clock.js

/* Pure time calculations. Luxon uses the browser's IANA time zone database. */
'use strict';
const LinearClock = (() => {
  const { DateTime } = luxon;

  function createDay(date, zone) {
    const start = DateTime.fromISO(date, { zone }).startOf('day');
    if (!start.isValid || start.toISODate() !== date) throw new Error('Invalid date or time zone.');
    const end = start.plus({ days: 1 }).startOf('day');
    return { start, end, duration: end.toMillis() - start.toMillis(), zone };
  }

  function percentage(time, day) {
    return Math.max(0, Math.min(100, (time.toMillis() - day.start.toMillis()) / day.duration * 100));
  }

  function hourTicks(day) {
    const ticks = [];
    // Walk actual instants: repeated wall-clock hours remain distinct. Include
    // whole local hours even after a 30-minute DST change (e.g. Lord Howe).
    for (let time = day.start; time < day.end; time = time.plus({ minutes: 1 })) {
      if (time.minute === 0 || time.equals(day.start)) {
        ticks.push({ time, percent: percentage(time, day), label: time.toFormat('H:mm') });
      }
    }
    ticks.push({ time: day.end, percent: 100, label: day.end.toFormat('H:mm') });
    return ticks;
  }

  function parseSunTime(value, day) {
    if (typeof value !== 'string') return null;
    const time = DateTime.fromISO(value, { zone: 'utc' }).setZone(day.zone);
    // v1 uses Unix-epoch placeholders for polar events. Adjacent-day events
    // are valid, but dates far outside the requested day are not.
    if (!time.isValid || time < day.start.minus({ days: 1 }) || time > day.end.plus({ days: 1 })) return null;
    return time;
  }

  function sunModel(times, day) {
    const sunrise = parseSunTime(times.sunrise, day);
    const sunset = parseSunTime(times.sunset, day);
    const dawn = parseSunTime(times.civil_twilight_begin, day);
    const dusk = parseSunTime(times.civil_twilight_end, day);
    const empty = () => ({ startPercent: 0, sizePercent: 0 });
    const segment = (start, end) => {
      const a = percentage(start, day);
      const b = percentage(end, day);
      return { startPercent: a, sizePercent: Math.max(0, b - a) };
    };
    let kind = 'unavailable';
    let segments = Array.from({ length: 5 }, empty);
    if (sunrise && sunset && sunrise <= sunset) {
      // Missing civil twilight at high latitudes means twilight continues
      // to the edge of the day. Do not invent a night or wrap negative spans.
      const begin = dawn || day.start;
      const end = dusk || day.end;
      if (begin <= sunrise && sunset <= end) {
        kind = 'normal';
        segments = [segment(day.start, begin), segment(begin, sunrise),
          segment(sunrise, sunset), segment(sunset, end), segment(end, day.end)];
      }
    } else if (!sunrise && !sunset && times.day_length != null) {
      const length = Number(times.day_length);
      if (length === 86400) {
        kind = 'polar-day';
        segments[2] = segment(day.start, day.end);
      } else if (length === 0) {
        kind = 'polar-night';
        if (dawn && dusk && dawn <= dusk) {
          segments[0] = segment(day.start, dawn);
          segments[1] = segment(dawn, dusk);
          segments[4] = segment(dusk, day.end);
        } else {
          segments[0] = segment(day.start, day.end);
        }
      }
    }
    return { sunrise, sunset, dawn, dusk, kind, segments };
  }

  return { createDay, percentage, hourTicks, parseSunTime, sunModel };
})();