const PHOTO_JOB_ACTIONS = new Set(['ai', 'ai_face', 'ai_upscale', 'enhance', 'restore', 'rollback']);
const LESSON_REPORT_TEXT_MAX = 5000;
const LESSON_REPORT_TOPIC_MAX = 300;
const BACKUP_FORMAT_VERSION = 2;
const BACKUP_MIN_FORMAT_VERSION = 1;
const BACKUP_TABLES = [
  'groups', 'students', 'entries', 'project_files', 'branches', 'users', 'user_branches',
  'group_photos', 'entry_photos', 'modules', 'student_photos', 'share_links', 'photo_jobs',
  'lesson_reports', 'lesson_report_versions', 'audit_log', 'notifications',
  'notification_reads', 'banned_ips',
];
const BACKUP_SEQUENCE_TABLES = [
  'groups', 'students', 'entries', 'project_files', 'branches', 'users', 'group_photos',
  'entry_photos', 'modules', 'student_photos', 'share_links', 'photo_jobs', 'lesson_reports',
  'lesson_report_versions', 'audit_log', 'notifications',
];

function isSupportedBackupVersion(data) {
  if (!data || typeof data !== 'object' || !Array.isArray(data.groups)) return false;
  const v = Number(data.version);
  return Number.isInteger(v) && v >= BACKUP_MIN_FORMAT_VERSION && v <= BACKUP_FORMAT_VERSION;
}

function restoredCounts(ndata) {
  const out = {};
  for (const tbl of BACKUP_TABLES) out[tbl] = Array.isArray(ndata[tbl]) ? ndata[tbl].length : 0;
  out.settings = Object.keys(ndata.settings || {}).length;
  return out;
}

const SAFE_NAME = /^[\w,.()-]+$/;

function isSafeUploadPath(p) {
  if (typeof p !== 'string' || !p.startsWith('/uploads/')) return false;
  const name = p.slice('/uploads/'.length);
  return name !== '' && !name.includes('/') && !name.includes('..') && SAFE_NAME.test(name);
}

function reqInt(v) {
  const n = Number(v);
  if (!Number.isInteger(n)) throw new Error('Invalid integer');
  return n;
}

function optInt(v, lo = -Infinity, hi = Infinity) {
  if (v === null || v === undefined || v === '') return null;
  const n = Number(v);
  if (!Number.isInteger(n) || n < lo || n > hi) throw new Error('Invalid integer');
  return n;
}

function reqStr(v, max) {
  if (typeof v !== 'string') throw new Error('Invalid string');
  const s = v.trim();
  if (!s || s.length > max) throw new Error('Invalid string length');
  return s;
}

function optStr(v, max) {
  if (v === null || v === undefined) return null;
  return reqStr(v, max);
}

function optTs(v) {
  if (v === null || v === undefined) return null;
  if (typeof v !== 'string' || !/^\d{4}-\d{2}-\d{2}[T ]\d{2}:\d{2}/.test(v)) throw new Error('Invalid timestamp');
  return v;
}

function reqTs(v) {
  const s = optTs(v);
  if (!s) throw new Error('Invalid timestamp');
  return s;
}

function optJsonText(v, max) {
  if (v === null || v === undefined) return null;
  if (typeof v === 'object') {
    if (Array.isArray(v)) throw new Error('Invalid json');
    v = JSON.stringify(v);
  }
  const s = String(v);
  if (!s || s.length > max) throw new Error('Invalid json');
  return s;
}

function reqIp(v) {
  const s = reqStr(v, 64);
  if (!/^[0-9a-fA-F:.]+$/.test(s)) throw new Error('Invalid ip');
  return s;
}

function optTime(v) {
  if (v === null || v === undefined) return null;
  if (typeof v !== 'string' || !/^\d{2}:\d{2}(:\d{2})?$/.test(v)) throw new Error('Invalid time');
  return v;
}

function optDate(v) {
  if (v === null || v === undefined) return null;
  if (typeof v !== 'string' || !/^\d{4}-\d{2}-\d{2}$/.test(v)) throw new Error('Invalid date');
  return v;
}

