function getField(fieldName) {
	// Returns the object specified.
	return document.getElementById(fieldName);
}

function isEmpty(fieldName) {
	if(getField(fieldName).value == "")
		return true;
	else
		return false;
}

// Date validation routines.
function isInteger(s) {
	var i;
    for (i = 0; i < s.length; i++){   
        // Check that current character is number.
        var c = s.charAt(i);
        if (((c < "0") || (c > "9"))) return false;
    }
    // All characters are numbers.
    return true;
}

function stripCharsInBag(s, bag) {
	var i;
    var returnString = "";
    // Search through string's characters one by one.
    // If character is not in bag, append to returnString.
    for (i = 0; i < s.length; i++){   
        var c = s.charAt(i);
        if (bag.indexOf(c) == -1) returnString += c;
    }
    return returnString;
}

function daysInFebruary (year) {
	// February has 29 days in any year evenly divisible by four,
    // EXCEPT for centurial years which are not also divisible by 400.
    return (((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0))) ? 29 : 28 );
}

function DaysArray(n) {
	for (var i = 1; i <= n; i++) {
		this[i] = 31;
		if (i==4 || i==6 || i==9 || i==11) {this[i] = 30};
		if (i==2) {this[i] = 29};
   } 
   return this;
}

function isDate(fieldName) {
	// Returns true if a text field contains a valid date value.
	var dtStr = getField(fieldName).value;
	var minYear = 1900;
	var maxYear = 2100;
	var dtCh = "/";
	var daysInMonth = DaysArray(12);
	var pos1 = dtStr.indexOf(dtCh);
	var pos2 = dtStr.indexOf(dtCh, pos1+1);
	var strMonth = dtStr.substring(0, pos1);
	var strDay = dtStr.substring(pos1+1, pos2);
	var strYear = dtStr.substring(pos2+1);
	
	strYr = strYear;
	
	if (strDay.charAt(0) == "0" && strDay.length > 1) 
		strDay = strDay.substring(1);
	
	if (strMonth.charAt(0) == "0" && strMonth.length > 1) 
		strMonth=strMonth.substring(1);
		
	for (var i = 1; i <= 3; i++) {
		if (strYr.charAt(0) == "0" && strYr.length > 1) 
			strYr = strYr.substring(1);
	}
	
	month = parseInt(strMonth);
	day = parseInt(strDay);
	year = parseInt(strYr);
	
	if (pos1 == -1 || pos2 == -1)
		return false;
	
	if (strMonth.length < 1 || month < 1 || month > 12)
		return false;
	
	if (strDay.length < 1 || day < 1 || day > 31 || (month == 2 && day > daysInFebruary(year)) || day > daysInMonth[month])
		return false;
	
	if (strYear.length != 4 || year == 0 || year < minYear || year > maxYear)
		return false;
	
	if (dtStr.indexOf(dtCh,pos2+1) != -1 || isInteger(stripCharsInBag(dtStr, dtCh)) == false)
		return false;
			
	return true;
}

// Make sure the proper main page photo and logo appears.
window.onload = function() {
	// This function ensures that every page loaded in the content IFRAME
	// triggers the appropriate photo to appear to the left.
	if(window.contentCategory) {
		var newPhoto = null;
		
		if(top.document.getElementById("mainPagePhoto") && contentCategory != "") {
			newPhoto = "/images/mainPhoto_" + contentCategory + ".jpg";		
			top.document.getElementById("mainPagePhoto").src = newPhoto;
		}	
		
		// Be sure the GLEMP logo goes back atop the page.  It doesn't appear
		// on the home page because the main photo contains the logo.
		if(top.document.getElementById("topLeftLogo").src.indexOf("/images/blank.gif"))
			top.document.getElementById("topLeftLogo").src = "/images/glemp.gif";
	}
}