TimeUtil.java

/*
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

package com.facebook.common.time;

import java.util.TimeZone;

import static com.facebook.common.time.TimeConstants.*;

/**
 * Time utilities
 */
public class TimeUtil {

  private static final long[] TIME_UNITS = {MS_PER_DAY, MS_PER_HOUR, MS_PER_MINUTE, MS_PER_SECOND};
  private static final String[] TIME_UNITS_ABBR = {"d", "h", "m", "s", "ms"};

  /**
   * The API deals with seconds since the PST epoch, while pretty much everything else deals
   * with milliseconds since the UTC epoch.
   * @param utcTime time in milliseconds since the epoch in UTC time
   * @return time in seconds since the epoch in PST time zone
   */
  public static long utcToApiTime(long utcTime) {
    long apiTimeMs = utcTime + TimeZone.getTimeZone("PST").getRawOffset();
    return apiTimeMs / MS_PER_SECOND;
  }

  /**
   * The API deals with seconds since the PST epoch, while pretty much everything else deals
   * with milliseconds since the UTC epoch.
   * @param apiTime time in seconds since the epoch in PST time zone
   * @return time in milliseconds since the epoch in UTC time
   */
  public static long apiToUtcTime(long apiTime) {
    long apiTimeMs = apiTime * MS_PER_SECOND;
    return apiTimeMs - TimeZone.getTimeZone("PST").getRawOffset();
  }

  /**
   * Converts minutes to milliseconds.
   * It is implemented because current min API is 8,
   * but TimeUnit.MINUTES.toMillis was added to API 9.
   *
   * @param minutes value to be converted to milliseconds
   * @return milliseconds converted from given minutes
   */
  public static long minutesToMilliseconds(int minutes) {
    return minutes * MS_PER_MINUTE;
  }

  /**
   * Converts given time stamp to human readable string based on liveshare_picker_fragmentnow
   * @param whenMillis time stamp to be converted based on now
   * @param nowMillis current time stamp
   * @return human readable string indicating given time based on now
   */
  public static String whenFromNow(long whenMillis, long nowMillis) {
    if (whenMillis == nowMillis) {
      return "now";
    }
    StringBuilder sb = new StringBuilder();
    String lastWord = (whenMillis > nowMillis) ? "later" : "ago";
    long diff = Math.abs(whenMillis - nowMillis);
    sb.append(toHumanReadableTime(diff)).append(' ').append(lastWord);
    return sb.toString();
  }

  /**
   * Converts given time stamp to human readable string
   * @param milliseconds time stamp to be converted
   * @return human readable time
   */
  public static String toHumanReadableTime(long milliseconds) {
    StringBuilder sb = new StringBuilder();
    int len = TIME_UNITS.length;
    int i = 0;
    for ( ; i < len; i++) {
      long quotient = milliseconds / TIME_UNITS[i];
      if (quotient > 0) {
        if (sb.length() > 0) {
          sb.append(' ');
        }
        sb.append(quotient).append(TIME_UNITS_ABBR[i]);
        milliseconds = milliseconds % TIME_UNITS[i];
      }
    }
    if (sb.length() > 0) {
      if (milliseconds > 0) {
        sb.append(' ').append(milliseconds).append(TIME_UNITS_ABBR[i]);
      }
    } else {
      sb.append(milliseconds).append(TIME_UNITS_ABBR[i]);
    }
    return sb.toString();
  }
}