/* Browsernatives ES-Modul; wird ohne Build-Schritt ausgeliefert. */
const dateFormatter = new Intl.DateTimeFormat('de-DE', { weekday: 'long', day: 'numeric', month: 'long', year: 'numeric' });
const monthFormatter = new Intl.DateTimeFormat('de-DE', { month: 'long', year: 'numeric' });
const timeFormatter = new Intl.DateTimeFormat('de-DE', { hour: '2-digit', minute: '2-digit' });
const weekdays = ['Mo', 'Di', 'Mi', 'Do', 'Fr', 'Sa', 'So'];
const sessionProfileKey = 'sufw-booking-profile-v1';

function parseDateTime(value) { return new Date(value.replace(' ', 'T')); }
function parseDate(value) { return new Date(`${value}T12:00:00`); }

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

function eventDateRange(event) { return [event.startsAt.slice(0, 10), event.endsAt.slice(0, 10)]; }
function occursOnDate(event, date) { const [startDate, endDate] = eventDateRange(event); return startDate <= date && endDate >= date; }
export function getSlotsForDate(project, date, events = []) { return events.filter((event) => event.project === project && occursOnDate(event, date)); }
export function requiresIntroductionDetails(event = {}) { return event.project === 'produktionsschule' && event.introductionRequired === true; }

export function formatEventDuration(event) {
  const start = parseDateTime(event.startsAt);
  const end = parseDateTime(event.endsAt);
  const [startDate, endDate] = eventDateRange(event);
  if (startDate !== endDate) {
    const dayCount = Math.round((parseDate(endDate) - parseDate(startDate)) / 86400000) + 1;
    return `${dayCount} Tage`;
  }
  const hours = Math.round((end - start) / 3600000 * 10) / 10;
  return `${String(hours).replace('.', ',')} ${hours === 1 ? 'Stunde' : 'Stunden'}`;
}

function formatEventTime(event) { return `${timeFormatter.format(parseDateTime(event.startsAt))}–${timeFormatter.format(parseDateTime(event.endsAt))} Uhr`; }
function formatEventFormat(event) { return event.format === 'telefonisch' ? 'Telefonisch' : 'Vor Ort'; }

export function validateBookingField(fieldName, value) {
  const text = typeof value === 'string' ? value.trim() : '';
  if (fieldName === 'name') return text && text.length <= 160 ? '' : 'Bitte geben Sie Ihren Namen ein.';
  if (fieldName === 'email') return /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(text) && text.length <= 254 ? '' : 'Bitte geben Sie eine gültige E-Mail-Adresse ein.';
  if (fieldName === 'phone') return /^[0-9+()\-/\s]{6,64}$/.test(text) ? '' : 'Bitte geben Sie eine gültige Telefonnummer ein.';
  if (fieldName === 'introductionAttended') return value ? '' : 'Bitte bestätigen Sie die Teilnahme an einer Einführungsveranstaltung.';
  if (fieldName === 'introductionDate') return /^\d{4}-\d{2}-\d{2}$/.test(text) ? '' : 'Bitte geben Sie das Datum der Einführungsveranstaltung ein.';
  if (fieldName === 'privacy') return value ? '' : 'Bitte bestätigen Sie die Datenschutzhinweise.';
  return '';
}

export function validateBookingForm({ name = '', email = '', phone = '', privacyAccepted = false, introductionAttended = false, introductionDate = '', event = {} }) {
  const values = { name, email, phone, privacy: privacyAccepted };
  if (requiresIntroductionDetails(event)) Object.assign(values, { introductionAttended, introductionDate });
  return Object.fromEntries(Object.entries(values).map(([fieldName, value]) => [fieldName, validateBookingField(fieldName, value)]).filter(([, error]) => error));
}

