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

(function() {
  var fractalize, hex_coords, new_hex;

  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 array of hexagonal coordinates
  */

  hex_coords = function(config) {
    var char, current, dir, dir_i, directions, path, _i, _len, _ref;
    directions = [
      {
        x: +1,
        y: -1,
        z: 0
      }, {
        x: +1,
        y: 0,
        z: -1
      }, {
        x: 0,
        y: +1,
        z: -1
      }, {
        x: -1,
        y: +1,
        z: 0
      }, {
        x: -1,
        y: 0,
        z: +1
      }, {
        x: 0,
        y: -1,
        z: +1
      }
    ];
    /* start the walk from the origin cell, facing east
    */
    path = [
      {
        x: 0,
        y: 0,
        z: 0
      }
    ];
    dir_i = 0;
    _ref = config.fractal;
    for (_i = 0, _len = _ref.length; _i < _len; _i++) {
      char = _ref[_i];
      if (char === '+') {
        dir_i = (dir_i + 1) % directions.length;
      } else if (char === '-') {
        dir_i = dir_i - 1;
        if (dir_i === -1) dir_i = 5;
      } else if (char === 'F') {
        dir = directions[dir_i];
        current = path[path.length - 1];
        path.push({
          x: current.x + dir.x,
          y: current.y + dir.y,
          z: current.z + dir.z
        });
      }
    }
    return path;
  };

  window.main = function() {
    var colorify, coords, dx, dy, e, gosper, height, hexes, i, path_generator, radius, seq, svg, vis, width;
    width = 960;
    height = 500;
    svg = d3.select('body').append('svg').attr('width', width).attr('height', height);
    vis = svg.append('g').attr('transform', 'translate(540,10)');
    /* create the input sequence (random length between 2000 and 2401)
    */
    /* give the element a random class (A is more likely, C is less likely)
    */
    seq = (function() {
      var _ref, _results;
      _results = [];
      for (i = 0, _ref = 2000 + Math.floor(Math.random() * 401); 0 <= _ref ? i <= _ref : i >= _ref; 0 <= _ref ? i++ : i--) {
        _results.push(['A', 'A', 'A', 'A', 'B', 'B', 'C', 'D', 'D'][Math.floor(Math.random() * 9)]);
      }
      return _results;
    })();
    /* sort the sequence by class
    */
    seq.sort();
    /* create the Gosper curve
    */
    gosper = fractalize({
      axiom: 'A',
      steps: 4,
      rules: {
        A: 'A+BF++BF-FA--FAFA-BF+',
        B: '-FA+BFBF++BF+FA--FA-B'
      }
    });
    /* convert the curve into coordinates of hex cells
    */
    coords = hex_coords({
      fractal: gosper
    });
    /* create the GeoJSON hexes
    */
    hexes = {
      type: 'FeatureCollection',
      features: (function() {
        var _len, _results;
        _results = [];
        for (i = 0, _len = seq.length; i < _len; i++) {
          e = seq[i];
          _results.push(new_hex(coords[i], e));
        }
        return _results;
      })()
    };
    /* custom projection to make hexagons appear regular (y axis is also flipped)
    */
    radius = 5;
    dx = radius * 2 * Math.sin(Math.PI / 3);
    dy = radius * 1.5;
    path_generator = d3.geo.path().projection(d3.geo.transform({
      point: function(x, y) {
        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"]);
    /* draw the cells
    */
    return vis.selectAll('.hex').data(hexes.features).enter().append('path').attr('class', 'hex').attr('d', path_generator).attr('fill', function(d) {
      return colorify(d.properties['class']);
    }).attr('stroke', function(d) {
      return colorify(d.properties['class']);
    });
  };

  /* create a new hexagon
  */

  new_hex = function(c, e) {
    /* conversion from hex coordinates to rect
    */
    var x, y;
    x = 2 * (c.x + c.z / 2.0);
    y = 2 * c.z;
    return {
      type: 'Feature',
      geometry: {
        type: 'Polygon',
        coordinates: [[[x, y + 2], [x + 1, y + 1], [x + 1, y], [x, y - 1], [x - 1, y], [x - 1, y + 1], [x, y + 2]]]
      },
      properties: {
        'class': e
      }
    };
  };

}).call(this);