(function () {
  const loginView = document.getElementById("loginView");
  const adminView = document.getElementById("adminView");
  const loginForm = document.getElementById("loginForm");
  const passwordInput = document.getElementById("passwordInput");
  const loginMessage = document.getElementById("loginMessage");
  const addDateMessage = document.getElementById("addDateMessage");
  const datesList = document.getElementById("datesList");
  const dateCount = document.getElementById("dateCount");
  const emptyDates = document.getElementById("emptyDates");
  const logoutBtn = document.getElementById("logoutBtn");
  const monthLabel = document.getElementById("monthLabel");
  const weekdayRow = document.getElementById("weekdayRow");
  const dayGrid = document.getElementById("dayGrid");
  const prevMonthBtn = document.getElementById("prevMonthBtn");
  const nextMonthBtn = document.getElementById("nextMonthBtn");
  const saveDatesBtn = document.getElementById("saveDatesBtn");
  const weekdays = ["Mo", "Di", "Mi", "Do", "Fr", "Sa", "So"];
  const months = ["Januar", "Februar", "März", "April", "Mai", "Juni", "Juli", "August", "September", "Oktober", "November", "Dezember"];
  const today = new Date();
  today.setHours(0, 0, 0, 0);
  let dates = [];
  let bookedDates = new Set();
  let draftDates = new Map();
  let viewYear = today.getFullYear();
  let viewMonth = today.getMonth();

  function setMessage(element, message, success) {
    element.textContent = message;
    element.classList.toggle("is-success", Boolean(success));
  }

  function toDateKey(date) {
    return `${date.getFullYear()}-${String(date.getMonth() + 1).padStart(2, "0")}-${String(date.getDate()).padStart(2, "0")}`;
  }

  function formatDate(date) {
    return new Date(`${date}T00:00:00`).toLocaleDateString("de-DE", { weekday: "short", day: "2-digit", month: "2-digit", year: "numeric" });
  }

  async function request(path, options) {
    const response = await fetch(path, { ...options, headers: { "Content-Type": "application/json", ...(options && options.headers) } });
    const data = await response.json().catch(() => ({}));
    if (!response.ok) {
      const error = new Error(data.message || "Die Anfrage ist fehlgeschlagen.");
      error.status = response.status;
      throw error;
    }
    return data;
  }

  function showLogin(message) {
    adminView.classList.add("hidden");
    loginView.classList.remove("hidden");
    if (message) setMessage(loginMessage, message, false);
    passwordInput.focus();
  }

  function renderDates() {
    const plannedDates = Array.from(draftDates, ([date, type]) => ({ date, type })).sort((a, b) => a.date.localeCompare(b.date));
    datesList.innerHTML = "";
    dateCount.textContent = `${plannedDates.length} ${plannedDates.length === 1 ? "Termin" : "Termine"}`;
    emptyDates.classList.toggle("hidden", plannedDates.length !== 0);
    plannedDates.forEach((date) => {
      const row = document.createElement("li");
      row.className = "date-row";
      const label = document.createElement("span");
      label.className = "date-label";
      label.textContent = formatDate(date.date);
      const typeLabel = document.createElement("span");
      typeLabel.className = "date-type-label";
      typeLabel.textContent = date.type === "short" ? "Kurz" : "Lang";
      const deleteButton = document.createElement("button");
      deleteButton.className = "delete-date-btn";
      deleteButton.type = "button";
      deleteButton.textContent = "Entfernen";
      if (bookedDates.has(date.date)) {
        deleteButton.disabled = true;
        deleteButton.classList.add("is-booked");
        deleteButton.title = "Gebuchte Termine können nicht entfernt werden.";
      } else {
        deleteButton.addEventListener("click", () => {
          draftDates.delete(date.date);
          renderCalendar();
          renderDates();
          setMessage(addDateMessage, "Änderung vorgemerkt. Noch nicht gespeichert.", false);
        });
      }
      row.append(label, typeLabel, deleteButton);
      datesList.appendChild(row);
    });
  }

