module.exports = function date(format, timestamp) {
  //  discuss at: https://locutus.io/php/date/
  // original by: Carlos R. L. Rodrigues (https://www.jsfromhell.com)
  // original by: gettimeofday
  //    parts by: Peter-Paul Koch (https://www.quirksmode.org/js/beat.html)
  // improved by: Kevin van Zonneveld (https://kvz.io)
  // improved by: MeEtc (https://yass.meetcweb.com)
  // improved by: Brad Touesnard
  // improved by: Tim Wiel
  // improved by: Bryan Elliott
  // improved by: David Randall
  // improved by: Theriault (https://github.com/Theriault)
  // improved by: Theriault (https://github.com/Theriault)
  // improved by: Brett Zamir (https://brett-zamir.me)
  // improved by: Theriault (https://github.com/Theriault)
  // improved by: Thomas Beaucourt (https://www.webapp.fr)
  // improved by: JT
  // improved by: Theriault (https://github.com/Theriault)
  // improved by: Rafał Kukawski (https://blog.kukawski.pl)
  // improved by: Theriault (https://github.com/Theriault)
  //    input by: Brett Zamir (https://brett-zamir.me)
  //    input by: majak
  //    input by: Alex
  //    input by: Martin
  //    input by: Alex Wilson
  //    input by: Haravikk
  // bugfixed by: Kevin van Zonneveld (https://kvz.io)
  // bugfixed by: majak
  // bugfixed by: Kevin van Zonneveld (https://kvz.io)
  // bugfixed by: Brett Zamir (https://brett-zamir.me)
  // bugfixed by: omid (https://locutus.io/php/380:380#comment_137122)
  // bugfixed by: Chris (https://www.devotis.nl/)
  //      note 1: Uses global: locutus to store the default timezone
  //      note 1: Although the function potentially allows timezone info
  //      note 1: (see notes), it currently does not set
  //      note 1: per a timezone specified by date_default_timezone_set(). Implementers might use
  //      note 1: $locutus.currentTimezoneOffset and
  //      note 1: $locutus.currentTimezoneDST set by that function
  //      note 1: in order to adjust the dates in this function
  //      note 1: (or our other date functions!) accordingly
  //   example 1: date('H:m:s \\m \\i\\s \\m\\o\\n\\t\\h', 1062402400)
  //   returns 1: '07:09:40 m is month'
  //   example 2: date('F j, Y, g:i a', 1062462400)
  //   returns 2: 'September 2, 2003, 12:26 am'
  //   example 3: date('Y W o', 1062462400)
  //   returns 3: '2003 36 2003'
  //   example 4: var $x = date('Y m d', (new Date()).getTime() / 1000)
  //   example 4: $x = $x + ''
  //   example 4: var $result = $x.length // 2009 01 09
  //   returns 4: 10
  //   example 5: date('W', 1104534000)
  //   returns 5: '52'
  //   example 6: date('B t', 1104534000)
  //   returns 6: '999 31'
  //   example 7: date('W U', 1293750000.82); // 2010-12-31
  //   returns 7: '52 1293750000'
  //   example 8: date('W', 1293836400); // 2011-01-01
  //   returns 8: '52'
  //   example 9: date('W Y-m-d', 1293974054); // 2011-01-02
  //   returns 9: '52 2011-01-02'
  //        test: skip-1 skip-2 skip-5

  let jsdate, f
  // Keep this here (works, but for code commented-out below for file size reasons)
  // var tal= [];
  const txtWords = [
    'Sun',
    'Mon',
    'Tues',
    'Wednes',
    'Thurs',
    'Fri',
    'Satur',
    'January',
    'February',
    'March',
    'April',
    'May',
    'June',
    'July',
    'August',
    'September',
    'October',
    'November',
    'December',
  ]
  // trailing backslash -> (dropped)
  // a backslash followed by any character (including backslash) -> the character
  // empty string -> empty string
  const formatChr = /\\?(.?)/gi
  const formatChrCb = function (t, s) {
    return f[t] ? f[t]() : s
  }
  const _pad = function (n, c) {
    n = String(n)
    while (n.length < c) {
      n = '0' + n
    }
    return n
  }
  f = {
    // Day
    d: function () {
      // Day of month w/leading 0; 01..31
      return _pad(f.j(), 2)
    },
    D: function () {
      // Shorthand day name; Mon...Sun
      return f.l().slice(0, 3)
    },
    j: function () {
      // Day of month; 1..31
      return jsdate.getDate()
    },
    l: function () {
      // Full day name; Monday...Sunday
      return txtWords[f.w()] + 'day'
    },
    N: function () {
      // ISO-8601 day of week; 1[Mon]..7[Sun]
      return f.w() || 7
    },
    S: function () {
      // Ordinal suffix for day of month; st, nd, rd, th
      const j = f.j()
      let i = j % 10
      if (i <= 3 && parseInt((j % 100) / 10, 10) === 1) {
        i = 0
      }
      return ['st', 'nd', 'rd'][i - 1] || 'th'
    },
    w: function () {
      // Day of week; 0[Sun]..6[Sat]
      return jsdate.getDay()
    },
    z: function () {
      // Day of year; 0..365
      const a = new Date(f.Y(), f.n() - 1, f.j())
      const b = new Date(f.Y(), 0, 1)
      return Math.round((a - b) / 864e5)
    },

    // Week
    W: function () {
      // ISO-8601 week number
      const a = new Date(f.Y(), f.n() - 1, f.j() - f.N() + 3)
      const b = new Date(a.getFullYear(), 0, 4)
      return _pad(1 + Math.round((a - b) / 864e5 / 7), 2)
    },

