/**
 * rebreak-imap-idle — IMAP IDLE Daemon
 *
 * Hält pro aktivem MailConnection-Eintrag eine persistente IMAP-IDLE-Session.
 * Wenn der Server "EXISTS" meldet (neue Mail), feuert der Daemon sofort
 * POST /api/mail/scan-internal gegen das lokale Backend — ohne 30min-Warte.
 *
 * Auth-Methoden:
 *   app_password      — Gmail, iCloud, GMX, etc. (App-Password / IMAP-Passwort)
 *   oauth2_microsoft  — Outlook / Hotmail / O365 via XOAUTH2 (ImapFlow-nativ)
 *
 * Env-Vars (via Infisical-Wrapper):
 *   DATABASE_URL         — Postgres-Connection-String
 *   ADMIN_SECRET         — Header-Secret für /api/mail/scan-internal
 *   ENCRYPTION_KEY       — AES-256 Key (gleicher wie im Backend, 32+ Zeichen)
 *   BACKEND_URL          — z.B. http://127.0.0.1:3016 (default: 3016)
 *   MS_OAUTH_CLIENT_ID   — Azure App Registration Client ID
 *   NODE_ENV             — production / staging
 *
 * Starten:
 *   node index.mjs
 *
 * Prozess-Signale:
 *   SIGTERM / SIGINT → graceful shutdown (alle IMAP-Sessions schließen)
 */

import { ImapFlow } from "imapflow";
import pg from "pg";
import { createCipheriv, createDecipheriv, randomBytes } from "crypto";

// ─── Config ──────────────────────────────────────────────────────────────────

const BACKEND_URL =
  process.env.BACKEND_URL ||
  (process.env.NODE_ENV === "production"
    ? "http://127.0.0.1:3015"
    : "http://127.0.0.1:3016");

const ADMIN_SECRET =
  process.env.NUXT_ADMIN_SECRET || process.env.ADMIN_SECRET || "";

const MS_OAUTH_CLIENT_ID =
  process.env.MS_OAUTH_CLIENT_ID || "";

const DB_REFRESH_INTERVAL_MS = 5 * 60 * 1000;   // 5 min — neue Connections entdecken

// IDLE_RENEW von 25min → 10min: GMX dropped IDLE-connections silent vor 25min
// → exists-events kommen nie an + ImapFlow.idle() hängt ohne reject. 10min
// deckt alle bekannten Provider-Timeouts ab:
//   GMX           ~10-15min (aggressivster Provider)
//   Gmail         ~29min
//   iCloud        ~29min
//   outlook.office365.com ~29min (Microsoft dokumentiert 29min IDLE-Timeout)
// Trade-off: alle 10min full reconnect-cycle. Vertretbar.
const IDLE_RENEW_INTERVAL_MS = 10 * 60 * 1000;  // 10 min

// NOOP-heartbeat alle 2min während IDLE: detect silent-drops (GMX-pattern).
// Wenn NOOP fehlschlägt → close → loop iteriert → reconnect.
const IDLE_NOOP_INTERVAL_MS  = 2 * 60 * 1000;   // 2 min

// Token-Refresh-Schwelle: wenn Access-Token in weniger als 5min abläuft, vor
// dem IMAP-Connect refreshen. Verhindert Mid-Session-Expiry.
const TOKEN_EXPIRY_THRESHOLD_MS = 5 * 60 * 1000; // 5 min

// Bei AUTHENTICATIONFAILED: max. 3 Refresh-Versuche bevor Connection als
// auth_broken markiert und der Daemon sie aufgibt.
const MAX_AUTH_RETRIES = 3;

const RECONNECT_DELAYS_MS    = [1000, 5000, 30_000]; // exponential backoff
const RECONNECT_LOOP_DELAY_MS = 60 * 1000;

