(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports, require('vega-util'), require('d3-time'), require('d3-array')) :
  typeof define === 'function' && define.amd ? define(['exports', 'vega-util', 'd3-time', 'd3-array'], factory) :
  (global = global || self, factory(global.vega = {}, global.vega, global.d3, global.d3));
}(this, (function (exports, vegaUtil, d3Time, d3Array) { 'use strict';

  const YEAR = 'year';
  const QUARTER = 'quarter';
  const MONTH = 'month';
  const WEEK = 'week';
  const DATE = 'date';
  const DAY = 'day';
  const DAYOFYEAR = 'dayofyear';
  const HOURS = 'hours';
  const MINUTES = 'minutes';
  const SECONDS = 'seconds';
  const MILLISECONDS = 'milliseconds';

  const TIME_UNITS = [
    YEAR,
    QUARTER,
    MONTH,
    WEEK,
    DATE,
    DAY,
    DAYOFYEAR,
    HOURS,
    MINUTES,
    SECONDS,
    MILLISECONDS
  ];

  const UNITS = TIME_UNITS.reduce((o, u, i) => (o[u] = 1 + i, o), {});

  function timeUnits(units) {
    const u = vegaUtil.array(units).slice(),
          m = {};

    // check validity
    if (!u.length) vegaUtil.error('Missing time unit.');

    u.forEach(unit => {
      if (vegaUtil.hasOwnProperty(UNITS, unit)) {
        m[unit] = 1;
      } else {
        vegaUtil.error(`Invalid time unit: ${unit}.`);
      }
    });

    const numTypes = (
      (m[WEEK] || m[DAY] ? 1 : 0) +
      (m[QUARTER] || m[MONTH] || m[DATE] ? 1 : 0) +
      (m[DAYOFYEAR] ? 1 : 0)
    );

    if (numTypes > 1) {
      vegaUtil.error(`Incompatible time units: ${units}`);
    }

    // ensure proper sort order
    u.sort((a, b) => UNITS[a] - UNITS[b]);

    return u;
  }

  const defaultSpecifiers = {
    [YEAR]: '%Y ',
    [QUARTER]: 'Q%q ',
    [MONTH]: '%b ',
    [DATE]: '%d ',
    [WEEK]: 'W%U ',
    [DAY]: '%a ',
    [DAYOFYEAR]: '%j ',
    [HOURS]: '%H:00',
    [MINUTES]: '00:%M',
    [SECONDS]: ':%S',
    [MILLISECONDS]: '.%L',
    [`${YEAR}-${MONTH}`]: '%Y-%m ',
    [`${YEAR}-${MONTH}-${DATE}`]: '%Y-%m-%d ',
    [`${HOURS}-${MINUTES}`]: '%H:%M'
  };

  function timeUnitSpecifier(units, specifiers) {
    const s = vegaUtil.extend({}, defaultSpecifiers, specifiers),
          u = timeUnits(units),
          n = u.length;

    let fmt = '', start = 0, end, key;

    for (start=0; start<n; ) {
      for (end=u.length; end > start; --end) {
        key = u.slice(start, end).join('-');
        if (s[key] != null) {
          fmt += s[key];
          start = end;
          break;
        }
      }
    }

    return fmt.trim();
  }

  const t0 = new Date;

  function localYear(y) {
    t0.setFullYear(y);
    t0.setMonth(0);
    t0.setDate(1);
    t0.setHours(0, 0, 0, 0);
    return t0;
  }

  function dayofyear(d) {
    return localDayOfYear(new Date(d));
  }

  function week(d) {
    return localWeekNum(new Date(d));
  }

  function localDayOfYear(d) {
    return d3Time.timeDay.count(localYear(d.getFullYear()) - 1, d);
  }

  function localWeekNum(d) {
    return d3Time.timeWeek.count(localYear(d.getFullYear()) - 1, d);
  }

  function localFirst(y) {
    return localYear(y).getDay();
  }

  function localDate(y, m, d, H, M, S, L) {
    if (0 <= y && y < 100) {
      var date = new Date(-1, m, d, H, M, S, L);
      date.setFullYear(y);
      return date;
    }
    return new Date(y, m, d, H, M, S, L);
  }

  function utcdayofyear(d) {
    return utcDayOfYear(new Date(d));
  }

  function utcweek(d) {
    return utcWeekNum(new Date(d));
  }

  function utcDayOfYear(d) {
    const y = Date.UTC(d.getUTCFullYear(), 0, 1);
    return d3Time.utcDay.count(y - 1, d);
  }

  function utcWeekNum(d) {
    const y = Date.UTC(d.getUTCFullYear(), 0, 1);
    return d3Time.utcWeek.count(y - 1, d);
  }

  function utcFirst(y) {
    t0.setTime(Date.UTC(y, 0, 1));
    return t0.getUTCDay();
  }