function reqDate(v) {
  const s = optDate(v);
  if (!s) throw new Error('Invalid date');
  return s;
}

function optBool(v) {
  if (v === null || v === undefined) return null;
  return !!v;
}

function reqToken(v) {
  if (typeof v !== 'string' || !/^[0-9a-f]{16,64}$/.test(v)) throw new Error('Invalid token');
  return v;
}

function reqUploadPath(v, max) {
  if (typeof v !== 'string' || v.length > max) throw new Error('Invalid path');
  if (!isSafeUploadPath(v)) throw new Error('Invalid upload path');
  return v;
}

function optUploadPath(v, max) {
  if (v === null || v === undefined) return null;
  return reqUploadPath(v, max);
}

const ORIGINALS_PATH_RE = /^\/uploads\/\.originals\/[\w.,()-]+$/;

function optOriginalsPath(v, max) {
  if (v === null || v === undefined) return null;
  if (typeof v !== 'string' || v.length > max || !ORIGINALS_PATH_RE.test(v)) throw new Error('Invalid originals path');
  return v;
}

function reqPhotoRefPath(v, max) {
  if (typeof v !== 'string' || v.length > max) throw new Error('Invalid photo path');
  if (isSafeUploadPath(v) || ORIGINALS_PATH_RE.test(v)) return v;
  throw new Error('Invalid photo path');
}

function optPhotoRefPath(v, max) {
  if (v === null || v === undefined) return null;
  return reqPhotoRefPath(v, max);
}

function photoRefKey(p) {
  if (typeof p !== 'string') return null;
  if (isSafeUploadPath(p) || ORIGINALS_PATH_RE.test(p)) return p.slice('/uploads/'.length);
  return null;
}

const AI_STATUSES = new Set(['pending', 'processing', 'done', 'skipped', 'error', 'reverted']);

function optAiText(v, max) {
  if (v === null || v === undefined) return null;
  return reqStr(v, max);
}

function reqAiStatus(v, fallback) {
  if (v === null || v === undefined) return fallback;
  const s = String(v);
  if (s === 'processing') return 'pending';
  return AI_STATUSES.has(s) ? s : fallback;
}

const PROFILE_HREF_RE = /^(https?:\/\/|mailto:|tel:|\/|#)/i;
const PROFILE_EMAIL_RE = /^[\w.+-]+@[\w-]+\.[\w.-]{2,}$/;

function profText(v, max) {
  if (v === null || v === undefined) return null;
  if (typeof v !== 'string') throw new Error('Ожидалась строка');
  const s = v.trim();
  if (!s) return null;
  if (s.length > max) throw new Error('Слишком длинное значение');
  return s;
}

function profIcon(v) {
  const s = String(v || '').trim().toLowerCase();
  return /^[a-z0-9-]{1,32}$/.test(s) ? s : 'link';
}

function profHref(v) {
  const s = String(v || '').trim();
  if (!s || s.length > 500) return null;
  return (PROFILE_HREF_RE.test(s) || PROFILE_EMAIL_RE.test(s)) ? s : null;
}

function profList(v, max, fn) {
  if (v === null || v === undefined) return [];
  if (!Array.isArray(v)) throw new Error('Ожидался список');
  const out = [];
  for (const item of v.slice(0, max)) {
    const row = fn(item);
    if (row) out.push(row);
  }
  return out;
}

