watcher.js

var Client = require('node-rest-client').Client;
var client = new Client();

// Keys are stringified userId-questionId pairs
// Values are the last activity time
var watcher = {};

var url = 'https://api.stackexchange.com/2.2/';
var questionAnswerUrlAppend = '?site=stackoverflow';

function getLastActivityTime(questionId) {
	var questionUrl = url + '/questions/' + questionId + questionAnswerUrlAppend;

	console.log(questionUrl);

	var lastActivityDate = 0;

    client.get(questionUrl, function (data, response) {
    	lastActivityDate = data.items[0].last_activity_date;
        console.log("Last Activity Date - " + lastActivityDate); 
    });

    return lastActivityDate;
}

function checkForUpdates(callback) {
	console.log("Checking for updates");
	
	console.log(watcher);

	for(toWatchObj in watcher) {
		currentTime = watcher[toWatchObj];
	
		console.log(toWatchObj);

		var questionId = toWatchObj.split(",")[1];
		var userId = toWatchObj.split(",")[0];

		console.log("Question id: " + questionId);

		var newTime = getLastActivityTime(questionId);

		console.log("Current known last activity time: " + currentTime);

		if (newTime + 10 > currentTime){
			console.log("Sending message to bot")
			event = {'userId': userId}
			callback(userId, questionId);
			watcher[questionId] =  newTime;
		}
	}
}

module.exports = {

	getWatchList: function(userId){
		console.log("Inside getWatchList");
		var map = {};
		for(toWatchObj in watcher) {
			currentTime = watcher[toWatchObj];
	
			console.log(toWatchObj);

			var questionId = toWatchObj.split(",")[1];
			var userId = toWatchObj.split(",")[0];

			if(!(userId in map)){
				map[userId]=[];
			}
			map[userId].push(questionId);
			
		}
		return map;
	},
	addWatcher: function (userId, questionId) {
		console.log("Now watching for userId = " + userId + ", questionId = " + questionId);
		watcher[[userId, questionId]] = getLastActivityTime(questionId);
	},

	startWatcher: function (callback) {
		console.log("Starting watcher");
		setInterval(function(){checkForUpdates(callback);}, 300000);
	}
};