let allStudents = [];
let allGroups = [];
let groupOptionsLoaded = false;
let sPage = 1;
const S_PAGE_SIZE = 25;
let sSearchTimer = null;
let aSearchTimer = null;
let attachGroupLoaded = false;

async function loadGroupOptions(sel, selected) {
  if (!groupOptionsLoaded) {
    const res = await fetch(`${API}/api/groups`, { headers: hdr() });
    allGroups = await res.json();
    groupOptionsLoaded = true;
    const filt = document.getElementById('studentGroupFilter');
    if (filt && filt.options.length <= 1) {
      filt.innerHTML = `<option value="">Все группы</option>` +
        allGroups.map(g => `<option value="${g.id}">${esc(g.name)}</option>`).join('');
    }
  }
  if (sel) {
    sel.innerHTML = `<option value="">— не привязана —</option>` +
      allGroups.map(g => `<option value="${g.id}" ${selected == g.id ? 'selected' : ''}>${esc(g.name)}</option>`).join('');
  }
}

async function loadStudents() {
  const res = await fetch(`${API}/api/students`, { headers: hdr() });
  allStudents = await res.json();
  renderStudents();
}

function renderStudents() {
  const q = document.getElementById('studentSearch').value.trim().toLowerCase();
  const gid = document.getElementById('studentGroupFilter').value;
  let filtered = q ? allStudents.filter(s => s.name.toLowerCase().includes(q)) : allStudents;
  if (gid) filtered = filtered.filter(s => String(s.group_id) === gid);
  const totalPages = Math.max(1, Math.ceil(filtered.length / S_PAGE_SIZE));
  if (sPage > totalPages) sPage = 1;
  const slice = filtered.slice((sPage - 1) * S_PAGE_SIZE, sPage * S_PAGE_SIZE);
  const list = document.getElementById('studentList');
  if (!slice.length) { list.innerHTML = '<div style="color:var(--muted);text-align:center;padding:32px">Ничего не найдено</div>'; }
  else {
    list.innerHTML = slice.map(s => `
      <div class="item">
        <input class="name-input student-name-input" id="sname-${s.id}" value="${esc(s.name)}">
        <select class="group-select" id="sgroup-${s.id}"></select>
        <div class="student-actions">
          <button class="btn-save" data-save-student="${s.id}">Сохранить</button>
          <button class="btn-link" data-copy-student="${esc(s.name)}" title="Скопировать ссылку с подстановкой имени">Ссылка</button>
          <button class="btn-del" data-del-student="${s.id}" title="Удалить">&times;</button>
        </div>
      </div>
    `).join('');
    slice.forEach(s => loadGroupOptions(document.getElementById(`sgroup-${s.id}`), s.group_id));
  }
  renderPager(document.getElementById('pager'), sPage, totalPages, goStudentPage);
}

function goStudentPage(p) {
  sPage = p;
  renderStudents();
}

async function addStudent() {
  const input = document.getElementById('newStudent');
  const name = input.value.trim();
  if (!name) return;
  const res = await fetch(`${API}/api/students`, { method: 'POST', headers: hdrJson(), body: JSON.stringify({ name }) });
  if (res.ok) { input.value = ''; loadStudents(); fillAutocomplete(); showToast(`Добавлен: ${name}`); }
  else { const e = await res.json(); alert(e.error); }
}

async function saveStudent(id) {
  const name = document.getElementById(`sname-${id}`).value.trim();
  if (!name) return;
  const group_id = document.getElementById(`sgroup-${id}`).value;
  const res = await fetch(`${API}/api/students/${id}`, { method: 'PUT', headers: hdrJson(), body: JSON.stringify({ name, group_id }) });
  if (res.ok) { loadStudents(); fillAutocomplete(); showToast(`Сохранено: ${name}`); }
  else { const e = await res.json(); alert(e.error); }
}

async function delStudent(id) {
  if (!confirm('Удалить ученика из списка? Старые записи останутся.')) return;
  await fetch(`${API}/api/students/${id}`, { method: 'DELETE', headers: hdr() });
  loadStudents();
  fillAutocomplete();
}

function openBatchAdd() {
  document.getElementById('batchText').value = '';
  loadGroupOptions(document.getElementById('batchGroup'), '');
  document.getElementById('batchModal').classList.add('open');
}

function closeBatchAdd() {
  document.getElementById('batchModal').classList.remove('open');
}

async function batchAdd() {
  const raw = document.getElementById('batchText').value;
  const names = [...new Set(raw.split('\n').map(s => s.trim()).filter(Boolean))];
  if (!names.length) return;
  const group_id = document.getElementById('batchGroup').value;
  let added = 0, dupes = 0;
  for (const name of names) {
    const res = await fetch(`${API}/api/students`, { method: 'POST', headers: hdrJson(), body: JSON.stringify({ name, group_id: group_id || null }) });
    if (res.ok) added++;
    else if (res.status === 409) dupes++;
  }
  closeBatchAdd();
  loadStudents();
  fillAutocomplete();
  showToast(`Добавлено: ${added}${dupes ? `, дубликатов: ${dupes}` : ''}`);
}

document.getElementById('newStudent').addEventListener('keydown', e => { if (e.key === 'Enter') addStudent(); });
document.getElementById('batchForm').addEventListener('submit', e => {
  e.preventDefault();
  batchAdd();
});
document.getElementById('studentSearch').addEventListener('input', () => {
  clearTimeout(sSearchTimer);
  sSearchTimer = setTimeout(() => { sPage = 1; renderStudents(); }, 300);
});
document.getElementById('studentGroupFilter').addEventListener('change', () => { sPage = 1; renderStudents(); });