// ─── DB-Pool (direktes pg, kein Prisma — Daemon ist kein Nitro-Kontext) ─────

const pool = new pg.Pool({ connectionString: process.env.DATABASE_URL });

async function updateConnectionError(connId, errorText) {
  await pool.query(
    `UPDATE rebreak.mail_connections
     SET last_connect_error = $1, last_connect_error_at = NOW()
     WHERE id = $2`,
    [errorText, connId],
  );
}

async function clearConnectionError(connId) {
  await pool.query(
    `UPDATE rebreak.mail_connections
     SET last_connect_error = NULL, last_connect_error_at = NULL
     WHERE id = $1`,
    [connId],
  );
}

async function updateIdleHeartbeat(connId) {
  await pool.query(
    `UPDATE rebreak.mail_connections
     SET last_idle_heartbeat_at = NOW()
     WHERE id = $1`,
    [connId],
  );
}

/**
 * Lädt alle aktiven MailConnections inkl. OAuth-Felder und consent_at.
 * Consent-Gate: connections ohne consent_at werden geladen aber vom
 * IDLE-Loop nicht gescannt (nur gehalten — kein Delete).
 */
async function loadActiveConnections() {
  const { rows } = await pool.query(
    `SELECT id,
            user_id               AS "userId",
            email,
            imap_host             AS "imapHost",
            imap_port             AS "imapPort",
            password_encrypted    AS "passwordEncrypted",
            reject_unauthorized   AS "rejectUnauthorized",
            use_starttls          AS "useStarttls",
            auth_method           AS "authMethod",
            oauth_access_token    AS "oauthAccessToken",
            oauth_refresh_token   AS "oauthRefreshToken",
            oauth_token_expiry    AS "oauthTokenExpiry",
            consent_at            AS "consentAt"
     FROM rebreak.mail_connections
     WHERE is_active = true`,
  );
  return rows;
}

// ─── Crypto (analog zu server/utils/crypto.ts) ───────────────────────────────

const AES_ALGO   = "aes-256-gcm";
const KEY_LENGTH = 32;

function getKey() {
  const raw =
    process.env.NUXT_ENCRYPTION_KEY || process.env.ENCRYPTION_KEY || "";
  if (!raw || raw.length < KEY_LENGTH) {
    return Buffer.alloc(
      KEY_LENGTH,
      raw.padEnd(KEY_LENGTH, "0").slice(0, KEY_LENGTH),
    );
  }
  return Buffer.from(raw.slice(0, KEY_LENGTH), "utf8");
}

function decrypt(stored) {
  const parts = stored.split(":");
  if (parts.length !== 3) throw new Error("Invalid encrypted format");
  const [ivHex, tagHex, dataHex] = parts;
  const decipher = createDecipheriv(
    AES_ALGO,
    getKey(),
    Buffer.from(ivHex, "hex"),
  );
  decipher.setAuthTag(Buffer.from(tagHex, "hex"));
  return decipher.update(Buffer.from(dataHex, "hex")) + decipher.final("utf8");
}

function encrypt(plaintext) {
  const key = getKey();
  const iv = randomBytes(12); // 96-bit IV für AES-256-GCM
  const cipher = createCipheriv(AES_ALGO, key, iv);
  const encrypted = Buffer.concat([
    cipher.update(plaintext, "utf8"),
    cipher.final(),
  ]);
  const tag = cipher.getAuthTag();
  return `${iv.toString("hex")}:${tag.toString("hex")}:${encrypted.toString("hex")}`;
}

// ─── Microsoft Token Refresh (inline, kein Prisma-Kontext) ───────────────────

const MS_TOKEN_ENDPOINT =
  "https://login.microsoftonline.com/common/oauth2/v2.0/token";

// MUSS identisch zu backend/server/utils/ms-oauth.ts MS_OAUTH_SCOPES sein.
// Microsoft V2.0 erlaubt im /token-Exchange nur Scopes EINES Resource-Servers
// — `User.Read` (graph.microsoft.com) mit `IMAP.AccessAsUser.All`
// (outlook.office.com) wirft AADSTS70011. `email` ist ein OIDC-Standard-Scope
// und damit cross-resource-kompatibel; liefert den email-Claim ins id_token.
const MS_OAUTH_SCOPES = [
  "https://outlook.office.com/IMAP.AccessAsUser.All",
  "offline_access",
  "openid",
  "email",
].join(" ");

