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 user accounts only —
 *                            excludes computers, service accounts (sa_*), trust accounts
 *                            and the built-in Administrator/Gast)
 *   LDAP_ATTRIBUTES        - Comma-separated LDAP attributes
 *
 * Rollen (Fix 2, überarbeitet): Rollen werden AUSSCHLIESSLICH über die App
 * verwaltet (Nutzerverwaltung). Der Sync legt neue User immer als 'user' an
 * und ändert die Rolle bestehender User NIE — AD-Gruppen fließen nicht in
 * App-Rechte ein.
 */

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;
// Fix 1: Standard-Filter nur echte Benutzerkonten — keine Computer ($), keine
// Service-Accounts (sa_*), keine Trust-Accounts, nicht deaktivierte Konten.
// 1.2.840.113556.1.4.803 = LDAP_MATCHING_RULE_BIT_AND (userAccountControl-Bits)
// Bit 2 = ACCOUNTDISABLE, Bit 512 = NORMAL_ACCOUNT (nur echte Benutzerkonten
// haben dieses Bit; Computer = 4096, Domain-Controller = 8192 haben es NICHT).
const LDAP_FILTER = process.env.LDAP_FILTER
  || '(&(objectClass=user)(sAMAccountName=*)(!(sAMAccountName=*$))(!(sAMAccountName=sa_*))'
     + '(!(sAMAccountName=Administrator))(!(sAMAccountName=Gast))'
     + '(!(userAccountControl:1.2.840.113556.1.4.803:=2))'
     + '(userAccountControl:1.2.840.113556.1.4.803:=512))';
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);
}

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

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

      adUsers.push({
        email: email || (username + '@ad.local'),
        name,
        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;

    // H2: Statements innerhalb der Transaktion über txDb erzeugen.
    // WICHTIG (PostgreSQL): Ein UNIQUE-Verstoß bricht die GESAMTE Transaktion
    // ab ("current transaction is aborted") — ein try/catch um den Insert
    // hilft dort nicht. Daher werden Kollisionen VOR dem Insert per SELECT
    // erkannt (ON CONFLICT wäre die Alternative, ist aber im gemeinsamen
    // SQLite/PG-SQL-Dialekt nicht portabel).
    const syncTransaction = db.transaction(async function () {
      const txDb = this;
      // Rollen werden app-seitig verwaltet: neue User immer 'user', bestehende
      // User behalten ihre in der App gesetzte Rolle (Sync fasst role nie an).
      const insertStmt = txDb.prepare('INSERT INTO users (email, password, name, role, status, source, username) VALUES (?, ?, ?, \'user\', \'inaktiv\', \'ad\', ?)');
      const updateStmt = txDb.prepare('UPDATE users SET name = ?, username = ? WHERE id = ?');
      const emailExistsStmt = txDb.prepare('SELECT id FROM users WHERE LOWER(email) = LOWER(?)');
      const usernameExistsStmt = txDb.prepare('SELECT id FROM users WHERE LOWER(username) = LOWER(?)');

      for (const adUser of adUsers) {
        const existing = existingMap[adUser.email];
        if (existing) {
          await updateStmt.run(adUser.name, adUser.username, existing.id);
          updated++;
          delete existingMap[adUser.email];
        } else {
          // Kollisions-Precheck: E-Mail oder Username bereits belegt?
          const emailTaken = await emailExistsStmt.get(adUser.email);
          if (emailTaken) {
            console.warn('[LDAP] E-Mail bereits vorhanden:', adUser.email);
            continue;
          }
          const usernameTaken = adUser.username ? await usernameExistsStmt.get(adUser.username) : null;
          if (usernameTaken) {
            console.warn('[LDAP] Username bereits vorhanden:', adUser.username);
            continue;
          }
          try {
            await insertStmt.run(adUser.email, 'LDAP_AUTH', adUser.name, adUser.username);
            inserted++;
          } catch (err) {
            // Fallback für Race-Conditions zwischen Precheck und Insert
            if (err.message?.includes('UNIQUE constraint') || err.message?.includes('duplicate key')) {
              console.warn('[LDAP] E-Mail bereits vorhanden (Race):', 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()));

    // H3: Mass-deletion protection — a single failed/empty LDAP result must not
    // wipe the entire AD user base (and their tasks via ON DELETE CASCADE).
    // Abort the sync if we would remove more than LDAP_MAX_DELETE_PCT (default 25%)
    // of the currently known AD users, or if the LDAP search returned zero entries.
    const LDAP_MAX_DELETE_PCT = parseInt(process.env.LDAP_MAX_DELETE_PCT) || 25;
    let removed = 0;
    if (toRemove.length > 0) {
      if (adUsers.length === 0) {
        console.warn('[LDAP] Sync lieferte 0 Nutzer — Löschen abgebrochen (Schutz gegen Massenlöschung).');
      } else {
        const deleteRatio = (toRemove.length / existingRows.length) * 100;
        if (deleteRatio > LDAP_MAX_DELETE_PCT) {
          console.warn(`[LDAP] ${toRemove.length} von ${existingRows.length} AD-Nutzern würden gelöscht werden (${deleteRatio.toFixed(1)}% > ${LDAP_MAX_DELETE_PCT}% Schwellwert) — Löschen abgebrochen.`);
        } else {
          const removeIds = toRemove.map(r => r.id).filter(id => Number.isInteger(id));
          if (removeIds.length > 0) {
            const placeholders = removeIds.map(() => '?').join(',');
            await db.prepare(`DELETE FROM users WHERE id IN (${placeholders}) AND source = 'ad'`).run(...removeIds);
            removed = removeIds.length;
          }
        }
      }
    }

    console.log('[LDAP] Sync abgeschlossen: ' + inserted + ' neu, ' + updated + ' aktualisiert, ' + removed + ' entfernt');

    // Fix 1 (Cleanup): Bereits kontaminierte Konten entfernen — Computer-Accounts
    // ($-Suffix), Service-Accounts (sa_*) und der eingebaute Administrator/Gast.
    // Diese sollten laut geschärftem Filter nie mehr gesynct werden; der Cleanup
    // räumt Bestände auf, die vor dem Fix angelegt wurden. Läuft nur, wenn der
    // Standard-Filter aktiv ist (bei Custom-Filter entscheidet der Betreiber).
    const isDefaultFilter = !process.env.LDAP_FILTER;
    if (isDefaultFilter) {
      const junkRows = await db.prepare(
        `SELECT id FROM users WHERE source = 'ad' AND (username LIKE '%$' OR username LIKE 'sa\\_%' ESCAPE '\\' OR LOWER(username) IN ('administrator', 'gast'))`
      ).all();
      const cleanupIds = junkRows.map(r => r.id).filter(id => Number.isInteger(id));
      if (cleanupIds.length > 0) {
        const placeholders = cleanupIds.map(() => '?').join(',');
        const del = await db.prepare(`DELETE FROM users WHERE id IN (${placeholders}) AND source = 'ad'`).run(...cleanupIds);
        console.log('[LDAP] Cleanup: ' + del.changes + ' Computer-/Service-Accounts 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 };