var sendReq 	= getXmlHttpRequestObject();
var receiveReq 	= getXmlHttpRequestObject();
var lastMessage = 0;
var mTimer;
//Function for initializating the page.
function startChat() {
	//Set the focus to the Message Box.
	document.getElementById('txt_message').focus();
	//Start Recieving Messages.
	getChatText();
}		

//Gets the browser specific XmlHttpRequest Object
function getXmlHttpRequestObject() {
	return (window.XMLHttpRequest) ? new XMLHttpRequest() : ((window.ActiveXObject) ? new ActiveXObject('Microsoft.XMLHTTP') : false);
}

//Gets the current messages from the server
function getChatText() {
	if (receiveReq.readyState == 4 || receiveReq.readyState == 0) {
		receiveReq.open("GET", 'Chat/getChat.php?chat=1&last=' + lastMessage, true);
		receiveReq.onreadystatechange = handleReceiveChat; 
		receiveReq.send(null);
	}			
}

//Add a message to the chat server.
function sendChatText() {
	if(document.getElementById('txt_message').value == '') {
		return;
	}
	if (sendReq.readyState == 4 || sendReq.readyState == 0) {
		sendReq.open("POST", 'Chat/getChat.php?chat=1&last=' + lastMessage, true);
		sendReq.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
		sendReq.onreadystatechange = handleSendChat; 
		var param = 'message=' + document.getElementById('txt_message').value;
		param += '&name=' + getCookie('UserName');
		param += '&chat=1';
		sendReq.send(param);
		document.getElementById('txt_message').value = '';
	}							
}
//When our message has been sent, update our page.
function handleSendChat() {
	//Clear out the existing timer so we don't have 
	//multiple timer instances running.
	clearInterval(mTimer);
	getChatText();
}
//Function for handling the return of chat text
function handleReceiveChat() {
	if (receiveReq.readyState == 4) {
		var chat_div = document.getElementById('div_chat');
		var xmldoc = receiveReq.responseXML;
		var message_nodes = xmldoc.getElementsByTagName("message"); 
		var n_messages = message_nodes.length
		for (i = 0; i < n_messages; i++) {
			var user_node = message_nodes[i].getElementsByTagName("user");
			var text_node = message_nodes[i].getElementsByTagName("text");
			var time_node = message_nodes[i].getElementsByTagName("time");
			chat_div.innerHTML += user_node[0].firstChild.nodeValue + '&nbsp;says:&nbsp;';
			chat_div.innerHTML += '<font class="chat_time">' + time_node[0].firstChild.nodeValue + '</font><br />';
			chat_div.innerHTML += text_node[0].firstChild.nodeValue + '<br />';
			chat_div.scrollTop = chat_div.scrollHeight;
			lastMessage = (message_nodes[i].getAttribute('id'));
		}
		mTimer = setTimeout('getChatText();',5000); //Refresh our chat in 2 seconds
	}
}
//This functions handles when the user presses enter.  Instead of submitting the form, we
//send a new message to the server and return false.
function blockSubmit() {
	sendChatText();
	return false;
}
//This cleans out the database so we can start a new chat session.
function resetChat() {
	if (sendReq.readyState == 4 || sendReq.readyState == 0) {
		sendReq.open("POST", 'Chat/getChat.php?chat=1&last=' + lastMessage, true);
		sendReq.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
		sendReq.onreadystatechange = handleResetChat; 
		var param = 'action=reset';
		sendReq.send(param);
		document.getElementById('txt_message').value = '';
	}							
}
//This function handles the response after the page has been refreshed.
function handleResetChat() {
	document.getElementById('div_chat').innerHTML = '';
	getChatText();
}