/**
 * Refresht Microsoft Access+Refresh-Token direkt via HTTP.
 * Race-Condition-Strategie (Optimistic Concurrency):
 *   1. Lese aktuelle oauth_token_expiry aus DB als "Fingerprint" des aktuellen Stands.
 *   2. POST an MS Token-Endpoint.
 *   3. UPDATE ... WHERE oauth_token_expiry = <gelesener Wert>
 *      → affected_rows = 0: anderer Prozess hat parallel refresht.
 *        Dann: frischen token lesen + zurückgeben (kein doppelter Refresh!).
 *        Doppelter Refresh würde MS-Refresh-Token-Rotation verletzen →
 *        AADSTS70043 beim nächsten Versuch.
 *   4. Gibt plaintext Access-Token zurück, sofort für IMAP nutzbar.
 *
 * Wirft wenn:
 *   - Connection nicht gefunden / kein Refresh-Token
 *   - MS Token-Endpoint antwortet mit Fehler (revoked/expired Refresh-Token)
 */
async function refreshAndSaveTokensDaemon(connectionId, clientId) {
  // Step 1: Aktuellen Token-Stand lesen
  const { rows } = await pool.query(
    `SELECT oauth_refresh_token, oauth_access_token, oauth_token_expiry
     FROM rebreak.mail_connections
     WHERE id = $1 AND auth_method = 'oauth2_microsoft'`,
    [connectionId],
  );

  const conn = rows[0];
  if (!conn?.oauth_refresh_token) {
    throw new Error(
      `Connection ${connectionId} has no oauth_refresh_token — cannot refresh`,
    );
  }

  const currentExpiry = conn.oauth_token_expiry;
  const decryptedRefreshToken = decrypt(conn.oauth_refresh_token);

  // Step 2: MS Token-Endpoint
  const body = new URLSearchParams({
    grant_type: "refresh_token",
    client_id: clientId,
    refresh_token: decryptedRefreshToken,
    scope: MS_OAUTH_SCOPES,
  });

  const res = await fetch(MS_TOKEN_ENDPOINT, {
    method: "POST",
    headers: { "Content-Type": "application/x-www-form-urlencoded" },
    body: body.toString(),
  });

  if (!res.ok) {
    const errText = await res.text().catch(() => "unknown");
    throw new Error(`MS token refresh failed (${res.status}): ${errText}`);
  }

  const data = await res.json();
  if (!data.access_token) {
    throw new Error("MS refresh response missing access_token");
  }

  const newExpiry = new Date(Date.now() + data.expires_in * 1000);
  // MS rotiert Refresh-Tokens — wenn kein neuer kommt, den alten behalten
  const newRefreshToken = data.refresh_token ?? decryptedRefreshToken;

  const encryptedAccess  = encrypt(data.access_token);
  const encryptedRefresh = encrypt(newRefreshToken);

  // Step 3: Optimistic update — nur wenn oauth_token_expiry noch gleich wie gelesen
  // IS NOT DISTINCT FROM deckt NULL=NULL korrekt ab (vs. = das NULL!=NULL behandelt)
  const result = await pool.query(
    `UPDATE rebreak.mail_connections
     SET oauth_access_token  = $1,
         oauth_refresh_token = $2,
         oauth_token_expiry  = $3
     WHERE id = $4
       AND oauth_token_expiry IS NOT DISTINCT FROM $5`,
    [encryptedAccess, encryptedRefresh, newExpiry, connectionId, currentExpiry],
  );

  if (result.rowCount === 0) {
    // Step 4: Anderer Prozess hat parallel refresht — lese deren frischen Token
    const { rows: fresh } = await pool.query(
      `SELECT oauth_access_token FROM rebreak.mail_connections WHERE id = $1`,
      [connectionId],
    );
    if (!fresh[0]?.oauth_access_token) {
      throw new Error(
        `Concurrent refresh for ${connectionId} detected but no token found`,
      );
    }
    return decrypt(fresh[0].oauth_access_token);
  }

