// if two digit year input dates after this year considered 20 century.
var NUM_CENTYEAR = 30;
// is time input control required by default
var BUL_TIMECOMPONENT = false;
// are year scrolling buttons required by default
var BUL_YEARSCROLL = true;

var calendars = [];
var RE_NUM = /^\d+$/;

function calendar2(obj_target) {

	this.gen_date = cal_gen_date2;
	this.gen_time = cal_gen_time2;
	this.gen_tsmp = cal_gen_tsmp2;
	this.prs_date = cal_prs_date2;
	this.prs_time = cal_prs_time2;
	this.prs_tsmp = cal_prs_tsmp2;
	this.popup    = cal_popup2;

	// validate input parameters
	if (!obj_target) { return cal_error("Error calling the calendar: no target control specified"); }
	if (obj_target.value == null) { return cal_error("Error calling the calendar: parameter specified is not valid tardet control"); }
	this.target = obj_target;
	this.time_comp = BUL_TIMECOMPONENT;
	this.year_scroll = BUL_YEARSCROLL;
	
	// register in global collections
	this.id = calendars.length;
	calendars[this.id] = this;
}

function cal_popup2 (str_datetime) {
	this.dt_current = this.prs_tsmp(str_datetime ? str_datetime : this.target.value);
	if (!this.dt_current) { return; }

	var obj_calwindow = window.open(
		'calendar.html?datetime=' + this.dt_current.valueOf()+ '&id=' + this.id, 'Calendar', 'width=200,height='+(this.time_comp ? 215 : 190) + ',status=no,resizable=no,top=200,left=200,dependent=yes,alwaysRaised=yes');
	obj_calwindow.opener = window;
	obj_calwindow.focus();
}

// timestamp generating function
function cal_gen_tsmp2 (dt_datetime) {
	return(this.gen_date(dt_datetime) + ' ' + this.gen_time(dt_datetime));
}

// date generating function
function cal_gen_date2 (dt_datetime) {
	return (
		(dt_datetime.getMonth() < 9 ? '0' : '') + (dt_datetime.getMonth() + 1) + '-' + (dt_datetime.getDate() < 10 ? '0' : '') + dt_datetime.getDate() + '-' + dt_datetime.getFullYear());
}
// time generating function
function cal_gen_time2 (dt_datetime) {
	return (
		(dt_datetime.getHours() < 10 ? '0' : '') + dt_datetime.getHours() + ":" + (dt_datetime.getMinutes() < 10 ? '0' : '') + (dt_datetime.getMinutes()) + ":" + (dt_datetime.getSeconds() < 10 ? '0' : '') + (dt_datetime.getSeconds()));
}

// timestamp parsing function
function cal_prs_tsmp2 (str_datetime) {
	// if no parameter specified return current timestamp
	if (!str_datetime) { return (new Date()); }

	// if positive integer treat as milliseconds from epoch
	if (RE_NUM.exec(str_datetime)) { return new Date(str_datetime); }
		
	// else treat as date in string format
	var arr_datetime = str_datetime.split(' ');
	return this.prs_time(arr_datetime[1], this.prs_date(arr_datetime[0]));
}

// date parsing function
function cal_prs_date2 (str_date) {

	var arr_date = str_date.split('-');

	if (arr_date.length != 3) { return alert ("Invalid date format: '" + str_date + "'.\nFormat accepted is mm-dd-yyyy."); }
	if (!arr_date[1]) { return alert ("Invalid date format: '" + str_date + "'.\nNo day of month value can be found."); }
	if (!RE_NUM.exec(arr_date[1])) { return alert ("Invalid day of month value: '" + arr_date[1] + "'.\nAllowed values are unsigned integers."); }
	if (!arr_date[0]) { return alert ("Invalid date format: '" + str_date + "'.\nNo month value can be found."); }
	if (!RE_NUM.exec(arr_date[0])) { return alert ("Invalid month value: '" + arr_date[0] + "'.\nAllowed values are unsigned integers."); }
	if (!arr_date[2]) { return alert ("Invalid date format: '" + str_date + "'.\nNo year value can be found."); }
	if (!RE_NUM.exec(arr_date[2])) { return alert ("Invalid year value: '" + arr_date[2] + "'.\nAllowed values are unsigned integers."); }

	var dt_date = new Date();

	if (arr_date[0] < 1 || arr_date[0] > 12) { return alert ("Invalid month value: '" + arr_date[0] + "'.\nAllowed range is 01-12."); }
	dt_date.setMonth(arr_date[0]-1);
	 
	if (arr_date[2] < 100) { arr_date[2] = Number(arr_date[2]) + (arr_date[2] < NUM_CENTYEAR ? 2000 : 1900); }
	dt_date.setFullYear(arr_date[2]);

	var dt_numdays = new Date(arr_date[1], arr_date[0], 0);
	dt_date.setDate(arr_date[1]);
	if (dt_date.getMonth() != (arr_date[0]-1)) { return alert ("Invalid day of month value: '" + arr_date[1] + "'.\nAllowed range is 01-"+dt_numdays.getDate()+"."); }

	return (dt_date);
}

// time parsing function
function cal_prs_time2 (str_time, dt_date) {

	if (!dt_date) { return null; }
	var arr_time = String(str_time ? str_time : '').split(':');

	if (!arr_time[0]) { dt_date.setHours(0); }
	else if (RE_NUM.exec(arr_time[0])) {
		if (arr_time[0] < 24) { dt_date.setHours(arr_time[0]); }
		else { return cal_error ("Invalid hours value: '" + arr_time[0] + "'.\nAllowed range is 00-23."); } }
	else { return cal_error ("Invalid hours value: '" + arr_time[0] + "'.\nAllowed values are unsigned integers."); }
	
	if (!arr_time[1]) { dt_date.setMinutes(0); }
	else if (RE_NUM.exec(arr_time[1])) {
		if (arr_time[1] < 60) { dt_date.setMinutes(arr_time[1]); }
		else { return cal_error ("Invalid minutes value: '" + arr_time[1] + "'.\nAllowed range is 00-59."); } }
	else { return cal_error ("Invalid minutes value: '" + arr_time[1] + "'.\nAllowed values are unsigned integers."); }

	if (!arr_time[2]) { dt_date.setSeconds(0); }
	else if (RE_NUM.exec(arr_time[2])) {
		if (arr_time[2] < 60) { dt_date.setSeconds(arr_time[2]); }
		else { return cal_error ("Invalid seconds value: '" + arr_time[2] + "'.\nAllowed range is 00-59."); } }
	else { return cal_error ("Invalid seconds value: '" + arr_time[2] + "'.\nAllowed values are unsigned integers."); }

	dt_date.setMilliseconds(0);
	return dt_date;
}

function cal_error (str_message) {
	alert (str_message);
	return null;
}