const API = '/api';

/* ── токен ────────────────────────────────────────────────────────────── */
function getToken()        { return localStorage.getItem('ls_token'); }
function setToken(t)       { localStorage.setItem('ls_token', t); }
function removeToken()     { localStorage.removeItem('ls_token'); }
function getUser()         { return JSON.parse(localStorage.getItem('ls_user') || 'null'); }
function setUser(u)        { localStorage.setItem('ls_user', JSON.stringify(u)); }
function removeUser()      { localStorage.removeItem('ls_user'); }

function isLoggedIn()      { return !!getToken(); }

function logout() {
  removeToken();
  removeUser();
  window.location.href = '/login';
}

/* ── базовый fetch ────────────────────────────────────────────────────── */
async function req(method, path, body) {
  const headers = { 'Content-Type': 'application/json' };
  const token = getToken();
  if (token) headers['Authorization'] = `Bearer ${token}`;

  const res = await fetch(API + path, {
    method,
    headers,
    body: body ? JSON.stringify(body) : undefined,
  });

  const data = await res.json().catch(() => ({}));
  if (!res.ok) {
    if (res.status === 401) {
      localStorage.removeItem('ls_token'); localStorage.removeItem('ls_user');
      if (window.location.pathname !== '/login') { window.location.href = '/login'; return; }
      throw Object.assign(new Error(data.error || 'Unauthorized'), { status: 401, data });
    }
    if (res.status === 403) {
      if (typeof LS !== 'undefined' && LS.toast) LS.toast('Нет доступа', 'error');
      throw Object.assign(new Error(data.error || 'Forbidden'), { status: 403, data });
    }
    throw Object.assign(new Error(data.error || 'Request failed'), { status: res.status, data });
  }
  return data;
}

/* ── auth ─────────────────────────────────────────────────────────────── */
async function register(email, password, name) {
  const data = await req('POST', '/auth/register', { email, password, name });
  setToken(data.token);
  setUser(data.user);
  return data;
}

async function login(email, password) {
  const data = await req('POST', '/auth/login', { email, password });
  setToken(data.token);
  setUser(data.user);
  return data;
}

async function fetchMe() {
  return req('GET', '/auth/me');
}

async function updateProfile(data) {
  const result = await req('PATCH', '/auth/profile', data);
  if (result.token) setToken(result.token);
  if (result.user)  setUser(result.user);
  return result;
}

/* ── subjects ─────────────────────────────────────────────────────────── */
async function getSubjects()             { return req('GET',   '/subjects'); }
async function updateSubject(slug, data) { return req('PATCH', `/subjects/${slug}`, data); }
async function getTopics(slug)           { return req('GET',   `/subjects/${slug}/topics`); }

/* ── sessions ─────────────────────────────────────────────────────────── */
async function startSession(subject_slug, mode = 'exam', count = 25, topic_id = null, test_id = null) {
  return req('POST', '/sessions', { subject_slug, mode, count, topic_id, test_id });
}

async function sendAnswer(session_id, question_id, option_id, time_spent_sec, answer_text, chosen_options) {
  // Retry up to 3x on network failures (loss of answer is unacceptable mid-test).
  // Server is idempotent: same (session, question) overwrites; safe to retry.
  // Don't retry on 4xx (validation/auth errors).
  const body = { question_id, option_id, time_spent_sec, answer_text, chosen_options };
  let lastErr;
  for (let attempt = 0; attempt < 3; attempt++) {
    try {
      return await req('POST', `/sessions/${session_id}/answer`, body);
    } catch (e) {
      lastErr = e;
      const code = e?.status || 0;
      if (code >= 400 && code < 500) throw e;        // permanent error — abort
      await new Promise(r => setTimeout(r, 300 * (attempt + 1) ** 2)); // 300, 1200, 2700ms
    }
  }
  throw lastErr;
}

async function finishSession(session_id) {
  return req('POST', `/sessions/${session_id}/finish`);
}

async function getResult(session_id) {
  return req('GET', `/sessions/${session_id}/result`);
}

async function getHistory(page = 1, limit = 20) {
  return req('GET', `/sessions/history?page=${page}&limit=${limit}`);
}

async function getSessionQuestions(id) {
  return req('GET', `/sessions/${id}/questions`);
}

async function getWeakTopics() {
  return req('GET', '/sessions/weak-topics');
}
async function getStudentStats() {
  return req('GET', '/sessions/stats');
}

/* ── questions ────────────────────────────────────────────────────────── */
async function getQuestions(subject, topic_id, sort, page, limit) {
  const p = new URLSearchParams();
  if (subject)  p.set('subject',  subject);
  if (topic_id) p.set('topic_id', topic_id);
  if (sort)     p.set('sort',     sort);
  if (page)     p.set('page',     page);
  if (limit)    p.set('limit',    limit);
  const data = await req('GET', `/questions?${p}`);
  // API returns { rows, total, page, limit } — extract rows for compat
  return Array.isArray(data) ? data : data.rows;
}
async function createQuestion(data)      { return req('POST',   '/questions',            data); }
async function duplicateQuestion(id)     { return req('POST',   `/questions/${id}/copy`, {}); }
async function updateQuestion(id, data)  { return req('PUT',    `/questions/${id}`,      data); }
async function deleteQuestion(id)        { return req('DELETE', `/questions/${id}`); }
async function importQuestions(formData) {
  const token = getToken();
  const headers = {};
  if (token) headers['Authorization'] = `Bearer ${token}`;
  const res  = await fetch(API + '/questions/import', { method: 'POST', headers, body: formData });
  const data = await res.json().catch(() => ({}));
  if (!res.ok) throw Object.assign(new Error(data.error || 'Request failed'), { status: res.status, data });
  return data;
}

/* ── admin ────────────────────────────────────────────────────────────── */
async function adminGetStats()              { return req('GET',   '/admin/stats'); }
async function adminGetOverview()           { return req('GET',   '/admin/overview'); }
async function adminGlobalSearch(q) {
  // Limits are hardcoded server-side (top 5 users / 3 tests / 3 classes).
  return req('GET', `/admin/search?q=${encodeURIComponent(q)}`);
}
async function adminGetUsers(params = {})   {
  const p = new URLSearchParams();
  if (params.page)  p.set('page',  params.page);
  if (params.limit) p.set('limit', params.limit);
  if (params.role)  p.set('role',  params.role);
  if (params.q)     p.set('q',     params.q);
  // Returns { users, total, page, limit } (or { users, nextCursor, limit } if cursor used)
  return req('GET', `/admin/users?${p}`);
}
async function adminUpdateRole(id, role)    { return req('PATCH', `/admin/users/${id}/role`, { role }); }
async function adminGetUserSessions(id)     { return req('GET',   `/admin/users/${id}/sessions`); }
async function adminGetSessions(params = {}) {
  const p = new URLSearchParams();
  if (params.subject)  p.set('subject',  params.subject);
  if (params.user_id)  p.set('user_id',  params.user_id);
  if (params.limit)    p.set('limit',    params.limit);
  if (params.offset)   p.set('offset',   params.offset);
  return req('GET', `/admin/sessions?${p}`);
}
async function adminGetSessionDetail(id)    { return req('GET',   `/admin/sessions/${id}`); }
async function adminDeleteSession(id)       { return req('DELETE',`/admin/sessions/${id}`); }
async function adminClearUserSessions(id)  { return req('POST', `/admin/users/${id}/sessions/clear`); }
async function adminUpdateUser(id, data)   { return req('PATCH',  `/admin/users/${id}`, data); }
async function adminBanUser(id, banned)    { return req('PATCH',  `/admin/users/${id}/ban`, { banned }); }
async function adminDeleteUser(id)         { return req('DELETE', `/admin/users/${id}`); }

/* ── classes (teacher/admin) ──────────────────────────────────────────── */
async function getClasses()                    { return req('GET',    '/classes'); }
async function createClass(data)               { return req('POST',   '/classes', data); }
async function getClassDetail(id)              { return req('GET',    `/classes/${id}`); }
async function updateClass(id, data)           { return req('PATCH',  `/classes/${id}`, data); }
async function deleteClass(id)                 { return req('DELETE', `/classes/${id}`); }
async function kickMember(classId, userId)     { return req('DELETE', `/classes/${classId}/members/${userId}`); }
async function regenerateInviteCode(classId)   { return req('POST',   `/classes/${classId}/new-code`); }
async function classJournal(classId)           { return req('GET',    `/classes/${classId}/journal`); }
async function createAssignment(classId, data)  { return req('POST',   `/classes/${classId}/assignments`, data); }
async function createDirectAssignment(data)     { return req('POST',   '/assignments', data); }
async function updateAssignment(id, data)       { return req('PUT',    `/assignments/${id}`,  data); }
async function deleteAssignment(id)             { return req('DELETE', `/assignments/${id}`); }

/* ── classes (student) ────────────────────────────────────────────────── */
async function joinClass(invite_code)          { return req('POST',   '/classes/join', { invite_code }); }
async function myClasses()                     { return req('GET',    '/classes/student/my'); }
async function getStudents()                   { return req('GET',    '/classes/students'); }
async function classFeed(classId)              { return req('GET',    `/classes/${classId}/feed`); }

/* ── assignments (student) ────────────────────────────────────────────── */
async function myAssignments()                 { return req('GET',    '/assignments/my'); }
async function teacherAssignments()            { return req('GET',    '/assignments/teacher'); }
async function startAssignment(id)             { return req('POST',   `/assignments/${id}/start`); }
async function assignmentResults(id)           { return req('GET',    `/assignments/${id}/results`); }
async function assignmentSessionReview(assignment_id, session_id) {
  return req('GET', `/assignments/${assignment_id}/sessions/${session_id}/review`);
}
async function assignmentQuestionStats(id)         { return req('GET', `/assignments/${id}/question-stats`); }

/* ── tests ────────────────────────────────────────────────────────────── */
async function getTests(subject) {
  const p = subject ? `?subject=${subject}` : '';
  return req('GET', `/tests${p}`);
}
async function createTest(data)                    { return req('POST',   '/tests', data); }
async function getTest(id)                         { return req('GET',    `/tests/${id}`); }
async function updateTest(id, data)                { return req('PUT',    `/tests/${id}`, data); }
async function deleteTest(id)                      { return req('DELETE', `/tests/${id}`); }
async function addQuestionsToTest(id, question_ids){ return req('POST',   `/tests/${id}/questions`, { question_ids }); }
async function removeQFromTest(tid, qid)           { return req('DELETE', `/tests/${tid}/questions/${qid}`); }

/* ── gamification ────────────────────────────────────────────────────── */
async function getGamificationMe()        { return req('GET', '/gamification/me'); }
async function getGamAchievements()       { return req('GET', '/gamification/achievements'); }
async function getLeaderboard(params = {}) {
  const p = new URLSearchParams();
  if (params.class_id) p.set('class_id', params.class_id);
  if (params.period)   p.set('period',   params.period);
  return req('GET', `/gamification/leaderboard?${p}`);
}
async function getXPHistory(limit)        { return req('GET', `/gamification/xp-history?limit=${limit || 20}`); }
async function getChallenges()            { return req('GET', '/gamification/challenges'); }
async function claimChallenge(id)         { return req('POST', `/gamification/challenges/${id}/claim`); }
async function setGoalTier(tier)          { return req('POST', '/gamification/goal-tier', { tier }); }
async function getFrames()                { return req('GET', '/gamification/frames'); }
async function setFrame(frame)            { return req('POST', '/gamification/frame', { frame }); }
async function reportLabActivity(reactionsDiscovered) { return req('POST', '/gamification/lab-activity', { reactionsDiscovered: reactionsDiscovered || 0 }); }

/* ── утилиты ──────────────────────────────────────────────────────────── */
function escapeHtml(str) {
  if (typeof str !== 'string') return str;
  return str.replace(/&/g,'&amp;').replace(/</g,'&lt;').replace(/>/g,'&gt;').replace(/"/g,'&quot;');
}
const esc = escapeHtml;

function parseDate(dateStr) {
  if (!dateStr) return new Date(0);
  return new Date(dateStr.replace(' ', 'T') + (dateStr.includes('Z') || dateStr.includes('+') ? '' : 'Z'));
}

function fmtRelTime(dateStr) {
  const d = parseDate(dateStr);
  const m = Math.floor((Date.now() - d.getTime()) / 60000);
  if (m < 1) return 'только что';
  if (m < 60) return `${m} мин назад`;
  const h = Math.floor(m / 60);
  if (h < 24) return `${h} ч назад`;
  return d.toLocaleDateString('ru', { day: 'numeric', month: 'short' });
}

function safeHref(link) { return link && /^\/[a-z]/.test(link) ? link : '#'; }

function requireAuth() {
  if (!isLoggedIn()) {
    window.location.href = '/login';
    return false;
  }
  return true;
}

