// holds an instance of XMLHttpRequest
var xmlHttpd = createXmlHttpRequestObject();
 
// read a file from the server
function subscribe() {
	// only continue if xmlHttpd isn't void
	if (xmlHttpd) {
		// try to connect to the server
		try {
			// get the name
			var fname = document.getElementById("sName").value;
			
			// get the email
			var email = document.getElementById("sEmail").value;
			
			
			if (trimText(fname).length < 1){
				alert("Please provide a name!");
				document.getElementById("sName").focus();
			}
			
			else if (isValidEmail(email)==false){
				alert("Please provide a valid email address!");
				document.getElementById("sEmail").focus();
			}
			// Continue Execution
			else {
				// Show Processing Text
				document.getElementById('errText').innerHTML = "Saving...";
			
				// Hide the Contact Form
				document.getElementById('myDivContact').style.visibility = 'hidden';	
				
				// create the params string
				var params = "name=" + fname + "&email=" + email;			
				// initiate the asynchronous HTTP request
				xmlHttpd.open("GET", "ajax_save_contact.php?" + params, true);
				xmlHttpd.onreadystatechange = handleRequestStateChange;
				xmlHttpd.send(null);
			}
		}
		// display the error in case of failure
		catch (e) {
			alert("Can't connect to server:\n" + e.toString());
		}
	}
}

// function called when the state of the HTTP request changes
function handleRequestStateChange() {
	// when readyState is 4, we are ready to read the server response
	if (xmlHttpd.readyState == 4) {
		// continue only if HTTP status is "OK"
		if (xmlHttpd.status == 200) {
			try {
				// do something with the response from the server
				handleServerResponse();
			}
			catch(e) {
				// display error message
				alert("Error reading the response: " + e.toString());
			}
		} 
		else {
			// display status message
			alert("There was a problem retrieving the data:\n" + 
			xmlHttpd.statusText);
		}
	}
}

// handles the response received from the server
function handleServerResponse() {
	// retrieve the server's response packaged as an XML DOM object
	var xmlResponse = xmlHttpd.responseXML;
	// catching potential errors with IE and Opera
	if (!xmlResponse || !xmlResponse.documentElement)
		throw("Invalid XML structure:\n" + xmlHttpd.responseText);
	
	// catching potential errors with Firefox
	var rootNodeName = xmlResponse.documentElement.nodeName;
	if (rootNodeName == "parsererror") 
		throw("Invalid XML structure:\n" + xmlHttpd.responseText);
	// getting the root element (the document element)
	xmlRoot = xmlResponse.documentElement;
	// testing that we received the XML document we expect
	if (rootNodeName != "response" || !xmlRoot.getElementsByTagName("result")[0].firstChild.data)
		throw("Invalid XML structure:\n" + xmlHttpd.responseText);
	// the value we need to display is the child of the root <response> element
	//responseText = xmlRoot.firstChild.data;
	responseText = xmlRoot.getElementsByTagName("result")[0].firstChild.data;
	// build message
	var mesg = (responseText == "1") ? "Details saved successfully. Thank You!" : "Unable to complete request. Please try later!";
	// display the message
	document.getElementById("errText").innerHTML = mesg;
	// Make the contact form visible
	document.getElementById('myDivContact').style.visibility = 'visible';
	// Set default email address value
	document.getElementById('sName').value = 'Name';
	document.getElementById('sEmail').value = 'Primary Email';
}