(function() {
  var drag, get_intersection, height, intersection, lines_data, points_data, redraw, svg, width;

  get_intersection = function(p0, p1, p2, p3) {
    var s, s1_x, s1_y, s2_x, s2_y, t;

    s1_x = p1.x - p0.x;
    s1_y = p1.y - p0.y;
    s2_x = p3.x - p2.x;
    s2_y = p3.y - p2.y;
    s = (-s1_y * (p0.x - p2.x) + s1_x * (p0.y - p2.y)) / (-s2_x * s1_y + s1_x * s2_y);
    t = (s2_x * (p0.y - p2.y) - s2_y * (p0.x - p2.x)) / (-s2_x * s1_y + s1_x * s2_y);
    if (s >= 0 && s <= 1 && t >= 0 && t <= 1) {
      return {
        x: p0.x + (t * s1_x),
        y: p0.y + (t * s1_y)
      };
    }
    return null;
  };

  points_data = [
    {
      x: -200,
      y: 200
    }, {
      x: 200,
      y: -200
    }, {
      x: -200,
      y: -200
    }, {
      x: 200,
      y: 200
    }
  ];

  lines_data = [
    {
      start: points_data[0],
      end: points_data[1]
    }, {
      start: points_data[2],
      end: points_data[3]
    }
  ];

  svg = d3.select('svg');

  width = svg.node().getBoundingClientRect().width;

  height = svg.node().getBoundingClientRect().height;

  svg.attr({
    viewBox: "" + (-width / 2) + " " + (-height / 2) + " " + width + " " + height
  });

  drag = d3.behavior.drag().origin(function(d) {
    return d;
  });

  drag.on('drag', function(d) {
    d.x = d3.event.x;
    d.y = d3.event.y;
    return redraw();
  });

  redraw = function() {
    var intersection_data, lines, points;

    lines = svg.selectAll('.line').data(lines_data);
    lines.enter().append('line').attr({
      "class": 'line'
    });
    lines.attr({
      x1: function(l) {
        return l.start.x;
      },
      y1: function(l) {
        return l.start.y;
      },
      x2: function(l) {
        return l.end.x;
      },
      y2: function(l) {
        return l.end.y;
      }
    });
    points = svg.selectAll('.point').data(points_data);
    points.enter().append('circle').call(drag).attr({
      "class": 'point',
      r: 8
    });
    points.attr({
      cx: function(p) {
        return p.x;
      },
      cy: function(p) {
        return p.y;
      }
    });
    intersection_data = get_intersection(points_data[0], points_data[1], points_data[2], points_data[3]);
    if (typeof intersection !== "undefined" && intersection !== null) {
      return intersection.attr({
        cx: intersection_data != null ? intersection_data.x : 0,
        cy: intersection_data != null ? intersection_data.y : 0,
        display: intersection_data != null ? 'inline' : 'none'
      });
    }
  };

  redraw();

  intersection = svg.append('circle').attr({
    "class": 'intersection',
    r: 4
  });

}).call(this);