/* ── SVG-иконки ──────────────────────────────────────────────────────── */
const _ICONS = {
  trophy:     '<path d="M6 9H4V5h16v4h-2"/><path d="M6 9a6 6 0 006 6 6 6 0 006-6"/><path d="M12 15v3m-4 3h8" stroke-linecap="round"/>',
  target:     '<circle cx="12" cy="12" r="10"/><circle cx="12" cy="12" r="6"/><circle cx="12" cy="12" r="2"/>',
  flame:      '<path d="M12 2c.5 3.5-1.5 6-1.5 6 1 1.5 3 2 3 5a4 4 0 01-8 0c0-2 .5-3 1.5-4.5C8.5 6.5 7 4.5 7 4.5S9.5 2 12 2z"/>',
  zap:        '<path d="M13 2L3 14h9l-1 8 10-12h-9l1-8z"/>',
  sparkles:   '<path d="M12 2l1.5 4.5L18 8l-4.5 1.5L12 14l-1.5-4.5L6 8l4.5-1.5L12 2zm6 10l1 2.5L21.5 16 19 17l-1 2.5-1-2.5L14.5 16 17 15l1-2.5zM4 16l.75 2L7 18.75 4.75 19.5 4 22l-.75-2.5L1 18.75 3.25 18 4 16z" fill="currentColor" stroke="none"/>',
  diamond:    '<path d="M2.7 9l4-6h10.6l4 6L12 22 2.7 9z"/><path d="M2.7 9h18.6" stroke-linecap="round"/>',
  'book-open':'<path d="M2 3h6a4 4 0 014 4v14a3 3 0 00-3-3H2V3zm20 0h-6a4 4 0 00-4 4v14a3 3 0 013-3h7V3z"/>',
  running:    '<circle cx="14" cy="4" r="2" fill="currentColor" stroke="none"/><path d="M18 9l-4.35 2.17-2.18-2.58L7 12l1.5 1.5 2.5-2 1.73 2.05L10 17l-3 4m7-8l2 4h3"/>',
  'check-circle':'<path d="M22 11.08V12a10 10 0 11-5.93-9.14M22 4L12 14.01l-3-3"/>',
  hundred:    '<text x="12" y="16" text-anchor="middle" font-size="14" font-weight="bold" fill="currentColor" stroke="none" font-family="sans-serif">100</text>',
  school:     '<path d="M2 10l10-6 10 6-10 6z"/><path d="M6 13v5c0 1.5 2.7 3 6 3s6-1.5 6-3v-5"/><path d="M22 10v6" stroke-linecap="round"/>',
  'file-text':'<path d="M14 2H6a2 2 0 00-2 2v16a2 2 0 002 2h12a2 2 0 002-2V8l-6-6z"/><path d="M14 2v6h6M16 13H8m8 4H8m2-8H8"/>',
  books:      '<rect x="2" y="4" width="6" height="16" rx="1"/><rect x="10" y="2" width="6" height="18" rx="1"/><path d="M18 5l3.5 15.5-1 .2L17 5.5l1-.5z"/>',
  star:       '<path d="M12 2l3.09 6.26L22 9.27l-5 4.87L18.18 21 12 17.27 5.82 21 7 14.14 2 9.27l6.91-1.01L12 2z"/>',
  crown:      '<path d="M2 17l3-10 4 4 3-6 3 6 4-4 3 10z" fill="currentColor" stroke="none"/><rect x="2" y="17" width="20" height="3" rx="1" fill="currentColor" stroke="none"/>',
  brain:      '<path d="M9.5 2a4.5 4.5 0 00-3.8 6.9A4 4 0 004 13a4 4 0 003 3.87V21h2v-4.13A4 4 0 0012 13v-1m2.5-10a4.5 4.5 0 013.8 6.9A4 4 0 0020 13a4 4 0 00-3 3.87V21h-2v-4.13A4 4 0 0012 13v-1"/>',
  party:      '<path d="M5.8 11.3L2 22l10.7-3.8M5.8 11.3l4.8 4.8m-4.8-4.8L12 2l1.2 5.3m-2.4 8.6L22 12l-5.3-1.2M15 4l2 2m-8 8l2 2"/>',
  'thumbs-up':'<path d="M14 9V5a3 3 0 00-6 0v1l-2 6v7a1 1 0 001 1h9.28a2 2 0 001.94-1.57l1.56-7A2 2 0 0017.86 9H14z"/>',
  muscle:     '<path d="M7 11c0-2 1-4 3-4s3 2 3 2 1-2 3-2 3 2 3 4v4a6 6 0 01-6 6H9a6 6 0 01-6-6v-2c0-2 1-3 2-3s2 1 2 3"/>',
  trash:      '<path d="M3 6h18M8 6V4a2 2 0 012-2h4a2 2 0 012 2v2m3 0v14a2 2 0 01-2 2H7a2 2 0 01-2-2V6h14zM10 11v6m4-6v6"/>',
  'help-circle':'<circle cx="12" cy="12" r="10"/><path d="M9.09 9a3 3 0 015.83 1c0 2-3 3-3 3m.08 4h.01"/>',
  clipboard:  '<path d="M16 4h2a2 2 0 012 2v14a2 2 0 01-2 2H6a2 2 0 01-2-2V6a2 2 0 012-2h2"/><rect x="8" y="2" width="8" height="4" rx="1"/>',
  lock:       '<rect x="3" y="11" width="18" height="11" rx="2"/><path d="M7 11V7a5 5 0 0110 0v4"/>',
  check:      '<path d="M20 6L9 17l-5-5"/>',
  x:          '<path d="M18 6L6 18M6 6l12 12"/>',
  'x-close':  '<path d="M18 6L6 18M6 6l12 12"/>',
  square:     '<rect x="3" y="3" width="18" height="18" rx="2"/>',
  'alert-tri':'<path d="M10.29 3.86L1.82 18a2 2 0 001.71 3h16.94a2 2 0 001.71-3L13.71 3.86a2 2 0 00-3.42 0z"/><path d="M12 9v4m0 4h.01"/>',
  info:       '<circle cx="12" cy="12" r="10"/><path d="M12 16v-4m0-4h.01"/>',
  warning:    '<path d="M10.29 3.86L1.82 18a2 2 0 001.71 3h16.94a2 2 0 001.71-3L13.71 3.86a2 2 0 00-3.42 0z"/><path d="M12 9v4m0 4h.01"/>',
  'check-sq': '<path d="M9 11l3 3L22 4"/><path d="M21 12v7a2 2 0 01-2 2H5a2 2 0 01-2-2V5a2 2 0 012-2h11"/>',
  'bar-chart':'<path d="M12 20V10M18 20V4M6 20v-4"/>',
  lightbulb:  '<path d="M9 18h6m-5 2h4M12 2a7 7 0 00-4 12.7V17h8v-2.3A7 7 0 0012 2z"/>',
  image:      '<rect x="3" y="3" width="18" height="18" rx="2"/><circle cx="8.5" cy="8.5" r="1.5"/><path d="M21 15l-5-5L5 21"/>',
  link:       '<path d="M10 13a5 5 0 007.54.54l3-3a5 5 0 00-7.07-7.07l-1.72 1.71m4.54 5.07a5 5 0 00-7.54-.54l-3 3a5 5 0 007.07 7.07l1.71-1.71"/>',
  pin:        '<path d="M12 2a7 7 0 00-7 7c0 5.25 7 13 7 13s7-7.75 7-13a7 7 0 00-7-7z"/><circle cx="12" cy="9" r="2.5"/>',
  video:      '<rect x="2" y="5" width="14" height="14" rx="2"/><path d="M22 7l-6 4 6 4V7z"/>',
  explosion:  '<path d="M12 2l2 6 6-2-4 5 5 3-6 1 1 6-4-4-4 4 1-6-6-1 5-3-4-5 6 2z"/>',
  clock:      '<circle cx="12" cy="12" r="10"/><path d="M12 6v6l4 2"/>',
  atom:       '<circle cx="12" cy="12" r="2"/><ellipse cx="12" cy="12" rx="10" ry="4" fill="none"/><ellipse cx="12" cy="12" rx="10" ry="4" fill="none" transform="rotate(60 12 12)"/><ellipse cx="12" cy="12" rx="10" ry="4" fill="none" transform="rotate(120 12 12)"/>',
  droplet:    '<path d="M12 2.69l5.66 5.66a8 8 0 11-11.31 0z"/>',
  compass:    '<circle cx="12" cy="12" r="10"/><path d="M16.24 7.76l-2.12 6.36-6.36 2.12 2.12-6.36z"/>',
  moon:       '<path d="M21 12.79A9 9 0 1111.21 3 7 7 0 0021 12.79z"/>',
  'grip-v':   '<circle cx="9" cy="5" r="1" fill="currentColor" stroke="none"/><circle cx="15" cy="5" r="1" fill="currentColor" stroke="none"/><circle cx="9" cy="12" r="1" fill="currentColor" stroke="none"/><circle cx="15" cy="12" r="1" fill="currentColor" stroke="none"/><circle cx="9" cy="19" r="1" fill="currentColor" stroke="none"/><circle cx="15" cy="19" r="1" fill="currentColor" stroke="none"/>',
  'arrow-up': '<path d="M12 19V5m-7 7l7-7 7 7"/>',
  'arrow-down':'<path d="M12 5v14m7-7l-7 7-7-7"/>',
  shuffle:    '<path d="M16 3h5v5M4 20L21 3M21 16v5h-5M15 15l6 6M4 4l5 5"/>',
  coins:      '<circle cx="8" cy="14" r="6"/><path d="M18 8a6 6 0 00-6 6"/><circle cx="16" cy="10" r="6"/>',
  'shopping-bag':'<path d="M6 2L3 6v14a2 2 0 002 2h14a2 2 0 002-2V6l-3-4H6zM3 6h18M16 10a4 4 0 01-8 0"/>',
  gift:       '<path d="M20 12v10H4V12M2 7h20v5H2V7z"/><path d="M12 22V7m0 0a4 3 0 10-4-3m4 3a4 3 0 114-3"/>',
  dna:        '<path d="M2 15c6.667-6 13.333 0 20-6M2 9c6.667 6 13.333 0 20 6M7 21c0-4 4-4 4-8s-4-4-4-8M17 21c0-4-4-4-4-8s4-4 4-8"/>',
};

function lsIcon(name, size = 18, cls = '') {
  const d = _ICONS[name];
  if (!d) return '';
  return `<svg xmlns="http://www.w3.org/2000/svg" width="${size}" height="${size}" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"${cls ? ` class="${cls}"` : ''} style="display:inline-block;vertical-align:middle;flex-shrink:0">${d}</svg>`;
}

/* ── Toast-уведомления ────────────────────────────────────────────────── */
function lsToast(message, type = 'info', duration = 3500) {
  // нормализация типа: иначе неизвестный класс (напр. 'warning' вместо 'warn')
  // остаётся без фонового градиента → белый текст сливается со страницей
  const _tAlias = { warning: 'warn', danger: 'error', err: 'error', fail: 'error', ok: 'success' };
  type = _tAlias[type] || type;
  if (!['success', 'error', 'info', 'warn'].includes(type)) type = 'info';
  if (!document.getElementById('ls-toast-style')) {
    const s = document.createElement('style');
    s.id = 'ls-toast-style';
    s.textContent = `
      #ls-toast-wrap{position:fixed;bottom:24px;right:24px;z-index:99999;display:flex;flex-direction:column;gap:10px;pointer-events:none;}
      .ls-toast{display:flex;align-items:center;gap:10px;padding:12px 18px;border-radius:14px;min-width:220px;max-width:360px;
        font-family:'Manrope',sans-serif;font-size:0.875rem;font-weight:600;color:#fff;pointer-events:auto;
        box-shadow:0 8px 32px rgba(15,23,42,0.22);transform:translateX(120%);opacity:0;
        transition:transform .28s cubic-bezier(.34,1.56,.64,1),opacity .22s ease;}
      .ls-toast.show{transform:translateX(0);opacity:1;}
      .ls-toast.hide{transform:translateX(120%);opacity:0;}
      .ls-toast.success{background:linear-gradient(135deg,#00C87A,#06B96E);}
      .ls-toast.error  {background:linear-gradient(135deg,#F15BB5,#E0335E);}
      .ls-toast.info   {background:linear-gradient(135deg,#06D6E0,#9B5DE5);}
      .ls-toast.warn   {background:linear-gradient(135deg,#FF9F1C,#E07A00);}
      .ls-toast-icon{font-size:1.1rem;flex-shrink:0;}
      .ls-toast-msg{flex:1;line-height:1.4;}
      .ls-toast-close{background:none;border:none;color:rgba(255,255,255,0.7);font-size:1rem;cursor:pointer;padding:0 2px;flex-shrink:0;line-height:1;}
      .ls-toast-close:hover{color:#fff;}
    `;
    document.head.appendChild(s);
  }
  let wrap = document.getElementById('ls-toast-wrap');
  if (!wrap) {
    wrap = document.createElement('div');
    wrap.id = 'ls-toast-wrap';
    wrap.setAttribute('aria-live', 'polite');
    wrap.setAttribute('aria-atomic', 'false');
    document.body.appendChild(wrap);
  }

  const _tIcons = { success: 'check-circle', error: 'x-close', info: 'info', warn: 'warning' };
  const el = document.createElement('div');
  el.className = `ls-toast ${type}`;
  el.setAttribute('role', type === 'error' ? 'alert' : 'status');
  el.innerHTML = `<span class="ls-toast-icon">${lsIcon(_tIcons[type] || 'info', 18)}</span><span class="ls-toast-msg"></span><button class="ls-toast-close" aria-label="Закрыть уведомление" onclick="this.closest('.ls-toast').remove()">${lsIcon('x-close', 14)}</button>`;
  el.querySelector('.ls-toast-msg').textContent = message;
  // Progress bar — thin line at bottom that drains over the toast duration
  const bar = document.createElement('span');
  bar.className = 'ls-toast-bar';
  bar.style.setProperty('--toast-dur', (duration / 1000).toFixed(2) + 's');
  el.appendChild(bar);
  wrap.appendChild(el);
  requestAnimationFrame(() => requestAnimationFrame(() => el.classList.add('show')));

  const hide = () => {
    el.classList.add('hide');
    setTimeout(() => el.remove(), 320);
  };
  const timer = setTimeout(hide, duration);
  el.querySelector('.ls-toast-close').addEventListener('click', () => { clearTimeout(timer); hide(); });
}

