spotthestation-rss-reader/main.js

Converts a NASA Spot The Station RSS file to a Javascript object.

var parseString = require('xml2js').parseString;
var util = require('util');

var ISS = function() {};

ISS.prototype.parseRSS = function(contents, callback) {
	parseString(contents, function(err, result) {
		if (err) {
			callback(err);
		}
		else if (result && result.rss && result.rss.channel[0]) {
			var feedObj = rssSightingsToJSON(result.rss.channel[0]);
			if (callback) {
				callback(null, feedObj);
			}
		} else {
			if (callback) {
				callback(new Error('Unexpected XML'));
			}
		}
	});
};

ISS.prototype.formatRSSLink = function (country, region, city) {
	// Could change, but convenient.
	var template = 'http://spotthestation.nasa.gov/sightings/view.cfm?country=%s&region=%s&city=%s';
	return util.format(template, country, region, city);
};

function parseTitle(s) {
	// e.g. "2015-01-08 ISS Sighting"
	var re = /[0-9]{4}-[0-9]{2}-[0-9]{2} (.*$)/g;
	var t = s.replace(re, "$1");
	return t;
}

function getFields(desc) {
	// e.g.
	// Date: Tuesday Jan 6, 2015 <br/>
	// Time: 7:21 AM <br/>
	// Duration: 1 minute <br/>
	// Maximum Elevation: 14 ° <br/>
	// Approach: 11 ° above S <br/>
	// Departure: 14 ° above SSE <br/>
	var fields = ["Date",
				  "Time",
				  "Duration",
				  "Maximum Elevation",
				  "Approach",
				  "Departure"];
	var ret = {};
	fields.forEach(function(s) {
		var rgx = new RegExp(s + ": (.*) <br\/>");
		var matches = rgx.exec(desc);
		if (matches.length > 1) {
			ret[s] = matches[1];
		}
	});
	return ret;
}

function getElapsedTime(oldDate, elapsed) {
	var dur = elapsed.match('[0-9]+')[0];
	return new Date(oldDate.getTime() + 1000 * 60 * parseInt(dur));
}

function makeSighting(title, data, guid) {
	var ret = {};
	ret.Title = title;
	ret.Start = new Date(data.Date + ' ' + data.Time);
	ret.Finish = getElapsedTime(ret.Start, data['Duration']);
	ret.Duration = data['Duration'];
	ret.MaxElevation = data['Maximum Elevation'];
	ret.Approach = data['Approach'];
	ret.Departure = data['Departure'];
	ret.guid = guid;
	return ret;
}

function rssSightingsToJSON(data) {
	var result = {};
	result.title = data.title[0];
	result.desc = data.description[0];
	result.uri = data.link[0];
	result.sightings = [];
	data.item.forEach(function(item) {
		var sightingFields = getFields(item.description[0]);
		var sightingTitle = parseTitle(item.title[0]);
		var sightingDetails = makeSighting(sightingTitle, sightingFields, item.guid[0]);
		result.sightings.push(sightingDetails);
	});
	return result;
}

module.exports = ISS;