function exportStudentsCSV() {
  const gid = document.getElementById('studentGroupFilter').value;
  const list = gid ? allStudents.filter(s => String(s.group_id) === gid) : allStudents;
  if (!list.length) { alert('Нет данных для экспорта'); return; }
  const rows = [['Фамилия Имя', 'Группа', 'Ссылка на страницу']];
  list.forEach(s => {
    rows.push([
      s.name,
      s.group_name || '',
      `${location.origin}/?nameInput=${encodeURIComponent(s.name)}`
    ]);
  });
  const csv = rows.map(r => r.map(c => `"${String(c).replace(/"/g, '""')}"`).join(';')).join('\n');
  const blob = new Blob(['\uFEFF' + csv], { type: 'text/csv;charset=utf-8' });
  const url = URL.createObjectURL(blob);
  const a = document.createElement('a');
  a.href = url;
  const groupName = gid ? (allGroups.find(g => g.id == gid)?.name || 'group') : 'all';
  a.download = `students_${groupName.replace(/[\\/:*?"<>|]/g, '_')}.csv`;
  a.click();
  URL.revokeObjectURL(url);
  showToast(`Экспортировано: ${list.length}`);
}

async function exportStudentsUrls() {
  const gid = document.getElementById('studentGroupFilter').value;
  const list = gid ? allStudents.filter(s => String(s.group_id) === gid) : allStudents;
  if (!list.length) { alert('Нет данных для экспорта'); return; }
  const groupName = gid ? (allGroups.find(g => g.id == gid)?.name || 'group') : 'all';
  await exportStudentUrlZip(list, `students_${groupName.replace(/[\\/:*?"<>|]/g, '_')}.zip`);
  showToast(`Экспортировано: ${list.length}`);
}

async function openBatchAttach() {
  const sel = document.getElementById('attachGroup');
  if (!attachGroupLoaded) {
    const res = await fetch(`${API}/api/groups`, { headers: hdr() });
    const groups = await res.json();
    sel.innerHTML = `<option value="">— выберите группу —</option>` +
      groups.map(g => `<option value="${g.id}">${esc(g.name)}</option>`).join('');
    attachGroupLoaded = true;
  }
  document.getElementById('attachSearch').value = '';
  renderAttachList();
  document.getElementById('attachModal').classList.add('open');
}

function closeBatchAttach() {
  document.getElementById('attachModal').classList.remove('open');
}

function renderAttachList() {
  const q = document.getElementById('attachSearch').value.trim().toLowerCase();
  const filtered = q ? allStudents.filter(s => s.name.toLowerCase().includes(q)) : allStudents;
  const list = document.getElementById('attachList');
  if (!filtered.length) { list.innerHTML = '<div style="color:var(--muted);text-align:center;padding:16px">Никого не найдено</div>'; return; }
  list.innerHTML = filtered.map(s => `
    <label>
      <input type="checkbox" value="${s.id}">
      <span>${esc(s.name)}</span>
      <span class="cur">${s.group_name ? esc(s.group_name) : ''}</span>
    </label>
  `).join('');
}

async function batchAttach() {
  const group_id = document.getElementById('attachGroup').value;
  const ids = [...document.querySelectorAll('#attachList input[type=checkbox]:checked')].map(c => c.value);
  if (!group_id) { alert('Выберите группу'); return; }
  if (!ids.length) { alert('Выберите учеников'); return; }
  const res = await fetch(`${API}/api/students/batch-group`, {
    method: 'POST',
    headers: hdrJson(),
    body: JSON.stringify({ group_id, student_ids: ids })
  });
  if (res.ok) {
    const r = await res.json();
    closeBatchAttach();
    loadStudents();
    showToast(`Прикреплено: ${r.updated}`);
  } else { const e = await res.json(); alert(e.error); }
}

document.getElementById('attachForm').addEventListener('submit', e => {
  e.preventDefault();
  batchAttach();
});
document.getElementById('attachSearch').addEventListener('input', () => {
  clearTimeout(aSearchTimer);
  aSearchTimer = setTimeout(renderAttachList, 300);
});

document.getElementById('addStudentBtn').addEventListener('click', addStudent);
document.getElementById('batchAddBtn').addEventListener('click', openBatchAdd);
document.getElementById('batchAttachBtn').addEventListener('click', openBatchAttach);
document.getElementById('exportStudentsCsvBtn').addEventListener('click', exportStudentsCSV);
document.getElementById('exportStudentsUrlsBtn').addEventListener('click', exportStudentsUrls);
document.getElementById('batchModal').addEventListener('click', e => { if (e.target === e.currentTarget) closeBatchAdd(); });
document.getElementById('attachModal').addEventListener('click', e => { if (e.target === e.currentTarget) closeBatchAttach(); });
document.getElementById('batchCancelBtn').addEventListener('click', closeBatchAdd);
document.getElementById('attachCancelBtn').addEventListener('click', closeBatchAttach);

document.getElementById('studentList').addEventListener('click', e => {
  const sv = e.target.closest('[data-save-student]');
  if (sv) { saveStudent(parseInt(sv.dataset.saveStudent, 10)); return; }
  const cp = e.target.closest('[data-copy-student]');
  if (cp) { copyStudentLink(cp.dataset.copyStudent); return; }
  const dl = e.target.closest('[data-del-student]');
  if (dl) { delStudent(parseInt(dl.dataset.delStudent, 10)); }
});

(async () => {
  if (await checkAuth()) {
    buildSidebar(document.body.dataset.page);
    fillAutocomplete();
    loadGroupOptions();
    loadStudents();
  }
})();