/* ── State helpers: единый паттерн loading/empty/error ───────────────────
   Usage:
     LS.state.loading(el)             // spinner
     LS.state.empty(el, msg, icon?)   // "пусто" с иконкой
     LS.state.error(el, err, retry?)  // ошибка + "Повторить"
   ──────────────────────────────────────────────────────────────────────── */
function _ensureStateStyles() {
  if (document.getElementById('ls-state-style')) return;
  const s = document.createElement('style');
  s.id = 'ls-state-style';
  s.textContent = `
    .ls-state { padding: 40px 20px; text-align: center; color: #56687A; font-size: .9rem; }
    .ls-state-icon { width: 36px; height: 36px; margin: 0 auto 10px; opacity: .55; display: block; stroke: currentColor; fill: none; stroke-width: 1.6; }
    .ls-state-spin { width: 32px; height: 32px; border: 3px solid rgba(155,93,229,.15); border-top-color: #9B5DE5; border-radius: 50%; animation: ls-spin .8s linear infinite; margin: 8px auto; display: block; }
    @keyframes ls-spin { to { transform: rotate(360deg); } }
    .ls-state-title { font-family: 'Unbounded', sans-serif; font-weight: 700; color: #1F2937; margin-bottom: 4px; font-size: .92rem; }
    .ls-state-msg   { line-height: 1.5; }
    .ls-state-btn   {
      margin-top: 14px; padding: 8px 18px; border-radius: 999px;
      border: 1.5px solid #9B5DE5; background: transparent; color: #9B5DE5;
      font-family: 'Manrope', sans-serif; font-size: .82rem; font-weight: 700;
      cursor: pointer; transition: all .15s;
    }
    .ls-state-btn:hover { background: #9B5DE5; color: #fff; }
  `;
  document.head.appendChild(s);
}

const lsState = {
  loading(el, msg) {
    if (!el) return;
    _ensureStateStyles();
    el.innerHTML = `<div class="ls-state"><div class="ls-state-spin"></div>${msg ? `<div class="ls-state-msg">${escapeHtml(msg)}</div>` : ''}</div>`;
  },
  empty(el, msg = 'Пусто', icon = 'inbox') {
    if (!el) return;
    _ensureStateStyles();
    el.innerHTML = `<div class="ls-state">${lsIcon(icon, 36) ? `<div style="margin-bottom:10px;display:flex;justify-content:center;opacity:.55">${lsIcon(icon, 36)}</div>` : ''}<div class="ls-state-msg">${escapeHtml(msg)}</div></div>`;
  },
  error(el, err, retryFn) {
    if (!el) return;
    _ensureStateStyles();
    const msg = (err && err.message) || String(err || 'Ошибка');
    const retryId = 'lse-retry-' + Math.random().toString(36).slice(2, 8);
    el.innerHTML = `<div class="ls-state">
      <div style="margin-bottom:10px;display:flex;justify-content:center;opacity:.55;color:#F94144">${lsIcon('alert-circle', 36)}</div>
      <div class="ls-state-title">Не удалось загрузить</div>
      <div class="ls-state-msg">${escapeHtml(msg)}</div>
      ${retryFn ? `<button class="ls-state-btn" id="${retryId}">Повторить</button>` : ''}
    </div>`;
    if (retryFn) {
      const btn = el.querySelector('#' + retryId);
      if (btn) btn.addEventListener('click', () => { lsState.loading(el); retryFn(); });
    }
  },
};

/* ── Skeleton-заглушки ────────────────────────────────────────────────── */
function lsSkeleton(count = 3, variant = 'card') {
  if (!document.getElementById('ls-skeleton-style')) {
    const s = document.createElement('style');
    s.id = 'ls-skeleton-style';
    s.textContent = `
      @keyframes ls-shimmer{from{background-position:-600px 0}to{background-position:600px 0}}
      .ls-sk{
        border-radius:12px;
        background:linear-gradient(90deg,rgba(155,93,229,0.06) 20%,rgba(155,93,229,0.15) 40%,rgba(255,255,255,0.65) 50%,rgba(155,93,229,0.15) 60%,rgba(155,93,229,0.06) 80%);
        background-size:1200px 100%;
        animation:ls-shimmer 1.8s infinite ease-in-out;
      }
      .ls-sk-card{display:flex;align-items:center;gap:18px;padding:18px 20px;border:1.5px solid rgba(155,93,229,0.08);border-radius:18px;margin-bottom:10px;background:rgba(255,255,255,0.7);}
      .ls-sk-icon{width:48px;height:48px;border-radius:12px;flex-shrink:0;}
      .ls-sk-body{flex:1;display:flex;flex-direction:column;gap:8px;}
      .ls-sk-title{height:14px;border-radius:6px;width:55%;}
      .ls-sk-meta{height:10px;border-radius:6px;width:80%;}
      .ls-sk-right{width:56px;display:flex;flex-direction:column;gap:8px;align-items:flex-end;}
      .ls-sk-pct{width:42px;height:22px;border-radius:8px;}
      .ls-sk-btn{width:80px;height:32px;border-radius:999px;}
      .ls-sk-row{height:48px;border-radius:12px;margin-bottom:10px;}
    `;
    document.head.appendChild(s);
  }
  if (variant === 'row') {
    return Array.from({ length: count }, () =>
      `<div class="ls-sk ls-sk-row"></div>`
    ).join('');
  }
  return Array.from({ length: count }, () => `
    <div class="ls-sk-card">
      <div class="ls-sk ls-sk-icon"></div>
      <div class="ls-sk-body">
        <div class="ls-sk ls-sk-title"></div>
        <div class="ls-sk ls-sk-meta"></div>
      </div>
      <div class="ls-sk-right">
        <div class="ls-sk ls-sk-pct"></div>
        <div class="ls-sk ls-sk-btn"></div>
      </div>
    </div>`).join('');
}

/* ── Красивый диалог подтверждения ───────────────────────────────────── */
function lsConfirm(message, { title = 'Подтверждение', confirmText = 'Подтвердить', danger = true } = {}) {
  return new Promise(resolve => {
    if (!document.getElementById('ls-confirm-style')) {
      const s = document.createElement('style');
      s.id = 'ls-confirm-style';
      s.textContent = `
        .ls-ov{position:fixed;inset:0;z-index:9000;display:flex;align-items:center;justify-content:center;padding:20px;
          background:rgba(15,23,42,0.45);backdrop-filter:blur(12px);opacity:0;transition:opacity .2s ease;}
        .ls-ov.open{opacity:1;}
        .ls-box{background:#fff;border-radius:24px;padding:36px 40px;width:100%;max-width:420px;text-align:center;
          box-shadow:0 40px 100px rgba(15,23,42,0.24);transform:scale(.9) translateY(12px);transition:transform .22s ease;}
        .ls-ov.open .ls-box{transform:scale(1) translateY(0);}
        .ls-icon{font-size:2.4rem;margin-bottom:12px;}
        .ls-title{font-family:'Unbounded',sans-serif;font-size:1rem;font-weight:800;color:#0F172A;margin-bottom:10px;}
        .ls-msg{font-size:0.88rem;color:#3D4F6B;line-height:1.65;white-space:pre-line;margin-bottom:28px;}
        .ls-btns{display:flex;gap:10px;justify-content:center;}
        .ls-cancel{padding:10px 26px;min-height:44px;border:1.5px solid rgba(15,23,42,0.2);border-radius:999px;background:transparent;
          font-family:'Manrope',sans-serif;font-size:0.88rem;font-weight:600;color:#56687A;cursor:pointer;transition:all .2s;}
        .ls-cancel:hover{border-color:#9B5DE5;color:#9B5DE5;}
        .ls-ok{padding:10px 28px;min-height:44px;border:none;border-radius:999px;color:#fff;
          font-family:'Manrope',sans-serif;font-size:0.88rem;font-weight:700;cursor:pointer;transition:opacity .2s;
          background:linear-gradient(135deg,#06D6E0,#9B5DE5);}
        .ls-ok.danger{background:linear-gradient(135deg,#F15BB5,#9B5DE5);}
        .ls-ok:hover{opacity:.88;}
      `;
      document.head.appendChild(s);
    }

    const prevFocus = document.activeElement;
    const el = document.createElement('div');
    el.className = 'ls-ov';
    el.setAttribute('role', 'dialog');
    el.setAttribute('aria-modal', 'true');
    el.setAttribute('aria-labelledby', 'ls-dlg-title');
    el.innerHTML = `
      <div class="ls-box">
        <div class="ls-icon">${danger ? lsIcon('trash', 36) : lsIcon('help-circle', 36)}</div>
        <div class="ls-title" id="ls-dlg-title"></div>
        <div class="ls-msg"></div>
        <div class="ls-btns">
          <button class="ls-cancel">Отмена</button>
          <button class="ls-ok${danger ? ' danger' : ''}"></button>
        </div>
      </div>`;
    el.querySelector('.ls-title').textContent = title;
    el.querySelector('.ls-msg').textContent   = message;
    el.querySelector('.ls-ok').textContent    = confirmText;
    document.body.appendChild(el);
    requestAnimationFrame(() => el.classList.add('open'));

    const done = result => {
      el.classList.remove('open');
      setTimeout(() => { el.remove(); prevFocus?.focus(); }, 230);
      resolve(result);
    };

    el.querySelector('.ls-cancel').onclick = () => done(false);
    el.querySelector('.ls-ok').onclick     = () => done(true);
    el.addEventListener('click', e => { if (e.target === el) done(false); });
    el.addEventListener('keydown', e => {
      if (e.key === 'Tab') {
        const btns = [...el.querySelectorAll('button')];
        if (e.shiftKey && document.activeElement === btns[0]) {
          e.preventDefault(); btns[btns.length - 1].focus();
        } else if (!e.shiftKey && document.activeElement === btns[btns.length - 1]) {
          e.preventDefault(); btns[0].focus();
        }
      }
      if (e.key === 'Enter')  { e.preventDefault(); done(true); }
      if (e.key === 'Escape') { e.preventDefault(); done(false); }
    });
    setTimeout(() => el.querySelector('.ls-cancel').focus(), 10);
  });
}

/* ────────────────────────────────────────────────────────────────────────
   LS.modal — universal form/content modal
   Companion to LS.confirm. Use for forms, pickers, editors — anything
   that's not a simple yes/no confirmation.