  return data.access_token;
}

/**
 * Markiert eine Connection als "auth_broken" — kein weiterer Retry im Daemon.
 * User sieht den Error im Frontend (last_connect_error = 'auth_revoked').
 */
async function markConnectionAuthBroken(connectionId) {
  await pool.query(
    `UPDATE rebreak.mail_connections
     SET last_connect_error = 'auth_revoked',
         last_connect_error_at = NOW()
     WHERE id = $1`,
    [connectionId],
  );
}

// ─── Credentials-Resolution ──────────────────────────────────────────────────

/**
 * Gibt die IMAP-Credentials für eine Connection zurück.
 * auth_method-aware:
 *
 *   app_password     → { type: 'password', user, pass }
 *   oauth2_microsoft → { type: 'xoauth2',  user, accessToken }
 *
 * Für OAuth: wenn Token in <5min abläuft, wird vor Connect refresht.
 * Das ist der "proaktive" Refresh-Path (Hot-Path).
 *
 * Der "reaktive" Refresh-Path (Cold-Path) liegt in runSession():
 * AUTHENTICATIONFAILED während laufender Session → refreshAndSaveTokensDaemon()
 * → neuer ImapFlow-Connect mit frischem Token.
 *
 * FORCE_REFRESH_FOR_TEST: wenn env IDLE_FORCE_TOKEN_REFRESH=1 gesetzt ist,
 * wird IMMER refresht unabhängig von Expiry. Nur für manuelle Tests.
 */
async function getCredentialsForConnection(conn) {
  if (conn.authMethod === "oauth2_microsoft") {
    const forceRefresh = process.env.IDLE_FORCE_TOKEN_REFRESH === "1";
    const fiveMinFromNow = Date.now() + TOKEN_EXPIRY_THRESHOLD_MS;
    const isExpiring =
      !conn.oauthTokenExpiry ||
      new Date(conn.oauthTokenExpiry).getTime() < fiveMinFromNow;

    if (forceRefresh || isExpiring) {
      const reason = forceRefresh ? "IDLE_FORCE_TOKEN_REFRESH=1" : "token expiring <5min";
      // NIEMALS Token-Werte loggen — nur Fakt dass refresht wird
      console.log(`[idle/${conn.email}] proactive token refresh (${reason})`);
      const accessToken = await refreshAndSaveTokensDaemon(conn.id, MS_OAUTH_CLIENT_ID);
      return { type: "xoauth2", user: conn.email, accessToken };
    }

    // Token noch gültig — direkt entschlüsseln
    if (!conn.oauthAccessToken) {
      throw new Error(`Connection ${conn.id} has no oauth_access_token`);
    }
    const accessToken = decrypt(conn.oauthAccessToken);
    return { type: "xoauth2", user: conn.email, accessToken };
  }

  // Bestand: Gmail / iCloud / GMX / Custom-IMAP → App-Password
  if (!conn.passwordEncrypted) {
    throw new Error(`Connection ${conn.id} has no password_encrypted`);
  }
  const pass = decrypt(conn.passwordEncrypted);
  return { type: "password", user: conn.email, pass };
}

// ─── Logging ─────────────────────────────────────────────────────────────────

function log(email, msg) {
  // NIEMALS password/accessToken/credentials loggen. email ist safe.
  console.log(`[idle/${email}] ${msg}`);
}

function logError(email, msg, err) {
  // responseText = IMAP-Serverantwort (z.B. "NO [AUTHENTICATIONFAILED] Invalid credentials")
  // Credentials tauchen NICHT in err.responseText auf — ImapFlow legt sie nicht rein.
  const errMsg = err?.responseText || err?.message || String(err);
  console.error(`[idle/${email}] ${msg}: ${errMsg}`);
}

