const { Client } = require('ldapts');

/**
 * LDAP / Active Directory Sync Module (ldapts)
 * 
 * Reads users from LDAP/AD and syncs them into the local SQLite database.
 * AD users are identified by source='ad' and cannot be edited/deleted locally.
 * 
 * Punkt 1: Migrated from ldapjs to ldapts
 * Punkt 7: Proper client cleanup with try/finally
 * 
 * ENV variables:
 *   LDAP_SERVER            - e.g. pidc02.seatle.intra
 *   LDAP_PORT              - e.g. 389 (LDAP) or 636 (LDAPS), default: 389
 *   LDAP_SEARCH_BASE       - e.g. DC=SEATLE,DC=INTRA
 *   LDAP_DOMAIN            - e.g. SEATLE (used for reference)
 *   LDAP_IGNORE_CERT_ERRORS- true/false (default: false)
 *   LDAP_BIND_USER         - Service account in user@domain.fqdn format
 *   LDAP_BIND_PASSWORD     - Password for the service account
 *   LDAP_SYNC_INTERVAL     - Sync interval in ms (default: 300000 = 5 min)
 *   LDAP_FILTER            - Custom LDAP filter (default: active users)
 *   LDAP_ATTRIBUTES        - Comma-separated LDAP attributes
 */

const LDAP_SERVER = process.env.LDAP_SERVER || '';
const LDAP_PORT = parseInt(process.env.LDAP_PORT) || 389;
const LDAP_SEARCH_BASE = process.env.LDAP_SEARCH_BASE || '';
const LDAP_DOMAIN = process.env.LDAP_DOMAIN || '';
const LDAP_IGNORE_CERT_ERRORS = (process.env.LDAP_IGNORE_CERT_ERRORS || 'false').toLowerCase() === 'true';
const LDAP_BIND_USER = process.env.LDAP_BIND_USER || '';
const LDAP_BIND_PASSWORD = process.env.LDAP_BIND_PASSWORD || '';
const LDAP_SYNC_INTERVAL = parseInt(process.env.LDAP_SYNC_INTERVAL) || 300000;
const LDAP_FILTER = process.env.LDAP_FILTER || '(&(objectClass=user)(!(userAccountControl:1.2.840.113556.1.4.803:=2)))';
const LDAP_ATTRIBUTES = (process.env.LDAP_ATTRIBUTES || 'mail,displayName,memberOf,distinguishedName,sAMAccountName').split(',').map(a => a.trim());

let syncTimer = null;
let isSyncing = false; // Punkt 9: Sync lock to prevent concurrent syncs

function isLDAPConfigured() {
  return !!(LDAP_SERVER && LDAP_SEARCH_BASE && LDAP_BIND_USER && LDAP_BIND_PASSWORD);
}

function extractRole(memberOf) {
  if (!memberOf) return 'user';
  const groups = Array.isArray(memberOf) ? memberOf : [memberOf];
  const groupStrings = groups.map(g => String(g).toLowerCase());
  if (groupStrings.some(g => g.includes('admin') || g.includes('domain admins') || g.includes('domänen-admins'))) {
    return 'admin';
  }
  return 'user';
}

async function syncLDAPUsers(db) {
  if (!isLDAPConfigured()) {
    console.log('[LDAP] Nicht konfiguriert - LDAP-Sync deaktiviert.');
    return;
  }
  // Punkt 9: Prevent concurrent sync runs
  if (isSyncing) {
    console.log('[LDAP] Sync bereits aktiv - übersprungen.');
    return;
  }
  isSyncing = true;

  const useTLS = LDAP_PORT === 636;
  const url = useTLS ? `ldaps://${LDAP_SERVER}:${LDAP_PORT}` : `ldap://${LDAP_SERVER}:${LDAP_PORT}`;

  console.log('[LDAP] Starte Synchronisation mit', url);

  const client = new Client({
    url,
    tlsOptions: useTLS && LDAP_IGNORE_CERT_ERRORS ? { rejectUnauthorized: false } : undefined,
    connectTimeout: 10000,
  });

  try {
    await client.bind(LDAP_BIND_USER, LDAP_BIND_PASSWORD);
    console.log('[LDAP] Bind erfolgreich, suche Nutzer...');

    const { searchEntries } = await client.search(LDAP_SEARCH_BASE, {
      filter: LDAP_FILTER,
      scope: 'sub',
      attributes: LDAP_ATTRIBUTES,
    });

    const adUsers = [];

    for (const entry of searchEntries) {
      // ldapts may return attributes as arrays; normalize to single values
      const rawMail = Array.isArray(entry.mail) ? entry.mail[0] : entry.mail;
      const rawName = Array.isArray(entry.displayName) ? entry.displayName[0] : entry.displayName;
      const rawCn = Array.isArray(entry.cn) ? entry.cn[0] : entry.cn;
      const rawDN = Array.isArray(entry.distinguishedName) ? entry.distinguishedName[0] : entry.distinguishedName;
      const rawSAM = Array.isArray(entry.sAMAccountName) ? entry.sAMAccountName[0] : entry.sAMAccountName;
      const rawMemberOf = Array.isArray(entry.memberOf) ? entry.memberOf : (entry.memberOf ? [entry.memberOf] : []);

      const email = (rawMail || '').toLowerCase().trim();
      const name = rawName || rawCn || '';
      const distinguishedName = rawDN || '';
      const memberOf = rawMemberOf;
      const username = (rawSAM || '').trim();

      if (!email && !username) continue; // Skip users without email AND username

      adUsers.push({
        email: email || (username + '@ad.local'),
        name,
        role: extractRole(memberOf),
        distinguishedName,
        username,
      });
    }

    console.log('[LDAP] Gefunden:', adUsers.length, 'Nutzer');

