time_utils.js

// module "time_utils"
//
// Utility functions useful to work with time and durations.
//
// This module functions usually receive or return a {d, h, m, s} object
// or a number of milliseconds representing a time or a duration.
//
// The {h, m, s} object encapsulates a "time" (eg: 12:30:00).
// Note: a "time" needs the day set to 0/undefined, otherwise it is a "duration".
//
// The {d, h, m, s} object encapsulates a "duration" in number of days, hours,
// minutes and seconds (eg. 3d 20h 35m 20s).
// Note that if a field is undefined then its value is zero.
//

const ONE_SECOND = 1000;
const ONE_MINUTE = 60 * ONE_SECOND;
const ONE_HOUR = 60 * ONE_MINUTE;
const ONE_DAY = 24 * ONE_HOUR;

/**
 * @param {object} time {d, h, m, s}
 * @returns the milliseconds contained in the passed time object
 */
exports.encodeTime = (time) => {
  time = safeTime(time);
  return time.d * ONE_DAY + time.h * ONE_HOUR + time.m * ONE_MINUTE + time.s * ONE_SECOND;
}

// internal use, set to zero all the undefined fields
function safeTime(time) {
  return { d: time.d || 0, h: time.h || 0, m: time.m || 0, s: time.s || 0 };
}

/**
 * @param {int} millis the number of milliseconds
 * @returns a time object {d, h, m, s} built from the milliseconds
 */
exports.decodeTime = (millis) => {
  if (typeof millis !== "number") throw "Only a number can be decoded";
  var d = Math.floor(millis / ONE_DAY);
  millis -= d * ONE_DAY;
  var h = Math.floor(millis / ONE_HOUR);
  millis -= h * ONE_HOUR;
  var m = Math.floor(millis / ONE_MINUTE);
  millis -= m * ONE_MINUTE;
  var s = Math.floor(millis / ONE_SECOND);
  return { d: d, h: h, m: m, s: s };
}

/** 
 * @param {object|int} value {h, m} object or milliseconds
 * @returns an human-readable time string like "10:25"
 * @throws an exception if d != 0 or h > 23 or m > 59
 */
exports.formatTime = (value) => {
  var time = safeTime(typeof value === "object" ? value : exports.decodeTime(value));
  if (time.d != 0) throw "days not supported here";
  if (time.h < 0 || time.h > 23) throw "Invalid value: must be 0 <= h <= 23";
  if (time.m < 0 || time.m > 59) throw "Invalid value: must be 0 <= m <= 59";
  return time.h + ":" + ("0" + time.m).substr(-2);
}

/**
 * @param {object|int} value {d, h, m, s} object or milliseconds
 * @param {boolean} compact `true` to remove all whitespaces between the values
 * @returns an human-readable duration string like "3d 1h 10m 45s" (or "3d1h10m45s" if `compact` is `true`)
 */
exports.formatDuration = (value, compact) => {
  compact = compact || false;
  var duration = "";
  var time = safeTime(typeof value === "object" ? value : exports.decodeTime(value));
  if (time.d > 0) duration += time.d + "d ";
  if (time.h > 0) duration += time.h + "h ";
  if (time.m > 0) duration += time.m + "m ";
  if (time.s > 0) duration += time.s + "s"
  duration = duration.trim()
  return compact ? duration.replace(" ", "") : duration;
}

exports.getCurrentTimeMillis = () => {
  var time = new Date();
  return (time.getHours() * 3600 + time.getMinutes() * 60 + time.getSeconds()) * 1000;
}