function gidReadCookie( name )
{
	var _COOKIE = null;
	var _COOKIES = document.cookie.split( ';' );
	var matchName = name + "=";
	for( var i=0; i<_COOKIES.length; i++ )
	{
		_COOKIE = _COOKIES[i];
		while( _COOKIE.charAt(0)==' ' )
			_COOKIE = _COOKIE.substring( 1, _COOKIE.length );
		if( _COOKIE.indexOf(matchName)==0 )
			return _COOKIE.substring( matchName.length, _COOKIE.length );
	}
	return null;
}

/**
 * Writes a cookie.
 * 
 * @param string name
 * @param string value
 * @param integer days 0 for session only.
 * @param string path
 * @return void
 */
function gidWriteCookie( name, value, days, path )
{
	var expires = "; expires=";
	if( days )
	{
		var date = new Date();
		date.setTime( date.getTime() + (days*24*60*60*1000) );
		expires += date.toGMTString();
	}
	else
	{
		expires += 0;
	}
	document.cookie = name + "=" + value + expires + "; path=" + path;
}

function addCompareID( id )
{
	id = id.toString();
	var nameCookie = 'compare';
	var newValue = null;
	var value = gidReadCookie( nameCookie );
	if( value )
	{
		var ids = value.split( '|' );
		if( ids.length == 1 )
		{
			if( ids != id )
				ids.push( id );
			else
				return;
		}
		else
		{
			if( ids.length >= 3 )
			{
				alert( "The maximum number of plans you can compare at a time is 3" );
				return; // TODO: unselect the option box.
			}
			else
			{
				if( -1 == ids.indexOf(id) )
					ids.push( id );
				else
					return;
			}
		}
		newValue = ids.join( '|' );
	}
	else
	{
		newValue = id;
	}
	gidWriteCookie( nameCookie, newValue, 0, '/' );
}

/**
 * Figure out the checkbox checked status for each hosting plan being (checked or unchecked) compared.
 * Depending on the action, the plan ID will be appended to or removed from the cookie.
 *
 * @param string cbid Input element (Checkbox) ID.
 * @param string id Web hosting plan ID.
 * @return void
 */
function comparisonCB( cbid, id )
{
	var nameCookie = 'compare';
	if( document.getElementById(cbid).checked == true )
		comparisonIDAdd( cbid, id, nameCookie, 3 );
	else
		comparisonIDDel( cbid, id, nameCookie );
}

/**
 * Add a web hosting plan ID to the cookie. Also stops adding beyond the maximum IDs allowed.
 * 
 * @access private
 * @param string cbid Checkbox (input) ID.
 * @param string id Web hosting plan ID.
 * @param string nameCookie Name of cookie.
 * @param integer maxID Maximum IDs allowed.
 * @return void Writes a cookie.
 */
function comparisonIDAdd( cbid, id, nameCookie, maxID )
{
	var newValue = null; // new value to set the cookie at the end.
	var ids = loadComparisonIDs( nameCookie ); // an array of IDs.
	if( -1 == ids.indexOf(id) ) // only unique IDs accepted.
	{
		if( ids.length >= maxID )
		{
			window.alert( "You may compare up to " + maxID + " web hosting plans at a time only." );
			document.getElementById(cbid).checked = false; // unchecks this checkbox.
			return; // skip writing the cookie.
		}
		ids.push( id );
	}
	else
	{
		return; // duplicate hosting plan ID, nothing to do.
	}
	newValue = ids.join( '|' );
	gidWriteCookie( nameCookie, newValue, 0, '/' );
}

/**
 * Delete a web hosting plan ID from the cookie.
 * 
 * @access private
 * @param string cbid Checkbox (input) ID.
 * @param string id Web hosting plan ID.
 * @param string nameCookie Name of cookie.
 * @return void Writes a cookie.
 */
function comparisonIDDel( cbid, id, nameCookie )
{
	var newValue = null; // new value to set the cookie at the end.
	var ids = loadComparisonIDs( nameCookie ); // an array of IDs.
	var delIndex = ids.indexOf(id);
	if( -1 == delIndex )
		return;
	else
		ids.splice( delIndex, 1 ); // removing this ID from the array.
	
	var expires = (newValue=ids.join('|')) ? 0 : -1; // delete the cookie if value is empty.
	gidWriteCookie( nameCookie, newValue, expires, '/' );
}

/**
 * Reads domain cookies.
 * 
 * @param string name Name of cookie to read.
 * @return string Value of cookie (or NULL).
 */
function gidReadCookie( name )
{
	var _COOKIE = null;
	var _COOKIES = document.cookie.split( ';' );
	var matchName = name + "=";
	for( var i=0; i<_COOKIES.length; i++ )
	{
		_COOKIE = _COOKIES[i];
		while( _COOKIE.charAt(0)==' ' )
			_COOKIE = _COOKIE.substring( 1, _COOKIE.length );
		if( _COOKIE.indexOf(matchName)==0 )
			return _COOKIE.substring( matchName.length, _COOKIE.length );
	}
	return null;
}

/**
 * Writes a cookie.
 * 
 * @param string name Name of cookie.
 * @param string value Value of cookie.
 * @param integer days 0 for session only.
 * @param string path
 * @return void
 */
function gidWriteCookie( name, value, days, path )
{
	var expires = "; expires=";
	if( days )
	{
		var date = new Date();
		date.setTime( date.getTime() + (days*24*60*60*1000) );
		expires += date.toGMTString();
	}
	else
	{
		expires += 0;
	}
	document.cookie = name + "=" + value + expires + "; path=" + path;
}

/**
 * Reads the cookie and converts the value, i.e. a string of IDs e.g. 
 * <code>23|12|1009</code>, into an array.
 *
 * @access private
 * @param string nameCookie Cookie Name
 * @return array
 */
function loadComparisonIDs( nameCookie )
{
	var ids = new Array();
	var value = gidReadCookie( nameCookie ); // reads the existing cookie value, if any.
	if( value )
		ids = value.split( '|' );
	return ids;
}