   Usage:
     const m = LS.modal({
       title: 'Назначить чтение',
       content: htmlString | DOMElement,
       size: 'sm' | 'md' | 'lg',   // 420 / 560 / 720 px
       actions: [
         { label: 'Отмена',     onClick: () => m.close() },
         { label: 'Назначить',  primary: true, onClick: async () => { ... } },
       ],
       onClose: () => { ... },
     });
     // Returns { close, root, setBody, setActions, setError }
   ──────────────────────────────────────────────────────────────────────── */
function lsModal({ title = '', content = '', size = 'md', actions = [], onClose, dismissible = true } = {}) {
  if (!document.getElementById('ls-modal-style')) {
    const s = document.createElement('style');
    s.id = 'ls-modal-style';
    s.textContent = `
      .ls-mov{position:fixed;inset:0;z-index:9000;display:flex;align-items:flex-start;justify-content:center;
        padding:60px 20px 20px;background:rgba(15,23,42,0.55);backdrop-filter:blur(8px);
        opacity:0;transition:opacity .18s ease;overflow-y:auto;}
      .ls-mov.open{opacity:1;}
      .ls-mod{background:#fff;border-radius:18px;width:100%;
        box-shadow:0 24px 80px rgba(15,23,42,0.28);
        transform:scale(.96) translateY(-12px);transition:transform .22s ease;
        display:flex;flex-direction:column;max-height:calc(100vh - 80px);}
      .ls-mod.sm{max-width:420px;} .ls-mod.md{max-width:560px;} .ls-mod.lg{max-width:720px;}
      .ls-mov.open .ls-mod{transform:scale(1) translateY(0);}
      .ls-mod-hdr{display:flex;align-items:center;justify-content:space-between;
        padding:18px 22px 14px;border-bottom:1px solid rgba(15,23,42,.08);flex-shrink:0;}
      .ls-mod-title{font-family:'Unbounded',sans-serif;font-size:1rem;font-weight:800;color:#0F172A;}
      .ls-mod-x{width:32px;height:32px;border:none;background:transparent;color:#56687A;
        cursor:pointer;border-radius:8px;display:flex;align-items:center;justify-content:center;
        transition:background .12s;flex-shrink:0;margin-left:12px;}
      .ls-mod-x:hover{background:rgba(15,23,42,.06);color:#0F172A;}
      .ls-mod-x svg{width:18px;height:18px;}
      .ls-mod-body{padding:18px 22px;overflow-y:auto;flex:1;}
      .ls-mod-err{margin:0 22px 14px;padding:9px 12px;border-radius:8px;font-size:.84rem;
        background:rgba(241,91,68,.1);border:1px solid rgba(241,91,68,.3);color:#F94144;display:none;}
      .ls-mod-err.visible{display:block;}
      .ls-mod-act{display:flex;gap:10px;justify-content:flex-end;
        padding:14px 22px 18px;border-top:1px solid rgba(15,23,42,.08);flex-shrink:0;}
      .ls-mod-btn{padding:9px 18px;border-radius:10px;border:1.5px solid rgba(15,23,42,0.18);
        background:transparent;color:#0F172A;font-family:'Manrope',sans-serif;
        font-size:.88rem;font-weight:700;cursor:pointer;transition:all .15s;}
      .ls-mod-btn:hover{border-color:#9B5DE5;color:#9B5DE5;}
      .ls-mod-btn.primary{background:#9B5DE5;border-color:#9B5DE5;color:#fff;}
      .ls-mod-btn.primary:hover{background:#7e3eca;border-color:#7e3eca;color:#fff;}
      .ls-mod-btn.danger{background:#F94144;border-color:#F94144;color:#fff;}
      .ls-mod-btn.danger:hover{background:#d62a2d;border-color:#d62a2d;}
      .ls-mod-btn:disabled{opacity:.55;cursor:not-allowed;}
      @media (max-width:540px){.ls-mov{padding:20px 12px;}.ls-mod-hdr,.ls-mod-body,.ls-mod-act{padding-left:16px;padding-right:16px;}}
    `;
    document.head.appendChild(s);
  }

  const prevFocus = document.activeElement;
  const ov = document.createElement('div');
  ov.className = 'ls-mov';
  ov.setAttribute('role', 'dialog');
  ov.setAttribute('aria-modal', 'true');
  ov.innerHTML = `
    <div class="ls-mod ${size}" onclick="event.stopPropagation()">
      <div class="ls-mod-hdr">
        <div class="ls-mod-title"></div>
        <button class="ls-mod-x" aria-label="Закрыть">${lsIcon('x-close', 18)}</button>
      </div>
      <div class="ls-mod-body"></div>
      <div class="ls-mod-err"></div>
      <div class="ls-mod-act"></div>
    </div>`;
  ov.querySelector('.ls-mod-title').textContent = title;
  const bodyEl = ov.querySelector('.ls-mod-body');
  const errEl  = ov.querySelector('.ls-mod-err');
  const actEl  = ov.querySelector('.ls-mod-act');

  function setBody(c) {
    bodyEl.innerHTML = '';
    if (typeof c === 'string') bodyEl.innerHTML = c;
    else if (c instanceof Node) bodyEl.appendChild(c);
  }
  function setError(msg) {
    if (!msg) { errEl.classList.remove('visible'); return; }
    errEl.textContent = msg;
    errEl.classList.add('visible');
  }
  function setActions(arr) {
    actEl.innerHTML = '';
    (arr || []).forEach((a, i) => {
      const b = document.createElement('button');
      b.className = 'ls-mod-btn' + (a.primary ? ' primary' : '') + (a.danger ? ' danger' : '');
      b.textContent = a.label || (a.primary ? 'OK' : 'Отмена');
      if (a.id) b.id = a.id;
      b.addEventListener('click', e => {
        e.preventDefault();
        if (typeof a.onClick === 'function') a.onClick();
        else if (a.close !== false) close();
      });
      actEl.appendChild(b);
    });
    actEl.style.display = (arr && arr.length) ? '' : 'none';
  }

  setBody(content);
  setActions(actions);
  document.body.appendChild(ov);
  requestAnimationFrame(() => ov.classList.add('open'));

  function close() {
    ov.classList.remove('open');
    setTimeout(() => {
      ov.remove();
      prevFocus?.focus?.();
      if (typeof onClose === 'function') onClose();
    }, 230);
  }

  ov.querySelector('.ls-mod-x').onclick = () => { if (dismissible) close(); };
  if (dismissible) {
    ov.addEventListener('click', e => { if (e.target === ov) close(); });
  }
  const onKey = e => {
    if (e.key === 'Escape' && dismissible) { e.preventDefault(); close(); }
  };
  document.addEventListener('keydown', onKey);
  const _close = close;
  close = () => { document.removeEventListener('keydown', onKey); _close(); };

  // Focus first focusable element inside body, or close button
  setTimeout(() => {
    const focusable = bodyEl.querySelector('input,select,textarea,button') || ov.querySelector('.ls-mod-x');
    focusable?.focus?.();
  }, 50);

  return { close, root: ov, body: bodyEl, setBody, setActions, setError };
}

/* ── renderNavAvatar — paint the sidebar avatar (image or initials) ──
   Exported via LS.refreshNavAvatar so pages that update avatar_url
   (profile preset picker, upload flow) can re-paint without reload.

   Stale-cache recovery: if the cached user has no `avatar_url` field
   (e.g. logged in before login was returning it), fetch /auth/me once
   in the background and re-paint when it returns. */
let _navAvatarFetchInflight = false;
function renderNavAvatar(el, user) {
  if (!el) return;
  const u = user || getUser();
  const url = u?.avatar_url;
  if (url) {
    el.innerHTML = `<img src="/avatars/${escapeHtml(url)}?t=${Date.now()}" alt="" style="width:100%;height:100%;object-fit:cover;border-radius:inherit;display:block">`;
    el.style.background = 'transparent';
    return;
  }
  // No url yet — paint initials, then opportunistically refresh from /auth/me
  // if the field is absent (not just empty). `null` means "verified absent",
  // `undefined` means "we never fetched and might be stale".
  const initials = (u?.name || 'LS').split(' ').slice(0, 2).map(w => w[0]?.toUpperCase() || '').join('') || 'LS';
  el.textContent = initials;
  el.style.background = '';
  if (u && u.avatar_url === undefined && !_navAvatarFetchInflight && isLoggedIn()) {
    _navAvatarFetchInflight = true;
    fetchMe().then(fresh => {
      if (!fresh) return;
      const merged = { ...getUser(), ...fresh, avatar_url: fresh.avatar_url ?? null };
      setUser(merged);
      const newEl = document.getElementById('nav-avatar');
      if (newEl) renderNavAvatar(newEl, merged);
    }).catch(() => {}).finally(() => { _navAvatarFetchInflight = false; });
  }
}
function refreshNavAvatar() {
  renderNavAvatar(document.getElementById('nav-avatar'));
}

/* ── applyRoleSidebar — reveal teacher/admin sidebar items ───────────── */
function applyRoleSidebar(user) {
  if (!user) return;
  if (['teacher', 'admin'].includes(user.role)) {
    document.querySelectorAll('.sb-teacher-only').forEach(el => el.style.display = '');
  }
}

/* ── initPage — consolidates page init boilerplate ─────────────────── */
function initPage({ requireLogin = true } = {}) {
  if (requireLogin && !requireAuth()) return null;
  const user = getUser();
  const isTeacher = user && ['teacher', 'admin'].includes(user.role);
  const isAdmin = user?.role === 'admin';

  // Nav avatar — render uploaded avatar if available, otherwise initials.
  const navUser = document.getElementById('nav-user');
  const navAvatar = document.getElementById('nav-avatar');
  if (navUser) navUser.textContent = user?.name || user?.email || '';
  if (navAvatar) renderNavAvatar(navAvatar, user);

  // Sidebar collapsed state
  if (localStorage.getItem('ls_sb_collapsed') === '1') {
    document.querySelector('.app-layout')?.classList.add('sb-collapsed');
  }

  // Sidebar toggle wiring (skip if sidebar.js already wired it via data-sb-wired)
  const togBtn = document.querySelector('.sb-toggle');
  if (togBtn && !togBtn.dataset.sbWired) {
    togBtn.addEventListener('click', () => {
      const layout = document.querySelector('.app-layout');
      const collapsed = layout.classList.toggle('sb-collapsed');
      localStorage.setItem('ls_sb_collapsed', collapsed ? '1' : '0');
    });
  }

  // Sidebar active link (fallback for pages without sidebar.js)
  const currentPath = location.pathname.replace(/\.html$/, '').replace(/^\//, '') || 'dashboard';
  document.querySelectorAll('.sidebar .sb-link').forEach(a => {
    const href = a.getAttribute('href')?.replace(/^\//, '').replace(/\.html$/, '') || '';
    if (href && href === currentPath) a.classList.add('active');
  });

  // Cosmetics
  applyCosmetics();

  // Hide disabled game features in sidebar
  hideDisabledFeatures();

  // Board link — показываем всем залогиненным пользователям
  const boardEl = document.getElementById('btn-board') || document.getElementById('sbl-board');
  if (boardEl) boardEl.style.display = '';

  // Teacher-only sidebar items
  applyRoleSidebar(user);

  return { user, isTeacher, isAdmin };
}

/* ── Feature flags (cached per page load, bust on demand) ───────────── */
let _featuresCache = null;
/* Synchronous mirror of features.gamification, populated on first
   loadFeatures() resolve. Used by xp.js to bail out without network. */
let _gamificationEnabled = null;
function isGamificationEnabled() {
  // Default to true when the cache hasn't resolved yet — page-load order
  // means some code runs before /api/features. The CSS kill-switch
  // (body.no-gamification) catches the visual side regardless.
  return _gamificationEnabled !== false;
}
async function loadFeatures() {
  if (_featuresCache) return _featuresCache;
  try {
    _featuresCache = await apiFetch('/api/features');
  } catch { _featuresCache = {}; }
  _gamificationEnabled = _featuresCache.gamification !== false;
  return _featuresCache;
}
function clearFeaturesCache() { _featuresCache = null; _gamificationEnabled = null; }

/**
 * Show board sidebar link only for teachers/admins and students in a class.
 * Call after LS.initPage(). Uses features cache (_no_class flag).
 */
async function showBoardIfAllowed() {
  const el = document.getElementById('btn-board') || document.getElementById('sbl-board');
  if (!el) return;
  const user = getUser();
  if (!user) return;
  if (user.role === 'teacher' || user.role === 'admin') { el.style.display = ''; return; }
  // Student: check if in a class
  const feats = await loadFeatures();
  if (!feats._no_class) el.style.display = '';
}

async function hideDisabledFeatures() {
  const feats = await loadFeatures();
  const map = {
    hangman:       ['/hangman'],
    crossword:     ['/crossword'],
    pet:           ['/pet'],
    red_book:      ['/red-book', '/red-book.html', '/red-book-ecosystem.html', '/red-book-biomes.html'],
    collection:    ['/collection.html', '/collection'],
    lab:           ['/lab'],
    knowledge_map: ['/knowledge-map'],
    flashcards:    ['/flashcards'],
    board:         ['/board'],
    biochem:       ['/biochem', '/biochem-library', '/biochem-reactions'],
    live_quiz:     ['/live-quiz'],
    classroom:     ['/classroom'],
    exam9:         ['/exam9', '/exam9.html'],
    textbooks:     ['/textbooks', '/textbooks.html', '/textbook'],
  };
  for (const [key, hrefs] of Object.entries(map)) {
    if (feats[key] === false) {
      hrefs.forEach(href => {
        document.querySelectorAll(`[href="${href}"]`).forEach(el => el.style.display = 'none');
      });
      // Redirect away if currently on a disabled page
      const cur = window.location.pathname;
      if (hrefs.some(h => cur === h || cur === h.replace('.html', ''))) {
        window.location.href = '/dashboard.html';
      }
    }
  }
  if (feats.gamification === false) {
    document.body.classList.add('no-gamification');
    // If student is already viewing achievements or shop tab, redirect to account tab
    const active = document.querySelector('#tab-achievements.active, #tab-shop.active');
    if (active) {
      document.querySelector('[onclick*="tab-account"]')?.click();
    }
  }

