l10n_date.js

/* -*- Mode: js; js-indent-level: 2; indent-tabs-mode: nil -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */

'use strict';

/**
 * This lib relies on `l10n.js' to implement localizable date/time strings.
 *
 * The proposed `DateTimeFormat' object should provide all the features that are
 * planned for the `Intl.DateTimeFormat' constructor, but the API does not match
 * exactly the ES-i18n draft.
 *   - https://bugzilla.mozilla.org/show_bug.cgi?id=769872
 *   - http://wiki.ecmascript.org/doku.php?id=globalization:specification_drafts
 *
 * Besides, this `DateTimeFormat' object provides two features that aren't
 * planned in the ES-i18n spec:
 *   - a `toLocaleFormat()' that really works (i.e. fully translated);
 *   - a `fromNow()' method to handle relative dates ("pretty dates").
 *
 * WARNING: this library relies on the non-standard `toLocaleFormat()' method,
 * which is specific to Firefox -- no other browser is supported.
 */

navigator.mozL10n.DateTimeFormat = function(locales, options) {
  var _ = navigator.mozL10n.get;

  // https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Date/toLocaleFormat
  //
  // Deprecated. Please, use Intl API instead
  function localeFormat(d, format) {
    var tokens = format.match(/(%E.|%O.|%.)/g);

    for (var i = 0; tokens && i < tokens.length; i++) {
      var value = '';

      // http://pubs.opengroup.org/onlinepubs/007908799/xsh/strftime.html
      switch (tokens[i]) {
        // localized day/month names
        case '%a':
          value = _('weekday-' + d.getDay() + '-short');
          break;
        case '%A':
          value = _('weekday-' + d.getDay() + '-long');
          break;
        case '%b':
        case '%h':
          value = _('month-' + d.getMonth() + '-short');
          break;
        case '%B':
          value = _('month-' + d.getMonth() + '-long');
          break;
        case '%Eb':
          value = _('month-' + d.getMonth() + '-genitive');
          break;

        // like %H, but in 12-hour format and without any leading zero
        case '%I':
          value = d.getHours() % 12 || 12;
          break;

        // like %d, without any leading zero
        case '%e':
          value = d.getDate();
          break;

        // %p: 12 hours format (AM/PM)
        case '%p':
          value = d.getHours() < 12 ? _('time_am') : _('time_pm');
          break;

        // localized date/time strings
        case '%c':
        case '%x':
        case '%X':
          // ensure the localized format string doesn't contain any %c|%x|%X
          var tmp = _('dateTimeFormat_' + tokens[i]);
          if (tmp && !(/(%c|%x|%X)/).test(tmp)) {
            value = localeFormat(d, tmp);
          }
          break;

        // other tokens don't require any localization
      }

      format = format.replace(tokens[i], value || d.toLocaleFormat(tokens[i]));
    }

    return format;
  }

  /**
   * Returns the parts of a number of seconds
   */
  function relativeParts(seconds) {
    seconds = Math.abs(seconds);
    var descriptors = {};
    var units = [
      'years', 86400 * 365,
      'months', 86400 * 30,
      'weeks', 86400 * 7,
      'days', 86400,
      'hours', 3600,
      'minutes', 60
    ];

    if (seconds < 60) {
      return {
        minutes: Math.round(seconds / 60)
      };
    }

    for (var i = 0, uLen = units.length; i < uLen; i += 2) {
      var value = units[i + 1];
      if (seconds >= value) {
        descriptors[units[i]] = Math.floor(seconds / value);
        seconds -= descriptors[units[i]] * value;
      }
    }
    return descriptors;
  }

  /**
   * Returns a translated string which respresents the
   * relative time before or after a date.
   *
   * Deprecated: Please, use relativeDate for now
   *
   * @param {String|Date} time before/after the currentDate.
   * @param {String} useCompactFormat whether to use a compact display format.
   * @param {Number} maxDiff returns a formatted date if the diff is greater.
   */
  function prettyDate(time, useCompactFormat, maxDiff) {
    maxDiff = maxDiff || 86400 * 10; // default = 10 days

    switch (time.constructor) {
      case String: // timestamp
        time = parseInt(time);
        break;
      case Date:
        time = time.getTime();
        break;
    }

    var secDiff = (Date.now() - time) / 1000;
    if (isNaN(secDiff)) {
      return _('incorrectDate');
    }

    if (Math.abs(secDiff) > 60) {
      // round milliseconds up if difference is over 1 minute so the result is
      // closer to what the user would expect (1h59m59s300ms diff should return
      // "in 2 hours" instead of "in an hour")
      secDiff = secDiff > 0 ? Math.ceil(secDiff) : Math.floor(secDiff);
    }

    if (secDiff > maxDiff) {
      return localeFormat(new Date(time), '%x');
    }

    var f = useCompactFormat ? '-short' : '-long';
    var parts = relativeParts(secDiff);

    var affix = secDiff >= 0 ? '-ago' : '-until';
    for (var i in parts) {
      return _(i + affix + f, { value: parts[i]});
    }
  }

  /**
   * Async clone of prettyDate.
   * Temporary solution while we're waiting for Intl extension to support
   * relative dates.
   */
  function relativeDate(time, useCompactFormat, maxDiff) {
    maxDiff = maxDiff || 86400 * 10; // default = 10 days

    switch (time.constructor) {
      case String: // timestamp
        time = parseInt(time);
        break;
      case Date:
        time = time.getTime();
        break;
    }

    var secDiff = (Date.now() - time) / 1000;
    if (isNaN(secDiff)) {
      return navigator.mozL10n.formatValue('incorrectDate');
    }

    if (Math.abs(secDiff) > 60) {
      // round milliseconds up if difference is over 1 minute so the result is
      // closer to what the user would expect (1h59m59s300ms diff should return
      // "in 2 hours" instead of "in an hour")
      secDiff = secDiff > 0 ? Math.ceil(secDiff) : Math.floor(secDiff);
    }

    if (secDiff > maxDiff) {
      var dateString = new Date(time).toLocaleString(navigator.languages, {
        year: 'numeric',
        month: 'numeric',
        day: 'numeric'
      });
      return Promise.resolve(dateString);
    }

    var f = useCompactFormat ? '-short' : '-long';
    var parts = relativeParts(secDiff);

    var affix = secDiff >= 0 ? '-ago' : '-until';
    for (var i in parts) {
      return navigator.mozL10n.formatValue(i + affix + f, { value: parts[i]});
    }
  }

  // API
  return {
    localeFormat: localeFormat,
    fromNow: prettyDate,
    relativeDate: relativeDate,
    relativeParts: relativeParts
  };
};