/*
Code taken from:
http://www.kryogenix.org/code/browser/sorttable/

   1.  Include the Javascript library, by putting a link to it in the HEAD of your page, like so:

<script src="sorttable.js"></script>

   2. Mark your table as a sortable one by giving it a class of "sortable":

<table class="sortable">

   3. Ensure that your table has an ID:

<table class="sortable" id="unique_id">

And that's all you need. Your table will now have column sorting available by clicking the headers. 
For niceness, you might want to add the following styles to your stylesheet, or make up some of your own based on this:

table.sortable a.sortheader {
    background-color:#eee;
    color:#666666;
    font-weight: bold;
    text-decoration: none;
    display: block;
}
table.sortable span.sortarrow {
    color: black;
    text-decoration: none;
}

CHANGES: I changed line 107 so that it can sort negative numbers as well.
*/

addEvent(window, "load", sortables_init);

var SORT_COLUMN_INDEX;

function sortables_init() {
    // Find all tables with class sortable and make them sortable
    if (!document.getElementsByTagName) return;
    tbls = document.getElementsByTagName("table");
    for (ti=0;ti<tbls.length;ti++) {
        thisTbl = tbls[ti];
        if (((' '+thisTbl.className+' ').indexOf("sortable") != -1) && (thisTbl.id)) {
            //initTable(thisTbl.id);
            ts_makeSortable(thisTbl);
        }
    }
}

function ts_makeSortable(table) {
    if (table.rows && table.rows.length > 0) {
        var firstRow = table.rows[0];
    }
    if (!firstRow) return;
    
    // We have a first row: assume it's the header, and make its contents clickable links
    for (var i=0;i<firstRow.cells.length;i++) {
        var cell = firstRow.cells[i];
        var txt = ts_getInnerText(cell);
        cell.innerHTML = '<a href="#" class="sortheader" '+ 
        'onclick="ts_resortTable(this, '+i+');return false;">' + 
        txt+'<span class="sortarrow">&nbsp;&nbsp;&nbsp;</span></a>';
    }
}

function ts_getInnerText(el) {
	if (typeof el == "string") return el;
	if (typeof el == "undefined") { return el };
	if (el.innerText) return el.innerText;	//Not needed but it is faster
	var str = "";
	
	var cs = el.childNodes;
	var l = cs.length;
	for (var i = 0; i < l; i++) {
		switch (cs[i].nodeType) {
			case 1: //ELEMENT_NODE
				str += ts_getInnerText(cs[i]);
				break;
			case 3:	//TEXT_NODE
				str += cs[i].nodeValue;
				break;
		}
	}
	return str;
}

function ts_resortTable(lnk,clid) {
    // get the span
    var span;
    for (var ci=0;ci<lnk.childNodes.length;ci++) {
        if (lnk.childNodes[ci].tagName && lnk.childNodes[ci].tagName.toLowerCase() == 'span') span = lnk.childNodes[ci];
    }
    var spantext = ts_getInnerText(span);
    var td = lnk.parentNode;
    var column = clid || td.cellIndex;
    var table = getParent(td,'TABLE');
    
    // Work out a type for the column
    if (table.rows.length <= 1) return;
    var itm = ts_getInnerText(table.rows[1].cells[column]);
    sortfn = ts_sort_caseinsensitive;
    if (itm.match(/^\d\d[\/-]\d\d[\/-]\d\d\d\d$/)) sortfn = ts_sort_date;
    if (itm.match(/^\d\d[\/-]\d\d[\/-]\d\d$/)) sortfn = ts_sort_date;
    if (itm.match(/^[£$]/)) sortfn = ts_sort_currency;
    if (itm.match(/^[-\d\.]+$/)) sortfn = ts_sort_numeric;
    SORT_COLUMN_INDEX = column;
    var firstRow = new Array();
    var newRows = new Array();
    for (i=0;i<table.rows[0].length;i++) { firstRow[i] = table.rows[0][i]; }
    for (j=1;j<table.rows.length;j++) { newRows[j-1] = table.rows[j]; }

    newRows.sort(sortfn);

    if (span.getAttribute("sortdir") == 'down') {
        ARROW = '&nbsp;&nbsp;&uarr;';
        newRows.reverse();
        span.setAttribute('sortdir','up');
    } else {
        ARROW = '&nbsp;&nbsp;&darr;';
        span.setAttribute('sortdir','down');
    }
    