export function canSubmitBookingForm(privacyAccepted) { return privacyAccepted; }
export function bookingConfirmationMessage(appointmentTitle) { return `Ihre Anfrage für ${appointmentTitle} wurde gespeichert. Bitte bestätigen Sie den Link aus der E-Mail innerhalb von 30 Minuten.`; }
function escapeHtml(value) { return String(value).replace(/[&<>'"]/g, (character) => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', "'": '&#39;', '"': '&quot;' })[character]); }

function createMonthDates(month) {
  const first = new Date(month.getFullYear(), month.getMonth(), 1);
  const dates = new Array((first.getDay() + 6) % 7).fill(null);
  const lastDay = new Date(month.getFullYear(), month.getMonth() + 1, 0).getDate();
  for (let day = 1; day <= lastDay; day += 1) dates.push(new Date(month.getFullYear(), month.getMonth(), day));
  return dates;
}

function loadSessionProfile() {
  try { const profile = JSON.parse(sessionStorage.getItem(sessionProfileKey) ?? '{}'); return typeof profile === 'object' && profile ? profile : {}; } catch { return {}; }
}
function saveSessionProfile(profile) { try { sessionStorage.setItem(sessionProfileKey, JSON.stringify(profile)); } catch { /* Speicherung ist optional. */ } }

function showFieldError(form, fieldName, error) {
  const field = form.elements.namedItem(fieldName);
  if (!field) return;
  const errorId = `sufw-booking-${fieldName}-error`;
  let message = form.querySelector(`#${errorId}`);
  if (!message) {
    message = document.createElement('span');
    message.id = errorId;
    message.className = 'sufw-booking__field-error';
    message.setAttribute('role', 'alert');
    const host = fieldName === 'privacy' || fieldName === 'introductionAttended' ? field.closest('label') : field;
    host.insertAdjacentElement('afterend', message);
    field.setAttribute('aria-describedby', errorId);
  }
  message.textContent = error;
  message.hidden = !error;
  field.setAttribute('aria-invalid', error ? 'true' : 'false');
}

function openConfirmationDialog(container, event) {
  const dialog = document.createElement('dialog');
  dialog.className = 'sufw-booking__dialog';
  dialog.setAttribute('aria-labelledby', 'sufw-booking-confirmation-title');
  dialog.innerHTML = `<section class="sufw-booking__form"><header class="sufw-booking__form-header"><p class="sufw-booking__eyebrow">E-Mail bestätigen</p><h2 id="sufw-booking-confirmation-title">Fast geschafft</h2><p>${escapeHtml(bookingConfirmationMessage(event.title))}</p></header><p class="sufw-booking__appointment"><strong>${escapeHtml(event.project === 'perspektivwerk' ? 'PerspektivWerk' : 'Produktionsschule')}</strong><br>${escapeHtml(dateFormatter.format(parseDate(event.startsAt.slice(0, 10))))} · ${formatEventTime(event)} · ${escapeHtml(event.title)}</p><p>Bitte prüfen Sie Ihr E-Mail-Postfach und bestätigen Sie dort Ihre Anfrage.</p><div class="sufw-booking__form-actions"><button type="button" data-close-confirmation>Schließen</button></div></section>`;
  dialog.querySelector('[data-close-confirmation]').addEventListener('click', () => dialog.close());
  dialog.addEventListener('close', () => dialog.remove());
  container.append(dialog);
  if (typeof dialog.showModal === 'function') dialog.showModal(); else { dialog.setAttribute('open', ''); dialog.querySelector('[data-close-confirmation]').focus(); }
}

