/*

Name: jsDate
Desc: VBScript native Date functions emulated for Javascript
Author: Rob Eberhardt, Slingshot Solutions - http://slingfive.com/
History:
	2005-08-04	v0.94		scrapped new dateDiff approach to better match VBScript's simplistic Y/M/Q
	2005-08-03	v0.93		fixed dateDiff/leapyear bug with yyyy/m/q intervals
	2004-11-26	v0.91		fixed datePart/ww bug, added weekdayName() & monthName()
	2004-08-30	v0.9		brand new
	
*/

// used by dateAdd, dateDiff, datePart, weekdayName, and monthName
// note: less strict than VBScript's isDate, since JS allows invalid dates to overflow (e.g. Jan 32 transparently becomes Feb 1)
function isDate(p_Expression){
	return !isNaN(new Date(p_Expression));		// <<--- this needs checking
}


// REQUIRES: isDate()
function dateAdd(p_Interval, p_Number, p_Date){
	if(!isDate(p_Date)){return "invalid date: '" + p_Date + "'";}
	if(isNaN(p_Number)){return "invalid number: '" + p_Number + "'";}
	
	if (p_Date.length != 10){ alert( "invalid date format.  Must use mm/dd/yyyy format. "); Contests.ContestStartDate.value = "";  return "";}
	
	p_Number = new Number(p_Number);
	var dt = new Date(p_Date);
	switch(p_Interval.toLowerCase()){
		case "yyyy": {// year
			dt.setFullYear(dt.getFullYear() + p_Number);
			break;
		}
		case "q": {		// quarter
			dt.setMonth(dt.getMonth() + (p_Number*3));
			break;
		}
		case "m": {		// month
			dt.setMonth(dt.getMonth() + p_Number);
			break;
		}
		case "y":		// day of year
		case "d":		// day
		case "w": {		// weekday
			dt.setDate(dt.getDate() + p_Number);
			break;
		}
		case "ww": {	// week of year
			dt.setDate(dt.getDate() + (p_Number*7));
			break;
		}
		case "h": {		// hour
			dt.setHours(dt.getHours() + p_Number);
			break;
		}
		case "n": {		// minute
			dt.setMinutes(dt.getMinutes() + p_Number);
			break;
		}
		case "s": {		// second
			dt.setSeconds(dt.getSeconds() + p_Number);
			break;
		}
		case "ms": {		// second
			dt.setMilliseconds(dt.getMilliseconds() + p_Number);
			break;
		}
		default: {
			return "invalid interval: '" + p_Interval + "'";
		}
	}
	return dt;
}



// REQUIRES: isDate()
// NOT SUPPORTED: firstdayofweek and firstweekofyear (defaults for both)
function dateDiff(p_Interval, p_Date1, p_Date2, p_firstdayofweek, p_firstweekofyear){
	if(!isDate(p_Date1)){return "invalid date: '" + p_Date1 + "'";}
	if(!isDate(p_Date2)){return "invalid date: '" + p_Date2 + "'";}
	var dt1 = new Date(p_Date1);
	var dt2 = new Date(p_Date2);

	// get ms between dates (UTC) and make into "difference" date
	var iDiffMS = dt2.valueOf() - dt1.valueOf();
	var dtDiff = new Date(iDiffMS);

	// calc various diffs
	var nYears  = dt2.getUTCFullYear() - dt1.getUTCFullYear();
	var nMonths = dt2.getUTCMonth() - dt1.getUTCMonth() + (nYears!=0 ? nYears*12 : 0);
	var nQuarters = parseInt(nMonths/3);	//<<-- different than VBScript, which watches rollover not completion
	
	var nMilliseconds = iDiffMS;
	var nSeconds = parseInt(iDiffMS/1000);
	var nMinutes = parseInt(nSeconds/60);
	var nHours = parseInt(nMinutes/60);
	var nDays  = parseInt(nHours/24);
	var nWeeks = parseInt(nDays/7);


	// return requested difference
	var iDiff = 0;		
	switch(p_Interval.toLowerCase()){
		case "yyyy": return nYears;
		case "q": return nQuarters;
		case "m": return nMonths;
		case "y": 		// day of year
		case "d": return nDays;
		case "w": return nDays;
		case "ww":return nWeeks;		// week of year	// <-- inaccurate, WW should count calendar weeks (# of sundays) between
		case "h": return nHours;
		case "n": return nMinutes;
		case "s": return nSeconds;
		case "ms":return nMilliseconds;	// millisecond	// <-- extension for JS, NOT available in VBScript
		default: return "invalid interval: '" + p_Interval + "'";
	}
}