    // We appendChild rows that already exist to the tbody, so it moves them rather than creating new ones
    // don't do sortbottom rows
    for (i=0;i<newRows.length;i++) { if (!newRows[i].className || (newRows[i].className && (newRows[i].className.indexOf('sortbottom') == -1))) table.tBodies[0].appendChild(newRows[i]);}
    // do sortbottom rows only
    for (i=0;i<newRows.length;i++) { if (newRows[i].className && (newRows[i].className.indexOf('sortbottom') != -1)) table.tBodies[0].appendChild(newRows[i]);}
    
    // Delete any other arrows there may be showing
    var allspans = document.getElementsByTagName("span");
    for (var ci=0;ci<allspans.length;ci++) {
        if (allspans[ci].className == 'sortarrow') {
            if (getParent(allspans[ci],"table") == getParent(lnk,"table")) { // in the same table as us?
                allspans[ci].innerHTML = '&nbsp;&nbsp;&nbsp;';
            }
        }
    }
        
    span.innerHTML = ARROW;
}

function getParent(el, pTagName) {
	if (el == null) return null;
	else if (el.nodeType == 1 && el.tagName.toLowerCase() == pTagName.toLowerCase())	// Gecko bug, supposed to be uppercase
		return el;
	else
		return getParent(el.parentNode, pTagName);
}
function ts_sort_date(a,b) {
    // y2k notes: two digit years less than 50 are treated as 20XX, greater than 50 are treated as 19XX
    aa = ts_getInnerText(a.cells[SORT_COLUMN_INDEX]);
    bb = ts_getInnerText(b.cells[SORT_COLUMN_INDEX]);
    if (aa.length == 10) {
        dt1 = aa.substr(6,4)+aa.substr(3,2)+aa.substr(0,2);
    } else {
        yr = aa.substr(6,2);
        if (parseInt(yr) < 50) { yr = '20'+yr; } else { yr = '19'+yr; }
        dt1 = yr+aa.substr(3,2)+aa.substr(0,2);
    }
    if (bb.length == 10) {
        dt2 = bb.substr(6,4)+bb.substr(3,2)+bb.substr(0,2);
    } else {
        yr = bb.substr(6,2);
        if (parseInt(yr) < 50) { yr = '20'+yr; } else { yr = '19'+yr; }
        dt2 = yr+bb.substr(3,2)+bb.substr(0,2);
    }
    if (dt1==dt2) return 0;
    if (dt1<dt2) return -1;
    return 1;
}

function ts_sort_currency(a,b) { 
    aa = ts_getInnerText(a.cells[SORT_COLUMN_INDEX]).replace(/[^0-9.]/g,'');
    bb = ts_getInnerText(b.cells[SORT_COLUMN_INDEX]).replace(/[^0-9.]/g,'');
    return parseFloat(aa) - parseFloat(bb);
}

function ts_sort_numeric(a,b) { 
    aa = parseFloat(ts_getInnerText(a.cells[SORT_COLUMN_INDEX]));
    if (isNaN(aa)) aa = 0;
    bb = parseFloat(ts_getInnerText(b.cells[SORT_COLUMN_INDEX])); 
    if (isNaN(bb)) bb = 0;
    return aa-bb;
}

function ts_sort_caseinsensitive(a,b) {
    aa = ts_getInnerText(a.cells[SORT_COLUMN_INDEX]).toLowerCase();
    bb = ts_getInnerText(b.cells[SORT_COLUMN_INDEX]).toLowerCase();
    if (aa==bb) return 0;
    if (aa<bb) return -1;
    return 1;
}

function ts_sort_default(a,b) {
    aa = ts_getInnerText(a.cells[SORT_COLUMN_INDEX]);
    bb = ts_getInnerText(b.cells[SORT_COLUMN_INDEX]);
    if (aa==bb) return 0;
    if (aa<bb) return -1;
    return 1;
}


function addEvent(elm, evType, fn, useCapture)
// addEvent and removeEvent
// cross-browser event handling for IE5+,  NS6 and Mozilla
// By Scott Andrew
{
  if (elm.addEventListener){
    elm.addEventListener(evType, fn, useCapture);
    return true;
  } else if (elm.attachEvent){
    var r = elm.attachEvent("on"+evType, fn);
    return r;
  } else {
    alert("Handler could not be removed");
  }
}