'use strict';

const fs = require('fs');
require('./patch-ldap-dn');
const ldap = require('ldapjs');
const config = require('./config');

function urlScheme(url) {
  const match = /^([a-z0-9+.-]+):\/\//i.exec(String(url || ''));
  return match ? match[1].toLowerCase() : '';
}

class LdapError extends Error {
  constructor(message, code, status) {
    super(message);
    this.name = 'LdapError';
    this.ldapCode = code;
    this.status = status || 500;
  }
}

function mapLdapError(err) {
  if (!err) return err;
  const code = err.code;
  switch (code) {
    case 49: return new LdapError('Неверный логин или пароль', code, 401);
    case 68: return new LdapError('Запись уже существует', code, 409);
    case 32: return new LdapError('Объект не найден', code, 404);
    case 50: return new LdapError('Недостаточно прав для выполнения операции', code, 403);
    case 53: return new LdapError('Операция запрещена сервером', code, 500);
    case 19: return new LdapError('Нарушение ограничений (например, слишком короткий пароль)', code, 400);
    case 14: return new LdapError('Операция недоступна', code, 500);
    case 52: return new LdapError('Сервер недоступен', code, 500);
    case 80: return new LdapError('Не удалось подключиться к LDAP-серверу', code, 502);
    default: return new LdapError(err.message || 'Ошибка LDAP', code, 500);
  }
}

function unescapeDN(value) {
  return String(value).replace(/\\[0-9a-fA-F]{2}/g, (m) => String.fromCharCode(parseInt(m.slice(1), 16)));
}

function getRDNName(dn) {
  if (!dn) return '';
  const first = dn.split(',').shift();
  if (!first) return '';
  const eq = first.indexOf('=');
  return eq === -1 ? unescapeDN(first) : unescapeDN(first.slice(eq + 1));
}

function getCN(dn) {
  const name = getRDNName(dn);
  return name;
}

function escapeDNValue(value) {
  return String(value).replace(/([,\\#+<>;"=])/g, '\\$1');
}

function escapeFilter(value) {
  return String(value).replace(/[\\*()\0]/g, (ch) => '\\' + ch.charCodeAt(0).toString(16).padStart(2, '0'));
}

function buildBindNames(login) {
  const names = [];
  const netbios = config.domain.split('.')[0].toUpperCase();
  if (login.includes('@') || login.startsWith('CN=') || login.startsWith('OU=') || login.includes(',')) {
    names.push(login);
  } else {
    names.push(`${login}@${config.domain}`);
    names.push(`${netbios}\\${login}`);
    names.push(login);
  }
  return names;
}

async function connect() {
  const scheme = urlScheme(config.ldapUrl);
  const clientOpts = {
    url: config.ldapUrl,
    connectTimeout: 10000,
    timeout: 15000,
    reconnect: false
  };

  if (scheme === 'ldaps' || scheme === 'ldap') {
    const tlsOptions = { rejectUnauthorized: config.tlsRejectUnauthorized };
    if (config.caFile) {
      try {
        tlsOptions.ca = [fs.readFileSync(config.caFile)];
      } catch (err) {
        throw new LdapError(`Не удалось прочитать файл CA: ${config.caFile}: ${err.message}`, 0, 502);
      }
    }
    clientOpts.tlsOptions = tlsOptions;
  }

  const client = ldap.createClient(clientOpts);

  await new Promise((resolve, reject) => {
    let settled = false;
    const timer = setTimeout(() => {
      if (settled) return;
      settled = true;
      reject(new LdapError('Не удалось подключиться к LDAP-серверу (таймаут)', 0, 502));
      try { client.destroy(); } catch (e) {}
    }, 15000);

    client.once('connect', () => {
      if (settled) return;
      settled = true;
      clearTimeout(timer);
      resolve();
    });
    client.on('error', (err) => {
      if (settled) return;
      settled = true;
      clearTimeout(timer);
      reject(new LdapError(`Ошибка подключения к LDAP-серверу: ${err.message || err.code}`, 0, 502));
      try { client.destroy(); } catch (e) {}
    });
  });

  client.on('error', () => {});

  if (config.encryptTraffic && scheme === 'ldap') {
    try {
      await new Promise((resolve, reject) => {
        client.starttls({}, null, (err) => (err ? reject(err) : resolve()));
      });
    } catch (err) {
      if (err && err.code === 52) {
        throw new LdapError(
          'StartTLS отклонён сервером (код 52): на контроллере домена не настроен LDAPS/TLS. ' +
          'Включите LDAPS на DC или установите ENCRYPT_TRAFFIC=false',
          0,
          502
        );
      }
      throw new LdapError(`StartTLS не удался (проверьте LDAP_URL или ENCRYPT_TRAFFIC): ${err.message || err.code}`, 0, 502);
    }
  }
  return client;
}

