TaroTime/app/ui-home-calendar.js

 (function () {
  "use strict";

  let config = {};
  let lastNowSkyGeoKey = "";
  let lastNowSkySourceUrl = "";
  const NOW_SKY_WRAPPER_PATH = "app/stellarium-now-wrapper.html";
  const NOW_SKY_FOV_DEGREES = "220";

  function getNowSkyLayerEl() {
    return config.nowSkyLayerEl || null;
  }

  function getNowPanelEl() {
    return config.nowPanelEl || null;
  }

  function getCurrentGeo() {
    return config.getCurrentGeo?.() || null;
  }

  function normalizeGeoForSky(geo) {
    const latitude = Number(geo?.latitude);
    const longitude = Number(geo?.longitude);

    if (!Number.isFinite(latitude) || !Number.isFinite(longitude)) {
      return null;
    }

    return {
      latitude: Number(latitude.toFixed(4)),
      longitude: Number(longitude.toFixed(4))
    };
  }

  function buildStellariumObserverUrl(geo) {
    const normalizedGeo = normalizeGeoForSky(geo);
    if (!normalizedGeo) {
      return "";
    }

    const wrapperUrl = new URL(NOW_SKY_WRAPPER_PATH, window.location.href);
    wrapperUrl.searchParams.set("lat", String(normalizedGeo.latitude));
    wrapperUrl.searchParams.set("lng", String(normalizedGeo.longitude));
    wrapperUrl.searchParams.set("elev", "0");
    wrapperUrl.searchParams.set("date", new Date().toISOString());
    wrapperUrl.searchParams.set("az", "0");
    wrapperUrl.searchParams.set("alt", "90");
    wrapperUrl.searchParams.set("fov", NOW_SKY_FOV_DEGREES);

    return wrapperUrl.toString();
  }

  function syncNowSkyBackground(geo, force = false) {
    const nowSkyLayerEl = getNowSkyLayerEl();
    if (!nowSkyLayerEl || !geo) {
      return;
    }

    const normalizedGeo = normalizeGeoForSky(geo);
    if (!normalizedGeo) {
      return;
    }

    const geoKey = `${normalizedGeo.latitude.toFixed(4)},${normalizedGeo.longitude.toFixed(4)}`;
    const stellariumUrl = buildStellariumObserverUrl(normalizedGeo);
    if (!stellariumUrl) {
      return;
    }

    if (!force && geoKey === lastNowSkyGeoKey && stellariumUrl === lastNowSkySourceUrl) {
      return;
    }

    if (stellariumUrl === lastNowSkySourceUrl) {
      return;
    }

    nowSkyLayerEl.src = stellariumUrl;
    lastNowSkyGeoKey = geoKey;
    lastNowSkySourceUrl = stellariumUrl;
  }

  function syncNowPanelTheme(referenceDate = new Date()) {
    const nowPanelEl = getNowPanelEl();
    if (!nowPanelEl) {
      return;
    }

    const currentGeo = getCurrentGeo();
    if (!currentGeo || !window.SunCalc) {
      nowPanelEl.classList.remove("is-day");
      nowPanelEl.classList.add("is-night");
      return;
    }

    const sunPosition = window.SunCalc.getPosition(referenceDate, currentGeo.latitude, currentGeo.longitude);
    const sunAltitudeDeg = (sunPosition.altitude * 180) / Math.PI;
    const isDaytime = sunAltitudeDeg >= -4;

    nowPanelEl.classList.toggle("is-day", isDaytime);
    nowPanelEl.classList.toggle("is-night", !isDaytime);
  }

  function init(nextConfig = {}) {
    config = {
      ...config,
      ...nextConfig
    };
  }

  window.TarotHomeUi = {
    ...(window.TarotHomeUi || {}),
    init,
    syncNowSkyBackground,
    syncNowPanelTheme
  };
})();