function sanitizeStudentProfile(raw) {
  if (raw === null || raw === undefined) return null;
  if (typeof raw !== 'object' || Array.isArray(raw)) throw new Error('Ожидался объект профиля');
  const out = {
    role: profText(raw.role, 200),
    status: profText(raw.status, 60),
    status_note: profText(raw.status_note, 120),
    city: profText(raw.city, 120),
    mentor: profText(raw.mentor, 150),
    joined: profText(raw.joined, 120),
    bio: profText(raw.bio, 2000),
    quote: profText(raw.quote, 300),
    tags: profList(raw.tags, 20, t => profText(t, 40)),
    achievements: profList(raw.achievements, 40, a => profText(a, 200)),
    contacts: profList(raw.contacts, 20, c => {
      if (!c || typeof c !== 'object') return null;
      const label = profText(c.label, 120);
      if (!label) return null;
      return { icon: profIcon(c.icon), label, href: profHref(c.href) };
    }),
    skills: profList(raw.skills, 80, s => {
      if (!s || typeof s !== 'object') return null;
      const name = profText(s.name, 120);
      if (!name) return null;
      const value = (s.value === null || s.value === undefined || s.value === '') ? null : optInt(s.value, 0, 100);
      return { group: profText(s.group, 80) || 'Навыки', name, level: profText(s.level, 40), value };
    }),
    experience: profList(raw.experience, 30, e => {
      if (!e || typeof e !== 'object') return null;
      const title = profText(e.title, 160);
      if (!title) return null;
      return {
        title,
        company: profText(e.company, 160),
        period: profText(e.period, 80),
        date: profText(e.date, 40),
        badge: profText(e.badge, 40),
        description: profText(e.description, 800),
        tags: profList(e.tags, 10, t => profText(t, 40)),
      };
    }),
    education: profList(raw.education, 60, m => {
      if (!m || typeof m !== 'object') return null;
      const module = profText(m.module, 200);
      if (!module) return null;
      const progress = (m.progress === null || m.progress === undefined || m.progress === '') ? null : optInt(m.progress, 0, 100);
      return { module, progress, grade: profText(m.grade, 80), teacher: profText(m.teacher, 150) };
    }),
    stats: profList(raw.stats, 12, s => {
      if (!s || typeof s !== 'object') return null;
      const label = profText(s.label, 80);
      const value = (s.value === null || s.value === undefined) ? null : String(s.value).trim().slice(0, 20);
      if (!label || !value) return null;
      return {
        icon: profIcon(s.icon || 'star'),
        value,
        suffix: profText(s.suffix, 20),
        label,
        hint: profText(s.hint, 120),
        delta: profText(s.delta, 60),
      };
    }),
  };
  const hasData = Object.values(out).some(v => (Array.isArray(v) ? v.length > 0 : v !== null));
  return hasData ? out : null;
}

