/*
 * Antiscroll: cross-browser native OS X Lion scrollbars
 * https://github.com/Automattic/antiscroll
 * v0.9
 */

(function ($) {

  /**
   * Augment jQuery prototype.
   */

  $.fn.antiscroll = function (options) {
    return this.each(function () {
      if ($(this).data('antiscroll')) {
        $(this).data('antiscroll').destroy();
      }

      $(this).data('antiscroll', new $.Antiscroll(this, options));
    });
  };

  /**
   * Expose constructor.
   */

  $.Antiscroll = Antiscroll;

  /**
   * Antiscroll pane constructor.
   *
   * @param {Element|jQuery} main pane
   * @parma {Object} options
   * @api public
   */

  function Antiscroll (el, opts) {
    this.el = $(el);
    this.options = opts || {};

    this.x = (false !== this.options.x) || this.options.forceHorizontal;
    this.y = (false !== this.options.y) || this.options.forceVertical;
    this.autoHide = false !== this.options.autoHide;
    this.padding = undefined == this.options.padding ? 2 : this.options.padding;

    this.inner = this.el.find('.antiscroll-inner');
    this.inner.css({
        'width':  '+=' + (this.y ? scrollbarSize() : 0)
      , 'height': '+=' + (this.x ? scrollbarSize() : 0)
    });

    this.refresh();
  };

  /**
   * refresh scrollbars
   *
   * @api public
   */

  Antiscroll.prototype.refresh = function() {
    var needHScroll = this.inner.get(0).scrollWidth > this.el.width() + (this.y ? scrollbarSize() : 0), 
	    needVScroll = this.inner.get(0).scrollHeight > this.el.height() + (this.x ? scrollbarSize() : 0);

    if (this.x) {
      if (!this.horizontal && needHScroll) {
        this.horizontal = new Scrollbar.Horizontal(this);
      } else if (this.horizontal && !needHScroll)  {
        this.horizontal.destroy();
        this.horizontal = null;
      } else if (this.horizontal) {
        this.horizontal.update();
      }
    }

    if (this.y) {
      if (!this.vertical && needVScroll) {
        this.vertical = new Scrollbar.Vertical(this);
      } else if (this.vertical && !needVScroll)  {
        this.vertical.destroy();
        this.vertical = null;
      } else if (this.vertical) {
        this.vertical.update();
      }
    }
  };

  /**
   * Cleans up.
   *
   * @return {Antiscroll} for chaining
   * @api public
   */

  Antiscroll.prototype.destroy = function () {
    if (this.horizontal) {
      this.horizontal.destroy();
      this.horizontal = null
    }
    if (this.vertical) {
      this.vertical.destroy();
      this.vertical = null
    }
    return this;
  };

  /**
   * Rebuild Antiscroll.
   *
   * @return {Antiscroll} for chaining
   * @api public
   */

  Antiscroll.prototype.rebuild = function () {
    this.destroy();
    this.inner.attr('style', '');
    Antiscroll.call(this, this.el, this.options);
    return this;
  };

  /**
   * Scrollbar constructor.
   *
   * @param {Element|jQuery} element
   * @api public
   */

  function Scrollbar (pane) {
    this.pane = pane;
    this.pane.el.append(this.el);
    this.innerEl = this.pane.inner.get(0);

    this.dragging = false;
    this.enter = false;
    this.shown = false;

    // hovering
    this.pane.el.mouseenter($.proxy(this, 'mouseenter'));
    this.pane.el.mouseleave($.proxy(this, 'mouseleave'));

    // dragging
    this.el.mousedown($.proxy(this, 'mousedown'));

    // scrolling
    this.innerPaneScrollListener = $.proxy(this, 'scroll');
    this.pane.inner.scroll(this.innerPaneScrollListener);

    // wheel -optional-
    this.innerPaneMouseWheelListener = $.proxy(this, 'mousewheel');
    this.pane.inner.bind('mousewheel', this.innerPaneMouseWheelListener);