function openBookingDialog(container, event, state) {
  const profile = loadSessionProfile();
  const requiresIntroduction = requiresIntroductionDetails(event);
  const dialog = document.createElement('dialog');
  dialog.className = 'sufw-booking__dialog';
  dialog.setAttribute('aria-labelledby', 'sufw-booking-form-title');
  dialog.innerHTML = `<form class="sufw-booking__form" novalidate><header class="sufw-booking__form-header"><p class="sufw-booking__eyebrow">Termin verbindlich anmelden</p><h2 id="sufw-booking-form-title">Ihre Angaben</h2><p class="sufw-booking__appointment"><strong>${escapeHtml(event.title)}</strong><br>${escapeHtml(dateFormatter.format(parseDate(event.startsAt.slice(0, 10))))} · ${formatEventTime(event)} · ${escapeHtml(formatEventDuration(event))} · ${escapeHtml(formatEventFormat(event))}</p></header><p class="sufw-booking__required"><span aria-hidden="true">*</span> Pflichtfeld</p><p class="sufw-booking__form-errors" role="alert" hidden></p><div class="sufw-booking__form-grid"><label>Vor- und Nachname <span aria-hidden="true">*</span><input name="name" type="text" autocomplete="name" maxlength="160" required value="${escapeHtml(profile.name ?? '')}"></label><label>E-Mail-Adresse <span aria-hidden="true">*</span><input name="email" type="email" autocomplete="email" maxlength="254" required value="${escapeHtml(profile.email ?? '')}"></label><label>Telefonnummer <span aria-hidden="true">*</span><input name="phone" type="tel" autocomplete="tel" maxlength="64" required value="${escapeHtml(profile.phone ?? '')}"></label></div>${requiresIntroduction ? '<fieldset class="sufw-booking__conditional"><legend>Voraussetzung für Probearbeiten</legend><label class="sufw-booking__consent"><input name="introductionAttended" type="checkbox" value="accepted"><span>Ich habe an einer Einführungsveranstaltung teilgenommen. <span aria-hidden="true">*</span></span></label><label>Datum der Einführungsveranstaltung <span aria-hidden="true">*</span><input name="introductionDate" type="date"></label></fieldset>' : ''}<label class="sufw-booking__consent"><input name="privacy" type="checkbox" value="accepted" required><span>Ich habe die Datenschutzhinweise nach Art. 13 DSGVO gelesen und stimme der Verarbeitung meiner Angaben zur Terminplanung zu. <span aria-hidden="true">*</span></span></label><div class="sufw-booking__form-actions"><button type="button" class="sufw-booking__secondary" data-close-dialog>Abbrechen</button><button type="submit" data-submit-booking disabled>Verbindlich anmelden</button></div></form>`;
  const form = dialog.querySelector('form');
  const submitButton = dialog.querySelector('[data-submit-booking]');
  const privacy = form.elements.namedItem('privacy');
  const fieldNames = ['name', 'email', 'phone', 'privacy', ...(requiresIntroduction ? ['introductionAttended', 'introductionDate'] : [])];
  const formError = form.querySelector('.sufw-booking__form-errors');
  const validateField = (fieldName) => {
    const field = form.elements.namedItem(fieldName);
    const value = fieldName === 'privacy' || fieldName === 'introductionAttended' ? field.checked : field.value;
    const error = validateBookingField(fieldName, value);
    showFieldError(form, fieldName, error);
    return error;
  };
  fieldNames.forEach((fieldName) => {
    const field = form.elements.namedItem(fieldName);
    field.addEventListener(field.type === 'checkbox' ? 'change' : 'input', () => validateField(fieldName));
    if (field.type !== 'checkbox') field.addEventListener('blur', () => validateField(fieldName));
  });
  privacy.addEventListener('change', () => { submitButton.disabled = !canSubmitBookingForm(privacy.checked); });
  form.addEventListener('submit', async (submitEvent) => {
    submitEvent.preventDefault();
    const values = Object.fromEntries(new FormData(form).entries());
    const booking = { name: values.name ?? '', email: values.email ?? '', phone: values.phone ?? '', privacyAccepted: privacy.checked, introductionAttended: form.elements.namedItem('introductionAttended')?.checked ?? false, introductionDate: values.introductionDate ?? '', event };
    const errors = validateBookingForm(booking);
    fieldNames.forEach((fieldName) => showFieldError(form, fieldName, errors[fieldName] ?? ''));
    if (Object.keys(errors).length) { form.elements.namedItem(Object.keys(errors)[0]).focus(); return; }
    submitButton.disabled = true;
    formError.hidden = true;
    try {
      const response = await fetch(state.apiUrl, { method: 'POST', credentials: 'same-origin', headers: { 'Content-Type': 'application/json', 'X-SUFW-Booking-CSRF': state.csrfToken }, body: JSON.stringify({ project: event.project, eventId: event.id, name: booking.name, email: booking.email, phone: booking.phone, privacyAccepted: true, introductionAttended: booking.introductionAttended, introductionDate: booking.introductionDate }) });
      const result = await response.json();
      if (!response.ok) throw new Error(result.error ?? 'Die Anmeldung konnte nicht gespeichert werden.');
      saveSessionProfile({ name: booking.name, email: booking.email, phone: booking.phone });
      dialog.close();
      await state.reload();
      openConfirmationDialog(container, event);
    } catch (error) {
      formError.textContent = error instanceof Error ? error.message : 'Die Anmeldung konnte nicht gespeichert werden.';
      formError.hidden = false;
      submitButton.disabled = false;
    }
  });
  dialog.querySelector('[data-close-dialog]').addEventListener('click', () => dialog.close());
  dialog.addEventListener('close', () => dialog.remove());
  container.append(dialog);
  if (typeof dialog.showModal === 'function') dialog.showModal(); else { dialog.setAttribute('open', ''); form.elements.namedItem('name').focus(); }
}