async function bind(client, login, password) {
  const names = buildBindNames(login);
  let lastErr = null;
  for (const name of names) {
    try {
      await new Promise((resolve, reject) => {
        client.bind(name, password, (err) => (err ? reject(err) : resolve()));
      });
      return name;
    } catch (err) {
      lastErr = err;
    }
  }
  throw mapLdapError(lastErr);
}

async function close(client) {
  return new Promise((resolve) => {
    if (!client || client.destroyed) return resolve();
    try {
      client.unbind((err) => {
        try { client.destroy(); } catch (e) {}
        resolve();
      });
    } catch (err) {
      try { client.destroy(); } catch (e) {}
      resolve();
    }
  });
}

function searchEntries(client, base, options) {
  return new Promise((resolve, reject) => {
    const entries = [];
    client.search(base, options, (err, res) => {
      if (err) return reject(mapLdapError(err));
      res.on('searchEntry', (entry) => entries.push(entry));
      res.on('error', (e) => reject(mapLdapError(e)));
      res.on('end', (result) => {
        if (result && result.status !== 0) {
          return reject(new LdapError(`Ошибка поиска LDAP (статус ${result.status})`, result.status, 500));
        }
        resolve(entries);
      });
    });
  });
}

function entryToObject(entry) {
  const obj = {};
  const dn = entry.dn ? entry.dn.toString() : String(entry.objectName || '');
  if (dn) obj.dn = dn;
  const alwaysArray = new Set(['memberOf', 'objectClass', 'proxyAddresses']);
  for (const attr of entry.attributes || []) {
    const vals = attr.values || [];
    if (alwaysArray.has(attr.type) || vals.length > 1) {
      obj[attr.type] = vals;
    } else {
      obj[attr.type] = vals[0];
    }
  }
  return obj;
}

function addEntry(client, dn, attributes) {
  return new Promise((resolve, reject) => {
    const entry = {};
    for (const a of attributes || []) {
      entry[a.attr] = a.vals;
    }
    client.add(dn, entry, (err) => (err ? reject(mapLdapError(err)) : resolve()));
  });
}

function normalizeChange(change) {
  const mod = change.modification || {};
  const key = Object.keys(mod)[0];
  const values = mod[key];
  return {
    operation: change.operation,
    modification: {
      type: key,
      values: Array.isArray(values) ? values : [values]
    }
  };
}

function modifyEntry(client, dn, changes) {
  return new Promise((resolve, reject) => {
    client.modify(dn, (changes || []).map(normalizeChange), (err) => (err ? reject(mapLdapError(err)) : resolve()));
  });
}

async function setPassword(client, userDN, password) {
  const value = Buffer.from('"' + password + '"', 'utf16le');
  await modifyEntry(client, userDN, [{ operation: 'replace', modification: { unicodePwd: [value] } }]);
}

// ================= Public auth (port of the Go service) =================

async function authenticate(username, password, mode) {
  if (!username) throw new LdapError('Username is required', 0, 400);
  if (!password) throw new LdapError('Password is required', 0, 400);

  const client = await connect();
  try {
    await bind(client, username, password);

    // Rebind as admin to read user info (like the Go service did with the service account)
    if (config.adminLogin && config.adminPassword) {
      try {
        await bind(client, config.adminLogin, config.adminPassword);
      } catch (err) {
        console.warn(
          `⚠ Административная привязка не удалась (ADMIN_LOGIN/ADMIN_PASSWORD): ${err.message || err.code}. ` +
          `Проверьте учётные данные в .env (пароли с '#' нужно брать в кавычки). Возвращаются базовые данные.`
        );
        return { success: true, username };
      }
    }

    return await getUserInfo(client, username, mode);
  } finally {
    await close(client);
  }
}

async function getUserInfo(client, username, mode) {
  let attributes = ['dn', 'sAMAccountName'];

  if (mode !== 'groups' && mode !== 'description') {
    attributes.push('memberOf', 'mail', 'displayName', 'cn', 'description');
  }
  if (mode === 'description') attributes.push('description');
  if (mode === 'groups') attributes.push('memberOf');
  if (mode === 'all') attributes = ['*', '+'];

  const entries = await searchEntries(client, config.baseDN, {
    scope: 'sub',
    filter: `(sAMAccountName=${escapeFilter(username)})`,
    attributes
  });

  if (entries.length === 0) throw new LdapError('User not found', 0, 404);
  const entry = entryToObject(entries[0]);

