/**
 * Due to the fact that DataTables moves DOM elements around (mainly TR 
 * elements for sorting and filtering) it can at times be a little tricky
 * to get the next row based on another, while taking into account pagination,
 * filtering, sorting etc. This function is designed to address exactly this
 * situation. It takes two parameters, the target node, and a boolean
 * indicating if the adjacent row retrieved should be the next (true, or no
 * value) or the previous (false).
 *  @name fnGetAdjacentTr
 *  @anchor fnGetAdjacentTr
 *  @author <a href="http://sprymedia.co.uk">Allan Jardine</a>
 *
 *  @example
 *    $(document).ready(function() {
 *        var oTable = $('#example').dataTable();
 *         
 *        var n1 = $('#example tbody tr:eq(2)')[0];
 *        var nNext = oTable.fnGetAdjacentTr( n1 );
 *        var nPrev = oTable.fnGetAdjacentTr( n1, false );
 *    } );
 */

$.fn.dataTableExt.oApi.fnGetAdjacentTr  = function ( oSettings, nTr, bNext )
{
	/* Find the node's position in the aoData store */
	var iCurrent = oSettings.oApi._fnNodeToDataIndex( oSettings, nTr );
	 
	/* Convert that to a position in the display array */
	var iDisplayIndex = $.inArray( iCurrent, oSettings.aiDisplay );
	if ( iDisplayIndex == -1 )
	{
		/* Not in the current display */
		return null;
	}
	 
	/* Move along the display array as needed */
	iDisplayIndex += (typeof bNext=='undefined' || bNext) ? 1 : -1;
	 
	/* Check that it within bounds */
	if ( iDisplayIndex < 0 || iDisplayIndex >= oSettings.aiDisplay.length )
	{
		/* There is no next/previous element */
		return null;
	}
	 
	/* Return the target node from the aoData store */
	return oSettings.aoData[ oSettings.aiDisplay[ iDisplayIndex ] ].nTr;
};