// ** BEGIN GENERAL FUNCTIONS **

function isEmpty(inputStr) {
	if (inputStr == "" || inputStr == null) {
		return true	
	}
	return false
}

function inRange(inputStr, lo, hi) {
	var num = parseInt(inputStr, 10)
	if (num < lo || num > hi) {
		return false	
	}
	return true
}

// extract front part of string prior to searchString
function getFront(mainStr,searchStr) {
	foundOffset = mainStr.indexOf(searchStr)
	if (foundOffset == -1) {
		return null	
	}
	return mainStr.substring(0,foundOffset)
}
// extract back end of string after searchString
function getEnd(mainStr,searchStr) {
	foundOffset = mainStr.indexOf(searchStr)
	if (foundOffset == -1) {
		return null
	}
	return mainStr.substring(foundOffset+searchStr.length,mainStr.length)
}
// replace searchString with replaceString
function replaceString(mainStr,searchStr,replaceStr) {
	var front = getFront(mainStr,searchStr)
	var end = getEnd(mainStr,searchStr)
	if (front != null && end != null) {
		return front + replaceStr + end
	}
	return null
}

 function select(field) {
 	field.focus()
 	field.select()
 }
 
// ** END GENERAL FUNCTIONS **

// ** BEGIN DATE VALIDATION **

function checkDate(field) {
	var inputStr = field.value
	if (!isEmpty(inputStr)) {
		// convert hypen delimiters to slashes
		while (inputStr.indexOf("-") != -1) {
			inputStr = replaceString(inputStr,"-","/")
		}
		var delim1 = inputStr.indexOf("/")
		var delim2 = inputStr.lastIndexOf("/")
		if (delim1 != -1 && delim1 == delim2) {
			//there is only one delimiter in the string
			alert("The date entered is not in an acceptable format.\n\nPlease use the following format:\nm/d/y, or m-d-y.")
			select(field)
			return false
		}
		if (delim1 != -1) {
			var mm = parseInt(inputStr.substring(0,delim1),10)
			var dd = parseInt(inputStr.substring(delim1 + 1,delim2),10)
			var yyyy = parseInt(inputStr.substring(delim2 + 1, inputStr.length),10)
		}
		if (isNaN(mm) || isNaN(dd) || isNaN(yyyy)) {
			// there is a non-numeric character in one of the component values
			alert("The date entered is not in an acceptable format.\n\nYou can enter dates in the following formats:\nm/d/y, or m-d-y.")
			select(field)
			return false
		}
		if (!inRange(mm,1,12)){
			// month value is not 1 through 12
			alert("Months must be entered between the range of 01 (January) and 12 (December).")
			select(field)
			return false
		}
		if (dd < 1 || dd > 31) {
			// date value is not 1 through 31
			alert("Days must be entered between the range of 01 and a maximum of 31.")
			select(field)
			return false
		}
		if (yyyy <=10) {
			// entered value is two digits, which we allow for 2000-2010
			yyyy += 2000
		}
		if (!checkMonthLength(mm,dd)) {
			select(field)
			return false
		}
		if (mm == 2 && (!checkLeapMonth(mm,dd,yyyy))) {
			select(field)
			return true
		}
		// return date as string to field
		field.value = monthDayFormat(mm) + "/" + monthDayFormat(dd) + "/" + yyyy
		return true
	}
}

// check the entered month for too high a value
function checkMonthLength(mm,dd) {
	var months = new Array("","January", "February","March","April","May","June","July","August","September","October","November","December")
	if ((mm == 4 || mm == 6 || mm == 9 || mm == 11) && dd > 30) {
		alert(months[mm] + " has only 30 days.")
		return false
	} else  if (dd > 31) {
		alert(months[mm] + "has only 31 days.")
		return false
	}
	return true
}

// check the entered February date for too high a value
function checkLeapMonth(mm,dd,yyyy) {
	if (yyyy % 4 > 0 && dd > 28) {
		alert("February of " + yyyy + " has only 28 days.")
		return false	
	} else if (dd > 29) {
		alert("February of " + yyyy + " has only 29 days.")
		return false
	}
	return true
}

// convert month or day number to string,
// padding with leading zero if needed
function monthDayFormat(val) {
          if (isNaN(val) || val == 0) {
             alert("Month or date value is not a number.")
             return false
          } else if (val < 10) {
             return "0" + val
          }
          return "" + val
}
// ** END DATE VALIDATION **