// http://javascript.internet.com/forms/check-email.html
// based on version 1.1.2

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)

	// Too many/few @'s or something; basically, this address doesn't
	// even fit the general mould of a valid e-mail address. 
	if (matchArray==null) {
		document.getElementById("err_email").innerText = "Your email address does not appear correct. Please check.";
//		alert("Your email address does not appear correct. Please check.")
//		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
		document.getElementById("err_email").innerText = "Your email address does not appear correct. Please check.";
//		alert("Your email address does not appear correct. Please check.")
//		alert("The username part of the email doesn't seem to be valid. Or you have entered two email addresses!\nPlease only enter one.")
		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) {
				document.getElementById("err_email").innerText = "Your email address does not appear correct. Please check.";
//				alert("Your email address does not appear correct. Please check.")
//				alert("Destination IP address is invalid!")
				return false
			}
		}
		return true
	}

	// Domain is symbolic name
	var domainArray=domain.match(domainPat)
	if (domainArray==null) {
		document.getElementById("err_email").innerText = "Your email address does not appear correct. Please check.";
//		alert("Your email address does not appear correct. Please check.")
//		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>10) {
		// the address must end in a two letter or three letter word.
		document.getElementById("err_email").innerText = "Your email address does not appear correct. Please check.";
//		alert("Your email address does not appear correct. Please check.")
//		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!"
		document.getElementById("err_email").innerText = "Your email address does not appear correct. Please check.";
//		alert("Your email address does not appear correct. Please check.")
//		alert(errStr)
		return false
	}
}