  function utcDate(y, m, d, H, M, S, L) {
    if (0 <= y && y < 100) {
      var date = new Date(Date.UTC(-1, m, d, H, M, S, L));
      date.setUTCFullYear(d.y);
      return date;
    }
    return new Date(Date.UTC(y, m, d, H, M, S, L));
  }

  function floor(units, step, get, inv, newDate) {
    const s = step || 1,
          b = vegaUtil.peek(units),
          _ = (unit, p, key) => {
            key = key || unit;
            return getUnit(get[key], inv[key], unit === b && s, p);
          };

    const t = new Date,
          u = vegaUtil.toSet(units),
          y = u[YEAR] ? _(YEAR) : vegaUtil.constant(2012),
          m = u[MONTH] ? _(MONTH)
            : u[QUARTER] ? _(QUARTER)
            : vegaUtil.zero,
          d = u[WEEK] && u[DAY] ? _(DAY, 1, WEEK + DAY)
            : u[WEEK] ? _(WEEK, 1)
            : u[DAY] ? _(DAY, 1)
            : u[DATE] ? _(DATE, 1)
            : u[DAYOFYEAR] ? _(DAYOFYEAR, 1)
            : vegaUtil.one,
          H = u[HOURS] ? _(HOURS) : vegaUtil.zero,
          M = u[MINUTES] ? _(MINUTES) : vegaUtil.zero,
          S = u[SECONDS] ? _(SECONDS) : vegaUtil.zero,
          L = u[MILLISECONDS] ? _(MILLISECONDS) : vegaUtil.zero;

    return function(v) {
      t.setTime(+v);
      const year = y(t);
      return newDate(year, m(t), d(t, year), H(t), M(t), S(t), L(t));
    };
  }

  function getUnit(f, inv, step, phase) {
    const u = step <= 1 ? f
      : phase ? (d, y) => phase + step * Math.floor((f(d, y) - phase) / step)
      : (d, y) => step * Math.floor(f(d, y) / step);
    return inv ? (d, y) => inv(u(d, y), y) : u;
  }

  // returns the day of the year based on week number, day of week,
  // and the day of the week for the first day of the year
  function weekday(week, day, firstDay) {
    return day + week * 7 - (firstDay + 6) % 7;
  }

  // -- LOCAL TIME --

  const localGet = {
    [YEAR]:         d => d.getFullYear(),
    [QUARTER]:      d => Math.floor(d.getMonth() / 3),
    [MONTH]:        d => d.getMonth(),
    [DATE]:         d => d.getDate(),
    [HOURS]:        d => d.getHours(),
    [MINUTES]:      d => d.getMinutes(),
    [SECONDS]:      d => d.getSeconds(),
    [MILLISECONDS]: d => d.getMilliseconds(),
    [DAYOFYEAR]:    d => localDayOfYear(d),
    [WEEK]:         d => localWeekNum(d),
    [WEEK + DAY]:   (d, y) => weekday(localWeekNum(d), d.getDay(), localFirst(y)),
    [DAY]:          (d, y) => weekday(1, d.getDay(), localFirst(y))
  };

  const localInv = {
    [QUARTER]: q => 3 * q,
    [WEEK]:    (w, y) => weekday(w, 0, localFirst(y))
  };

  function timeFloor(units, step) {
    return floor(units, step || 1, localGet, localInv, localDate);
  }

  // -- UTC TIME --

  const utcGet = {
    [YEAR]:         d => d.getUTCFullYear(),
    [QUARTER]:      d => Math.floor(d.getUTCMonth() / 3),
    [MONTH]:        d => d.getUTCMonth(),
    [DATE]:         d => d.getUTCDate(),
    [HOURS]:        d => d.getUTCHours(),
    [MINUTES]:      d => d.getUTCMinutes(),
    [SECONDS]:      d => d.getUTCSeconds(),
    [MILLISECONDS]: d => d.getUTCMilliseconds(),
    [DAYOFYEAR]:    d => utcDayOfYear(d),
    [WEEK]:         d => utcWeekNum(d),
    [DAY]:          (d, y) => weekday(1, d.getUTCDay(), utcFirst(y)),
    [WEEK + DAY]:   (d, y) => weekday(utcWeekNum(d), d.getUTCDay(), utcFirst(y))
  };

  const utcInv = {
    [QUARTER]: q => 3 * q,
    [WEEK]:    (w, y) => weekday(w, 0, utcFirst(y))
  };

  function utcFloor(units, step) {
    return floor(units, step || 1, utcGet, utcInv, utcDate);
  }

  const timeIntervals = {
    [YEAR]:         d3Time.timeYear,
    [QUARTER]:      d3Time.timeMonth.every(3),
    [MONTH]:        d3Time.timeMonth,
    [WEEK]:         d3Time.timeWeek,
    [DATE]:         d3Time.timeDay,
    [DAY]:          d3Time.timeDay,
    [DAYOFYEAR]:    d3Time.timeDay,
    [HOURS]:        d3Time.timeHour,
    [MINUTES]:      d3Time.timeMinute,
    [SECONDS]:      d3Time.timeSecond,
    [MILLISECONDS]: d3Time.timeMillisecond
  };

