RelativeTimeUtils.jsm

/* vim: sw=2 ts=2 sts=2 expandtab filetype=javascript
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

"use strict";

var EXPORTED_SYMBOLS = [ "RelativeTimeUtils" ];

/**
 * This module provides the RelativeTimeUtils object which contains useful methods
 * for displaying relative times.
 */

ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
ChromeUtils.import("resource://gre/modules/Services.jsm");

ChromeUtils.defineModuleGetter(this, "PluralForm",
                               "resource://gre/modules/PluralForm.jsm");

const MS_PER_DAY = 24 * 60 * 60 * 1000;

var localeNumberFormatCache = new Map();
function getLocaleNumberFormat(fractionDigits) {
  if (!localeNumberFormatCache.has(fractionDigits)) {
    localeNumberFormatCache.set(fractionDigits,
      new Services.intl.NumberFormat(undefined,
                        { maximumFractionDigits: fractionDigits,
                          minimumFractionDigits: fractionDigits }));
  }
  return localeNumberFormatCache.get(fractionDigits);
}

const kDownloadProperties =
  "chrome://mozapps/locale/downloads/downloads.properties";

var gStr = {
  timePair: "timePair2",
  timeLeftSingle: "timeLeftSingle2",
  timeLeftDouble: "timeLeftDouble2",
  timeFewSeconds: "timeFewSeconds",
  timeUnknown: "timeUnknown",
  yesterday: "yesterday",
  // Update timeSize in convertTimeUnits if changing the length of this array
  timeUnits: ["seconds", "minutes", "hours", "days"],
};

// This lazily initializes the string bundle upon first use.
Object.defineProperty(this, "gBundle", {
  configurable: true,
  enumerable: true,
  get() {
    delete this.gBundle;
    return this.gBundle = Services.strings.createBundle(kDownloadProperties);
  },
});


var RelativeTimeUtils = {
  /**
   * Converts a number of seconds to the two largest units. Time values are
   * whole numbers, and units have the correct plural/singular form.
   *
   * @param aSecs
   *        Seconds to convert into the appropriate 2 units
   * @return 4-item array [first value, its unit, second value, its unit]
   */
  convertTimeUnits: function DU_convertTimeUnits(aSecs) {
    // These are the maximum values for seconds, minutes, hours corresponding
    // with gStr.timeUnits without the last item
    let timeSize = [60, 60, 24];

    let time = aSecs;
    let scale = 1;
    let unitIndex = 0;

    // Keep converting to the next unit while we have units left and the
    // current one isn't the largest unit possible
    while ((unitIndex < timeSize.length) && (time >= timeSize[unitIndex])) {
      time /= timeSize[unitIndex];
      scale *= timeSize[unitIndex];
      unitIndex++;
    }

    let value = convertTimeUnitsValue(time);
    let units = convertTimeUnitsUnits(value, unitIndex);

    let extra = aSecs - value * scale;
    let nextIndex = unitIndex - 1;

    // Convert the extra time to the next largest unit
    for (let index = 0; index < nextIndex; index++)
      extra /= timeSize[index];

    let value2 = convertTimeUnitsValue(extra);
    let units2 = convertTimeUnitsUnits(value2, nextIndex);

    return [value, units, value2, units2];
  },
};

/**
 * Private helper for convertTimeUnits that gets the display value of a time
 *
 * @param aTime
 *        Time value for display
 * @return An integer value for the time rounded down
 */
function convertTimeUnitsValue(aTime) {
  return Math.floor(aTime);
}

/**
 * Private helper for convertTimeUnits that gets the display units of a time
 *
 * @param aTime
 *        Time value for display
 * @param aIndex
 *        Index into gStr.timeUnits for the appropriate unit
 * @return The appropriate plural form of the unit for the time
 */
function convertTimeUnitsUnits(aTime, aIndex) {
  // Negative index would be an invalid unit, so just give empty
  if (aIndex < 0)
    return "";

  return PluralForm.get(aTime, gBundle.GetStringFromName(gStr.timeUnits[aIndex]));
}