function renderComponent(container) {
  const project = container.dataset.project === 'produktionsschule' ? 'produktionsschule' : 'perspektivwerk';
  const now = new Date();
  const state = { apiUrl: container.dataset.apiUrl || 'booking/api.php', csrfToken: '', events: [], currentMonth: new Date(now.getFullYear(), now.getMonth(), 1), selectedDate: '' };
  const fetchEvents = async () => {
    const from = formatDateKey(state.currentMonth);
    const to = formatDateKey(new Date(state.currentMonth.getFullYear(), state.currentMonth.getMonth() + 1, 1));
    const response = await fetch(`${state.apiUrl}?${new URLSearchParams({ project, from, to })}`, { credentials: 'same-origin' });
    const result = await response.json();
    if (!response.ok) throw new Error(result.error ?? 'Der Kalender konnte nicht geladen werden.');
    state.events = result.events;
    state.csrfToken = result.csrfToken;
    if (!state.selectedDate && state.events.length) state.selectedDate = state.events[0].startsAt.slice(0, 10);
  };
  const render = () => {
    const slots = state.selectedDate ? getSlotsForDate(project, state.selectedDate, state.events) : [];
    const selectedLabel = state.selectedDate ? dateFormatter.format(parseDate(state.selectedDate)) : 'einen Tag';
    container.innerHTML = `<section class="sufw-booking" aria-labelledby="sufw-booking-title"><header class="sufw-booking__header"><p class="sufw-booking__eyebrow">Terminbuchung</p><h2 id="sufw-booking-title">${project === 'perspektivwerk' ? 'PerspektivWerk' : 'Produktionsschule'}</h2><p>Wählen Sie einen Tag. Termine zeigen Dauer, Format und freie Plätze.</p></header><div class="sufw-booking__legend" aria-label="Legende"><span><i class="sufw-booking__marker sufw-booking__marker--available"></i> Buchbar</span><span><i class="sufw-booking__marker sufw-booking__marker--booked"></i> Ausgebucht</span></div><div class="sufw-booking__month-nav"><button class="sufw-booking__nav" type="button" data-action="previous" aria-label="Vorheriger Monat">‹</button><h3 aria-live="polite">${monthFormatter.format(state.currentMonth)}</h3><button class="sufw-booking__nav" type="button" data-action="next" aria-label="Nächster Monat">›</button></div><div class="sufw-booking__weekdays" aria-hidden="true">${weekdays.map((weekday) => `<span>${weekday}</span>`).join('')}</div><div class="sufw-booking__calendar" role="grid" aria-label="Kalender ${monthFormatter.format(state.currentMonth)}">${createMonthDates(state.currentMonth).map((date) => {
      if (!date) return '<span class="sufw-booking__empty" aria-hidden="true"></span>';
      const key = formatDateKey(date); const daySlots = getSlotsForDate(project, key, state.events); const available = daySlots.some((event) => event.status === 'available'); const full = daySlots.length > 0 && !available; const selected = key === state.selectedDate;
      const label = daySlots.length ? `${dateFormatter.format(date)}: ${available ? 'Termine buchbar' : 'Termine ausgebucht'}` : dateFormatter.format(date);
