/**
 * Originally grabbed from the official RaphaelJS Documentation
 * http://raphaeljs.com/graffle.html
 * Adopted (arrows) and commented by Philipp Strathausen http://blog.ameisenbar.de
 * Licenced under the MIT licence.
 */

/**
 * Usage:
 * connect two shapes
 * parameters:
 *      source shape [or connection for redrawing],
 *      target shape,
 *      style with { fg : linecolor, bg : background color, directed: boolean }
 * returns:
 *      connection { draw = function() }
 */
Raphael.fn.connection = function Connection(obj1, obj2, style) {
  var selfRef = this;
  /* create and return new connection */
  var edge = {/*
    from : obj1,
    to : obj2,
    style : style,*/
    draw : function() {
      /* get bounding boxes of target and source */
      var bb1 = obj1.getBBox();
      var bb2 = obj2.getBBox();
      var off1 = 0;
      var off2 = 0;
      /* coordinates for potential connection coordinates from/to the objects */
      var p = [
        /* NORTH 1 */
        { x: bb1.x + bb1.width / 2, y: bb1.y - off1 },
        /* SOUTH 1 */
        { x: bb1.x + bb1.width / 2, y: bb1.y + bb1.height + off1 },
        /* WEST */
        { x: bb1.x - off1, y: bb1.y + bb1.height / 2 },
        /* EAST  1 */
        { x: bb1.x + bb1.width + off1, y: bb1.y + bb1.height / 2 },
        /* NORTH 2 */
        { x: bb2.x + bb2.width / 2, y: bb2.y - off2 },
        /* SOUTH 2 */
        { x: bb2.x + bb2.width / 2, y: bb2.y + bb2.height + off2 },
        /* WEST  2 */
        { x: bb2.x - off2, y: bb2.y + bb2.height / 2 },
        /* EAST  2 */
        { x: bb2.x + bb2.width + off2, y: bb2.y + bb2.height / 2 }
      ];
      
      /* distances between objects and according coordinates connection */
      var d = {}, dis = [], dx, dy;

      /*
       * find out the best connection coordinates by trying all possible ways
       */
      /* loop the first object's connection coordinates */
      for (var i = 0; i < 4; i++) {
        /* loop the seond object's connection coordinates */
        for (var j = 4; j < 8; j++) {
          dx = Math.abs(p[i].x - p[j].x);
          dy = Math.abs(p[i].y - p[j].y);
          if ((i === j - 4) || (((i !== 3 && j !== 6) || p[i].x < p[j].x) &&
            ((i !== 2 && j !== 7) || p[i].x > p[j].x) &&
            ((i !== 0 && j !== 5) || p[i].y > p[j].y) &&
            ((i !== 1 && j !== 4) || p[i].y < p[j].y)))
          {
            dis.push(dx + dy);
            d[dis[dis.length - 1].toFixed(3)] = [i, j];
          }
        }
      }
      var res = dis.length === 0 ? [0, 4] : d[Math.min.apply(Math, dis).toFixed(3)];
      /* bezier path */
      var x1 = p[res[0]].x,
          y1 = p[res[0]].y,
          x4 = p[res[1]].x,
          y4 = p[res[1]].y;
          dx = Math.max(Math.abs(x1 - x4) / 2, 10);
          dy = Math.max(Math.abs(y1 - y4) / 2, 10);
      var x2 = [ x1, x1, x1 - dx, x1 + dx ][res[0]].toFixed(3),
          y2 = [ y1 - dy, y1 + dy, y1, y1 ][res[0]].toFixed(3),
          x3 = [ 0, 0, 0, 0, x4, x4, x4 - dx, x4 + dx ][res[1]].toFixed(3),
          y3 = [ 0, 0, 0, 0, y1 + dy, y1 - dy, y4, y4 ][res[1]].toFixed(3);
      /* assemble path and arrow */
      var path = [ "M" + x1.toFixed(3), y1.toFixed(3),
          "C" + x2, y2, x3, y3, x4.toFixed(3), y4.toFixed(3) ].join(",");
      /* arrow */
      if(style && style.directed) {
        // magnitude, length of the last path vector 
        var mag = Math.sqrt((y4 - y3) * (y4 - y3) + (x4 - x3) * (x4 - x3));
        // vector normalisation to specified length  
        var norm = function(x,l){return (-x*(l||5)/mag);};
        // calculate array coordinates (two lines orthogonal to the path vector) 
        var arr = [
          { x:(norm(x4-x3)+norm(y4-y3)+x4).toFixed(3),
            y:(norm(y4-y3)+norm(x4-x3)+y4).toFixed(3) },
          { x:(norm(x4-x3)-norm(y4-y3)+x4).toFixed(3),
            y:(norm(y4-y3)-norm(x4-x3)+y4).toFixed(3) }
        ];
        path = path + ",M" + arr[0].x + "," + arr[0].y + ",L" + x4 + "," +
          y4 + ",L" + arr[1].x + "," + arr[1].y;
      }
      /* function to be used for moving existent path(s), e.g. animate() or attr() */
      var move = "attr";
      /* applying path(s) */
      edge.fg && edge.fg[move]({path:path}) ||
          (edge.fg = selfRef.path(path)
              .attr({ stroke: style && style.stroke || "#000", fill: "none" })
              .toBack());
      edge.bg && edge.bg[move]({path:path}) ||
          style && style.fill && (edge.bg = style.fill.split &&
              selfRef.path(path)
              .attr({ stroke: style.fill.split("|")[0], fill: "none",
                "stroke-width": style.fill.split("|")[1] || 3 }).toBack());
      /* setting label */
      style && style.label &&
          (edge.label && edge.label.attr({x:(x1+x4)/2, y:(y1+y4)/2}) ||
              (edge.label = selfRef.text((x1+x4)/2, (y1+y4)/2, style.label)
                .attr({fill: "#000", "font-size": style["font-size"] || "12px"})));
      style && style.label && style["label-style"] && edge.label &&
          edge.label.attr(style["label-style"]);
      style && style.callback && style.callback(edge);
    }
  };
  edge.draw();
  return edge;
};