    // show
    var initialDisplay = this.pane.options.initialDisplay;

    if (initialDisplay !== false) {
      this.show();
      if (this.pane.autoHide) {
          this.hiding = setTimeout($.proxy(this, 'hide'), parseInt(initialDisplay, 10) || 3000);
      }
    }
  };

  /**
   * Cleans up.
   *
   * @return {Scrollbar} for chaining
   * @api public
   */

  Scrollbar.prototype.destroy = function () {
    this.el.remove();
    this.pane.inner.unbind('scroll', this.innerPaneScrollListener);
    this.pane.inner.unbind('mousewheel', this.innerPaneMouseWheelListener);
    return this;
  };

  /**
   * Called upon mouseenter.
   *
   * @api private
   */

  Scrollbar.prototype.mouseenter = function () {
    this.enter = true;
    this.show();
  };

  /**
   * Called upon mouseleave.
   *
   * @api private
   */

  Scrollbar.prototype.mouseleave = function () {
    this.enter = false;

    if (!this.dragging) {
        if (this.pane.autoHide) {
            this.hide();
        }
    }
  };

  /**
   * Called upon wrap scroll.
   *
   * @api private
   */

  Scrollbar.prototype.scroll = function () {
    if (!this.shown) {
      this.show();
      if (!this.enter && !this.dragging) {
        if (this.pane.autoHide) {
            this.hiding = setTimeout($.proxy(this, 'hide'), 1500);
        }
      }
    }

    this.update();
  };

  /**
   * Called upon scrollbar mousedown.
   *
   * @api private
   */

  Scrollbar.prototype.mousedown = function (ev) {
    ev.preventDefault();

    this.dragging = true;

    this.startPageY = ev.pageY - parseInt(this.el.css('top'), 10);
    this.startPageX = ev.pageX - parseInt(this.el.css('left'), 10);

    // prevent crazy selections on IE
    this.el[0].ownerDocument.onselectstart = function () { return false; };

    var pane = this.pane,
	    move = $.proxy(this, 'mousemove'),
		self = this

    $(this.el[0].ownerDocument)
      .mousemove(move)
      .mouseup(function () {
        self.dragging = false;
        this.onselectstart = null;

        $(this).unbind('mousemove', move);

        if (!self.enter) {
          self.hide();
        }
      });
  };

  /**
   * Show scrollbar.
   *
   * @api private
   */

  Scrollbar.prototype.show = function (duration) {
    if (!this.shown && this.update()) {
      this.el.addClass('antiscroll-scrollbar-shown');
      if (this.hiding) {
        clearTimeout(this.hiding);
        this.hiding = null;
      }
      this.shown = true;
    }
  };

  /**
   * Hide scrollbar.
   *
   * @api private
   */

  Scrollbar.prototype.hide = function () {
    if (this.pane.autoHide !== false && this.shown) {
      // check for dragging
      this.el.removeClass('antiscroll-scrollbar-shown');
      this.shown = false;
    }
  };

  /**
   * Horizontal scrollbar constructor
   *
   * @api private
   */

  Scrollbar.Horizontal = function (pane) {
    this.el = $('<div class="antiscroll-scrollbar antiscroll-scrollbar-horizontal"/>', pane.el);
    Scrollbar.call(this, pane);
  };

  /**
   * Inherits from Scrollbar.
   */

  inherits(Scrollbar.Horizontal, Scrollbar);

  /**
   * Updates size/position of scrollbar.
   *
   * @api private
   */

  Scrollbar.Horizontal.prototype.update = function () {
    var paneWidth = this.pane.el.width(), 
	    trackWidth = paneWidth - this.pane.padding * 2,
		innerEl = this.pane.inner.get(0)

    this.el
      .css('width', trackWidth * paneWidth / innerEl.scrollWidth)
      .css('left', trackWidth * innerEl.scrollLeft / innerEl.scrollWidth);

    return paneWidth < innerEl.scrollWidth;
  };

  /**
   * Called upon drag.
   *
   * @api private
   */

  Scrollbar.Horizontal.prototype.mousemove = function (ev) {
    var trackWidth = this.pane.el.width() - this.pane.padding * 2, 
	    pos = ev.pageX - this.startPageX,
		barWidth = this.el.width(),
		innerEl = this.pane.inner.get(0)

