lib/timezones.js

  1. /**
  2.  * @file Handle timezones
  3.  * @author Antonio Olmo Titos <a@olmo-titos.info>
  4.  * @exports lib/timezones
  5.  */
  7. // External packages:
  8. const MOMENT_TIMEZONE = require('moment-timezone');
  10. // Internal packages:
  11. const LOGGING = require('./logging'),
  12.     UTIL = require('./util');
  14. // Constants:
  15. const // REGEX_TZ_CODE = /^[A-Z]{2,4}$/,
  16.     REGEX_TZ_CONTINENT_AND_COUNTRY = /^[^/]+\/[^/]+$/,
  17.     REGEX_REPLACE_DASHES = /_/gi,
  18.     FORMAT_DATETIME = 'ddd, D MMM Y, H:mm';
  20. // Variables:
  21. var zones;
  23. /**
  24.  * Set up timezones
  25.  */
  27. const setUp = function() {
  28.     if (zones)
  29.         LOGGING.warn(`“timezones.setUp()” called more than once`);
  30.     else {
  31.         zones = MOMENT_TIMEZONE.tz.names();
  32.         const // codes = zones.filter(v => { return v.match(REGEX_TZ_CODE); }),
  33.             continentAndCountry = zones.filter(function(v) {
  34.                 return v.match(REGEX_TZ_CONTINENT_AND_COUNTRY);
  35.             }),
  36.             // others = zones.filter(v => { return !v.match(REGEX_TZ_CODE) && !v.match(REGEX_TZ_CONTINENT_AND_COUNTRY); }),
  37.             continents = {UTC: {UTC: 'UTC/UTC'}};
  38.         continentAndCountry.forEach(function(i) {
  39.             const p = i.replace(REGEX_REPLACE_DASHES, '&nbsp;').split('/');
  40.             if ('Etc' !== p[0]) {
  41.                 if (!continents.hasOwnProperty(p[0]))
  42.                     continents[p[0]] = {};
  43.                 if (!continents[p[0]].hasOwnProperty(p[1]))
  44.                     continents[p[0]][p[1]] = i;
  45.             }
  46.         });
  47.         // Export more stuff:
  48.         // exports.tzCodes = codes;
  49.         exports.tzContinents = continents;
  50.         // exports.tzOthers = others;
  51.         exports.timezoneExists = timezoneExists;
  52.         exports.processTimezone = processTimezone;
  53.         exports.shiftTime = shiftTime;
  54.     }
  55. };
  57. /**
  58.  * Check if a string corresponds to a known timezone
  59.  * @param {String} tz - the string
  60.  * @returns {Boolean} whether it's a valid timezone
  61.  */
  63. const timezoneExists = function(tz) {
  64.     return zones.includes(tz);
  65. };
  67. /**
  68.  * @TODO: Document this.
  69.  */
  71. const processTimezone = function(data) {
  72.     const correctedTimezone = 'UTC/UTC' === data.tz ? 'UTC' : data.tz;
  73.     const m = new MOMENT_TIMEZONE().tz(correctedTimezone),
  74.         abbrs = m._z.abbrs,
  75.         offset = m._offset;
  76.     LOGGING.dir(m);
  77.     data.time = m.tz(correctedTimezone).format(FORMAT_DATETIME);
  78.     data.offset = UTIL.formatDuration(offset, true);
  79.     data.related = Array.from(new Set(abbrs));
  80.     LOGGING.dir(data);
  81. };
  83. /**
  84.  * Return the equivalent date-time in a different timezone
  85.  * @param {String} to - the target timezone
  86.  * @param {Object} time - (optional) the date-time (<code>now()</code> if not present)
  87.  * @returns {Object} the equivalent date-time
  88.  */
  90. const shiftTime = function(to, time) {
  91.     const t = time ? time : new MOMENT_TIMEZONE();
  92.     const result = t.tz(to).format();
  93.     return result;
  94. };
  96. // Export stuff:
  97. exports.setUp = setUp;