(() => {
  const rootSelector = "[data-story-calendar-root]";
  const daySelector = "[data-story-calendar-day]";
  const navSelector = "[data-story-calendar-nav]";
  const filterSelector = "[data-story-calendar-filter]";

  const calendarRoot = () => document.querySelector(rootSelector);
  const calendarDetail = () => calendarRoot()?.querySelector("[data-story-calendar-detail]");
  let detailResizeObserver = null;

  const eventElement = (event) => event.target instanceof Element ? event.target : null;

  const isPlainPrimaryClick = (event) =>
    event.button === 0 && !event.metaKey && !event.ctrlKey && !event.shiftKey && !event.altKey;

  const clearCalendarNotice = () => {
    calendarRoot()?.querySelectorAll("[data-story-calendar-notice]").forEach((notice) => notice.remove());
  };

  const showCalendarNotice = (message, state) => {
    clearCalendarNotice();
    const target = calendarDetail() || calendarRoot();
    if (!target) {
      return;
    }

    const notice = document.createElement("p");
    notice.className = `story-calendar-detail-notice ${state === "error" ? "is-error" : ""}`.trim();
    notice.dataset.storyCalendarNotice = "true";
    notice.textContent = message;
    target.prepend(notice);
  };

  const loadCalendarSurface = async (url, historyMode = "push") => {
    const root = calendarRoot();
    if (!root || !window.fetch) {
      return false;
    }

    root.setAttribute("aria-busy", "true");
    showCalendarNotice("Loading...", "loading");

    try {
      const response = await fetch(url, {
        headers: { "X-Requested-With": "XMLHttpRequest" },
        credentials: "same-origin"
      });

      if (!response.ok) {
        throw new Error("Calendar load failed");
      }

      root.innerHTML = await response.text();
      root.removeAttribute("aria-busy");
      watchCalendarHeight();

      if (window.history?.pushState && historyMode !== "none") {
        const nextUrl = new URL(url, window.location.href);
        const state = { storyCalendarUrl: nextUrl.toString() };
        if (historyMode === "replace") {
          window.history.replaceState(state, "", nextUrl.toString());
        } else {
          window.history.pushState(state, "", nextUrl.toString());
        }
      }

      return true;
    } catch {
      root.removeAttribute("aria-busy");
      showCalendarNotice("The calendar could not be loaded. Use the link or Apply button to retry.", "error");
      return false;
    }
  };

  const buildFilterUrl = (form) => {
    const formData = new FormData(form);
    const url = new URL(form.dataset.storyCalendarIndexUrl || form.action || window.location.href, window.location.href);
    url.search = "";

    for (const [key, value] of formData.entries()) {
      if (key === "__RequestVerificationToken" || value === "") {
        continue;
      }

      url.searchParams.set(key, value);
    }

    return url.toString();
  };

  const syncDetailHeight = () => {
    const month = calendarRoot()?.querySelector(".story-calendar-month");
    const detail = calendarDetail();
    if (!month || !detail) {
      return;
    }

    const monthHeight = Math.ceil(month.getBoundingClientRect().height);
    if (monthHeight > 0) {
      detail.style.height = `${monthHeight}px`;
      detail.style.maxHeight = `${monthHeight}px`;
    }
  };

  const watchCalendarHeight = () => {
    detailResizeObserver?.disconnect();
    detailResizeObserver = null;

    const month = calendarRoot()?.querySelector(".story-calendar-month");
    if (window.ResizeObserver && month) {
      detailResizeObserver = new ResizeObserver(syncDetailHeight);
      detailResizeObserver.observe(month);
    }

    window.requestAnimationFrame(syncDetailHeight);
  };

  const initialise = () => {
    if (!calendarRoot() || !window.fetch) {
      return;
    }

    window.history?.replaceState?.({ storyCalendarUrl: window.location.href }, "", window.location.href);

    document.addEventListener("click", async (event) => {
      if (!isPlainPrimaryClick(event)) {
        return;
      }

      const link = eventElement(event)?.closest(`${daySelector}, ${navSelector}`);
      if (!link || !link.isConnected || !calendarRoot()?.contains(link)) {
        return;
      }

      event.preventDefault();
      await loadCalendarSurface(link.href, "push");
    }, true);

    document.addEventListener("submit", async (event) => {
      const form = eventElement(event)?.closest(filterSelector);
      if (!form || !form.isConnected) {
        return;
      }

      event.preventDefault();
      await loadCalendarSurface(buildFilterUrl(form), "push");
    }, true);

    document.addEventListener("change", async (event) => {
      const select = eventElement(event)?.closest(`${filterSelector} select`);
      const form = select?.closest(filterSelector);
      if (!select || !form) {
        return;
      }

      await loadCalendarSurface(buildFilterUrl(form), "push");
    }, true);

    window.addEventListener("popstate", async () => {
      await loadCalendarSurface(window.location.href, "none");
    });

    window.addEventListener("resize", syncDetailHeight);
    watchCalendarHeight();
  };

  if (document.readyState === "loading") {
    document.addEventListener("DOMContentLoaded", initialise, { once: true });
  } else {
    initialise();
  }
})();