// FormBasic.js
//
// Required Includes: FormGlobal.js
//
// SUMMARY
//
// This is a set of JavaScript functions for validating basic input on 
// an HTML form.  Functions are provided to validate:
//
//	- dates (entry of year, month, and day and validity of combined date)
//
// Supporting utility functions validate that:
//
//  - characters are Letter, Digit, or LetterOrDigit
//  - strings are a Signed, Positive, Negative, Nonpositive, or
//    Nonnegative integer
//  - strings are a Float or a SignedFloat
//  - strings are Alphabetic, Alphanumeric, or Whitespace
//  - strings contain an integer within a specified range
//
// Many of the below functions take an optional parameter eok (for "emptyOK")
// which determines whether the empty string will return true or false.
// Default behavior is controlled by global variable defaultEmptyOK.
//
// BASIC DATA VALIDATION FUNCTIONS:
//
// isWhitespace (s)                    Check whether string s is empty or whitespace.
// isLetter (c)                        Check whether character c is an English letter 
// isDigit (c)                         Check whether character c is a digit 
// isLetterOrDigit (c)                 Check whether character c is a letter or digit.
// isInteger (s [,eok])                True if all characters in string s are numbers.
// isSignedInteger (s [,eok])          True if all characters in string s are numbers; leading + or - allowed.
// isPositiveInteger (s [,eok])        True if string s is an integer > 0.
// isNonnegativeInteger (s [,eok])     True if string s is an integer >= 0.
// isNegativeInteger (s [,eok])        True if s is an integer < 0.
// isNonpositiveInteger (s [,eok])     True if s is an integer <= 0.
// isFloat (s [,eok])                  True if string s is an unsigned floating point (real) number. (Integers also OK.)
// isSignedFloat (s [,eok])            True if string s is a floating point number; leading + or - allowed. (Integers also OK.)
// isAlphabetic (s [,eok])             True if string s is English letters 
// isAlphanumeric (s [,eok])           True if string s is English letters and numbers only.
// isYear (s [,eok])                   True if string s is a valid Year number.
// isIntegerInRange (s, a, b [,eok])   True if string s is an integer between a and b, inclusive.
// isMonth (s [,eok])                  True if string s is a valid month between 1 and 12.
// isDay (s [,eok])                    True if string s is a valid day between 1 and 31.
// daysInFebruary (year)               Returns number of days in February of that year.
// isDate (year, month, day)           True if string arguments form a valid date.
// isDateStr(s [,eok])                 True if string forms a valid date.

function makeArray(n) {
   for (var i = 1; i <= n; i++) {
      this[i] = 0
   } 
   return this
}

var daysInMonth = makeArray(12);
daysInMonth[1] = 31;
daysInMonth[2] = 29;   // must programmatically check this
daysInMonth[3] = 31;
daysInMonth[4] = 30;
daysInMonth[5] = 31;
daysInMonth[6] = 30;
daysInMonth[7] = 31;
daysInMonth[8] = 31;
daysInMonth[9] = 30;
daysInMonth[10] = 31;
daysInMonth[11] = 30;
daysInMonth[12] = 31;