function normalizeRestoreData(data) {
  const groups = (data.groups || []).map(x => ({
    id: reqInt(x.id),
    name: reqStr(x.name, 100),
    created_at: optTs(x.created_at),
    day_of_week: optInt(x.day_of_week, 0, 6),
    time_start: optTime(x.time_start),
    time_end: optTime(x.time_end),
    branch_id: optInt(x.branch_id, 0, 2147483647),
    tutor_id: optInt(x.tutor_id, 0, 2147483647),
    cover_path: optUploadPath(x.cover_path, 255),
    deleted_at: optTs(x.deleted_at),
    purge_at: optTs(x.purge_at),
  }));
  const students = (data.students || []).map(x => ({
    id: reqInt(x.id),
    name: reqStr(x.name, 150),
    created_at: optTs(x.created_at),
    group_id: optInt(x.group_id, 0, 2147483647),
    photo_path: optUploadPath(x.photo_path, 255),
    profile: sanitizeStudentProfile(x.profile),
  }));
  const entries = (data.entries || []).map(x => ({
    id: reqInt(x.id),
    student_name: reqStr(x.student_name, 150),
    group_id: reqInt(x.group_id),
    module_id: optInt(x.module_id, 0, 2147483647),
    description: reqStr(x.description, 100000),
    description_original: optAiText(x.description_original, 100000) ?? reqStr(x.description, 100000),
    description_ai: optAiText(x.description_ai, 100000),
    ai_status: reqAiStatus(x.ai_status, 'skipped'),
    ai_checked_at: optTs(x.ai_checked_at),
    ai_error: optAiText(x.ai_error, 500),
    photo_path: optUploadPath(x.photo_path, 255),
    photo_original_path: optOriginalsPath(x.photo_original_path, 255),
    deleted_at: optTs(x.deleted_at),
    purge_at: optTs(x.purge_at),
    created_at: optTs(x.created_at),
  }));
  const project_files = (data.project_files || []).map(x => ({
    id: reqInt(x.id),
    entry_id: optInt(x.entry_id, 0, 2147483647),
    token: reqToken(x.token),
    path: reqUploadPath(x.path, 255),
    name: reqStr(x.name, 255),
    detached_at: optTs(x.detached_at),
    created_at: optTs(x.created_at),
  }));
  const branches = (data.branches || []).map(x => ({
    id: reqInt(x.id),
    name: reqStr(x.name, 200),
    address: optStr(x.address, 1000),
    phone: optStr(x.phone, 50),
    created_at: optTs(x.created_at),
  }));
  const users = (data.users || []).map(x => ({
    id: reqInt(x.id),
    username: reqStr(x.username, 100),
    password_hash: reqStr(x.password_hash, 255),
    name: optStr(x.name, 150),
    role: (x.role === 'admin' || x.role === 'tutor') ? x.role : 'tutor',
    is_active: !!x.is_active,
    created_at: optTs(x.created_at),
  }));
  const user_branches = (data.user_branches || []).map(x => ({
    user_id: reqInt(x.user_id),
    branch_id: reqInt(x.branch_id),
  }));
  const modules = (data.modules || []).map(x => ({
    id: reqInt(x.id),
    name: reqStr(x.name, 200),
    lessons_count: optInt(x.lessons_count, 0, 10000) ?? 0,
    is_active: x.is_active !== false,
    photo_path: optUploadPath(x.photo_path, 255),
    created_at: optTs(x.created_at),
  }));
  const entry_photos = (data.entry_photos || []).map(x => ({
    id: reqInt(x.id),
    entry_id: reqInt(x.entry_id),
    photo_path: reqUploadPath(x.photo_path, 255),
    caption: optStr(x.caption, 10000),
    sort_order: optInt(x.sort_order, -2147483648, 2147483647),
    created_at: optTs(x.created_at),
  }));
  const student_photos = (data.student_photos || []).map(x => ({
    id: reqInt(x.id),
    student_id: reqInt(x.student_id),
    photo_path: reqUploadPath(x.photo_path, 255),
    created_at: optTs(x.created_at),
  }));
  const group_photos = (data.group_photos || []).map(x => ({
    id: reqInt(x.id),
    group_id: reqInt(x.group_id),
    photo_path: reqUploadPath(x.photo_path, 255),
    caption: optStr(x.caption, 10000),
    taken_at: optDate(x.taken_at),
    sort_order: optInt(x.sort_order, -2147483648, 2147483647),
    created_at: optTs(x.created_at),
  }));
  const share_links = (data.share_links || []).map(x => ({
    id: reqInt(x.id),
    token: optStr(x.token, 40),
    name: reqStr(x.name, 200),
    group_id: optInt(x.group_id, 0, 2147483647),
    student_name: optStr(x.student_name, 150),
    date_from: optDate(x.date_from),
    date_to: optDate(x.date_to),
    show_student_names: optBool(x.show_student_names),
    expires_at: optTs(x.expires_at),