  if (mode === 'description') {
    return { success: true, description: entry.description || '' };
  }

  if (mode === 'groups') {
    return { success: true, groups: (entry.memberOf || []).map(getCN).filter(Boolean) };
  }

  const result = {
    success: true,
    username: entry.sAMAccountName || username,
    full_name: entry.displayName || entry.cn || username,
    email: entry.mail || '',
    description: entry.description || '',
    groups: (entry.memberOf || []).map(getCN).filter(Boolean)
  };

  if (mode === 'all') {
    result.all_info = entry;
  }
  return result;
}

// ================= Admin: listing =================

async function listOUs() {
  const client = await connect();
  try {
    await bind(client, config.adminLogin, config.adminPassword);
    const entries = await searchEntries(client, config.baseDN, {
      scope: 'sub',
      filter: '(objectClass=organizationalUnit)',
      attributes: ['dn']
    });
    return entries.map((e) => {
      const obj = entryToObject(e);
      return { dn: obj.dn, name: getRDNName(obj.dn) };
    });
  } finally {
    await close(client);
  }
}

async function listGroups() {
  const client = await connect();
  try {
    await bind(client, config.adminLogin, config.adminPassword);
    const base = config.groupOU || config.baseDN;
    const entries = await searchEntries(client, base, {
      scope: 'sub',
      filter: '(objectClass=group)',
      attributes: ['dn', 'cn']
    });
    return entries.map((e) => {
      const obj = entryToObject(e);
      return { dn: obj.dn, cn: obj.cn || getCN(obj.dn) };
    });
  } finally {
    await close(client);
  }
}

function parseUser(entry) {
  const uac = parseInt(entry.userAccountControl, 10) || 0;
  return {
    dn: entry.dn,
    login: entry.sAMAccountName || '',
    full_name: entry.displayName || entry.cn || '',
    given_name: entry.givenName || '',
    sn: entry.sn || '',
    email: entry.mail || '',
    phone: entry.telephoneNumber || '',
    upn: entry.userPrincipalName || '',
    disabled: (uac & 0x0002) !== 0,
    groups: (entry.memberOf || []).map(getCN).filter(Boolean),
    member_of: entry.memberOf || []
  };
}

async function listUsers() {
  const client = await connect();
  try {
    await bind(client, config.adminLogin, config.adminPassword);
    const entries = await searchEntries(client, config.baseDN, {
      scope: 'sub',
      filter: '(&(objectClass=user)(objectCategory=person))',
      attributes: ['dn', 'sAMAccountName', 'displayName', 'cn', 'givenName', 'sn',
        'mail', 'telephoneNumber', 'userPrincipalName', 'userAccountControl', 'memberOf']
    });
    return entries.map((e) => parseUser(entryToObject(e)));
  } finally {
    await close(client);
  }
}

async function findUserByLogin(client, login) {
  const entries = await searchEntries(client, config.baseDN, {
    scope: 'sub',
    filter: `(sAMAccountName=${escapeFilter(login)})`,
    attributes: ['*']
  });
  if (entries.length === 0) throw new LdapError(`Пользователь "${login}" не найден`, 0, 404);
  return entryToObject(entries[0]);
}

async function getUser(login) {
  const client = await connect();
  try {
    await bind(client, config.adminLogin, config.adminPassword);
    const entry = await findUserByLogin(client, login);
    const user = parseUser(entry);
    user.ou = getParentDN(entry.dn);
    return user;
  } finally {
    await close(client);
  }
}

function getParentDN(dn) {
  const parts = dn.split(',');
  parts.shift();
  return parts.join(',');
}

async function resolveGroupDNs(client, groupCNs) {
  const dns = [];
  for (const cn of groupCNs || []) {
    const entries = await searchEntries(client, config.groupOU || config.baseDN, {
      scope: 'sub',
      filter: `(cn=${escapeFilter(cn)})`,
      attributes: ['dn']
    });
    if (entries.length > 0) dns.push(entryToObject(entries[0]).dn);
    else throw new LdapError(`Группа "${cn}" не найдена`, 0, 400);
  }
  return dns;
}