  // Student with no class — restrict to dashboard, homework, library, theory
  if (feats._no_class) {
    const classOnlyHrefs = [
      '/board', '/lab', '/hangman', '/crossword', '/pet',
      '/collection', '/collection.html', '/knowledge-map',
      '/red-book', '/red-book.html', '/red-book-ecosystem.html', '/red-book-biomes.html',
      '/flashcards', '/live-quiz',
    ];
    classOnlyHrefs.forEach(href => {
      document.querySelectorAll(`[href="${href}"]`).forEach(el => el.style.display = 'none');
    });
    // Redirect if currently on a class-required page
    const cur = window.location.pathname;
    const classOnlyPaths = [
      '/board', '/lab', '/hangman', '/crossword', '/pet',
      '/collection', '/collection-rb', '/knowledge-map',
      '/red-book', '/red-book-ecosystem', '/red-book-biomes', '/red-book-games',
      '/flashcards', '/live-quiz',
    ];
    if (classOnlyPaths.some(h => cur === h || cur === h + '.html')) {
      window.location.href = '/dashboard';
    }
    document.body.classList.add('no-class');
    document.body.classList.add('no-gamification'); // no class <svg class="ic" viewBox="0 0 24 24"><line x1="5" y1="12" x2="19" y2="12"/><polyline points="12 5 19 12 12 19"/></svg> no gamification
  }
}

/* ── generic authenticated fetch (full path like /api/courses) ─────── */
async function apiFetch(path, options = {}) {
  const token = getToken();
  const headers = { 'Content-Type': 'application/json', ...(options.headers || {}) };
  if (token) headers['Authorization'] = `Bearer ${token}`;
  // Auto-stringify plain object bodies so callers can pass `{ body: { ... } }`
  // like LS.post does. Strings / FormData / Blob / URLSearchParams pass through.
  const opts = { ...options, headers };
  if (opts.body && typeof opts.body === 'object'
      && !(opts.body instanceof FormData)
      && !(opts.body instanceof Blob)
      && !(opts.body instanceof URLSearchParams)
      && !(opts.body instanceof ArrayBuffer)) {
    opts.body = JSON.stringify(opts.body);
  }
  const res = await fetch(path, opts);
  if (res.status === 401) {
    removeToken(); removeUser();
    window.location.href = '/login';
    throw new Error('Session expired');
  }
  const data = await res.json().catch(() => ({}));
  if (!res.ok) throw Object.assign(new Error(data.error || 'Request failed'), { status: res.status, data });
  return data;
}

/* ── Biochemistry API ────────────────────────────────────────────────── */
async function biochemGetElements()      { return req('GET', '/biochem/elements'); }
async function biochemGetMolecules(p={}) { return req('GET', `/biochem/molecules?${new URLSearchParams(p)}`); }
async function biochemGetMolecule(id)    { return req('GET', `/biochem/molecules/${id}`); }
async function biochemValidate(atoms,bonds){ return req('POST','/biochem/validate',{atoms,bonds}); }
async function biochemAnalyze(atoms,bonds){ return req('POST','/biochem/analyze',{atoms,bonds}); }
async function biochemGetReactions()     { return req('GET', '/biochem/reactions'); }
async function biochemGetChallenges()    { return req('GET', '/biochem/challenges'); }
async function biochemSolveChallenge(id,payload)    { return req('POST',`/biochem/challenges/${id}/solve`,payload); }
async function biochemGetSaved()         { return req('GET', '/biochem/saved'); }
async function biochemSave(atoms,bonds,name){ return req('POST','/biochem/saved',{atoms,bonds,name}); }
async function biochemDeleteSaved(id)    { return req('DELETE',`/biochem/saved/${id}`); }
async function biochemGetPathways()                   { return req('GET', '/biochem/pathways'); }
async function biochemGetPathwayProgress()            { return req('GET', '/biochem/pathways/progress'); }
async function biochemSavePathwayProgress(pathway,step,completed){ return req('POST','/biochem/pathways/progress',{pathway,step,completed}); }

/* ── LS.prefs — server-synced user preferences ──────────────────────────
   Keys use dot-notation: 'wb.color', 'dashboard.hidden', etc.
   Writes are debounced (1.5 s) before flushing to /api/preferences.
   ─────────────────────────────────────────────────────────────────────── */
const _prefsCache = {};
let _prefsDirty    = false;
let _prefsTimer    = null;

// SYNC DISABLED (debug mode) — раскомментировать для включения синхронизации
async function _prefsLoad() { /* disabled */ }
function _prefsFlush()      { /* disabled */ }

// async function _prefsLoad() {
//     if (!isLoggedIn()) return;
//     try {
//         const data = await apiFetch('/api/preferences', { method: 'GET' });
//         Object.assign(_prefsCache, data);
//     } catch (e) {}
// }
//
// function _prefsFlush() {
//     if (!_prefsDirty) return;
//     _prefsDirty = false;
//     if (!isLoggedIn()) return;
//     apiFetch('/api/preferences', {
//         method: 'PATCH',
//         body: JSON.stringify(_prefsCache),
//     }).catch(() => {});
// }

const lsPrefs = {
    get(key, def) {
        const parts = key.split('.');
        let cur = _prefsCache;
        for (const k of parts) {
            if (cur === undefined || cur === null) return def;
            cur = cur[k];
        }
        return cur !== undefined ? cur : def;
    },
    set(key, value) {
        const parts = key.split('.');
        let cur = _prefsCache;
        for (let i = 0; i < parts.length - 1; i++) {
            if (!cur[parts[i]] || typeof cur[parts[i]] !== 'object' || Array.isArray(cur[parts[i]])) {
                cur[parts[i]] = {};
            }
            cur = cur[parts[i]];
        }
        cur[parts[parts.length - 1]] = value;
        _prefsDirty = true;
        clearTimeout(_prefsTimer);
        _prefsTimer = setTimeout(_prefsFlush, 1500);
    },
    async init() { await _prefsLoad(); },
    flush()      { clearTimeout(_prefsTimer); _prefsFlush(); },
};

window.LS = {
  getToken, setToken, removeToken,
  getUser, setUser, removeUser,
  isLoggedIn, logout, requireAuth,
  register, login, fetchMe, updateProfile,
  getSubjects, updateSubject, getTopics,
  startSession, sendAnswer, finishSession, getResult, getHistory, getWeakTopics, getStudentStats, getSessionQuestions,
  adminGetStats, adminGetOverview, adminGlobalSearch, adminGetUsers, adminUpdateRole, adminGetUserSessions, adminGetSessions, adminGetSessionDetail, adminDeleteSession, adminClearUserSessions, adminUpdateUser, adminBanUser, adminDeleteUser,
  getQuestions, createQuestion, duplicateQuestion, updateQuestion, deleteQuestion, importQuestions,
  getClasses, createClass, getClassDetail, updateClass, deleteClass, kickMember, addClassMember, createAssignment, createDirectAssignment, updateAssignment, deleteAssignment,
  regenerateInviteCode, classJournal,
  joinClass, myClasses, getStudents, classFeed,
  getAnnouncements, createAnnouncement, deleteAnnouncement,
  getNotifications, markNotifRead, markAllNotifsRead, connectSSE,
  listTemplates, saveTemplate, deleteTemplate, bulkCreateAssignment,
  myAssignments, teacherAssignments, startAssignment, assignmentResults, assignmentSessionReview, assignmentQuestionStats,
  getTests, createTest, getTest, updateTest, deleteTest, addQuestionsToTest, removeQFromTest,
  getGamificationMe, getGamAchievements, getLeaderboard, getXPHistory, getChallenges, claimChallenge, setGoalTier, getFrames, setFrame, reportLabActivity,
  getFiles, uploadFile, uploadMaterialFile, downloadFileUrl, deleteFile, getFileAccess, assignFile, unassignFile,
  getFolders, createFolder, renameFolder, deleteFolder, moveFile,
  getFolderAccess, clearFolderAccess, assignFolder, unassignFolder, getStudentsList,
  submitWork, resubmitWork, getMySubmissions, getClassSubmissions, reviewSubmission, deleteSubmission, submissionDownloadUrl,
  getPermissions, permissionsLog, setClassPermission, permissionsPresets, applyClassPreset, setPermission, getUserPermissions, setUserPermission, resetUserPermissions,
  listRoles, createRole, updateRoleDef, deleteRole, rolePermissions,
  accessCatalog, accessTargets, accessSummary, accessClassOpen, accessMatrix, accessLog, accessRules, accessSetRule,
  getCourseTemplates, saveCourseTemplate, createFromCourseTemplate, deleteCourseTemplate,
  getLessonTemplates, saveLessonTemplate, createFromLessonTemplate, deleteLessonTemplate,
  getBookmarks, addBookmark, removeBookmark, removeBookmarkByEntity, checkBookmark,
  globalSearch,
  getShopItems, purchaseItem, getUserPurchases, getCoins, getMyActiveCosmetics, activateShopItem,
  adminShopGetItems, adminShopCreateItem, adminShopUpdateItem, adminShopDeleteItem, adminShopAwardCoins, adminShopStats,
  adminGamAward, adminGamReset, adminGamStats, adminGamGetUser,
  parentGetLinks, parentCreateLink, parentUpdateLink, parentDeleteLink,
  crCreateSession, crGetSession, crEndSession, crGetActiveByClass, crGetMyActive,
  crJoin, crLeave, crSendChat, crGetChat, crGetAttendance, crSignal, crGetOnlineStudents, crGetMySession,
  crGetMyHistory, crGetClassHistory, crGetSessionSummary, crExportChatUrl, crGetAllNotes, crDeleteHistory,
  crAdminGetAllHistory, crAdminGetTeachersList,
  listMaterials, saveMaterial, updateMaterial, deleteMaterial, shareMaterial, getActivity,
  createMaterialCollection, updateMaterialCollection, deleteMaterialCollection,
  assistantContext, assistantSeen, assistantDismiss, assistantSettings, assistantAsk, assistantFlashcards,
  adminGetAssistant, adminSaveAssistant, adminTestAssistant, adminReindexTextbooks,
  fcListDecks, fcCreateDeck, fcAddCard,
  escapeHtml, esc,
  parseDate, fmtRelTime, safeHref,
  initPage,
  applyRoleSidebar,
  icon: lsIcon,
  confirm: lsConfirm,
  modal:   lsModal,
  toast: lsToast,
  state: lsState,
  skeleton: lsSkeleton,
  api: apiFetch,
  get:  (path) => apiFetch(path, { method: 'GET' }),
  post: (path, body) => apiFetch(path, { method: 'POST', body: JSON.stringify(body) }),
  put:  (path, body) => apiFetch(path, { method: 'PUT',  body: JSON.stringify(body) }),
  del:   (path) => apiFetch(path, { method: 'DELETE' }),
  patch: (path, body) => apiFetch(path, { method: 'PATCH', body: JSON.stringify(body) }),
  applyCosmetics: applyCosmetics,
  refreshNavAvatar,
  renderNavAvatar,
  isGamificationEnabled,
  loadFeatures,
  clearFeaturesCache,
  hideDisabledFeatures,
  showBoardIfAllowed,
  biochemGetElements, biochemGetMolecules, biochemGetMolecule, biochemValidate, biochemAnalyze,
  biochemGetReactions, biochemGetChallenges, biochemSolveChallenge,
  biochemGetSaved, biochemSave, biochemDeleteSaved,
  biochemGetPathways, biochemGetPathwayProgress, biochemSavePathwayProgress,
  prefs: lsPrefs,
};

/* ═══════════════════════════════════════════════════════════════════════
   Global Cosmetics Applier — call on any page after auth
   ═══════════════════════════════════════════════════════════════════════ */
async function applyCosmetics() {
  if (!isLoggedIn()) return;
  // Skip the round-trip entirely when gamification is off. Server will
  // 404 anyway, but a synchronous bail-out keeps the network quiet.
  if (!isGamificationEnabled()) return;
  try {
    const c = await getMyActiveCosmetics();
    if (!c) return;

    // ── Background: paint a fixed div behind the whole UI ──
    // The element is created on demand and reused on subsequent calls
    // so swapping backgrounds doesn't flash. A second fixed div sits
    // ON TOP of it (#ls-bg-veil, z-index:-1 vs bg-fx -2) acting as a
    // translucent veil so vibrant animations don't drown out the UI.
    // The tone attr on <body> lets the veil darken for dark presets.
    const DARK_BG_SLUGS = new Set([
      'dark', 'stars', 'aurora', 'nebula', 'grid',
      // Phase migration-036 additions — all dark except 'clouds'.
      'sunset', 'rain', 'snow', 'fireflies', 'cyber-grid',
      'kaleidoscope', 'ocean', 'aurora-dance',
    ]);
    if (c.background && c.background.slug && c.background.slug !== 'none') {
      const slug = String(c.background.slug).replace(/[^a-z0-9_-]/gi, '');
      let bgEl = document.getElementById('ls-bg-fx');
      if (!bgEl) {
        bgEl = document.createElement('div');
        bgEl.id = 'ls-bg-fx';
        document.body.insertBefore(bgEl, document.body.firstChild);
      }
      bgEl.className = 'bg-' + slug;
      let veilEl = document.getElementById('ls-bg-veil');
      if (!veilEl) {
        veilEl = document.createElement('div');
        veilEl.id = 'ls-bg-veil';
        // Insert just after bg-fx so it paints above (same z-index gap).
        bgEl.parentNode.insertBefore(veilEl, bgEl.nextSibling);
      }
      document.body.dataset.bgTone = DARK_BG_SLUGS.has(slug) ? 'dark' : 'light';
    } else {
      // Active bg was cleared — remove both layers.
      document.getElementById('ls-bg-fx')?.remove();
      document.getElementById('ls-bg-veil')?.remove();
      delete document.body.dataset.bgTone;
    }