    access_password_hash: optStr(x.access_password_hash, 255),
    message: optStr(x.message, 2000),
    link_url: optStr(x.link_url, 500),
    show_student_message: optBool(x.show_student_message),
    show_entry_date: optBool(x.show_entry_date),
    show_group_photos: optBool(x.show_group_photos),
    created_at: optTs(x.created_at),
  }));
  const lesson_reports = (data.lesson_reports || []).map(x => ({
    id: reqInt(x.id),
    group_id: reqInt(x.group_id),
    lesson_date: reqDate(x.lesson_date),
    lesson_time: optTime(x.lesson_time),
    topic: optStr(x.topic, LESSON_REPORT_TOPIC_MAX),
    text: reqStr(x.text, LESSON_REPORT_TEXT_MAX),
    text_original: optStr(x.text_original, LESSON_REPORT_TEXT_MAX),
    text_ai: optStr(x.text_ai, LESSON_REPORT_TEXT_MAX),
    ai_status: optStr(x.ai_status, 20),
    ai_checked_at: optTs(x.ai_checked_at),
    ai_error: optStr(x.ai_error, 500),
    author_id: optInt(x.author_id, 0, 2147483647),
    branch_id: optInt(x.branch_id, 0, 2147483647),
    created_at: optTs(x.created_at),
    updated_at: optTs(x.updated_at),
  }));
  const lesson_report_versions = (data.lesson_report_versions || []).map(x => ({
    id: reqInt(x.id),
    lesson_report_id: reqInt(x.lesson_report_id),
    text: reqStr(x.text, LESSON_REPORT_TEXT_MAX),
    source: optStr(x.source, 20),
    author_id: optInt(x.author_id, 0, 2147483647),
    created_at: optTs(x.created_at),
  }));
  const settings = {};
  for (const [k, v] of Object.entries(data.settings || {})) {
    settings[reqStr(k, 100)] = reqStr(String(v), 10000);
  }
  const audit_log = (data.audit_log || []).map(x => ({
    id: reqInt(x.id),
    user_id: optInt(x.user_id, 0, 2147483647),
    action: reqStr(x.action, 100),
    target: optJsonText(x.target, 200000),
    ip: optStr(x.ip, 45),
    created_at: optTs(x.created_at),
  }));
  const NOTIFICATION_LEVELS = new Set(['info', 'success', 'warning', 'critical']);
  const notifications = (data.notifications || []).map(x => ({
    id: reqInt(x.id),
    type: reqStr(x.type, 50),
    level: (x.level && NOTIFICATION_LEVELS.has(x.level)) ? x.level : 'info',
    title: reqStr(x.title, 200),
    body: optStr(x.body, 2000),
    link: optStr(x.link, 255),
    target: optJsonText(x.target, 20000),
    admin_only: !!x.admin_only,
    branch_id: optInt(x.branch_id, 0, 2147483647),
    created_at: optTs(x.created_at),
  }));
  const notification_reads = (data.notification_reads || []).map(x => ({
    user_id: reqInt(x.user_id),
    notification_id: reqInt(x.notification_id),
    read_at: optTs(x.read_at),
  }));
  const banned_ips = (data.banned_ips || []).map(x => ({
    ip: reqIp(x.ip),
    reason: reqStr(x.reason, 100),
    banned_until: reqTs(x.banned_until),
    created_at: optTs(x.created_at),
  }));
  const PHOTO_JOB_STATUSES = new Set(['pending', 'processing', 'done', 'error', 'rejected']);
  const photo_jobs = (data.photo_jobs || []).map(x => ({
    id: reqInt(x.id),
    entry_id: reqInt(x.entry_id),
    action: (x.action && PHOTO_JOB_ACTIONS.has(x.action)) ? x.action : 'ai',
    params: optJsonText(x.params, 20000),
    before_path: optPhotoRefPath(x.before_path, 255),
    after_path: optPhotoRefPath(x.after_path, 255),
    status: (x.status && PHOTO_JOB_STATUSES.has(x.status)) ? x.status : 'pending',
    applied: !!x.applied,
    attempts: optInt(x.attempts, 0, 2147483647) ?? 0,
    error: optStr(x.error, 4000),
    created_at: optTs(x.created_at),
    finished_at: optTs(x.finished_at),
  }));
  return { groups, students, entries, project_files, settings, branches, users, user_branches, entry_photos, student_photos, group_photos, share_links, modules, photo_jobs, lesson_reports, lesson_report_versions, audit_log, notifications, notification_reads, banned_ips };
}

module.exports = {
  PHOTO_JOB_ACTIONS,
  LESSON_REPORT_TEXT_MAX,
  LESSON_REPORT_TOPIC_MAX,
  SAFE_NAME,
  isSafeUploadPath,
  photoRefKey,
  sanitizeStudentProfile,
  reqInt,
  optInt,
  reqStr,
  optStr,
  optTs,
  reqTs,
  optDate,
  optUploadPath,
  normalizeRestoreData,
  BACKUP_FORMAT_VERSION,
  BACKUP_MIN_FORMAT_VERSION,
  BACKUP_TABLES,
  BACKUP_SEQUENCE_TABLES,
  restoredCounts,
  isSupportedBackupVersion,
};