// ─── Auth-Fehler Detection ───────────────────────────────────────────────────

function isAuthError(err) {
  const text = (err?.responseText || err?.message || "").toUpperCase();
  return (
    text.includes("AUTHENTICATIONFAILED") ||
    text.includes("AUTHENTICATE") ||
    text.includes("INVALID CREDENTIALS") ||
    text.includes("AUTHENTICATION FAILED") ||
    // MS-spezifische Fehlercodes: AADSTS = Azure AD Token Service Error
    text.includes("AADSTS")
  );
}

// ─── Session-Registry ────────────────────────────────────────────────────────
// Map<connectionId, SessionHandle>

const sessions = new Map();

let shuttingDown = false;

// ─── Scan-Trigger ─────────────────────────────────────────────────────────────

async function triggerScan(conn) {
  try {
    const res = await fetch(`${BACKEND_URL}/api/mail/scan-internal`, {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
        "x-admin-secret": ADMIN_SECRET,
      },
      body: JSON.stringify({ userId: conn.userId }),
    });
    if (!res.ok) {
      log(conn.email, `scan-trigger HTTP ${res.status}`);
    } else {
      const data = await res.json().catch(() => ({}));
      log(
        conn.email,
        `scan-triggered → scanned=${data.scanned ?? "?"} blocked=${data.blocked ?? "?"}`,
      );
    }
  } catch (err) {
    logError(conn.email, "scan-trigger failed", err);
  }
}

// ─── IDLE-Session ─────────────────────────────────────────────────────────────

/**
 * Startet eine einzelne IDLE-Session für eine MailConnection.
 * Reconnect-Loop läuft intern — diese Funktion returned nie (bis shutdown).
 *
 * Auth-Retry-Loop (OAuth-spezifisch):
 *   Bei AUTHENTICATIONFAILED → Token refreshen → neu verbinden.
 *   Max MAX_AUTH_RETRIES (3) mal. Dann: markConnectionAuthBroken + exit.
 *   authRetries wird nach jedem erfolgreichen Connect resettet.
 *
 * Consent-Gate:
 *   conn.consentAt === null → IDLE-Verbindung wird gehalten (keep-alive),
 *   aber triggerScan() wird NICHT aufgerufen. exists-Events werden still ignoriert.
 *   Sobald der User consent erteilt (DB-Refresh-Cycle nach max. 5min),
 *   wird die Connection neu gestartet mit consentAt gesetzt.
 */
async function runSession(conn) {
  let attempt = 0;
  let authRetries = 0;

  while (!shuttingDown) {
    // Credentials holen (proaktiver Token-Refresh wenn nötig)
    let creds;
    try {
      creds = await getCredentialsForConnection(conn);
    } catch (err) {
      logError(conn.email, "credential resolution failed — session aborted", err);
      // Kein retry: kaputte Credentials oder Token-Refresh fehlgeschlagen
      // (z.B. Refresh-Token revoked). Als auth_broken markieren wenn OAuth.
      if (conn.authMethod === "oauth2_microsoft") {
        await markConnectionAuthBroken(conn.id).catch(() => {});
      } else {
        await updateConnectionError(conn.id, err?.message || String(err)).catch(() => {});
      }
      return;
    }

    const useImplicitTls = !conn.useStarttls;
    const imap = new ImapFlow({
      host: conn.imapHost,
      port: conn.imapPort,
      secure: useImplicitTls,
      ...(conn.useStarttls ? { requireTLS: true } : {}),
      // ImapFlow 1.2.18 unterstützt XOAUTH2 nativ:
      // { user, accessToken } → AUTHENTICATE XOAUTH2 <base64-token>
      // { user, pass }        → LOGIN oder PLAIN (je nach Server-Capability)
      auth: creds.type === "xoauth2"
        ? { user: creds.user, accessToken: creds.accessToken }
        : { user: creds.user, pass: creds.pass },
      logger: false,
      tls: { rejectUnauthorized: conn.rejectUnauthorized ?? true },
      // outlook.office365.com: disableCompression verhindert edge-cases bei
      // partial reads nach Reconnect. Gilt für oauth2_microsoft Connections.
      disableCompression: conn.imapHost.includes("office365"),
    });

