// JavaScript Document
function validName(form) {
    if (isBlank(form.fromName.value)) {
        alert("Please enter your Name.");
        form.fromName.focus();
        return false;
	}
	else if (isBlank(form.toName.value)) {
	    alert("Please enter your Friends Name.");
		form.toName.focus();
		return false;
	}
	return true;
}

function validFromEmail(form) {
    if (isBlank(form.fromAddress.value)) {
        alert("Please enter your email address.");
        form.fromAddress.focus();
        return false;
	}
	
	if (!checkEmailAddress(form.fromAddress.value)) {  
        alert("Please enter a valid email address.");
        form.fromAddress.focus();
        return false;
	}
	return true;
}

function validToEmail(form) {
    if (isBlank(form.toAddress.value)) {
        alert("Please enter your friend's email address.");
        form.toAddress.focus();
        return false;
	}

	if (!checkEmailAddress(form.toAddress.value)) {  
        alert("Please enter a valid email address.");
        form.toAddress.focus();
        return false;
	}
	return true;
}


function validateForm(form) {

    if (!validName(form)) return false;
    if (!validFromEmail(form)) return false;
    if (!validToEmail(form)) return false;
	return true;
}

function isBlank(s) {
	if (s == "") {
		return true;
	}
	for(var i = 0; i < s.length; i++) {
		var c = s.charAt(i);
		if ((c != ' ') && (c != '\n') && (c != '\t'))
			return false;
	}
	return true;
}

function checkEmailAddress( emailStr ) {

	var emailPat=/^(.+)@(.+)$/
	var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]"
	var validChars="\[^\\s" + specialChars + "\]"
	var quotedUser="(\"[^\"]*\")"
	var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/
	var atom=validChars + '+'
	var word="(" + atom + "|" + quotedUser + ")"
	var userPat=new RegExp("^" + word + "(\\." + word + ")*$")
	var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$")

	var matchArray=emailStr.match(emailPat)

	if (matchArray==null) {
		return false
	}

	var user=matchArray[1]
	var domain=matchArray[2]

	if (user.match(userPat)==null) {
	    return false
	}

	var IPArray=domain.match(ipDomainPat)
	if (IPArray!=null) {
		  for (var i=1;i<=4;i++) {
		    if (IPArray[i]>255) {
			return false
		    }
	    }
	    return true
	}

	var domainArray=domain.match(domainPat)
	if (domainArray==null) {
	    return false
	}


	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) {
	   return false
	}

	// Make sure there's a host name preceding the domain.
	if (len<2) {
	   return false
	}
	return true;
}