    // ── Frame: apply CSS to sidebar avatar on every page ──
    if (c.frame && c.frame.css) {
      const navAv = document.getElementById('nav-avatar');
      if (navAv) {
        // Strip any previously applied frame styles so swaps don't stack.
        if (navAv.dataset.frameApplied) {
          navAv.style.cssText = navAv.dataset.frameOrig || '';
        } else {
          navAv.dataset.frameOrig = navAv.style.cssText || '';
        }
        navAv.style.cssText += ';' + c.frame.css;
        navAv.dataset.frameApplied = '1';
      }
    }

    // ── Title: show under nav username ──
    if (c.title && c.title.text) {
      const nameEl = document.getElementById('nav-user');
      if (nameEl && !document.getElementById('nav-title-badge')) {
        const badge = document.createElement('div');
        badge.id = 'nav-title-badge';
        badge.textContent = c.title.text;
        badge.style.cssText = `font-size:0.55rem;font-weight:700;color:${c.title.color || '#9B5DE5'};margin-top:-2px;letter-spacing:0.5px;text-transform:uppercase;`;
        nameEl.after(badge);
      }
    }

    // ── Effect: particle animation on avatar ──
    if (c.effect && c.effect.effect) {
      _applyEffect(c.effect.effect);
    }
  } catch {}
}


function _applyEffect(name) {
  const avatar = document.getElementById('nav-avatar');
  if (!avatar) return;
  avatar.style.position = 'relative';

  if (name === 'pulse') {
    if (!document.getElementById('ls-pulse-style')) {
      const s = document.createElement('style');
      s.id = 'ls-pulse-style';
      s.textContent = `@keyframes ls-pulse{0%,100%{box-shadow:0 0 0 0 rgba(155,93,229,0.5)}50%{box-shadow:0 0 0 8px rgba(155,93,229,0)}} .ls-effect-pulse{animation:ls-pulse 2s infinite}`;
      document.head.appendChild(s);
    }
    avatar.classList.add('ls-effect-pulse');
  }

  if (name === 'sparkle') {
    if (!document.getElementById('ls-sparkle-style')) {
      const s = document.createElement('style');
      s.id = 'ls-sparkle-style';
      s.textContent = `
.ls-sparkle-wrap{position:relative;display:inline-flex}
.ls-sparkle{position:absolute;width:4px;height:4px;border-radius:50%;background:#FFD166;pointer-events:none;animation:ls-sparkle-fly 1.4s ease-out infinite}
@keyframes ls-sparkle-fly{0%{opacity:1;transform:translate(0,0) scale(1)}100%{opacity:0;transform:translate(var(--sx),var(--sy)) scale(0)}}`;
      document.head.appendChild(s);
    }
    const wrap = document.createElement('span');
    wrap.className = 'ls-sparkle-wrap';
    avatar.parentNode.insertBefore(wrap, avatar);
    wrap.appendChild(avatar);
    for (let i = 0; i < 5; i++) {
      const sp = document.createElement('span');
      sp.className = 'ls-sparkle';
      const angle = (i / 5) * Math.PI * 2;
      sp.style.cssText = `--sx:${Math.cos(angle) * 16}px;--sy:${Math.sin(angle) * 16}px;animation-delay:${i * 0.28}s;top:50%;left:50%;margin:-2px`;
      wrap.appendChild(sp);
    }
  }

  if (name === 'snow') {
    if (!document.getElementById('ls-snow-style')) {
      const s = document.createElement('style');
      s.id = 'ls-snow-style';
      s.textContent = `
.ls-snow-wrap{position:relative;display:inline-flex;overflow:visible}
.ls-snowflake{position:absolute;width:3px;height:3px;border-radius:50%;background:#fff;pointer-events:none;opacity:0.7;animation:ls-snow-fall 2s linear infinite}
@keyframes ls-snow-fall{0%{opacity:0.8;transform:translateY(-10px) translateX(0)}50%{transform:translateY(6px) translateX(4px)}100%{opacity:0;transform:translateY(18px) translateX(-2px)}}`;
      document.head.appendChild(s);
    }
    const wrap = document.createElement('span');
    wrap.className = 'ls-snow-wrap';
    avatar.parentNode.insertBefore(wrap, avatar);
    wrap.appendChild(avatar);
    for (let i = 0; i < 6; i++) {
      const fl = document.createElement('span');
      fl.className = 'ls-snowflake';
      fl.style.cssText = `left:${4 + i * 4}px;top:-4px;animation-delay:${i * 0.33}s`;
      wrap.appendChild(fl);
    }
  }
}

/* ── files (library) ──────────────────────────────────────────────────── */
async function getFiles(params = {}) {
  const p = new URLSearchParams();
  if (params.subject) p.set('subject', params.subject);
  if (params.my)      p.set('my', '1');
  return req('GET', `/files?${p}`);
}
async function uploadFile(formData) {
  const token = getToken();
  const res = await fetch(API + '/files', {
    method: 'POST',
    headers: token ? { 'Authorization': `Bearer ${token}` } : {},
    body: formData,
  });
  const data = await res.json().catch(() => ({}));
  if (!res.ok) throw Object.assign(new Error(data.error || 'Upload failed'), { status: res.status });
  return data;
}
/* Personal image upload for «Мои материалы» — any logged-in user (students too).
 * Separate from uploadFile() which is the teacher library (role + permission). */
async function uploadMaterialFile(formData) {
  const token = getToken();
  const res = await fetch(API + '/files/personal', {
    method: 'POST',
    headers: token ? { 'Authorization': `Bearer ${token}` } : {},
    body: formData,
  });
  const data = await res.json().catch(() => ({}));
  if (!res.ok) throw Object.assign(new Error(data.error || 'Upload failed'), { status: res.status });
  return data;
}
function downloadFileUrl(id) { return `${API}/files/${id}/download`; }
async function listMaterials()        { return req('GET',    '/materials'); }
async function saveMaterial(data)     { return req('POST',   '/materials', data); }
async function updateMaterial(id, d)  { return req('PATCH',  `/materials/${id}`, d); }
async function deleteMaterial(id)     { return req('DELETE', `/materials/${id}`); }
async function shareMaterial(id, d)   { return req('POST',   `/materials/${id}/share`, d); }
async function getActivity()          { return req('GET',    '/dashboard/activity'); }
async function createMaterialCollection(d)   { return req('POST',   '/materials/collections', d); }
async function updateMaterialCollection(id,d){ return req('PATCH',  `/materials/collections/${id}`, d); }
async function deleteMaterialCollection(id)  { return req('DELETE', `/materials/collections/${id}`); }
async function assistantContext()    { return req('GET',    '/assistant/context'); }
async function assistantSeen(ruleId) { return req('POST',   '/assistant/seen', { ruleId }); }
async function assistantDismiss(rid) { return req('POST',   '/assistant/dismiss', { ruleId: rid }); }
async function assistantSettings(d)  { return req('PATCH',  '/assistant/settings', d); }
async function assistantAsk(q, context, history) { return req('POST', '/assistant/ask', { q, context: context || undefined, history: history || undefined }); }
async function assistantFlashcards(text, title) { return req('POST', '/assistant/flashcards', { text, title }); }
async function adminGetAssistant()   { return req('GET',  '/admin/assistant'); }
async function adminSaveAssistant(d) { return req('PUT',  '/admin/assistant', d); }
async function adminTestAssistant(d) { return req('POST', '/admin/assistant/test', d || {}); }
async function adminReindexTextbooks() { return req('POST', '/admin/assistant/reindex', {}); }
async function fcListDecks()         { return req('GET',  '/flashcards/decks'); }
async function fcCreateDeck(d)       { return req('POST', '/flashcards/decks', d); }
async function fcAddCard(deckId, d)  { return req('POST', `/flashcards/decks/${deckId}/cards`, d); }
async function deleteFile(id)                        { return req('DELETE', `/files/${id}`); }
async function getFileAccess(id)                     { return req('GET',    `/files/${id}/access`); }
async function assignFile(id, data)                  { return req('POST',   `/files/${id}/assign`, data); }
async function unassignFile(id, type, targetId)      { return req('DELETE', `/files/${id}/assign/${encodeURIComponent(type)}/${targetId}`); }
async function getFolders()                          { return req('GET',    '/files/folders'); }
async function createFolder(name)                    { return req('POST',   '/files/folders', { name }); }
async function renameFolder(id, name)                { return req('PUT',    `/files/folders/${id}`, { name }); }
async function deleteFolder(id)                      { return req('DELETE', `/files/folders/${id}`); }
async function moveFile(id, folder_id)               { return req('PATCH',  `/files/${id}/move`, { folder_id }); }
async function getFolderAccess(id)                   { return req('GET',    `/files/folders/${id}/access`); }
async function clearFolderAccess(id)                 { return req('DELETE', `/files/folders/${id}/access`); }
async function assignFolder(id, data)                { return req('POST',   `/files/folders/${id}/assign`, data); }
async function unassignFolder(id, type, targetId)    { return req('DELETE', `/files/folders/${id}/assign/${encodeURIComponent(type)}/${targetId}`); }
async function getStudentsList()                     { const d = await req('GET', '/admin/users?role=student&limit=500'); return d.users || []; }

/* ── class members (admin/teacher) ──────────────────────────────────────── */
async function addClassMember(classId, email, user_id) { return req('POST', `/classes/${classId}/members`, user_id ? { user_id } : { email }); }

/* ── announcements ───────────────────────────────────────────────────────── */
async function getAnnouncements(classId)        { return req('GET',    `/classes/${classId}/announcements`); }
async function createAnnouncement(classId, text){ return req('POST',   `/classes/${classId}/announcements`, { text }); }
async function deleteAnnouncement(classId, id)  { return req('DELETE', `/classes/${classId}/announcements/${id}`); }

/* ── submissions ─────────────────────────────────────────────────────────── */
async function submitWork(formData) {
  const token = getToken();
  const res = await fetch(API + '/submissions', {
    method: 'POST',
    headers: token ? { 'Authorization': `Bearer ${token}` } : {},
    body: formData,
  });
  const data = await res.json().catch(() => ({}));
  if (!res.ok) throw Object.assign(new Error(data.error || 'Upload failed'), { status: res.status });
  return data;
}
async function resubmitWork(id, formData) {
  const token = getToken();
  const res = await fetch(API + `/submissions/${id}/resubmit`, {
    method: 'POST',
    headers: token ? { 'Authorization': `Bearer ${token}` } : {},
    body: formData,
  });
  const data = await res.json().catch(() => ({}));
  if (!res.ok) throw Object.assign(new Error(data.error || 'Upload failed'), { status: res.status });
  return data;
}
async function getMySubmissions()           { return req('GET',   '/submissions/my'); }
async function getClassSubmissions(classId) { return req('GET',   `/submissions?class_id=${classId}`); }
async function reviewSubmission(id, data)   { return req('PATCH', `/submissions/${id}`, data); }
async function deleteSubmission(id)         { return req('DELETE',`/submissions/${id}`); }
function submissionDownloadUrl(id)          { return `${API}/submissions/${id}/download`; }

/* ── permissions (admin only) ────────────────────────────────────────────── */
async function getPermissions()                            { return req('GET',    '/permissions'); }
async function permissionsLog(userId)                      { return req('GET',    userId ? `/permissions/log?user_id=${userId}` : '/permissions/log'); }
async function setClassPermission(classId, permission, enabled) { return req('POST', `/permissions/class/${classId}/bulk`, { permission, enabled }); }
async function permissionsPresets()                        { return req('GET',    '/permissions/presets'); }
async function listRoles()                                 { return req('GET',    '/roles'); }
async function createRole(name, label, baseRoles)          { return req('POST',   '/roles', { name, label, baseRoles }); }
async function updateRoleDef(name, body)                   { return req('PUT',    `/roles/${encodeURIComponent(name)}`, body); }
async function deleteRole(name)                            { return req('DELETE', `/roles/${encodeURIComponent(name)}`); }
async function rolePermissions(name)                       { return req('GET',    `/roles/${encodeURIComponent(name)}/permissions`); }
async function applyClassPreset(classId, preset)           { return req('POST',   `/permissions/class/${classId}/preset`, { preset }); }
async function setPermission(role, permission, enabled)    { return req('POST',   '/permissions', { role, permission, enabled }); }
async function getUserPermissions(uid)                     { return req('GET',    `/permissions/users/${uid}`); }
async function setUserPermission(uid, permission, enabled, days) { return req('POST',   `/permissions/users/${uid}`, days ? { permission, enabled, days } : { permission, enabled }); }
async function resetUserPermissions(uid, permission)       { return req('DELETE', `/permissions/users/${uid}/reset`, permission ? { permission } : undefined); }