    // Referenz ablegen damit shutdown() darauf zugreifen kann
    const handle = sessions.get(conn.id);
    if (handle) handle.imap = imap;

    try {
      await imap.connect();
      log(conn.email, `connected (${conn.imapHost}:${conn.imapPort}, auth=${creds.type})`);
      attempt = 0;    // Reset nach erfolgreicher Verbindung
      authRetries = 0; // Auth-Retry-Counter ebenfalls reset
      // Initial-Heartbeat: sofort nach erfolgreichem Connect schreiben damit
      // das Frontend "aktiv" zeigt statt bis zum ersten NOOP-Cycle zu warten
      // (NOOP-Cycle = alle 2min → worst-case 2min+, gemessene delay 2-9min).
      // Gilt für alle auth-Methoden (app_password + oauth2_microsoft) und
      // auch für den Re-Connect nach AUTHENTICATIONFAILED-Recovery, da beide
      // Paths durch diesen Block laufen.
      // last_connect_error wird gleichzeitig geclearet: ein zuvor failed-State
      // (z.B. abgelaufener Token) ist nach erfolgreichem Connect behoben.
      await Promise.all([
        updateIdleHeartbeat(conn.id).catch(() => {}),
        clearConnectionError(conn.id).catch(() => {}),
      ]);

      // Outlook/XOAUTH2 hat den Edge-Case dass getMailboxLock lautlos hängt
      // wenn der Server in einen ungültigen Zustand kommt — die Session
      // bleibt offen ohne Fortschritt bis der Renew-Timer (10min) ein
      // imap.close() schickt. Timeout-wrap macht das Failure-Mode explizit
      // → Auth-Retry-Loop greift sauber.
      await Promise.race([
        imap.getMailboxLock("INBOX"),
        new Promise((_, reject) =>
          setTimeout(() => reject(new Error("getMailboxLock timeout (30s)")), 30_000),
        ),
      ]);

      // Consent-Gate-Log: einmalig beim Connect — nur wenn consentAt fehlt
      if (!conn.consentAt) {
        log(
          conn.email,
          "consent_at=NULL — IDLE session held but scan/delete suspended. " +
          "Re-consent required via app.",
        );
      }

      // IDLE-Loop: alle IDLE_RENEW_INTERVAL_MS erneuern
      while (!shuttingDown && sessions.has(conn.id)) {
        const idlePromise = new Promise((resolve, reject) => {
          imap.idle().then(resolve).catch(reject);
        });

        // exists-event → sofort scannen (nur wenn consent erteilt)
        const onExists = () => {
          if (!conn.consentAt) {
            // Consent fehlt: exists-event ignorieren, Mail bleibt in Inbox.
            // UI zeigt Re-Consent-Modal (via /api/mail/pending-consent Endpoint).
            log(conn.email, "exists-event received — skipped (no consent_at)");
            return;
          }
          log(conn.email, "exists-event received (new mail)");
          triggerScan(conn); // fire-and-forget
        };
        imap.on("exists", onExists);

        // IDLE nach 10min erneuern
        // Gilt für: GMX (~10-15min), Gmail (~29min), iCloud (~29min), outlook.office365.com (~29min)
        const renewTimer = setTimeout(() => {
          log(conn.email, "idle renewing (10min threshold)");
          imap.close();
        }, IDLE_RENEW_INTERVAL_MS);

        // NOOP-heartbeat alle 2min: silent-drop early-detection (GMX-pattern).
        const noopTimer = setInterval(async () => {
          try {
            await imap.noop();
            await updateIdleHeartbeat(conn.id).catch(() => {});
          } catch (err) {
            logError(conn.email, "noop failed — connection dead, force reconnect", err);
            imap.close();
          }
        }, IDLE_NOOP_INTERVAL_MS);

        try {
          await idlePromise;
        } finally {
          clearInterval(noopTimer);
          clearTimeout(renewTimer);
          imap.removeListener("exists", onExists);
        }

        if (shuttingDown || !sessions.has(conn.id)) break;

        await sleep(500);
      }

      try { await imap.logout(); } catch { /* ignore */ }
      return; // Sauberer Exit (shutdown oder Connection entfernt)