  function renderCalendar() {
    monthLabel.textContent = `${months[viewMonth]} ${viewYear}`;
    weekdayRow.innerHTML = "";
    weekdays.forEach((day) => {
      const span = document.createElement("span");
      span.textContent = day;
      weekdayRow.appendChild(span);
    });
    dayGrid.innerHTML = "";
    const firstOfMonth = new Date(viewYear, viewMonth, 1);
    const leadingBlanks = (firstOfMonth.getDay() + 6) % 7;
    const daysInMonth = new Date(viewYear, viewMonth + 1, 0).getDate();
    for (let index = 0; index < leadingBlanks; index += 1) {
      const blank = document.createElement("span");
      blank.className = "day-cell is-empty";
      dayGrid.appendChild(blank);
    }
    for (let day = 1; day <= daysInMonth; day += 1) {
      const cellDate = new Date(viewYear, viewMonth, day);
      const key = toDateKey(cellDate);
      const type = draftDates.get(key);
      const isBooked = bookedDates.has(key);
      const button = document.createElement("button");
      button.type = "button";
      button.className = "day-cell";
      button.textContent = String(day);
      if (cellDate <= today) {
        button.disabled = true;
        button.classList.add("is-disabled");
      } else if (isBooked) {
        button.disabled = true;
        button.classList.add("is-booked");
      } else if (type) {
        button.classList.add(type === "short" ? "is-short" : "is-long");
      }
      if (cellDate.getTime() === today.getTime()) button.classList.add("is-today");
      button.setAttribute("aria-label", `${formatDate(key)}${isBooked ? ", gebucht" : type ? `, ${type === "short" ? "kurz" : "lang"}` : ", nicht verfügbar"}`);
      if (!isBooked && cellDate > today) button.addEventListener("click", () => {
        const nextType = type === undefined ? "short" : type === "short" ? "long" : undefined;
        if (nextType) draftDates.set(key, nextType); else draftDates.delete(key);
        renderCalendar();
        renderDates();
        setMessage(addDateMessage, "Änderung vorgemerkt. Noch nicht gespeichert.", false);
      });
      dayGrid.appendChild(button);
    }
    prevMonthBtn.disabled = viewYear === today.getFullYear() && viewMonth === today.getMonth();
  }

  async function loadDates() {
    try {
      const [loadedDates, loadedBookedDates] = await Promise.all([
        request("/api/admin/dates", { method: "GET" }),
        request(`/api/booked-dates?t=${Date.now()}`, { method: "GET" }),
      ]);
      dates = loadedDates;
      bookedDates = new Set((loadedBookedDates || []).filter((date) => typeof date === "string"));
      dates.sort((a, b) => a.date.localeCompare(b.date));
      draftDates = new Map(dates.map((date) => [date.date, date.type]));
      loginView.classList.add("hidden");
      adminView.classList.remove("hidden");
      renderCalendar();
      renderDates();
    } catch (error) {
      if (error.status === 401) showLogin();
      else showLogin("Die Termine konnten nicht geladen werden.");
    }
  }

  loginForm.addEventListener("submit", async (event) => {
    event.preventDefault();
    setMessage(loginMessage, "", false);
    try {
      await request("/api/admin/login", { method: "POST", body: JSON.stringify({ password: passwordInput.value }) });
      passwordInput.value = "";
      await loadDates();
    } catch (error) {
      setMessage(loginMessage, error.message, false);
    }
  });

  saveDatesBtn.addEventListener("click", async () => {
    saveDatesBtn.disabled = true;
    try {
      await request("/api/admin/dates/bulk", { method: "POST", body: JSON.stringify(Array.from(draftDates, ([date, type]) => ({ date, type }))) });
      dates = Array.from(draftDates, ([date, type]) => ({ date, type }));
      renderDates();
      setMessage(addDateMessage, "Änderungen gespeichert.", true);
    } catch (error) {
      if (error.status === 401) showLogin("Deine Anmeldung ist abgelaufen.");
      else setMessage(addDateMessage, error.message, false);
    } finally {
      saveDatesBtn.disabled = false;
    }
  });

  prevMonthBtn.addEventListener("click", () => {
    viewMonth -= 1;
    if (viewMonth < 0) { viewMonth = 11; viewYear -= 1; }
    renderCalendar();
  });
  nextMonthBtn.addEventListener("click", () => {
    viewMonth += 1;
    if (viewMonth > 11) { viewMonth = 0; viewYear += 1; }
    renderCalendar();
  });
  logoutBtn.addEventListener("click", async () => {
    try { await request("/api/admin/logout", { method: "POST" }); } finally { showLogin(); }
  });

  loadDates();
})();