const PAGE_SIZE = 20;
let page = 1;
let total = 0;
let searchTimer = null;
let groupsLoaded = false;

function lessonDateText(iso) {
  const s = String(iso || '').slice(0, 10);
  if (!s) return '';
  const d = new Date(s + 'T00:00:00');
  if (Number.isNaN(d.getTime())) return s;
  return d.toLocaleDateString('ru-RU', { day: '2-digit', month: '2-digit', year: '2-digit' });
}

function lessonWhenText(r) {
  const date = lessonDateText(r.lesson_date);
  const time = r.lesson_time ? String(r.lesson_time).slice(0, 5) : '';
  return time ? `${date}, ${time}` : date;
}

function lessonAuthorText(r) {
  const name = r.author_name || r.author_username;
  if (!name) return '';
  const upd = r.updated_at && r.created_at && new Date(r.updated_at).getTime() - new Date(r.created_at).getTime() > 60000;
  return upd ? `${name} · изменён ${notifyTime(r.updated_at)}` : name;
}

function lessonItemHtml(r) {
  const isToday = String(r.lesson_date).slice(0, 10) === lessonTodayIso();
  const author = lessonAuthorText(r);
  return `
    <div class="lesson-item" data-lesson="${r.id}">
      <div class="lesson-item-head">
        <span class="lesson-group">${esc(r.group_name || '')}</span>
        <span class="lesson-when"><i data-lucide="clock-3"></i>${esc(lessonWhenText(r))}</span>
        ${isToday ? '<span class="lesson-badge today">сегодня</span>' : ''}
        <div class="lesson-actions">
          <button type="button" class="btn-link" data-edit="${r.id}">Редактировать</button>
          ${isAdmin() ? `<button type="button" class="btn-link danger" data-del="${r.id}">Удалить</button>` : ''}
        </div>
      </div>
      <div class="lesson-text">${esc(r.text || '')}</div>
      ${author ? `<div class="lesson-author">${esc(author)}</div>` : ''}
    </div>`;
}

function renderLessons(items) {
  const list = document.getElementById('lessonsList');
  const state = document.getElementById('lessonsState');
  list.innerHTML = items.length
    ? items.map(lessonItemHtml).join('')
    : '<div class="empty">Отчётов пока нет</div>';
  if (state) {
    state.textContent = total ? `Показано ${items.length} из ${total}` : '';
  }
  renderIcons();
}

async function loadLessons() {
  const q = new URLSearchParams();
  const gid = document.getElementById('groupFilter').value;
  const df = document.getElementById('dateFrom').value;
  const dt = document.getElementById('dateTo').value;
  const search = document.getElementById('searchInput').value.trim();
  if (gid) q.set('group_id', gid);
  if (df) q.set('date_from', df);
  if (dt) q.set('date_to', dt);
  if (search) q.set('search', search);
  q.set('limit', String(PAGE_SIZE));
  q.set('offset', String((page - 1) * PAGE_SIZE));
  const list = document.getElementById('lessonsList');
  try {
    const res = await fetch(`${API}/api/lesson-reports?${q.toString()}`, { headers: hdr() });
    if (!res.ok) {
      list.innerHTML = `<div class="empty">Ошибка загрузки (${res.status})</div>`;
      return;
    }
    const data = await res.json();
    total = Number(data.total) || 0;
    const maxPage = Math.max(1, Math.ceil(total / PAGE_SIZE));
    if (page > maxPage) { page = maxPage; return loadLessons(); }
    renderLessons(data.items || []);
    renderPager(document.getElementById('pager'), page, maxPage, p => { page = p; loadLessons(); });
  } catch {
    list.innerHTML = '<div class="empty">Ошибка сети</div>';
  }
}

async function loadGroupFilter() {
  if (groupsLoaded) return;
  const sel = document.getElementById('groupFilter');
  const groups = await loadLessonGroups();
  groups.forEach(g => {
    const o = document.createElement('option');
    o.value = g.id;
    o.textContent = g.branch_name ? `${g.name} (${g.branch_name})` : g.name;
    sel.appendChild(o);
  });
  groupsLoaded = true;
}

async function deleteLesson(id) {
  if (!confirm('Удалить отчёт о занятии?')) return;
  const res = await fetch(`${API}/api/lesson-reports/${id}`, { method: 'DELETE', headers: hdr() });
  const data = await res.json().catch(() => ({}));
  if (!res.ok) { showToast(data.error || 'Не удалось удалить отчёт'); return; }
  showToast('Отчёт удалён');
  loadLessons();
}

function onLessonReportSaved() {
  loadLessons();
}

document.getElementById('lessonsList').addEventListener('click', e => {
  const edit = e.target.closest('[data-edit]');
  if (edit) { openLessonModal({ id: edit.dataset.edit }); return; }
  const del = e.target.closest('[data-del]');
  if (del) { deleteLesson(del.dataset.del); }
});

document.getElementById('addLessonBtn').addEventListener('click', () => {
  openLessonModal({ groupId: document.getElementById('groupFilter').value });
});

document.getElementById('groupFilter').addEventListener('change', () => { page = 1; loadLessons(); });
document.getElementById('dateFrom').addEventListener('change', () => { page = 1; loadLessons(); });
document.getElementById('dateTo').addEventListener('change', () => { page = 1; loadLessons(); });
document.getElementById('searchInput').addEventListener('input', () => {
  clearTimeout(searchTimer);
  searchTimer = setTimeout(() => { page = 1; loadLessons(); }, 350);
});

(async () => {
  if (!(await checkAuth())) return;
  buildSidebar(document.body.dataset.page);
  await loadGroupFilter();
  loadLessons();
})();