// ================= Admin: create / update / block =================

async function createUser({ ouDn, fio, login, password, email, phone, groupCNs }) {
  const client = await connect();
  try {
    await bind(client, config.adminLogin, config.adminPassword);

    const existing = await searchEntries(client, config.baseDN, {
      scope: 'sub',
      filter: `(sAMAccountName=${escapeFilter(login)})`,
      attributes: ['dn']
    });
    if (existing.length > 0) {
      throw new LdapError(`Логин "${login}" уже занят`, 0, 409);
    }

    const cn = escapeDNValue(fio || login);
    const userDN = `CN=${cn},${ouDn || config.baseDN}`;

    const attributes = [
      { attr: 'objectClass', vals: ['top', 'person', 'organizationalPerson', 'user'] },
      { attr: 'sAMAccountName', vals: [login] },
      { attr: 'userPrincipalName', vals: [`${login}@${config.domain}`] },
      { attr: 'displayName', vals: [fio] },
      { attr: 'userAccountControl', vals: ['512'] }
    ];

    const nameParts = (fio || '').trim().split(/\s+/);
    if (nameParts[0]) attributes.push({ attr: 'givenName', vals: [nameParts[0]] });
    if (nameParts[1]) attributes.push({ attr: 'sn', vals: [nameParts.slice(1).join(' ')] });
    if (email) attributes.push({ attr: 'mail', vals: [email] });
    if (phone) attributes.push({ attr: 'telephoneNumber', vals: [phone] });

    await addEntry(client, userDN, attributes);

    if (password) {
      await setPassword(client, userDN, password);
    }

    const groupDNs = await resolveGroupDNs(client, groupCNs);
    for (const groupDN of groupDNs) {
      await modifyEntry(client, groupDN, [{ operation: 'add', modification: { member: [userDN] } }]);
    }

    return { success: true, dn: userDN, login };
  } finally {
    await close(client);
  }
}

async function updateUser(login, { fio, email, phone, password, groupCNs }) {
  const client = await connect();
  try {
    await bind(client, config.adminLogin, config.adminPassword);

    const entry = await findUserByLogin(client, login);
    const userDN = entry.dn;
    const changes = [];

    if (fio !== undefined) {
      changes.push({ operation: 'replace', modification: { displayName: [fio] } });
      const nameParts = (fio || '').trim().split(/\s+/);
      changes.push({
        operation: 'replace',
        modification: { givenName: [nameParts[0] || ''] }
      });
      changes.push({
        operation: 'replace',
        modification: { sn: [nameParts.slice(1).join(' ') || ''] }
      });
    }
    if (email !== undefined) {
      changes.push({ operation: 'replace', modification: { mail: [email || ''] } });
    }
    if (phone !== undefined) {
      changes.push({ operation: 'replace', modification: { telephoneNumber: [phone || ''] } });
    }

    if (changes.length > 0) {
      await modifyEntry(client, userDN, changes);
    }

    if (password) {
      await setPassword(client, userDN, password);
    }

    if (groupCNs !== undefined) {
      const currentGroupDNs = (entry.memberOf || []).map((d) => d.toLowerCase());
      const targetGroupDNs = await resolveGroupDNs(client, groupCNs);

      const toAdd = targetGroupDNs.filter((d) => !currentGroupDNs.includes(d.toLowerCase()));
      const toRemove = currentGroupDNs.filter(
        (d) => !targetGroupDNs.some((t) => t.toLowerCase() === d.toLowerCase())
      );

      for (const groupDN of toAdd) {
        await modifyEntry(client, groupDN, [{ operation: 'add', modification: { member: [userDN] } }]);
      }
      for (const groupDN of toRemove) {
        await modifyEntry(client, groupDN, [{ operation: 'delete', modification: { member: [userDN] } }]);
      }
    }

    return { success: true, dn: userDN, login };
  } finally {
    await close(client);
  }
}

async function setUserEnabled(login, enabled) {
  const client = await connect();
  try {
    await bind(client, config.adminLogin, config.adminPassword);

    const entry = await findUserByLogin(client, login);
    const userDN = entry.dn;
    const uac = parseInt(entry.userAccountControl, 10) || 0;
    const newUac = enabled ? (uac & ~0x0002) : (uac | 0x0002);

    await modifyEntry(client, userDN, [
      { operation: 'replace', modification: { userAccountControl: [String(newUac)] } }
    ]);

    return { success: true, dn: userDN, login, enabled };
  } finally {
    await close(client);
  }
}

async function testConnection() {
  const client = await connect();
  try {
    if (config.adminLogin && config.adminPassword) {
      await bind(client, config.adminLogin, config.adminPassword);
    }
    await searchEntries(client, config.baseDN, {
      scope: 'base',
      filter: '(objectClass=*)',
      attributes: ['distinguishedName']
    });
    return true;
  } finally {
    await close(client);
  }
}

module.exports = {
  LdapError,
  authenticate,
  getUserInfo,
  listOUs,
  listGroups,
  listUsers,
  getUser,
  createUser,
  updateUser,
  setUserEnabled,
  testConnection,
  buildBindNames,
  getCN,
  escapeFilter
};