    // Month
    F: function () {
      // Full month name; January...December
      return txtWords[6 + f.n()]
    },
    m: function () {
      // Month w/leading 0; 01...12
      return _pad(f.n(), 2)
    },
    M: function () {
      // Shorthand month name; Jan...Dec
      return f.F().slice(0, 3)
    },
    n: function () {
      // Month; 1...12
      return jsdate.getMonth() + 1
    },
    t: function () {
      // Days in month; 28...31
      return new Date(f.Y(), f.n(), 0).getDate()
    },

    // Year
    L: function () {
      // Is leap year?; 0 or 1
      const j = f.Y()
      return ((j % 4 === 0) & (j % 100 !== 0)) | (j % 400 === 0)
    },
    o: function () {
      // ISO-8601 year
      const n = f.n()
      const W = f.W()
      const Y = f.Y()
      return Y + (n === 12 && W < 9 ? 1 : n === 1 && W > 9 ? -1 : 0)
    },
    Y: function () {
      // Full year; e.g. 1980...2010
      return jsdate.getFullYear()
    },
    y: function () {
      // Last two digits of year; 00...99
      return f.Y().toString().slice(-2)
    },

    // Time
    a: function () {
      // am or pm
      return jsdate.getHours() > 11 ? 'pm' : 'am'
    },
    A: function () {
      // AM or PM
      return f.a().toUpperCase()
    },
    B: function () {
      // Swatch Internet time; 000..999
      const H = jsdate.getUTCHours() * 36e2
      // Hours
      const i = jsdate.getUTCMinutes() * 60
      // Minutes
      // Seconds
      const s = jsdate.getUTCSeconds()
      return _pad(Math.floor((H + i + s + 36e2) / 86.4) % 1e3, 3)
    },
    g: function () {
      // 12-Hours; 1..12
      return f.G() % 12 || 12
    },
    G: function () {
      // 24-Hours; 0..23
      return jsdate.getHours()
    },
    h: function () {
      // 12-Hours w/leading 0; 01..12
      return _pad(f.g(), 2)
    },
    H: function () {
      // 24-Hours w/leading 0; 00..23
      return _pad(f.G(), 2)
    },
    i: function () {
      // Minutes w/leading 0; 00..59
      return _pad(jsdate.getMinutes(), 2)
    },
    s: function () {
      // Seconds w/leading 0; 00..59
      return _pad(jsdate.getSeconds(), 2)
    },
    u: function () {
      // Microseconds; 000000-999000
      return _pad(jsdate.getMilliseconds() * 1000, 6)
    },

    // Timezone
    e: function () {
      // Timezone identifier; e.g. Atlantic/Azores, ...
      // The following works, but requires inclusion of the very large
      // timezone_abbreviations_list() function.
      /*              return that.date_default_timezone_get();
       */
      const msg = 'Not supported (see source code of date() for timezone on how to add support)'
      throw new Error(msg)
    },
    I: function () {
      // DST observed?; 0 or 1
      // Compares Jan 1 minus Jan 1 UTC to Jul 1 minus Jul 1 UTC.
      // If they are not equal, then DST is observed.
      const a = new Date(f.Y(), 0)
      // Jan 1
      const c = Date.UTC(f.Y(), 0)
      // Jan 1 UTC
      const b = new Date(f.Y(), 6)
      // Jul 1
      // Jul 1 UTC
      const d = Date.UTC(f.Y(), 6)
      return a - c !== b - d ? 1 : 0
    },
    O: function () {
      // Difference to GMT in hour format; e.g. +0200
      const tzo = jsdate.getTimezoneOffset()
      const a = Math.abs(tzo)
      return (tzo > 0 ? '-' : '+') + _pad(Math.floor(a / 60) * 100 + (a % 60), 4)
    },
    P: function () {
      // Difference to GMT w/colon; e.g. +02:00
      const O = f.O()
      return O.substr(0, 3) + ':' + O.substr(3, 2)
    },
    T: function () {
      // The following works, but requires inclusion of the very
      // large timezone_abbreviations_list() function.
      /*              var abbr, i, os, _default;
      if (!tal.length) {
        tal = that.timezone_abbreviations_list();
      }
      if ($locutus && $locutus.default_timezone) {
        _default = $locutus.default_timezone;
        for (abbr in tal) {
          for (i = 0; i < tal[abbr].length; i++) {
            if (tal[abbr][i].timezone_id === _default) {
              return abbr.toUpperCase();
            }
          }
        }
      }
      for (abbr in tal) {
        for (i = 0; i < tal[abbr].length; i++) {
          os = -jsdate.getTimezoneOffset() * 60;
          if (tal[abbr][i].offset === os) {
            return abbr.toUpperCase();
          }
        }
      }
      */
      return 'UTC'
    },
    Z: function () {
      // Timezone offset in seconds (-43200...50400)
      return -jsdate.getTimezoneOffset() * 60
    },

    // Full Date/Time
    c: function () {
      // ISO-8601 date.
      return 'Y-m-d\\TH:i:sP'.replace(formatChr, formatChrCb)
    },
    r: function () {
      // RFC 2822
      return 'D, d M Y H:i:s O'.replace(formatChr, formatChrCb)
    },
    U: function () {
      // Seconds since UNIX epoch
      return (jsdate / 1000) | 0
    },
  }

  const _date = function (format, timestamp) {
    jsdate =
      timestamp === undefined
        ? new Date() // Not provided
        : timestamp instanceof Date
          ? new Date(timestamp) // JS Date()
          : new Date(timestamp * 1000) // UNIX timestamp (auto-convert to int)
    return format.replace(formatChr, formatChrCb)
  }

  return _date(format, timestamp)
}