      return `<button type="button" role="gridcell" class="sufw-booking__day sufw-booking__day--${available ? 'available' : full ? 'booked' : 'none'}${selected ? ' is-selected' : ''}" data-date="${key}" aria-pressed="${selected}" aria-label="${escapeHtml(label)}"><time datetime="${key}">${date.getDate()}</time>${daySlots.length ? `<small>${available ? 'freie Plätze' : 'ausgebucht'}</small>` : ''}</button>`;
    }).join('')}</div><section class="sufw-booking__slots" aria-labelledby="sufw-slot-title"><h3 id="sufw-slot-title">Termine am ${escapeHtml(selectedLabel)}</h3>${slots.length ? `<ul>${slots.map((event) => `<li><button type="button" class="sufw-booking__slot" data-event-id="${event.id}" ${event.status === 'full' ? 'disabled aria-disabled="true"' : ''}><strong>${escapeHtml(formatEventTime(event))}</strong><span>${escapeHtml(event.title)}<small>${escapeHtml(formatEventDuration(event))} · ${escapeHtml(formatEventFormat(event))}</small></span><em>${event.status === 'available' ? `${event.availableCapacity} ${event.availableCapacity === 1 ? 'Platz frei' : 'Plätze frei'}` : 'Ausgebucht'}</em></button></li>`).join('')}</ul>` : '<p class="sufw-booking__empty-state">Für diesen Tag liegen keine Termine vor.</p>'}<p class="sufw-booking__status" role="status" aria-live="polite"></p></section></section>`;
    container.querySelector('[data-action="previous"]').addEventListener('click', async () => { state.currentMonth = new Date(state.currentMonth.getFullYear(), state.currentMonth.getMonth() - 1, 1); state.selectedDate = ''; await loadAndRender(); });
    container.querySelector('[data-action="next"]').addEventListener('click', async () => { state.currentMonth = new Date(state.currentMonth.getFullYear(), state.currentMonth.getMonth() + 1, 1); state.selectedDate = ''; await loadAndRender(); });
    container.querySelectorAll('[data-date]').forEach((button) => button.addEventListener('click', () => { state.selectedDate = button.dataset.date ?? ''; render(); }));
    container.querySelectorAll('[data-event-id]').forEach((button) => button.addEventListener('click', () => { const event = state.events.find((entry) => entry.id === button.dataset.eventId); if (event) openBookingDialog(container, event, state); }));
  };
  const loadAndRender = async () => {
    container.setAttribute('aria-busy', 'true');
    try { await fetchEvents(); render(); }
    catch (error) { container.innerHTML = `<p class="sufw-booking__load-error" role="alert">${escapeHtml(error instanceof Error ? error.message : 'Der Kalender konnte nicht geladen werden.')}</p>`; }
    finally { container.removeAttribute('aria-busy'); }
  };
  state.reload = loadAndRender;
  loadAndRender();
}

export function initializeBookingComponents(root = document) { root.querySelectorAll('[data-sufw-booking]').forEach(renderComponent); }
if (typeof document !== 'undefined') { if (document.readyState === 'loading') document.addEventListener('DOMContentLoaded', () => initializeBookingComponents()); else initializeBookingComponents(); }