import {
  $, api, esc, sortByName, showError, renderHeader,
  toIso, fromIso, formatDate, getMe, setMe,
} from './common.js';

renderHeader('kalender');

let members = [];
let events = [];
let me = getMe();

const todayIso = toIso(new Date());
let selectedDay = todayIso;
let viewMonth = fromIso(todayIso);
viewMonth.setDate(1);

const memberName = (id) => members.find((m) => m.id === id)?.name ?? '(gelöscht)';

// ---------- "Ich bin" ----------
function renderMe() {
  if (me && !members.some((m) => m.id === me)) me = null;
  $('#me-select').innerHTML = '<option value="">– bitte auswählen –</option>' +
    sortByName(members).map((m) =>
      `<option value="${m.id}" ${m.id === me ? 'selected' : ''}>${esc(m.name)}</option>`).join('');
  $('#me-hint').hidden = !!me;
  $('#event-form button[type=submit]').disabled = !me;
}

$('#me-select').addEventListener('change', (e) => {
  me = e.target.value || null;
  setMe(me);
  renderAll();
});

// ---------- Monatsansicht ----------
function renderCalendar() {
  const title = viewMonth.toLocaleDateString('de-DE', { month: 'long', year: 'numeric' });
  $('#month-title').textContent = title;

  // Raster beginnt am Montag vor (oder am) Monatsersten
  const start = new Date(viewMonth);
  start.setDate(1 - ((start.getDay() + 6) % 7));

  const byDate = new Map();
  for (const ev of events) {
    if (!byDate.has(ev.date)) byDate.set(ev.date, []);
    byDate.get(ev.date).push(ev);
  }

  let html = ['Mo', 'Di', 'Mi', 'Do', 'Fr', 'Sa', 'So'].map((d) => `<div class="dow">${d}</div>`).join('');
  const day = new Date(start);
  for (let i = 0; i < 42; i++) {
    const iso = toIso(day);
    const classes = ['cal-day'];
    if (day.getMonth() !== viewMonth.getMonth()) classes.push('other');
    if (iso === todayIso) classes.push('today');
    if (iso === selectedDay) classes.push('selected');
    const dayEvents = byDate.get(iso) || [];
    html += `
      <button class="${classes.join(' ')}" data-day="${iso}">
        <span class="num">${day.getDate()}</span>
        ${dayEvents.map((ev) => `<span class="ev ${ev.attendees.includes(me) ? 'mine' : ''}"
          title="${esc(ev.title)} (${ev.attendees.length} zugesagt)">${esc(ev.title)} · ${ev.attendees.length}</span>`).join('')}
      </button>`;
    day.setDate(day.getDate() + 1);
  }
  $('#calendar').innerHTML = html;
}

$('#calendar').addEventListener('click', (e) => {
  const cell = e.target.closest('[data-day]');
  if (!cell) return;
  selectedDay = cell.dataset.day;
  const d = fromIso(selectedDay);
  if (d.getMonth() !== viewMonth.getMonth()) viewMonth = new Date(d.getFullYear(), d.getMonth(), 1);
  renderAll();
  $('#day-title').scrollIntoView({ behavior: 'smooth', block: 'start' });
});

function shiftMonth(delta) {
  viewMonth = new Date(viewMonth.getFullYear(), viewMonth.getMonth() + delta, 1);
  renderCalendar();
}
$('#prev-month').addEventListener('click', () => shiftMonth(-1));
$('#next-month').addEventListener('click', () => shiftMonth(1));
$('#today-btn').addEventListener('click', () => {
  selectedDay = todayIso;
  viewMonth = fromIso(todayIso);
  viewMonth.setDate(1);
  renderAll();
});

// ---------- Termine ----------
function eventHtml(ev) {
  const going = ev.attendees.includes(me);
  const attendees = sortByName(ev.attendees.map((id) => ({ id, name: memberName(id) })));
  return `
    <div class="event">
      <h3>${esc(ev.title)}</h3>
      <div class="when">${formatDate(ev.date, true)}${ev.createdBy ? ` · eingetragen von ${esc(memberName(ev.createdBy))}` : ''}</div>
      ${ev.note ? `<div class="note">${esc(ev.note)}</div>` : ''}
      <div class="muted">${ev.attendees.length} zugesagt:</div>
      <div class="chips">
        ${attendees.length
          ? attendees.map((a) => `<span class="chip ${a.id === me ? 'me' : ''}">${esc(a.name)}</span>`).join('')
          : '<span class="muted">noch niemand</span>'}
      </div>
      <div class="row wrap">
        ${me ? (going
          ? `<button data-action="leave" data-id="${ev.id}">Absagen</button>`
          : `<button class="primary" data-action="join" data-id="${ev.id}">Ich bin dabei</button>`) : ''}
        <a class="button" href="/fahrt?termin=${ev.id}">Fahrt planen</a>
        <button class="link danger" data-action="delete" data-id="${ev.id}">Löschen</button>
      </div>
    </div>`;
}

function renderDay() {
  $('#day-title').textContent = fromIso(selectedDay).toLocaleDateString('de-DE', {
    weekday: 'long', day: 'numeric', month: 'long', year: 'numeric',
  });
  const dayEvents = events.filter((e) => e.date === selectedDay);
  $('#day-events').innerHTML = dayEvents.length
    ? dayEvents.map(eventHtml).join('')
    : '<p class="muted">An diesem Tag ist noch kein Spieltag eingetragen.</p>';
}

function renderUpcoming() {
  const upcoming = events.filter((e) => e.date >= todayIso);
  $('#upcoming').innerHTML = upcoming.length
    ? upcoming.map(eventHtml).join('')
    : '<p class="muted">Keine kommenden Spieltage.</p>';
}

document.addEventListener('click', async (e) => {
  const btn = e.target.closest('[data-action]');
  if (!btn) return;
  const { action, id } = btn.dataset;
  try {
    if (action === 'join') await api('PUT', `/events/${id}/attendees/${me}`);
    if (action === 'leave') await api('DELETE', `/events/${id}/attendees/${me}`);
    if (action === 'delete') {
      const ev = events.find((x) => x.id === id);
      if (!confirm(`Spieltag „${ev.title}“ am ${formatDate(ev.date)} wirklich löschen?`)) return;
      await api('DELETE', `/events/${id}`);
    }
    await load();
  } catch (err) {
    showError(err);
  }
});

$('#event-form').addEventListener('submit', async (e) => {
  e.preventDefault();
  try {
    await api('POST', '/events', {
      date: selectedDay,
      title: $('#event-title').value,
      note: $('#event-note').value,
      createdBy: me,
    });
    e.target.reset();
    await load();
  } catch (err) {
    showError(err);
  }
});

// ---------- Laden ----------
function renderAll() {
  renderMe();
  renderCalendar();
  renderDay();
  renderUpcoming();
}

async function load() {
  [members, events] = await Promise.all([api('GET', '/members'), api('GET', '/events')]);
  renderAll();
}

load().catch(showError);