/* ── content access (учебники / экзамены: открыть-закрыть классам/ученикам) ── */
async function accessCatalog()  { return req('GET', '/access/catalog'); }
async function accessTargets()  { return req('GET', '/access/targets'); }
async function accessSummary()  { return req('GET', '/access/summary'); }
async function accessClassOpen(classId) { return req('GET', `/access/class/${classId}`); }
async function accessMatrix()    { return req('GET', '/access/matrix'); }
async function accessLog(content_type, content_ref) {
  const p = new URLSearchParams({ content_type, content_ref });
  return req('GET', `/access/log?${p}`);
}
async function accessRules(content_type, content_ref) {
  const p = new URLSearchParams({ content_type, content_ref });
  return req('GET', `/access/rules?${p}`);
}
async function accessSetRule(content_type, content_ref, scope, target_id, allow) {
  return req('POST', '/access/rules', { content_type, content_ref, scope, target_id, allow });
}

/* ── notifications ───────────────────────────────────────────────────────── */
async function getNotifications()   { return req('GET',  '/notifications'); }
async function markNotifRead(id)    { return req('PATCH',`/notifications/${id}/read`); }
async function markAllNotifsRead()  { return req('POST', '/notifications/read-all'); }

/* ── SSE real-time notifications ─────────────────────────────────────────── */
/* ── Shared SSE singleton — all listeners share one EventSource ─────── */
let _sseShared = null;
let _sseRetryMs = 2000;
let _sseEverConnected = false;   // tracks whether SSE has successfully opened before
const _sseListeners = new Set();

function _sseConnect() {
  const token = getToken();
  if (!token) return;
  const url = `${API}/notifications/stream?token=${encodeURIComponent(token)}`;
  const es = new EventSource(url);
  _sseShared = es;
  es.onopen = () => {
    const isReconnect = _sseEverConnected;
    _sseEverConnected = true;
    _sseRetryMs = 2000;
    // Notify listeners of reconnect so they can re-sync missed state
    if (isReconnect) {
      for (const fn of _sseListeners) try { fn({ type: '_sse_reconnect' }); } catch {}
    }
  };
  es.onmessage = e => {
    let data; try { data = JSON.parse(e.data); } catch { return; }
    for (const fn of _sseListeners) try { fn(data); } catch {}
  };
  es.onerror = () => {
    es.close();
    _sseShared = null;
    const delay = Math.min(_sseRetryMs, 30000);
    _sseRetryMs = Math.min(_sseRetryMs * 2, 30000);
    setTimeout(_sseConnect, delay);
  };
}

function connectSSE(onEvent) {
  if (!getToken()) return null;
  _sseListeners.add(onEvent);
  if (!_sseShared) _sseConnect();
  return { close: () => _sseListeners.delete(onEvent) };
}

// Proactively close SSE when navigating away to prevent HTTP/1.1
// connection pool exhaustion during View Transition (old page stays alive ~260ms)
window.addEventListener('pagehide', () => {
  if (_sseShared) { _sseShared.close(); _sseShared = null; }
  _sseListeners.clear();
});

/* ── assignment templates ─────────────────────────────────────────────────── */
async function listTemplates()           { return req('GET',    '/assignments/templates'); }
async function saveTemplate(data)        { return req('POST',   '/assignments/templates', data); }
async function deleteTemplate(id)        { return req('DELETE', `/assignments/templates/${id}`); }
async function bulkCreateAssignment(data){ return req('POST',   '/assignments/bulk', data); }

/* ── templates (course & lesson) ───────────────────────────────────────── */
async function getCourseTemplates(params = {})   { const p = new URLSearchParams(); if (params.subject) p.set('subject', params.subject); if (params.my) p.set('my', '1'); return req('GET', `/templates/courses?${p}`); }
async function saveCourseTemplate(data)          { return req('POST',  '/templates/courses', data); }
async function createFromCourseTemplate(id, d)   { return req('POST',  `/templates/courses/${id}/create`, d); }
async function deleteCourseTemplate(id)          { return req('DELETE', `/templates/courses/${id}`); }
async function getLessonTemplates(params = {})    { const p = new URLSearchParams(); if (params.category) p.set('category', params.category); if (params.my) p.set('my', '1'); return req('GET', `/templates/lessons?${p}`); }
async function saveLessonTemplate(data)          { return req('POST',  '/templates/lessons', data); }
async function createFromLessonTemplate(id, d)   { return req('POST',  `/templates/lessons/${id}/create`, d); }
async function deleteLessonTemplate(id)          { return req('DELETE', `/templates/lessons/${id}`); }

/* ── shop ──────────────────────────────────────────────────────────────── */
async function getShopItems()                    { return req('GET',  '/shop/items'); }
async function purchaseItem(itemId)              { return req('POST', `/shop/items/${itemId}/purchase`); }
async function getUserPurchases()                { return req('GET',  '/shop/purchases'); }
async function getCoins()                        { return req('GET',  '/shop/coins'); }
async function getMyActiveCosmetics()            { return req('GET',  '/shop/my-active'); }
async function activateShopItem(itemId, type)    { return req('POST', '/shop/activate', { itemId, type }); }

/* ── shop admin ────────────────────────────────────────────────────────── */
async function adminShopGetItems()               { return req('GET',    '/shop/admin/items'); }
async function adminShopCreateItem(data)         { return req('POST',   '/shop/admin/items', data); }
async function adminShopUpdateItem(id, data)     { return req('PUT',    `/shop/admin/items/${id}`, data); }
async function adminShopDeleteItem(id)           { return req('DELETE', `/shop/admin/items/${id}`); }
async function adminShopAwardCoins(data)         { return req('POST',   '/shop/admin/award-coins', data); }
async function adminShopStats()                  { return req('GET',    '/shop/admin/stats'); }

/* ── bookmarks ────────────────────────────────────────────────────────── */
async function getBookmarks(type)                     { const p = type ? `?type=${type}` : ''; return req('GET', `/bookmarks${p}`); }
async function addBookmark(entityType, entityId)      { return req('POST', '/bookmarks', { entityType, entityId }); }
async function removeBookmark(id)                     { return req('DELETE', `/bookmarks/${id}`); }
async function removeBookmarkByEntity(type, entityId) { return req('DELETE', `/bookmarks/entity/${type}/${entityId}`); }
async function checkBookmark(type, entityId)          { return req('GET', `/bookmarks/check/${type}/${entityId}`); }

/* ── search ───────────────────────────────────────────────────────────── */
async function globalSearch(q, type, limit) {
  const p = new URLSearchParams({ q });
  if (type)  p.set('type', type);
  if (limit) p.set('limit', limit);
  return req('GET', `/search?${p}`);
}

/* ── parent link management (student side) ─────────────────────────────── */
async function parentGetLinks()          { return req('GET',    '/parent/my-links'); }
async function parentCreateLink(label)   { return req('POST',   '/parent/links', { label }); }
async function parentUpdateLink(id, d)   { return req('PATCH',  `/parent/links/${id}`, d); }
async function parentDeleteLink(id)      { return req('DELETE', `/parent/links/${id}`); }

/* ── classroom (online lesson) ─────────────────────────────────────────── */
async function crCreateSession(data)         { return req('POST',   '/classroom', data); }
async function crGetSession(id)              { return req('GET',    `/classroom/${id}`); }
async function crEndSession(id)              { return req('DELETE', `/classroom/${id}`); }
async function crGetActiveByClass(classId)   { return req('GET',    `/classroom/class/${classId}/active`); }
async function crGetMyActive()               { return req('GET',    '/classroom/my/active'); }
async function crGetMySession()              { return req('GET',    '/classroom/my/session'); }
async function crJoin(id)                    { return req('POST',   `/classroom/${id}/join`); }
async function crLeave(id)                   { return req('POST',   `/classroom/${id}/leave`); }
async function crSendChat(id, message)       { return req('POST',   `/classroom/${id}/chat`, { message }); }
async function crGetChat(id)                 { return req('GET',    `/classroom/${id}/chat`); }
async function crGetAttendance(id)           { return req('GET',    `/classroom/${id}/attendance`); }
async function crSignal(id, targetUserId, payload) { return req('POST', `/classroom/${id}/signal`, { target_user_id: targetUserId, payload }); }
async function crGetOnlineStudents()                { return req('GET',  '/classroom/online-students'); }
async function crGetMyHistory(page = 1)             { return req('GET',  `/classroom/my/history?page=${page}`); }
async function crGetClassHistory(classId, page = 1, search = '') {
  const q = search ? `&search=${encodeURIComponent(search)}` : '';
  return req('GET', `/classroom/class/${classId}/history?page=${page}${q}`);
}
async function crGetSessionSummary(id)              { return req('GET',  `/classroom/${id}/summary`); }
async function crExportChatUrl(id)                  { return `/api/classroom/${id}/chat/export`; }
async function crGetAllNotes(id)                    { return req('GET',  `/classroom/${id}/notes/all`); }
async function crDeleteHistory(id)                  { return req('DELETE', `/classroom/${id}/history`); }
async function crAdminGetAllHistory(p = {}) {
  const q = new URLSearchParams();
  if (p.page)      q.set('page',      p.page);
  if (p.limit)     q.set('limit',     p.limit);
  if (p.search)    q.set('search',    p.search);
  if (p.teacher)   q.set('teacher',   p.teacher);
  if (p.class_id)  q.set('class_id',  p.class_id);
  if (p.date_from) q.set('date_from', p.date_from);
  if (p.date_to)   q.set('date_to',   p.date_to);
  if (p.sort)      q.set('sort',      p.sort);
  return req('GET', `/classroom/admin/sessions?${q}`);
}
async function crAdminGetTeachersList() { return req('GET', '/classroom/admin/teachers-list'); }

/* ── gamification admin ────────────────────────────────────────────────── */
async function adminGamAward(data)               { return req('POST',   '/gamification/admin/award', data); }
async function adminGamReset(data)               { return req('POST',   '/gamification/admin/reset', data); }
async function adminGamStats()                   { return req('GET',    '/gamification/admin/stats'); }
async function adminGamGetUser(id)               { return req('GET',    `/gamification/admin/user/${id}`); }

/* ── Live Quiz Student Overlay ──────────────────────────────────────────── */
(function initLiveOverlay() {
  const token = getToken();
  if (!token) return;
  let payload; try { payload = JSON.parse(atob(token.split('.')[1])); } catch { return; }
  if (!payload || payload.role === 'teacher' || payload.role === 'admin') return;

  const STYLE = `
  #ls-live-overlay{position:fixed;inset:0;z-index:9000;background:rgba(10,2,32,0.92);
    backdrop-filter:blur(12px);display:none;align-items:center;justify-content:center;padding:20px;}
  #ls-live-overlay.open{display:flex;}
  .ls-live-box{background:#fff;border-radius:24px;padding:32px 28px;width:100%;max-width:520px;
    box-shadow:0 40px 120px rgba(0,0,0,0.5);position:relative;}
  .ls-live-badge{display:inline-flex;align-items:center;gap:6px;padding:4px 12px;border-radius:99px;
    background:rgba(155,93,229,0.1);color:#9B5DE5;font-size:0.72rem;font-weight:800;
    text-transform:uppercase;letter-spacing:.06em;margin-bottom:14px;}
  .ls-live-badge::before{content:'';width:7px;height:7px;border-radius:50%;
    background:#9B5DE5;animation:ls-live-pulse 1s ease infinite;}
  @keyframes ls-live-pulse{0%,100%{opacity:1;transform:scale(1)}50%{opacity:.5;transform:scale(1.3)}}
  .ls-live-q{font-size:1rem;line-height:1.65;color:#0F172A;margin-bottom:20px;font-weight:500;}
  .ls-live-opts{display:flex;flex-direction:column;gap:8px;margin-bottom:16px;}
  .ls-live-opt{display:flex;align-items:center;gap:12px;padding:12px 16px;border:1.5px solid #E2E8F0;
    border-radius:14px;cursor:pointer;transition:all .15s;font-size:.9rem;}
  .ls-live-opt:hover{border-color:#9B5DE5;background:rgba(155,93,229,.04);}
  .ls-live-opt.selected{border-color:#06D6E0;background:rgba(6,214,224,.07);}
  .ls-live-opt.correct{border-color:#06D6A0!important;background:rgba(6,214,160,.1)!important;color:#059652;}
  .ls-live-opt.wrong{border-color:#EF476F!important;background:rgba(239,71,111,.06)!important;color:#EF476F;}
  .ls-live-opt-key{width:28px;height:28px;border-radius:8px;background:#F1F5F9;
    display:flex;align-items:center;justify-content:center;font-size:.75rem;font-weight:700;
    color:#64748B;flex-shrink:0;transition:.15s;}
  .ls-live-opt.selected .ls-live-opt-key{background:#06D6E0;color:#fff;}
  .ls-live-opt.correct .ls-live-opt-key{background:#06D6A0;color:#fff;}
  .ls-live-opt.wrong   .ls-live-opt-key{background:#EF476F;color:#fff;}
  .ls-live-status{text-align:center;font-size:.84rem;color:var(--text-3);padding:8px 0;}
  .ls-live-result-bar-wrap{margin:4px 0;}
  .ls-live-result-bar{height:8px;border-radius:99px;background:#E2E8F0;margin-top:4px;overflow:hidden;}
  .ls-live-result-fill{height:100%;border-radius:99px;background:#9B5DE5;transition:width .6s ease;}
  .ls-live-result-fill.correct-fill{background:#06D6A0;}
  .ls-live-result-pct{font-size:.72rem;font-weight:700;color:#64748B;float:right;}
  `;

  const el = document.createElement('div');
  el.id = 'ls-live-overlay';
  el.setAttribute('role', 'dialog');
  el.setAttribute('aria-modal', 'true');
  el.setAttribute('aria-labelledby', 'lslq-text');
  el.innerHTML = `<div class="ls-live-box">
    <div class="ls-live-badge" aria-hidden="true"><svg class="ic" viewBox="0 0 24 24"><polygon points="13 2 3 14 12 14 11 22 21 10 12 10 13 2"/></svg> Live Quiz</div>
    <div class="ls-live-q" id="lslq-text"></div>
    <div class="ls-live-opts" id="lslq-opts" role="radiogroup" aria-label="Варианты ответа"></div>
    <div class="ls-live-status" id="lslq-status" aria-live="polite"></div>
  </div>`;

  const styleEl = document.createElement('style');
  styleEl.textContent = STYLE;

  document.addEventListener('DOMContentLoaded', () => {
    if (window._lsLiveOverriddenByClassroom) return;
    document.head.appendChild(styleEl);
    document.body.appendChild(el);
  });

  let currentLiveId = null;
  let answered      = false;