    // minimum top is 0, maximum is the track height
    var y = Math.min(Math.max(pos, 0), trackWidth - barWidth);

    innerEl.scrollLeft = (innerEl.scrollWidth - this.pane.el.width())
      * y / (trackWidth - barWidth);
  };

  /**
   * Called upon container mousewheel.
   *
   * @api private
   */

  Scrollbar.Horizontal.prototype.mousewheel = function (ev, delta, x, y) {
    if ((x < 0 && 0 == this.pane.inner.get(0).scrollLeft) ||
        (x > 0 && (this.innerEl.scrollLeft + Math.ceil(this.pane.el.width())
          == this.innerEl.scrollWidth))) {
      ev.preventDefault();
      return false;
    }
  };

  /**
   * Vertical scrollbar constructor
   *
   * @api private
   */

  Scrollbar.Vertical = function (pane) {
    this.el = $('<div class="antiscroll-scrollbar antiscroll-scrollbar-vertical"/>', pane.el);
    Scrollbar.call(this, pane);
  };

  /**
   * Inherits from Scrollbar.
   */

  inherits(Scrollbar.Vertical, Scrollbar);

  /**
   * Updates size/position of scrollbar.
   *
   * @api private
   */

  Scrollbar.Vertical.prototype.update = function () {
    var paneHeight = this.pane.el.height(), 
	    trackHeight = paneHeight - this.pane.padding * 2,
		innerEl = this.innerEl;
      
    var scrollbarHeight = trackHeight * paneHeight / innerEl.scrollHeight;
    scrollbarHeight = scrollbarHeight < 20 ? 20 : scrollbarHeight;
    
    var topPos = trackHeight * innerEl.scrollTop / innerEl.scrollHeight;
    
    if((topPos + scrollbarHeight) > trackHeight) {
        var diff = (topPos + scrollbarHeight) - trackHeight;
        topPos = topPos - diff - 3;
    }

    this.el
      .css('height', scrollbarHeight)
      .css('top', topPos);
	  
	  return paneHeight < innerEl.scrollHeight;
  };

  /**
   * Called upon drag.
   *
   * @api private
   */

  Scrollbar.Vertical.prototype.mousemove = function (ev) {
    var paneHeight = this.pane.el.height(),
	    trackHeight = paneHeight - this.pane.padding * 2,
		pos = ev.pageY - this.startPageY,
		barHeight = this.el.height(),
		innerEl = this.innerEl

    // minimum top is 0, maximum is the track height
    var y = Math.min(Math.max(pos, 0), trackHeight - barHeight);

    innerEl.scrollTop = (innerEl.scrollHeight - paneHeight)
      * y / (trackHeight - barHeight);
  };

  /**
   * Called upon container mousewheel.
   *
   * @api private
   */

  Scrollbar.Vertical.prototype.mousewheel = function (ev, delta, x, y) {
    if ((y > 0 && 0 == this.innerEl.scrollTop) ||
        (y < 0 && (this.innerEl.scrollTop + Math.ceil(this.pane.el.height())
          == this.innerEl.scrollHeight))) {
      ev.preventDefault();
      return false;
    }
  };

  /**
   * Cross-browser inheritance.
   *
   * @param {Function} constructor
   * @param {Function} constructor we inherit from
   * @api private
   */

  function inherits (ctorA, ctorB) {
    function f() {};
    f.prototype = ctorB.prototype;
    ctorA.prototype = new f;
  };

  /**
   * Scrollbar size detection.
   */

  var size;

  function scrollbarSize () {
    if (size === undefined) {
      var div = $(
          '<div class="antiscroll-inner" style="width:50px;height:50px;overflow-y:scroll;'
        + 'position:absolute;top:-200px;left:-200px;"><div style="height:100px;width:100%"/>'
        + '</div>'
      );

      $('body').append(div);
      var w1 = $(div).innerWidth();
      var w2 = $('div', div).innerWidth();
      $(div).remove();

      size = w1 - w2;
    }

    return size;
  };

})(jQuery);