    } catch (err) {
      logError(conn.email, "connection error", err);
      try { imap.close(); } catch { /* ignore */ }

      // ── AUTHENTICATIONFAILED-Recovery (OAuth-spezifisch) ──────────────────
      // Cold-Path: Token zwischen zwei IDLE-Renewals abgelaufen (>1h Session).
      // Oder: proaktiver Refresh ist fehlgeschlagen und wir landen hier.
      if (conn.authMethod === "oauth2_microsoft" && isAuthError(err)) {
        authRetries++;
        log(
          conn.email,
          `AUTHENTICATIONFAILED detected — refresh attempt ${authRetries}/${MAX_AUTH_RETRIES}`,
        );

        if (authRetries > MAX_AUTH_RETRIES) {
          // Auth dauerhaft revoked (User hat App-Permission entzogen o.ä.)
          // Connection als auth_broken markieren — User muss re-connecten.
          log(conn.email, `auth_broken after ${MAX_AUTH_RETRIES} retries — session stopped`);
          await markConnectionAuthBroken(conn.id).catch(() => {});
          sessions.delete(conn.id);
          return;
        }

        // Token refreshen — direkt hier im catch-Block.
        // Wenn der Refresh selbst fehlschlägt (revoked Refresh-Token),
        // wirft refreshAndSaveTokensDaemon — wir landen im äußeren catch
        // und der normale Reconnect-Backoff greift (attempt++).
        // Beim nächsten Attempt ruft getCredentialsForConnection() wieder refresh auf.
        try {
          const freshToken = await refreshAndSaveTokensDaemon(conn.id, MS_OAUTH_CLIENT_ID);
          // conn ist das ursprüngliche Objekt aus loadActiveConnections.
          // Wir patchen oauthAccessToken + oauthTokenExpiry inline damit
          // getCredentialsForConnection() beim nächsten Loop-Durchlauf
          // den frischen Token nutzt ohne erneuten DB-Read.
          conn.oauthAccessToken = encrypt(freshToken);
          conn.oauthTokenExpiry = new Date(Date.now() + 55 * 60 * 1000); // ~55min buffer
          log(conn.email, "token refreshed — reconnecting immediately");
          // Kein normaler Backoff nach Auth-Refresh — sofort neu verbinden.
          // attempt bleibt unverändert (auth-error != network-error).
          continue;
        } catch (refreshErr) {
          logError(conn.email, "token refresh failed after AUTHENTICATIONFAILED", refreshErr);
          // Refresh selbst gescheitert → normaler Backoff (Netz, Serverproblem o.ä.)
          // authRetries bleibt erhöht — beim nächsten Auth-Fehler zählt es weiter.
          await updateConnectionError(conn.id, refreshErr?.message || String(refreshErr)).catch(() => {});
        }
      } else {
        // Nicht-Auth-Fehler (Netz, TLS, etc.) — normal in DB schreiben
        const errText = err?.responseText || err?.message || String(err);
        await updateConnectionError(conn.id, errText).catch(() => {});
      }
    }

    if (shuttingDown || !sessions.has(conn.id)) return;

    // Exponential backoff
    const delay =
      attempt < RECONNECT_DELAYS_MS.length
        ? RECONNECT_DELAYS_MS[attempt]
        : RECONNECT_LOOP_DELAY_MS;
    attempt++;
    log(conn.email, `reconnecting in ${delay / 1000}s (attempt ${attempt})`);
    await sleep(delay);
  }
}

