gcalfilter/gcalfilter.js

This filters the private ICS feed from Google Calendar based on extendedProperties

var vcal = require('vcal');
var NodePie = require('nodepie');
var request = require('request');

var google_base_url = "https://www.google.com/calendar/";

var calendar_id = null;
var calendar_secret = null;

exports.set_calendar_id = function(id) {
	calendar_id = id;
}

exports.set_calendar_secret = function(secret) {
	calendar_secret = secret;
}

exports.filtered_ics_feed = function(filters, callback) {
	if(!calendar_id || !calendar_secret) {
		throw new Error("Can't filter an ICS feed if you don't provide a Calendar ID and Secret first");
	}
	
	var atom_url = google_base_url + "feeds/" + calendar_id + "/private-" + calendar_secret + "/basic";
	var ics_url = google_base_url + "ical/" + calendar_id + "/private-" + calendar_secret + "/basic.ics";
	
	var client_side_filtering_required = false;
	var client_side_filters = {};
	var request_url = atom_url;
	
	if(filters) {
		request_url += "?extq=";
		filters.forEach(function(filter) {
			if(typeof filter[1] == "string") {
				request_url += "[" + filter.join(":") + "]";
			} else {
				client_side_filtering_required = true;
				client_side_filters[filter[0]] = filter[1];
			}
		});
	}
	
	request({ uri: request_url }, function(err, res, atom_xml_body) {
		// console.log(request_url);
		var feed = new NodePie(atom_xml_body);
		feed.init();

		var matched_uids = [];
		var regexp = new RegExp(atom_url + "/(.*)");

		feed.getItems().forEach(function(item) {
			if(client_side_filtering_required) {
				for(var key in client_side_filters) {
					for(var index in item.element["gd:extendedProperty"]) {
						var property = item.element["gd:extendedProperty"][index];
						if(property.name === key) {
							if(client_side_filters[key].indexOf(property.value) === -1) {
								return;
							}
						}
					}
				}
			}
			
			// console.log(item.element);
			
			var permalink = item.getLink("self", "application/atom+xml");
			var uid = permalink.match(regexp)[1];
			matched_uids.push(uid);
		});

		request({ uri: ics_url }, function(err, res, ics_body) {
			var ics_json = vcal.parse_ics_string(ics_body);

			ics_json.VCALENDAR[0].VEVENT = ics_json.VCALENDAR[0].VEVENT.filter(function(element, index, array) {
				return matched_uids.indexOf(element.UID.replace("@google.com", "")) !== -1;
			});

			var new_ics = vcal.build_ics_string(ics_json);

			callback(new_ics);
		});
	});
};