/******************************************************************************
 * File:				incEmail.js	
 *	Author:				atsung
 *  Created:			05/20/2003	
 *	Description:		
 *
 *	Functions:			
 *	Notes:
 *	TODO:			
 *	History:
 */

/*=============================================================================
 * Public Function
 * Usage:	
 *
 * Input:	
 *
 * Output:		
 *			
 * Notes: 
 */
function CheckEmail(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("Please enter a valid e-mail address!");
		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 or four-letter word (like com, edu, gov, info) 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 three letter word.
		alert("The address extension must not be greater than four characters.");
		return (false);
	}

	// Make sure there's a host name preceding the domain.
	if (len < 2) {
		alert("This address is missing a hostname!");
		return (false);
	}

	// If we've gotten this far, everything's valid!
	return (true);
}