// ─── Session-Management ───────────────────────────────────────────────────────

function startSession(conn) {
  if (sessions.has(conn.id)) return; // bereits aktiv
  log(conn.email, "session starting");
  const handle = { conn, imap: null, promise: null };
  sessions.set(conn.id, handle);
  handle.promise = runSession(conn).catch((err) => {
    logError(conn.email, "session crashed (unhandled)", err);
    sessions.delete(conn.id);
  });
}

async function stopSession(connectionId, email) {
  const handle = sessions.get(connectionId);
  if (!handle) return;
  log(email ?? connectionId, "session stopping");
  sessions.delete(connectionId);
  if (handle.imap) {
    try { handle.imap.close(); } catch { /* ignore */ }
  }
  await handle.promise.catch(() => {});
}

// ─── DB-Refresh-Loop ──────────────────────────────────────────────────────────

async function refreshConnections() {
  let rows;
  try {
    rows = await loadActiveConnections();
  } catch (err) {
    console.error("[idle/db] loadActiveConnections failed:", err.message);
    return;
  }

  const activeIds = new Set(rows.map((r) => r.id));

  // Neue Connections starten
  for (const row of rows) {
    if (!sessions.has(row.id)) {
      startSession(row);
    }
  }

  // Entfernte Connections stoppen
  for (const [id, handle] of sessions.entries()) {
    if (!activeIds.has(id)) {
      await stopSession(id, handle.conn?.email);
    }
  }

  // Consent-Status für laufende Sessions aktualisieren.
  // Wenn ein User consent erteilt hat seit dem letzten DB-Refresh:
  // Die laufende Session bekommt conn.consentAt gesetzt — next exists-event
  // löst dann sofort triggerScan() aus. Kein Restart nötig.
  for (const row of rows) {
    const handle = sessions.get(row.id);
    if (handle && handle.conn.consentAt !== row.consentAt) {
      if (!handle.conn.consentAt && row.consentAt) {
        log(row.email, "consent_at received — scan/delete now active");
      }
      handle.conn.consentAt = row.consentAt;
    }
  }

  const consentPending = rows.filter((r) => !r.consentAt).length;
  console.log(
    `[idle/db] refreshed — ${activeIds.size} active connections, ${sessions.size} sessions` +
    (consentPending > 0 ? `, ${consentPending} pending consent` : ""),
  );
}

// ─── Graceful Shutdown ────────────────────────────────────────────────────────

async function shutdown(signal) {
  console.log(`[idle] received ${signal} — shutting down gracefully`);
  shuttingDown = true;

  const stopPromises = [];
  for (const [id, handle] of sessions.entries()) {
    stopPromises.push(stopSession(id, handle.conn?.email));
  }
  await Promise.allSettled(stopPromises);

  await pool.end().catch(() => {});
  console.log("[idle] shutdown complete");
  process.exit(0);
}

process.on("SIGTERM", () => shutdown("SIGTERM"));
process.on("SIGINT",  () => shutdown("SIGINT"));

// ─── Startup ──────────────────────────────────────────────────────────────────

function sleep(ms) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

function assertEnv() {
  const missing = [];
  if (!process.env.DATABASE_URL)  missing.push("DATABASE_URL");
  if (!ADMIN_SECRET)              missing.push("ADMIN_SECRET / NUXT_ADMIN_SECRET");
  if (!MS_OAUTH_CLIENT_ID)        missing.push("MS_OAUTH_CLIENT_ID");
  if (missing.length > 0) {
    console.error(
      `[idle] FEHLER: fehlende Env-Vars: ${missing.join(", ")}. Daemon startet nicht.`,
    );
    process.exit(1);
  }
}

async function main() {
  assertEnv();

  console.log(
    `[idle] starting — backend=${BACKEND_URL} env=${process.env.NODE_ENV ?? "unknown"}`,
  );

  await refreshConnections();

  setInterval(() => {
    if (!shuttingDown) refreshConnections();
  }, DB_REFRESH_INTERVAL_MS);
}

main().catch((err) => {
  console.error("[idle] fatal startup error:", err);
  process.exit(1);
});