function isWhitespace (s)
{   var reWhitespace = /^\s+$/
    return (isEmpty(s) || reWhitespace.test(s));
}
function isLetter (c)
{   var reLetter = /^[a-zA-Z]$/
	return reLetter.test(c)
}
function isDigit (c)
{   var reDigit = /^\d/
	return reDigit.test(c)
}
function isLetterOrDigit (c)
{   var reLetterOrDigit = /^([a-zA-Z]|\d)$/
	return reLetterOrDigit.test(c)
}
function isInteger (s)
{   
	var reInteger = /^\d+$/
	var i;
    if (isEmpty(s)) 
       if (isInteger.arguments.length == 1) return defaultEmptyOK;
       else return (isInteger.arguments[1] == true);
    return reInteger.test(s)
}
function isSignedInteger (s)
{   var reSignedInteger = /^([+-])?\d+$/
	if (isEmpty(s)) 
       if (isSignedInteger.arguments.length == 1) return defaultEmptyOK;
       else return (isSignedInteger.arguments[1] == true);
    else {
       return reSignedInteger.test(s)
    }
}
function isPositiveInteger (s)
{   var secondArg = defaultEmptyOK;
    if (isPositiveInteger.arguments.length > 1)
        secondArg = isPositiveInteger.arguments[1];
    return (isSignedInteger(s, secondArg)
         && ( (isEmpty(s) && secondArg)  || (parseInt (s) > 0) ) );
}
function isNonnegativeInteger (s)
{   var secondArg = defaultEmptyOK;
    if (isNonnegativeInteger.arguments.length > 1)
        secondArg = isNonnegativeInteger.arguments[1];
    return (isSignedInteger(s, secondArg)
         && ( (isEmpty(s) && secondArg)  || (parseInt (s) >= 0) ) );
}
function isNegativeInteger (s)
{   var secondArg = defaultEmptyOK;
    if (isNegativeInteger.arguments.length > 1)
        secondArg = isNegativeInteger.arguments[1];
    return (isSignedInteger(s, secondArg)
         && ( (isEmpty(s) && secondArg)  || (parseInt (s) < 0) ) );
}
function isNonpositiveInteger (s)
{   var secondArg = defaultEmptyOK;
    if (isNonpositiveInteger.arguments.length > 1)
        secondArg = isNonpositiveInteger.arguments[1];
    return (isSignedInteger(s, secondArg)
         && ( (isEmpty(s) && secondArg)  || (parseInt (s) <= 0) ) );
}
function isFloat (s)
{   var reFloat = /^((\d+(\.\d*)?)|((\d*\.)?\d+))$/
	if (isEmpty(s)) 
       if (isFloat.arguments.length == 1) return defaultEmptyOK;
       else return (isFloat.arguments[1] == true);
    return reFloat.test(s)
}
function isSignedFloat (s)
{   var reSignedFloat = /^((([+-])?\d+(\.\d*)?)|(([+-])?(\d*\.)?\d+))$/
	if (isEmpty(s)) 
       if (isSignedFloat.arguments.length == 1) return defaultEmptyOK;
       else return (isSignedFloat.arguments[1] == true);
    else {
       return reSignedFloat.test(s)
    }
}
function isAlphabetic (s)
{   var reAlphabetic = /^[a-zA-Z]+$/
	var i;
    if (isEmpty(s)) 
       if (isAlphabetic.arguments.length == 1) return defaultEmptyOK;
       else return (isAlphabetic.arguments[1] == true);
    else {
       return reAlphabetic.test(s)
    }
}
function isAlphanumeric (s)
{   var reAlphanumeric = /^[a-zA-Z0-9]+$/
	var i;
    if (isEmpty(s)) 
       if (isAlphanumeric.arguments.length == 1) return defaultEmptyOK;
       else return (isAlphanumeric.arguments[1] == true);
    else {
       return reAlphanumeric.test(s)
    }
}
function isYear (s)
{   if (isEmpty(s)) 
       if (isYear.arguments.length == 1) return defaultEmptyOK;
       else return (isYear.arguments[1] == true);
    if (!isNonnegativeInteger(s)) return false;
    return ((s.length == 2) || (s.length == 4));
}
function isIntegerInRange (s, a, b)
{   if (isEmpty(s)) 
       if (isIntegerInRange.arguments.length == 1) return defaultEmptyOK;
       else return (isIntegerInRange.arguments[1] == true);
    if (!isInteger(s, false)) return false;
    var num = parseInt (s);
    return ((num >= a) && (num <= b));
}
function isMonth (s)
{   if (isEmpty(s)) 
       if (isMonth.arguments.length == 1) return defaultEmptyOK;
       else return (isMonth.arguments[1] == true);
    return isIntegerInRange (s, 1, 12);
}
function isDay (s)
{   if (isEmpty(s)) 
       if (isDay.arguments.length == 1) return defaultEmptyOK;
       else return (isDay.arguments[1] == true);   
    return isIntegerInRange (s, 1, 31);
}
function daysInFebruary (year)
{   return (  ((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0) ) ) ? 29 : 28 );
}
function isDate (year, month, day)
{   if (! (isYear(year, false) && isMonth(month, false) && isDay(day, false))) return false;
    var intYear = parseInt(year);
    var intMonth = parseInt(month);
    var intDay = parseInt(day);
    if (intDay > daysInMonth[intMonth]) return false; 
    if ((intMonth == 2) && (intDay > daysInFebruary(intYear))) return false;
    return true;
}
function isDateStr(dateStr) {
    if (isEmpty(dateStr)) 
       if (isDateStr.arguments.length == 1) return defaultEmptyOK;
       else return (isDateStr.arguments[1] == true);
    else {
		var datePat = /^(\d{1,2})(\/|-)(\d{1,2})\2(\d{2}|\d{4})$/;
		var matchArray = dateStr.match(datePat);
		if (matchArray == null) {return false;}
		month = matchArray[1]; // parse date into variables
		day = matchArray[3];
		year = matchArray[4];
		if (month < 1 || month > 12) {return false;}
		if (day < 1 || day > 31) {return false;}
		if ((month==4 || month==6 || month==9 || month==11) && day==31) {return false}
		if (month == 2) {
			var isleap = (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0));
			if (day>29 || (day==29 && !isleap)) {return false;}
		}
	}
	return true
}