Used to create a plot like this: https://plot.ly/~jasoncrawford/17.embed

asteroidWatcher.js

var fs = require('fs');
var _ = require('underscore');
var csv = require('csv');
var Twitter = require('twitter');

function die(error) {
  console.error('fatal error');
  if (error) console.error('error', error);
  if (error.stack) console.error('stacktrace', error.stack);
  process.exit(-1);
}

var env = process.env;

//--------------------------------------------------------------------------------------------------
// Parsing

var energyUnitMap = [
  {name: 'kilotons', exponent: 3},
  {name: 'megatons', exponent: 6},
  {name: 'gigatons', exponent: 9},
]

function transformMatchData(matchData) {
  var data = _.pick(matchData, 'name', 'url');

  _.each(['distance', 'diameter', 'velocity', 'energy'], function (key) {
    data[key] = parseFloat(matchData[key]);
  })

  var energyUnits = matchData.energyUnits.replace(/\.+$/, '');  // strip trailing ...

  var unit = _.find(energyUnitMap, function (entry) {
    return entry.name.indexOf(energyUnits) === 0;
  })

  if (!unit) {
    console.error('unknown energy unit:', energyUnits);
    return undefined;
  }

  data.energy = data.energy * Math.pow(10, unit.exponent);

  return data;
}

// example:
// asteroid (2010 SX11) missed earth by 15 lunar distances: diameter ~47 m, velocity 7.73 km/s, energy ~1 megaton. http://t.co/VxWFWbZ6c8
var pattern = /asteroid \((.*)\) missed earth by ([\d\.]+) lunar distances: diameter ~?([\d\.]+) m, velocity ([\d\.]+) km\/s, energy ~?([\d\.]+) (.*). (http:\/\/.*)/
var patternKeys = ['name', 'distance', 'diameter', 'velocity', 'energy', 'energyUnits', 'url'];

function parseTweet(tweet) {
  var text = tweet.text;

  var match = text.match(pattern);
  if (!match) {
    console.warn('no match for tweet: ' + text);
    return undefined;
  }

  var matchData = _.object(patternKeys, match.slice(1));

  var data = transformMatchData(matchData);

  if (data) data.timestamp = tweet.created_at;

  return data;
}

//--------------------------------------------------------------------------------------------------
// CSV output

var columns = {
  name: 'Name',
  distance: 'Distance (lunar distances)',
  diameter: 'Diameter (m)',
  velocity: 'Velocity (km/s)',
  energy: 'Energy (tons)',
  url: 'URL',
}

var outfile = 'asteroids.csv';

function generateCSV(parsedTweets) {
  var stream = fs.createWriteStream(outfile);
  csv.stringify(parsedTweets, {columns: columns, header: true}).pipe(stream);
}

//--------------------------------------------------------------------------------------------------
// Twitter & output

var params = {
  screen_name: 'AsteroidMisses',
  count: 200,
  trim_user: 1,
}

function handleResponse(error, tweets, response) {
  if (error) die(error);
  console.log('tweets:', tweets.length);
  var parseResults = _(tweets).map(parseTweet);
  var parsedTweets = _(parseResults).compact();
  var errorCount = parseResults.length - parsedTweets.length;
  console.warn('parse errors:', errorCount);
  generateCSV(parsedTweets);
}

var client = new Twitter({
  consumer_key: env['TWITTER_CONSUMER_KEY'],
  consumer_secret: env['TWITTER_CONSUMER_SECRET'],
  access_token_key: env['TWITTER_ACCESS_TOKEN'],
  access_token_secret: env['TWITTER_ACCESS_TOKEN_SECRET'],
});

client.get('statuses/user_timeline', params, handleResponse);