(function ($) {

/**

 * Attaches sticky table headers.

 */

Drupal.behaviors.tableHeader = {

  attach: function (context, settings) {

    if (!$.support.positionFixed) {

      return;

    }

    $('table.sticky-enabled', context).once('tableheader', function () {

      $(this).data("drupal-tableheader", new Drupal.tableHeader(this));

    });

  }

};

/**

 * Constructor for the tableHeader object. Provides sticky table headers.

 *

 * @param table

 *   DOM object for the table to add a sticky header to.

 */

Drupal.tableHeader = function (table) {

  var self = this;

  this.originalTable = $(table);

  this.originalHeader = $(table).children('thead');

  this.originalHeaderCells = this.originalHeader.find('> tr > th');

  this.displayWeight = null;

  // React to columns change to avoid making checks in the scroll callback.

  this.originalTable.bind('columnschange', function (e, display) {

    // This will force header size to be calculated on scroll.

    self.widthCalculated = (self.displayWeight !== null && self.displayWeight === display);

    self.displayWeight = display;

  });

  // Clone the table header so it inherits original jQuery properties. Hide

  // the table to avoid a flash of the header clone upon page load.

  this.stickyTable = $('<table class="sticky-header"/>')

    .insertBefore(this.originalTable)

    .css({ position: 'fixed', top: '0px' });

  this.stickyHeader = this.originalHeader.clone(true)

    .hide()

    .appendTo(this.stickyTable);

  this.stickyHeaderCells = this.stickyHeader.find('> tr > th');

  this.originalTable.addClass('sticky-table');

  $(window)

    .bind('scroll.drupal-tableheader', $.proxy(this, 'eventhandlerRecalculateStickyHeader'))

    .bind('resize.drupal-tableheader', { calculateWidth: true }, $.proxy(this, 'eventhandlerRecalculateStickyHeader'))

    // Make sure the anchor being scrolled into view is not hidden beneath the

    // sticky table header. Adjust the scrollTop if it does.

    .bind('drupalDisplaceAnchor.drupal-tableheader', function () {

      window.scrollBy(0, -self.stickyTable.outerHeight());

    })

    // Make sure the element being focused is not hidden beneath the sticky

    // table header. Adjust the scrollTop if it does.

    .bind('drupalDisplaceFocus.drupal-tableheader', function (event) {

      if (self.stickyVisible && event.clientY < (self.stickyOffsetTop + self.stickyTable.outerHeight()) && event.$target.closest('sticky-header').length === 0) {

        window.scrollBy(0, -self.stickyTable.outerHeight());

      }

    })

    .triggerHandler('resize.drupal-tableheader');

  // We hid the header to avoid it showing up erroneously on page load;

  // we need to unhide it now so that it will show up when expected.

  this.stickyHeader.show();

};

/**

 * Event handler: recalculates position of the sticky table header.

 *

 * @param event

 *   Event being triggered.

 */

Drupal.tableHeader.prototype.eventhandlerRecalculateStickyHeader = function (event) {

  var self = this;

  var calculateWidth = event.data && event.data.calculateWidth;

  // Reset top position of sticky table headers to the current top offset.

  this.stickyOffsetTop = Drupal.settings.tableHeaderOffset ? eval(Drupal.settings.tableHeaderOffset + '()') : 0;

  this.stickyTable.css('top', this.stickyOffsetTop + 'px');

  // Save positioning data.

  var viewHeight = document.documentElement.scrollHeight || document.body.scrollHeight;

  if (calculateWidth || this.viewHeight !== viewHeight) {

    this.viewHeight = viewHeight;

    this.vPosition = this.originalTable.offset().top - 4 - this.stickyOffsetTop;

    this.hPosition = this.originalTable.offset().left;

    this.vLength = this.originalTable[0].clientHeight - 100;

    calculateWidth = true;

  }

  // Track horizontal positioning relative to the viewport and set visibility.

  var hScroll = document.documentElement.scrollLeft || document.body.scrollLeft;

  var vOffset = (document.documentElement.scrollTop || document.body.scrollTop) - this.vPosition;

  this.stickyVisible = vOffset > 0 && vOffset < this.vLength;

  this.stickyTable.css({ left: (-hScroll + this.hPosition) + 'px', visibility: this.stickyVisible ? 'visible' : 'hidden' });

  // Only perform expensive calculations if the sticky header is actually

  // visible or when forced.

  if (this.stickyVisible && (calculateWidth || !this.widthCalculated)) {

    this.widthCalculated = true;

    var $that = null;

    var $stickyCell = null;

    var display = null;

    var cellWidth = null;

    // Resize header and its cell widths.

    // Only apply width to visible table cells. This prevents the header from

    // displaying incorrectly when the sticky header is no longer visible.

    for (var i = 0, il = this.originalHeaderCells.length; i < il; i += 1) {

      $that = $(this.originalHeaderCells[i]);

      $stickyCell = this.stickyHeaderCells.eq($that.index());

      display = $that.css('display');

      if (display !== 'none') {

        cellWidth = $that.css('width');

        // Exception for IE7.

        if (cellWidth === 'auto') {

          cellWidth = $that[0].clientWidth + 'px';

        }

        $stickyCell.css({'width': cellWidth, 'display': display});

      }

      else {

        $stickyCell.css('display', 'none');

      }

    }

    this.stickyTable.css('width', this.originalTable.outerWidth());

  }

};

})(jQuery);