// REQUIRES: isDate(), dateDiff()
// NOT SUPPORTED: firstdayofweek and firstweekofyear (does system default for both)
function datePart(p_Interval, p_Date, p_firstdayofweek, p_firstweekofyear){
	if(!isDate(p_Date)){return "invalid date: '" + p_Date + "'";}

	var dtPart = new Date(p_Date);
	switch(p_Interval.toLowerCase()){
		case "yyyy": return dtPart.getFullYear();
		case "q": return parseInt(dtPart.getMonth()/3)+1;
		case "m": return dtPart.getMonth()+1;
		case "y": return dateDiff("y", "1/1/" + dtPart.getFullYear(), dtPart);			// day of year
		case "d": return dtPart.getDate();
		case "w": return dtPart.getDay();	// weekday
		case "ww":return dateDiff("ww", "1/1/" + dtPart.getFullYear(), dtPart);		// week of year
		case "h": return dtPart.getHours();
		case "n": return dtPart.getMinutes();
		case "s": return dtPart.getSeconds();
		case "ms":return dtPart.getMilliseconds();	// millisecond	// <-- extension for JS, NOT available in VBScript
		default: return "invalid interval: '" + p_Interval + "'";
	}
}


// REQUIRES: isDate()
// NOT SUPPORTED: firstdayofweek (does system default)
function weekdayName(p_Date, p_abbreviate){
	if(!isDate(p_Date)){return "invalid date: '" + p_Date + "'";}
	var dt = new Date(p_Date);
	var retVal = dt.toString().split(' ')[0];
	var retVal = Array('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday')[dt.getDay()];
	if(p_abbreviate==true){retVal = retVal.substring(0, 3)}	// abbr to 1st 3 chars
	return retVal;
}
// REQUIRES: isDate()
function monthName(p_Date, p_abbreviate){
	if(!isDate(p_Date)){return "invalid date: '" + p_Date + "'";}
	var dt = new Date(p_Date);	
	var retVal = Array('January','February','March','April','May','June','July','August','September','October','November','December')[dt.getMonth()];
	if(p_abbreviate==true){retVal = retVal.substring(0, 3)}	// abbr to 1st 3 chars
	return retVal;
}


function dateFormat(aDate, displayPat){
    /********************************************************
    *   Valid Masks:
    *   !mmmm = Long month (eg. January)
    *   !mmm = Short month (eg. Jan)
    *   !mm = Numeric date (eg. 07)
    *   !m = Numeric date (eg. 7)
    *   !dddd = Long day (eg. Monday)
    *   !ddd = Short day (eg. Mon)
    *   !dd = Numeric day (eg. 07)
    *   !d = Numeric day (eg. 7)
    *   !yyyy = Year (eg. 1999)
    *   !yy = Year (eg. 99)
   ********************************************************/

    intMonth = aDate.getMonth();
    intDate = aDate.getDate();
    intDay = aDate.getDay();
    intYear = aDate.getFullYear();

    var months_long =  new Array ('January','February','March','April',
       'May','June','July','August','September','October','November',
       'December')
    var months_short = new Array('Jan','Feb','Mar','Apr','May','Jun',
       'Jul','Aug','Sep','Oct','Nov','Dec')
    var days_long = new Array('Sunday','Monday','Tuesday','Wednesday',
       'Thursday','Friday','Saturday')
    var days_short = new Array('Sun','Mon','Tue','Wed','Thu','Fri',
        'Sat')

    var mmmm = months_long[intMonth]
    var mmm = months_short[intMonth]
    var mm = intMonth < 9?'0'+ (1 + intMonth) + '':(1+intMonth)+'';
    var m = 1+intMonth+'';
    var dddd = days_long[intDay];
    var ddd = days_short[intDay];
    var dd = intDate<10?'0'+intDate+'':intDate+'';
    var d = intDate+'';
    var yyyy = intYear;
	
    century = 0;
    while((intYear-century)>=100)
        century = century + 100;

    var yy = intYear - century
    if(yy<10)
        yy = '0' + yy + '';

    displayDate = new String(displayPat);

    displayDate = displayDate.replace(/!mmmm/i,mmmm);
    displayDate = displayDate.replace(/!mmm/i,mmm);
    displayDate = displayDate.replace(/!mm/i,mm);
    displayDate = displayDate.replace(/!m/i,m);
    displayDate = displayDate.replace(/!dddd/i,dddd);
    displayDate = displayDate.replace(/!ddd/i,ddd);
    displayDate = displayDate.replace(/!dd/i,dd);
    displayDate = displayDate.replace(/!d/i,d);
    displayDate = displayDate.replace(/!yyyy/i,yyyy);
    displayDate = displayDate.replace(/!yy/i,yy);

    return displayDate;
}







// ====================================

// bootstrap different capitalizations
function IsDate(p_Expression){
	return isDate(p_Expression);
}
function DateAdd(p_Interval, p_Number, p_Date){
	return dateAdd(p_Interval, p_Number, p_Date);
}
function DateDiff(p_interval, p_date1, p_date2, p_firstdayofweek, p_firstweekofyear){
	return dateDiff(p_interval, p_date1, p_date2, p_firstdayofweek, p_firstweekofyear);
}
function DatePart(p_Interval, p_Date, p_firstdayofweek, p_firstweekofyear){
	return datePart(p_Interval, p_Date, p_firstdayofweek, p_firstweekofyear);
}
function WeekdayName(p_Date){
	return weekdayName(p_Date);
}
function MonthName(p_Date){
	return monthName(p_Date);
}