• gpings.js

function storageAvailable(type) {
	try {
		var storage = window[type],
			x = '__storage_test__';
		storage.setItem(x, x);
		storage.removeItem(x);
		return true;
	}
	catch(e) {
		return false;
	}
}

var observeDOM = (function(){
    var MutationObserver = window.MutationObserver || window.WebKitMutationObserver,
        eventListenerSupported = window.addEventListener;

    return function(obj, callback){
        if( MutationObserver ){
            // define a new observer
            var obs = new MutationObserver(function(mutations, observer){
                if( mutations[0].addedNodes.length || mutations[0].removedNodes.length )
                    callback();
            });
            // have the observer observe foo for changes in children
            obs.observe( obj, { childList:true, subtree:true });
        }
        else if( eventListenerSupported ){
            obj.addEventListener('DOMNodeInserted', callback, false);
            obj.addEventListener('DOMNodeRemoved', callback, false);
        }
    }
})();

// add the button for adding a group
var btn = document.createElement("button");
btn.innerHTML = "add/remove a group";
btn.id = "group-add";
btn.className = "button";
btn.addEventListener("click", function(){
	if(!storageAvailable("localStorage")){
		alert("ERROR: no storage available/storage unsupported");
		return;
	}
	var groupName = prompt("enter the name of the group");
	// validate name--cannot have { or } in it.
	localStorage.chatGroups = localStorage.chatGroups || "{}";
	var ch = JSON.parse(localStorage.chatGroups);
	ch[groupName] = !ch[groupName];
	alert((ch[groupName] ? "You are now" : "You are no longer") + " listening to group notifications for @{"+ groupName + "}");
	localStorage.chatGroups = JSON.stringify(ch);
});
document.getElementById("chat-buttons").appendChild(btn);

var lastMessage = "";

observeDOM(document.getElementById("chat"), function(){
	// get groups
	if(!storageAvailable("localStorage")){
		alert("ERROR: no storage available/storage unsupported");
		return;
	}
	// get most recent message
	var msg = document.querySelector(".user-container:last-child [id^='message-']:last-child .content");
	// get innards
	var txt = msg.innerText || msg.innerHTML;
	if(lastMessage === txt) return;	// don't ping the same message twice
	lastMessage = txt;
	var groupPings = txt.match(/@\{[^{}]+?\}/g);
	if(!groupPings) return;
	
	var ch = JSON.parse(localStorage.chatGroups);
	
	// iterate through pings
	for(var i = 0; i < groupPings.length; i++){
		var ping = groupPings[i].slice(2, -1);
		// console.log(ch[ping], ping, ch);
		if(ch[ping]){
			// break and ping
			new Audio("http://cdn-chat.sstatic.net/chat/se.mp3").play();
			break;
		}
	}
});