function IsLetter() {

  var a = (event.keyCode >= 65) && (event.keyCode <= 90)
  var b = (event.keyCode >= 97) && (event.keyCode <= 122)
  var c = (event.keyCode >= 192) && (event.keyCode <= 221)
  var d = (event.keyCode >= 224) && (event.keyCode <= 255)
  var e = (event.keyCode == 32)

  return (a||b||c||d||e)
}

function IsDigit() {
  return ((event.keyCode >= 48) && (event.keyCode <= 57))
}


function isValidDateMinYear(dateStr, minYear) {
  // Checks for the following valid date formats: DD-MM-YYYY
  // YYYY>=minYear

  var datePat = /^(\d{1,2})(-)(\d{1,2})\2(\d{4})$/;

  var matchArray = dateStr.match(datePat);
  if (matchArray == null)
    return false;

  var day = matchArray[1];
  var month = matchArray[3];
  var year = matchArray[4];

  if (year<minYear)
    return false;

  if (month < 1 || month > 12 || day < 1 || day > 31 || ((month==4 || month==6 || month==9 || month==11) && day==31))
    return false;

  if (month == 2) {
    if (day>29 || (day==29 && !(year % 4 == 0 && (year % 100 != 0 || year % 400 == 0))))
      return false;
  }

  return true;
}


function isValidDate(dateStr) {
  // Checks for the following valid date formats: DD-MM-YYYY

  var datePat = /^(\d{1,2})(-)(\d{1,2})\2(\d{4})$/;

  var matchArray = dateStr.match(datePat);
  if (matchArray == null)
    return false;

  var day = matchArray[1];
  var month = matchArray[3];
  var year = matchArray[4];

  if (month < 1 || month > 12 || day < 1 || day > 31 || ((month==4 || month==6 || month==9 || month==11) && day==31))
    return false;

  if (month == 2) {
    if (day>29 || (day==29 && !(year % 4 == 0 && (year % 100 != 0 || year % 400 == 0))))
      return false;
  }

  return true;
}


function isValidTime(timeStr) {
  // Checks for the following valid date formats: HH:MM

  var timePat = /^(\d{1,2})(:)(\d{1,2})$/;

  var matchArray = timeStr.match(timePat);
  if (matchArray == null)
    return false;

  var hours = matchArray[1];
  var minutes = matchArray[3];

  if (hours < 0 || hours > 24 || minutes < 0 || minutes > 59)
    return false;
  else
    return true;
}


function trim(str) {
	// Returns the input String without the inicial and end spaces(' ')
	var result=str;
	while (result.charAt(0)==' '){
		result=result.substring(1,result.length);
	}
	while (result.charAt(result.length-1)==' '){
		result=result.substring(0,result.length-1);
	}
	return result;	
}

//just verifies if the string contains '@';
//must be improved
function isValidEmail(str) {
	var trimedStr = trim(str);
	if( !(trimedStr=='' || trimedStr==' ') ){
		for (i=0;i<trimedStr.length;i++){
			if(trimedStr.charAt(i)=='@') return true;
		}     
		return false;
	}else{
		return false;
	}
}


function emailCheck(emailStr) 
{
	/*
		The following pattern is used to check if the entered e-mail address
		fits the user@domain format.  It also is used to separate the username
		from the domain. 
	*/
	var emailPat=/^(.+)@(.+)$/

	/*
		The following string represents the pattern for matching all special
		characters.  We don't want to allow special characters in the address. 
		These characters include ( ) < > @ , ; : \ " . [ ]    
	*/
	var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]"

	/*
		The following string represents the range of characters allowed in a 
		username or domainname.  It really states which chars aren't allowed. 
	*/
	var validChars="\[^\\s" + specialChars + "\]"

	/*
		The following pattern applies if the "user" is a quoted string (in
		which case, there are no rules about which characters are allowed
		and which aren't; anything goes).  E.g. "jiminy cricket"@disney.com
		is a legal e-mail address. 
	*/
	var quotedUser="(\"[^\"]*\")"

	/*
		The following pattern applies for domains that are IP addresses,
		rather than symbolic names.  E.g. joe@[123.124.233.4] is a legal
		e-mail address. NOTE: The square brackets are required. 
	*/
	var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/

	/*
		The following string represents an atom (basically a series of
		non-special characters.) 
	*/
	var atom=validChars + '+'

	/*
		The following string represents one word in the typical username.
		For example, in john.doe@somewhere.com, john and doe are words.
		Basically, a word is either an atom or quoted string.
	*/
	var word="(" + atom + "|" + quotedUser + ")"

	// The following pattern describes the structure of the user
	var userPat=new RegExp("^" + word + "(\\." + word + ")*$")

	/*
		The following pattern describes the structure of a normal symbolic
		domain, as opposed to ipDomainPat, shown above. 
	*/
	var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$")
 

	/*
		Finally, let's start trying to figure out if the supplied address is
		valid.
	*/
 
	/*
		Begin with the coarse pattern to simply break up user@domain into
		different pieces that are easy to analyze.
	*/
	var matchArray=emailStr.match(emailPat)
	if (matchArray==null)
	{
		/*
			Too many/few @'s or something; basically, this address doesn't
			even fit the general mould of a valid e-mail address.
		*/
		//alert("Email address seems incorrect (check @ and .'s)")
		return false
	}
	var user=matchArray[1]
	var domain=matchArray[2]
 
	// See if "user" is valid 
	if (user.match(userPat)==null) 
	{
		// user is not valid
		//alert("The username doesn't seem to be valid.")
		return false
	}
 
	/*
		if the e-mail address is at an IP address (as opposed to a symbolic
		host name) make sure the IP address is valid.
	*/
	var IPArray=domain.match(ipDomainPat)
	if (IPArray!=null) 
	{
		// this is an IP address
		for (var i=1;i<=4;i++)
		{
			if (IPArray[i]>255) 
			{
				//alert("Destination IP address is invalid!")
				return false
			}
		}
	return true
	}
 
	// Domain is symbolic name
	var domainArray=domain.match(domainPat)
	if (domainArray==null) 
	{
		//alert("The domain name doesn't seem to be valid.")
		return false
	}
 
	/*
		domain name seems valid, but now make sure that it ends in a
		three-letter word (like com, edu, gov) or a two-letter word,
		representing country (uk, nl), and that there's a hostname preceding 
		the domain or country. 
	*/
 
	/* Now we need to break up the domain to get a count of how many atoms
		it consists of.
	*/
	var atomPat=new RegExp(atom,"g")
	var domArr=domain.match(atomPat)
	var len=domArr.length
	if (domArr[domArr.length-1].length<2 || 
		domArr[domArr.length-1].length>3) 
	{
		// the address must end in a two letter or three letter word.
		//alert("The address must end in a three-letter domain, or two letter country.")
		return false
	}
 
	// Make sure there's a host name preceding the domain.
	if (len<2) 
	{
		var errStr="This address is missing a hostname!"
		//alert(errStr)
		return false
	}
 
	// If we've gotten this far, everything's valid!
	return true;
}