MagicMirror/modules/newsfeed/fetcher.js

/* Magic Mirror
 * Fetcher
 *
 * By Michael Teeuw http://michaelteeuw.nl
 * MIT Licensed.
 */

var NewsFetcher = require('./newsfetcher.js'); 

/* Fetcher
 * Responsible for requesting an update on the set interval and broadcasting the data.
 *
 * attribute url string - URL of the news feed.
 * attribute reloadInterval number - Reload interval in milliseconds.
 */

var Fetcher = function(url, reloadInterval) {
	var self = this;
	var newsFetcher = new NewsFetcher();
	if (reloadInterval < 1000) {
		reloadInterval = 1000;
	}
	
	var reloadTimer = null;
	var items = [];

	var fetchFailedCallback = function() {};
	var itemsReceivedCallback = function() {};

	/* private methods */

	/* fetchNews()
	 * Request the new items from the newsFetcher.
	 */

	var fetchNews = function() {
		//console.log('Fetch news.');
		clearTimeout(reloadTimer);
		reloadTimer = null;
		newsFetcher.fetchNews(url, function(fetchedItems) {
			items = fetchedItems;
			self.broadcastItems();
			scheduleTimer();
		}, function(error) {
			fetchFailedCallback(self, error);
			scheduleTimer();
		});
	};

	/* scheduleTimer()
	 * Schedule the timer for the next update.
	 */

	var scheduleTimer = function() {
		//console.log('Schedule update timer.');
		clearTimeout(reloadTimer);
		reloadTimer = setTimeout(function() {
			fetchNews();
		}, reloadInterval);
	};

	/* public methods */

	/* setReloadInterval()
	 * Update the reload interval, but only if we need to increase the speed.
	 *
	 * attribute interval number - Interval for the update in milliseconds.
	 */
	this.setReloadInterval = function(interval) {
		if (interval > 1000 && interval < reloadInterval) {
			reloadInterval = interval;
		}
	};

	/* startFetch()
	 * Initiate fetchNews();
	 */
	this.startFetch = function() {
		fetchNews();
	};

	/* broadcastItems()
	 * Broadcast the exsisting items.
	 */
	this.broadcastItems = function() {
		if (items.length <= 0) {
			//console.log('No items to broadcast yet.');
			return;
		}
		//console.log('Broadcasting ' + items.length + ' items.');
		itemsReceivedCallback(self);
	};

	this.onReceive = function(callback) {
		itemsReceivedCallback = callback;
	};

	this.onError = function(callback) {
		fetchFailedCallback = callback;
	};

	this.url = function() {
		return url;
	};

	this.items = function() {
		return items;
	};
};

module.exports = Fetcher;