  const utcIntervals = {
    [YEAR]:         d3Time.utcYear,
    [QUARTER]:      d3Time.utcMonth.every(3),
    [MONTH]:        d3Time.utcMonth,
    [WEEK]:         d3Time.utcWeek,
    [DATE]:         d3Time.utcDay,
    [DAY]:          d3Time.utcDay,
    [DAYOFYEAR]:    d3Time.utcDay,
    [HOURS]:        d3Time.utcHour,
    [MINUTES]:      d3Time.utcMinute,
    [SECONDS]:      d3Time.utcSecond,
    [MILLISECONDS]: d3Time.utcMillisecond
  };

  function timeInterval(unit) {
    return timeIntervals[unit];
  }

  function utcInterval(unit) {
    return utcIntervals[unit];
  }

  function offset(ival, date, step) {
    return ival ? ival.offset(date, step) : undefined;
  }

  function timeOffset(unit, date, step) {
    return offset(timeInterval(unit), date, step);
  }

  function utcOffset(unit, date, step) {
    return offset(utcInterval(unit), date, step);
  }

  function sequence(ival, start, stop, step) {
    return ival ? ival.range(start, stop, step) : undefined;
  }

  function timeSequence(unit, start, stop, step) {
    return sequence(timeInterval(unit), start, stop, step);
  }

  function utcSequence(unit, start, stop, step) {
    return sequence(utcInterval(unit), start, stop, step);
  }

  const durationSecond = 1000,
        durationMinute = durationSecond * 60,
        durationHour = durationMinute * 60,
        durationDay = durationHour * 24,
        durationWeek = durationDay * 7,
        durationMonth = durationDay * 30,
        durationYear = durationDay * 365;

  const Milli   = [YEAR, MONTH, DATE, HOURS, MINUTES, SECONDS, MILLISECONDS],
        Seconds = Milli.slice(0, -1),
        Minutes = Seconds.slice(0, -1),
        Hours   = Minutes.slice(0, -1),
        Day     = Hours.slice(0, -1),
        Week    = [YEAR, WEEK],
        Month   = [YEAR, MONTH],
        Year    = [YEAR];

  const intervals = [
    [Seconds,  1,      durationSecond],
    [Seconds,  5,  5 * durationSecond],
    [Seconds, 15, 15 * durationSecond],
    [Seconds, 30, 30 * durationSecond],
    [Minutes,  1,      durationMinute],
    [Minutes,  5,  5 * durationMinute],
    [Minutes, 15, 15 * durationMinute],
    [Minutes, 30, 30 * durationMinute],
    [  Hours,  1,      durationHour  ],
    [  Hours,  3,  3 * durationHour  ],
    [  Hours,  6,  6 * durationHour  ],
    [  Hours, 12, 12 * durationHour  ],
    [    Day,  1,      durationDay   ],
    [   Week,  1,      durationWeek  ],
    [  Month,  1,      durationMonth ],
    [  Month,  3,  3 * durationMonth ],
    [   Year,  1,      durationYear  ]
  ];

  function bin(opt) {
    const ext = opt.extent,
          max = opt.maxbins || 40,
          target = Math.abs(vegaUtil.span(ext)) / max;

    let i = d3Array.bisector(i => i[2]).right(intervals, target),
        units, step;

    if (i === intervals.length) {
      units = Year,
      step = d3Array.tickStep(ext[0] / durationYear, ext[1] / durationYear, max);
    } else if (i) {
      i = intervals[target / intervals[i - 1][2] < intervals[i][2] / target ? i - 1 : i];
      units = i[0];
      step = i[1];
    } else {
      units = Milli;
      step = Math.max(d3Array.tickStep(ext[0], ext[1], max), 1);
    }

    return {units, step};
  }

  exports.DATE = DATE;
  exports.DAY = DAY;
  exports.DAYOFYEAR = DAYOFYEAR;
  exports.HOURS = HOURS;
  exports.MILLISECONDS = MILLISECONDS;
  exports.MINUTES = MINUTES;
  exports.MONTH = MONTH;
  exports.QUARTER = QUARTER;
  exports.SECONDS = SECONDS;
  exports.TIME_UNITS = TIME_UNITS;
  exports.WEEK = WEEK;
  exports.YEAR = YEAR;
  exports.dayofyear = dayofyear;
  exports.timeBin = bin;
  exports.timeFloor = timeFloor;
  exports.timeInterval = timeInterval;
  exports.timeOffset = timeOffset;
  exports.timeSequence = timeSequence;
  exports.timeUnitSpecifier = timeUnitSpecifier;
  exports.timeUnits = timeUnits;
  exports.utcFloor = utcFloor;
  exports.utcInterval = utcInterval;
  exports.utcOffset = utcOffset;
  exports.utcSequence = utcSequence;
  exports.utcdayofyear = utcdayofyear;
  exports.utcweek = utcweek;
  exports.week = week;

  Object.defineProperty(exports, '__esModule', { value: true });

})));