/*
	'##############################################################################
	'#####
	'						EMAIL CHECK FUNCTION
	'	OVERVIEW  - This function will take a string and check to see whether or
	'				not it fits all the rules for a valid Email address
	'	
	'	PROTOTYPE - function emailCheck (emailStr) 
	'	
	'   VARIABLE DEFINITIONS:
	'		Input  - 
	'				.emailStr = String to check whether or not its a valid Email
	'		
	'		Output - 
	'	
	'	RETURNS   - True if its a valid email, false if not
	'#####
	'##############################################################################
*/
	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>4) 
	{
	   // the address must end in a two letter or four letter word.
	   //alert("The address must end in a three-letter domain, four-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;
}