var Drag = {

  obj : null,
  init : function (o, oRoot, minX, maxX, minY, maxY, bSwapHorzRef, bSwapVertRef, fXMapper, fYMapper) {
 
    o.onmousedown = Drag.start;

    o.hmode = bSwapHorzRef ? false : true ;
    o.vmode = bSwapVertRef ? false : true ;

    o.root = oRoot && oRoot != null ? oRoot : o ;

    if (o.hmode  && isNaN(parseInt(o.root.style.left))) o.root.style.left = "0px";
    if (o.vmode  && isNaN(parseInt(o.root.style.top))) o.root.style.top = "0px";
    if (!o.hmode && isNaN(parseInt(o.root.style.right))) o.root.style.right = "0px";
    if (!o.vmode && isNaN(parseInt(o.root.style.bottom))) o.root.style.bottom = "0px";

    o.minX = typeof minX != 'undefined' ? minX : null;
    o.minY = typeof minY != 'undefined' ? minY : null;
    o.maxX = typeof maxX != 'undefined' ? maxX : null;
    o.maxY = typeof maxY != 'undefined' ? maxY : null;

    o.xMapper = fXMapper ? fXMapper : null;
    o.yMapper = fYMapper ? fYMapper : null;

    o.root.onDragStart = new Function();
    o.root.onDragEnd = new Function();
    o.root.onDrag = new Function();

  },
	
  start : function (e) {

    var o = Drag.obj = this;
    e = Drag.fixE(e);

    var y = parseInt(o.vmode ? o.root.style.top  : o.root.style.bottom);
    var x = parseInt(o.hmode ? o.root.style.left : o.root.style.right );
    o.root.onDragStart (x, y);

    o.lastMouseX = e.clientX;
    o.lastMouseY = e.clientY;

    if (o.hmode) {

      if (o.minX != null) o.minMouseX = e.clientX - x + o.minX;
      if (o.maxX != null) o.maxMouseX = o.minMouseX + o.maxX - o.minX;

    }

    else {

      if (o.minX != null) o.maxMouseX = -o.minX + e.clientX + x;
      if (o.maxX != null) o.minMouseX = -o.maxX + e.clientX + x;
			
    }

    if (o.vmode) {

      if (o.minY != null) o.minMouseY = e.clientY - y + o.minY;
      if (o.maxY != null) o.maxMouseY = o.minMouseY + o.maxY - o.minY;

    }

    else {

      if (o.minY != null) o.maxMouseY = -o.minY + e.clientY + y;
      if (o.maxY != null) o.minMouseY = -o.maxY + e.clientY + y;

    }

    document.onmousemove = Drag.drag;
    document.onmouseup = Drag.end;

    return false;

  },

  drag : function(e) {

    e = Drag.fixE(e);
    var o = Drag.obj;

    var ey = e.clientY;
    var ex = e.clientX;
    var y = parseInt(o.vmode ? o.root.style.top  : o.root.style.bottom);
    var x = parseInt(o.hmode ? o.root.style.left : o.root.style.right);
    var nx, ny;

    if (o.minX != null) ex = o.hmode ? Math.max(ex, o.minMouseX) : Math.min(ex, o.maxMouseX);
    if (o.maxX != null) ex = o.hmode ? Math.min(ex, o.maxMouseX) : Math.max(ex, o.minMouseX);
    if (o.minY != null) ey = o.vmode ? Math.max(ey, o.minMouseY) : Math.min(ey, o.maxMouseY);
    if (o.maxY != null) ey = o.vmode ? Math.min(ey, o.maxMouseY) : Math.max(ey, o.minMouseY);

    nx = x + ((ex - o.lastMouseX) * (o.hmode ? 1 : -1));
    ny = y + ((ey - o.lastMouseY) * (o.vmode ? 1 : -1));

    if (o.xMapper) {
  
      nx = o.xMapper(y);

    }

    else if (o.yMapper) {
  
      ny = o.yMapper(x);

    }

    Drag.obj.root.style[o.hmode ? "left" : "right"] = nx + "px";
    Drag.obj.root.style[o.vmode ? "top" : "bottom"] = ny + "px";
    Drag.obj.lastMouseX = ex;
    Drag.obj.lastMouseY	= ey;

    Drag.obj.root.onDrag(nx, ny);
    return false;

  },

  end : function() {

    document.onmousemove = null;
    document.onmouseup = null;

    Drag.obj.root.onDragEnd(parseInt(Drag.obj.root.style[Drag.obj.hmode ? "left" : "right"]), parseInt(Drag.obj.root.style[Drag.obj.vmode ? "top" : "bottom"]));
    Drag.obj = null;

  },

  fixE : function(e) {

    if (typeof e == 'undefined') e = window.event;
    if (typeof e.layerX == 'undefined') e.layerX = e.offsetX;
    if (typeof e.layerY == 'undefined') e.layerY = e.offsetY;

    return e;

  }

};