    // Sync LDAP users into database (async for PostgreSQL compatibility)
    const existingRows = await db.prepare('SELECT id, email, name, role, status FROM users WHERE source = \'ad\'').all();
    const existingMap = {};
    existingRows.forEach(row => { existingMap[row.email.toLowerCase()] = row; });

    let inserted = 0;
    let updated = 0;

    const insertStmt = db.prepare('INSERT INTO users (email, password, name, role, status, source, username) VALUES (?, ?, ?, ?, \'inaktiv\', \'ad\', ?)');
    const updateStmt = db.prepare('UPDATE users SET name = ?, username = ?, role = ? WHERE id = ?');

    const syncTransaction = db.transaction(async () => {
      for (const adUser of adUsers) {
        const existing = existingMap[adUser.email];
        if (existing) {
          await updateStmt.run(adUser.name, adUser.username, adUser.role, existing.id);
          updated++;
          delete existingMap[adUser.email];
        } else {
          try {
            await insertStmt.run(adUser.email, 'LDAP_AUTH', adUser.name, adUser.role, adUser.username);
            inserted++;
          } catch (err) {
            if (err.message && err.message.includes('UNIQUE constraint') || err.message?.includes('duplicate key')) {
              console.warn('[LDAP] E-Mail bereits vorhanden:', adUser.email);
            } else {
              console.error('[LDAP] Insert-Fehler:', err.message);
            }
          }
        }
      }
    });

    await syncTransaction();

    // Remove stale AD users
    const adEmails = adUsers.map(u => u.email.toLowerCase());
    const toRemove = existingRows.filter(r => !adEmails.includes(r.email.toLowerCase()));
    let removed = 0;
    if (toRemove.length > 0) {
      const removeIds = toRemove.map(r => r.id).filter(id => Number.isInteger(id));
      if (removeIds.length > 0) {
        const placeholders = removeIds.map(() => '?').join(',');
        await db.prepare(`DELETE FROM users WHERE id IN (${placeholders}) AND source = 'ad'`).run(...removeIds);
        removed = removeIds.length;
      }
    }

    console.log('[LDAP] Sync abgeschlossen: ' + inserted + ' neu, ' + updated + ' aktualisiert, ' + removed + ' entfernt');
  } catch (err) {
    console.error('[LDAP] Sync-Fehler:', err.message);
  } finally {
    await client.unbind().catch(() => {}); // Punkt 7: Always cleanup
    isSyncing = false; // Punkt 9: Release sync lock
  }
}

function startLDAPSync(db) {
  if (!isLDAPConfigured()) {
    console.log('[LDAP] LDAP-Sync nicht konfiguriert. Setze LDAP_SERVER, LDAP_SEARCH_BASE, LDAP_BIND_USER und LDAP_BIND_PASSWORD Umgebungsvariablen.');
    return;
  }

  // Initial sync
  syncLDAPUsers(db);

  // Periodic sync
  if (syncTimer) clearInterval(syncTimer);
  syncTimer = setInterval(() => {
    syncLDAPUsers(db);
  }, LDAP_SYNC_INTERVAL);

  console.log('[LDAP] Automatischer Sync alle ' + (LDAP_SYNC_INTERVAL / 1000) + ' Sekunden aktiviert.');
}

function stopLDAPSync() {
  if (syncTimer) {
    clearInterval(syncTimer);
    syncTimer = null;
    console.log('[LDAP] Sync gestoppt.');
  }
}

/**
 * Authenticate a user against LDAP/Active Directory.
 * Uses the sAMAccountName (username) to bind to the LDAP server.
 * Punkt 7: Proper client cleanup with try/finally
 */
async function authenticateLDAP(username, password) {
  if (!isLDAPConfigured()) {
    throw new Error('LDAP nicht konfiguriert.');
  }

  // VULN-11: LDAP Injection prevention - validate username
  const safeUsername = String(username || '').replace(/[*()\\\x00]/g, '').trim();
  if (!safeUsername || !/^[a-zA-Z0-9._-]+$/.test(safeUsername)) {
    throw new Error('Ungueltiger Anmeldename.');
  }

  const useTLS = LDAP_PORT === 636;
  const url = useTLS ? `ldaps://${LDAP_SERVER}:${LDAP_PORT}` : `ldap://${LDAP_SERVER}:${LDAP_PORT}`;

  // Build the bind DN: username@domain.fqdn (UPN format)
  const bindDomain = LDAP_BIND_USER.split('@')[1] || LDAP_DOMAIN;
  const bindDN = safeUsername + '@' + bindDomain;

  const client = new Client({
    url,
    tlsOptions: useTLS && LDAP_IGNORE_CERT_ERRORS ? { rejectUnauthorized: false } : undefined,
    connectTimeout: 10000,
  });

  try {
    await client.bind(bindDN, password);
    console.log('[LDAP] Authentifizierung erfolgreich für', bindDN);
    return { username: username, bindDN: bindDN };
  } catch (err) {
    console.log('[LDAP] Authentifizierung fehlgeschlagen für', bindDN, ':', err.message);
    throw new Error('Ungueltige Anmeldedaten.');
  } finally {
    await client.unbind().catch(() => {}); // Punkt 7: Always cleanup
  }
}

module.exports = { isLDAPConfigured, syncLDAPUsers, startLDAPSync, stopLDAPSync, authenticateLDAP };