var button_click_state = false;

function click_button(obj_ref) {

	if( button_click_state == false ) {
		open_window();
		button_click_state = true;
	} else {
		output_result('');
		button_click_state = false;
	}
}

function open_window() {

	var requestUrl = '/ajax/ean_box.htm';

	var ajax = new Ajax();
	ajax.Output = function(txt) { output_result(txt); }
	ajax.Request(requestUrl);
}

function close_window() {
	
	if( button_click_state == false ) {
		output_result('');
	}
}

function output_result(html) {

	var outputElement = document.getElementById('info_box');

	if ( outputElement != null && html != null ) {
		outputElement.innerHTML = html;
	}
}

function calculate_check_digit(ean_value) {

	var factor = 3;
	var sum = 0;

	for( var index = ean_value.length; index > 0; --index) {
		sum = sum + ean_value.substring (index-1, index) * factor;
		factor = 4 - factor;
	}

	var check_digit = ((1000 - sum) % 10);
	return check_digit;
}

function check_ean(ean_value) {

	var ean_length = ean_value.length;
	var ean_code = ean_value.substring( 0, ean_length-1 );
	var ean_code_check = ean_value.substr( ean_length-1, 1 );

	var check_digit = calculate_check_digit(ean_code);

	var outputIcon = document.getElementById('check_icon');

	if( ean_length > 7 && check_digit == ean_code_check ) {
		outputIcon.innerHTML = '<img src="../images/symbol_true.gif" width="20" height="20" border="0" alt="True" />';
	} else {
		outputIcon.innerHTML = '<img src="../images/symbol_false.gif" width="20" height="20" border="0" alt="False" />';
	}
}