  svg_path = function(config) {
    var angle, char, path, _i, _len, _ref;
    angle = 0.0;
    path = 'M0 0';
    _ref = config.fractal;
    for (_i = 0, _len = _ref.length; _i < _len; _i++) {
      char = _ref[_i];
      if (char === '+') {
        angle += config.angle;
      } else if (char === '-') {
        angle -= config.angle;
      } else if (char === 'F') {
        path += "l" + (config.side * Math.cos(angle)) + " " + (config.side * Math.sin(angle));
      }
    }
    return path;
  };

  curve = fractalize({
    axiom: '-L',
    steps: 4,
    rules: {
      L: 'LF+RFR+FL-F-LFLFL-FRFR+',
      R: '-LFLF+RFRFR+F+RF-LFL-FR'
    }
  });

  d = svg_path({
    fractal: curve,
    side: 6,
    angle: Math.PI / 2
  });

  width = 960;

  height = 500;

  svg = d3.select('body').append('svg').attr('width', width).attr('height', height);

  svg.append('path').attr('class', 'curve shadow').attr('d', d).attr('transform', 'translate(240,490)');

  /* animate the path
  */

  /* from Mike Bostock's stroke dash interpolation example http://bl.ocks.org/mbostock/5649592
  */

  tweenDash = function() {
    var i, l;
    l = this.getTotalLength();
    i = d3.interpolateString('0,' + l, l + ',' + l);
    return function(t) {
      return i(t);
    };
  };

  transition = function(path) {
    return path.transition().duration(20000).attrTween('stroke-dasharray', tweenDash);
  };

  svg.append('path').attr('class', 'curve').attr('d', d).attr('transform', 'translate(240,490)').call(transition);

}).call(this);