  /* render text that may contain \(...\) or \[...\] LaTeX using window.katex */
  function _mathHtml(text) {
    if (!text) return '';
    const kat = window.katex;
    if (!kat) { const d = document.createElement('span'); d.textContent = text; return d.innerHTML; }
    let out = '', i = 0;
    while (i < text.length) {
      const ii = text.indexOf('\\(', i), bi = text.indexOf('\\[', i);
      let next = -1, close = '', disp = false;
      if (ii >= 0 && (bi < 0 || ii <= bi)) { next = ii; close = '\\)'; disp = false; }
      else if (bi >= 0)                      { next = bi; close = '\\]'; disp = true;  }
      const plain = document.createElement('span');
      if (next < 0) { plain.textContent = text.slice(i); out += plain.innerHTML; break; }
      plain.textContent = text.slice(i, next); out += plain.innerHTML;
      const ci = text.indexOf(close, next + 2);
      if (ci < 0) { const p2 = document.createElement('span'); p2.textContent = text.slice(next); out += p2.innerHTML; break; }
      try { out += kat.renderToString(text.slice(next + 2, ci), { displayMode: disp, throwOnError: false }); }
      catch { const p2 = document.createElement('span'); p2.textContent = text.slice(next, ci + close.length); out += p2.innerHTML; }
      i = ci + close.length;
    }
    return out;
  }

  function openOverlay(liveId, question, options) {
    currentLiveId = liveId;
    answered      = false;
    document.getElementById('lslq-text').innerHTML = _mathHtml(question.text);
    const keys = 'АБВГДЕ';
    document.getElementById('lslq-opts').innerHTML = (options || []).map((o, i) => `
      <div class="ls-live-opt" role="radio" aria-checked="false" tabindex="0" data-id="${o.id}"
           onclick="window._lsLiveAnswer(${liveId},${o.id},this)"
           onkeydown="if(event.key===' '||event.key==='Enter'){event.preventDefault();window._lsLiveAnswer(${liveId},${o.id},this)}">
        <span class="ls-live-opt-key" aria-hidden="true">${keys[i] || i+1}</span>
        <span>${_mathHtml(o.text)}</span>
      </div>`).join('');
    document.getElementById('lslq-status').textContent = 'Выберите ответ';
    document.getElementById('ls-live-overlay').classList.add('open');
  }

  function showResults(options, stats) {
    const total = stats?.total || 1;
    document.getElementById('lslq-status').textContent =
      `Ответили: ${stats?.total || 0} · Правильно: ${stats?.correct || 0}`;
    document.querySelectorAll('.ls-live-opt').forEach(el => { el.onclick = null; el.style.cursor = 'default'; });
    const keys = 'АБВГДЕ';
    document.getElementById('lslq-opts').innerHTML = (options || []).map((o, i) => {
      const pct = total ? Math.round((o.chosen_count || 0) * 100 / total) : 0;
      const cls = o.is_correct ? 'correct' : '';
      return `<div class="ls-live-opt ${cls}" style="flex-direction:column;align-items:flex-start;gap:4px">
        <div style="display:flex;align-items:center;gap:10px;width:100%">
          <span class="ls-live-opt-key">${keys[i]||i+1}</span>
          <span style="flex:1">${_mathHtml(o.text)}</span>
          <span class="ls-live-result-pct">${pct}%</span>
        </div>
        <div class="ls-live-result-bar" style="width:100%">
          <div class="ls-live-result-fill ${o.is_correct?'correct-fill':''}" style="width:${pct}%"></div>
        </div>
      </div>`;
    }).join('');
  }

  window._lsLiveAnswer = async function(liveId, optionId, el) {
    if (answered) return;
    answered = true;
    document.querySelectorAll('.ls-live-opt').forEach(o => {
      o.onclick = null; o.onkeydown = null; o.style.cursor = 'default';
      o.setAttribute('aria-checked', 'false');
    });
    el.classList.add('selected');
    el.setAttribute('aria-checked', 'true');
    document.getElementById('lslq-status').innerHTML = 'Ответ отправлен <svg class="ic" viewBox="0 0 24 24"><polyline points="20 6 9 17 4 12"/></svg>';
    try {
      const r = await apiFetch(`/api/live/${liveId}/answer`, { method: 'POST', body: JSON.stringify({ option_id: optionId }) });
      if (r.is_correct === 1)  el.classList.replace('selected','correct');
      else if (r.is_correct === 0) el.classList.replace('selected','wrong');
    } catch {}
  };

  document.addEventListener('DOMContentLoaded', () => {
    if (window._lsLiveOverriddenByClassroom) return;
    connectSSE(d => {
      if (d.type === 'live_question') {
        openOverlay(d.liveId, d.question, d.question?.options);
      } else if (d.type === 'live_results') {
        showResults(d.options, d.stats);
      } else if (d.type === 'live_ended') {
        setTimeout(() => document.getElementById('ls-live-overlay')?.classList.remove('open'), 2000);
        document.getElementById('lslq-status').textContent = 'Сессия завершена';
      }
    });
  });
})();

/* ── Онлайн-урок: липкий верхний баннер + индикатор «В эфире» в сайдбаре ── */
/* Пока идёт урок — заметный баннер сверху на ЛЮБОЙ странице + пульс пункта   */
/* «Онлайн-урок» в сайдбаре. Зайти можно одним кликом откуда угодно.          */
(function initClassroomNotify() {
  const token = getToken();
  if (!token) return;
  let payload; try { payload = JSON.parse(atob(token.split('.')[1])); } catch { return; }
  // Только ученики (учителя сами начинают урок и обычно уже в нём)
  if (!payload || payload.role === 'teacher' || payload.role === 'admin') return;

  const onClassroomPage = () => window.location.pathname.replace(/\.html$/, '') === '/classroom';

  const STYLE = `
  #ls-cr-banner{position:fixed;top:14px;left:50%;z-index:8500;display:none;align-items:center;gap:14px;
    transform:translateX(-50%) translateY(-130%);
    padding:9px 10px 9px 18px;border-radius:999px;max-width:calc(100vw - 24px);
    background:linear-gradient(135deg,#1c1233,#2c1656);border:1.5px solid rgba(155,93,229,.55);
    box-shadow:0 16px 50px rgba(124,58,205,.45);
    transition:transform .4s cubic-bezier(.34,1.4,.64,1),opacity .25s;opacity:0;}
  #ls-cr-banner.open{display:flex;transform:translateX(-50%) translateY(0);opacity:1;}
  .ls-crb-dot{width:9px;height:9px;border-radius:50%;background:#F15BB5;flex-shrink:0;
    animation:ls-crb-pulse 1.3s ease infinite;}
  @keyframes ls-crb-pulse{0%{box-shadow:0 0 0 0 rgba(241,91,181,.55)}70%{box-shadow:0 0 0 9px rgba(241,91,181,0)}100%{box-shadow:0 0 0 0 rgba(241,91,181,0)}}
  .ls-crb-txt{color:#F3EEFF;font-size:.86rem;font-weight:600;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;
    font-family:'Manrope',sans-serif;}
  .ls-crb-txt b{font-weight:800;color:#fff;}
  .ls-crb-join{flex-shrink:0;display:inline-flex;align-items:center;gap:6px;padding:8px 18px;border-radius:999px;
    border:none;background:linear-gradient(135deg,#06D6E0,#9B5DE5);color:#fff;font-weight:800;font-size:.82rem;
    font-family:'Manrope',sans-serif;text-decoration:none;cursor:pointer;transition:opacity .15s,transform .15s;}
  .ls-crb-join:hover{opacity:.92;transform:translateY(-1px);}
  .ls-crb-x{flex-shrink:0;background:none;border:none;color:#8b7da8;cursor:pointer;padding:4px 8px;
    font-size:1.15rem;line-height:1;border-radius:8px;transition:color .15s;}
  .ls-crb-x:hover{color:#fff;}
  @media (max-width:768px){#ls-cr-banner{top:64px;left:12px;right:12px;transform:translateY(-130%);}
    #ls-cr-banner.open{transform:translateY(0);}.ls-crb-txt{white-space:normal;}}
  `;

  let bannerEl = null, dismissed = false, current = null;

  function buildBanner() {
    if (bannerEl) return bannerEl;
    const styleEl = document.createElement('style');
    styleEl.textContent = STYLE;
    document.head.appendChild(styleEl);
    bannerEl = document.createElement('div');
    bannerEl.id = 'ls-cr-banner';
    bannerEl.setAttribute('role', 'status');
    bannerEl.innerHTML =
      '<span class="ls-crb-dot"></span>' +
      '<span class="ls-crb-txt">Идёт онлайн-урок<span id="ls-crb-title"></span></span>' +
      '<a href="/classroom" class="ls-crb-join">' + lsIcon('video', 15) + ' Войти</a>' +
      '<button class="ls-crb-x" aria-label="Скрыть">&times;</button>';
    document.body.appendChild(bannerEl);
    bannerEl.querySelector('.ls-crb-x').onclick = () => { dismissed = true; bannerEl.classList.remove('open'); };
    return bannerEl;
  }

  function setSidebarLive(on) {
    const link = document.getElementById('btn-classroom');
    if (link) link.classList.toggle('is-live', on);
  }

  function goLive(session) {
    current = session || current;
    setSidebarLive(true);                       // пульс в сайдбаре — всегда
    if (onClassroomPage() || dismissed) return; // баннер не нужен на самой странице / если закрыли
    const b = buildBanner();
    const t = b.querySelector('#ls-crb-title');
    const title = current && current.title;
    t.textContent = '';
    if (title) { t.appendChild(document.createTextNode(': ')); const bold = document.createElement('b'); bold.textContent = title; t.appendChild(bold); }
    requestAnimationFrame(() => b.classList.add('open'));
  }

  function goEnded() {
    current = null; dismissed = false;
    setSidebarLive(false);
    if (bannerEl) bannerEl.classList.remove('open');
  }

  /* ── Мелодия-«вызов на урок» через общий движок LS.sfx ────────────────── */
  // sound.js подключён не на всех страницах — подгрузим лениво, затем играем
  // звук 'lesson_start'. Движок сам уважает мастер-тумблер, громкость, отдельный
  // тумблер «Вызов на урок» в профиле и разблокировку аудио по первому жесту.
  function ensureSfx(cb) {
    if (window.LS && LS.sfx) { if (cb) cb(); return; }
    let s = document.getElementById('ls-sound-loader');
    if (!s) {
      s = document.createElement('script');
      s.id = 'ls-sound-loader';
      s.src = '/js/sound.js';
      s.defer = true;
      document.head.appendChild(s);
    }
    if (cb) s.addEventListener('load', cb, { once: true });
  }

  function playLessonCall() {
    ensureSfx(() => { if (window.LS && LS.sfx) LS.sfx.play('lesson_start'); });
  }

  function ready(fn) {
    if (document.readyState !== 'loading') fn();
    else document.addEventListener('DOMContentLoaded', fn);
  }

  ready(() => {
    ensureSfx(); // заранее подгрузить движок звуков
    // Урок мог начаться ДО загрузки страницы — спросим сервер
    if (typeof LS !== 'undefined' && LS.api) {
      LS.api('/api/classroom/my/active')
        .then(r => { const s = r && r.sessions && r.sessions[0]; if (s) goLive(s); })
        .catch(() => {});
    }
    // Реалтайм: старт/конец урока
    connectSSE(d => {
      if (d.type === 'classroom_started') { dismissed = false; playLessonCall(); goLive({ title: d.title, sessionId: d.sessionId }); }
      else if (d.type === 'classroom_ended') goEnded();
    });
  });
})();