/**
 * Hintergrundaufgaben, ausgefuehrt vom Kubernetes-CronJob (scripts/worker.ts).
 *
 * Kein In-Process-Timer: jeder Lauf arbeitet den aktuellen Stand ab. Die
 * Folgeraten zieht Stripe Billing ein; der Worker legt nur fehlende
 * Ratenplaene an und gleicht verlorene Webhooks ab. Mehrere gleichzeitige
 * Laeufe sind unschaedlich, weil Stripe-Aufrufe Idempotenzschluessel tragen
 * und jede Verbuchung idempotent ist.
 */
import { audit, WORKER } from "./audit";
import type { Db } from "./db";
import { flushEmails } from "./email";
import { eachBooking, ensureInstallmentSchedule, holdSchedulesInReview, settleInstallmentInvoice, stopCanceledInstallmentPlans } from "./installment-billing";
import { applyCheckoutExpired, applyFirstPaymentFailed, type EventContext } from "./payment-events";
import type { PaymentGateway } from "./payment-gateway";
import { purgeRateLimits } from "./rate-limit";
import { settleCheckoutSession, type HandlerContext } from "./webhook";

/** Stripe stellt Rechnungen erst rund eine Stunde nach Faelligkeit fertig. */
const RECONCILE_AFTER_MS = 6 * 60 * 60_000;

function eventCtx(ctx: HandlerContext): EventContext {
  return { ...ctx, actor: WORKER };
}

/**
 * Gibt abgelaufene Reservierungen frei. Vorher wird immer Stripe gefragt:
 * wurde die Session doch bezahlt (Webhook verloren), wird die Zahlung
 * verbucht statt der Platz freigegeben.
 */
export async function releaseExpiredReservations(db: Db, gateway: PaymentGateway, ctx: HandlerContext) {
  const expired = await db.seatReservation.findMany({
    where: { status: "ACTIVE", expiresAt: { lt: ctx.now } },
    include: { booking: { select: { id: true, livemode: true, stripeCheckoutSessionId: true } } },
    take: 100,
  });
  let released = 0;
  let settled = 0;
  for (const reservation of expired) {
    const booking = reservation.booking;
    const sameMode = booking.livemode === (gateway.mode === "live");
    if (booking.stripeCheckoutSessionId && sameMode) {
      let session = await gateway.retrieveCheckoutSession(booking.stripeCheckoutSessionId);
      if (session.status === "open") {
        await gateway.expireCheckoutSession(session.id);
        session = await gateway.retrieveCheckoutSession(session.id);
      }
      if (session.status === "complete") {
        await settleCheckoutSession(db, gateway, session, ctx, WORKER);
        settled++;
        continue;
      }
    }
    const result = await db.$transaction((tx) =>
      applyCheckoutExpired(tx, booking.id, null, { ...eventCtx(ctx), reason: "reservation_expired" }),
    );
    if (result === "released") released++;
  }
  return { released, settled };
}

/**
 * Legt den Stripe-Ratenplan fuer bestaetigte Ratenbuchungen an, falls das
 * direkt nach der ersten Zahlung scheiterte oder die Buchung erst spaeter
 * bestaetigt wurde (Pruefung im Adminbereich).
 */
export async function createMissingSchedules(db: Db, gateway: PaymentGateway, ctx: HandlerContext) {
  const bookings = await db.booking.findMany({
    where: {
      status: "CONFIRMED",
      planType: { not: "FULL" },
      stripeScheduleId: null,
      livemode: gateway.mode === "live",
      installments: { some: { seq: { gt: 1 }, status: "PENDING" } },
    },
    select: { id: true },
    take: 50,
  });
  const summary = { created: 0, needsReview: 0, failed: 0 };
  for (const booking of bookings) {
    try {
      const outcome = await ensureInstallmentSchedule(db, gateway, booking.id, ctx, WORKER);
      if (outcome === "created") summary.created++;
      if (outcome === "needs_review") summary.needsReview++;
    } catch (error) {
      console.error(`[worker] Ratenplan fuer Buchung ${booking.id} nicht angelegt: ${error instanceof Error ? error.message : "unbekannt"}`);
      summary.failed++;
    }
  }
  return summary;
}

/**
 * Faengt verlorene Rechnungs-Webhooks auf: Ist eine Folgerate seit
 * RECONCILE_AFTER_MS faellig und nicht verbucht, fragt der Worker Stripe
 * nach den Rechnungen des Zeitplans und verbucht bezahlte.
 */
export async function reconcileInstallmentInvoices(db: Db, gateway: PaymentGateway, ctx: HandlerContext) {
  const bookings = await db.booking.findMany({
    where: {
      stripeScheduleId: { not: null },
      livemode: gateway.mode === "live",
      installments: {
        some: {
          seq: { gt: 1 },
          status: { in: ["PENDING", "FAILED", "REQUIRES_ACTION"] },
          dueAt: { lt: new Date(ctx.now.getTime() - RECONCILE_AFTER_MS) },
        },
      },
    },
    select: { id: true, stripeScheduleId: true },
    take: 50,
  });
  let settled = 0;
  const failed = await eachBooking(bookings, "abgleichen", async (booking) => {
    const invoices = await gateway.listScheduleInvoices(booking.stripeScheduleId!);
    for (const invoice of invoices.filter((i) => i.status === "paid")) {
      if (await settleInstallmentInvoice(db, gateway, invoice, ctx, WORKER)) settled++;
    }
  });
  return { checked: bookings.length, settled, failed };
}

/** Faengt verzoegerte erste Zahlungen (SEPA) auf, deren Ergebnis-Webhook ausblieb. */
export async function reconcileStuck(db: Db, gateway: PaymentGateway, ctx: HandlerContext) {
  let resolved = 0;
  // Verzoegerte erste Zahlungen (SEPA), deren Ergebnis-Webhook ausblieb.
  const processing = await db.booking.findMany({
    where: {
      status: "PENDING",
      paymentStatus: "PROCESSING",
      livemode: gateway.mode === "live",
      updatedAt: { lt: new Date(ctx.now.getTime() - 24 * 60 * 60_000) },
      stripeCheckoutSessionId: { not: null },
    },
    take: 50,
  });
  for (const booking of processing) {
    const session = await gateway.retrieveCheckoutSession(booking.stripeCheckoutSessionId!);
    if (session.paymentStatus === "paid") {
      await settleCheckoutSession(db, gateway, session, ctx, WORKER);
      resolved++;
    } else if (session.paymentIntentId) {
      const pi = await gateway.retrievePaymentIntent(session.paymentIntentId);
      if (pi.status === "requires_payment_method" || pi.status === "canceled") {
        await db.$transaction((tx) => applyFirstPaymentFailed(tx, booking.id, eventCtx(ctx)));
        resolved++;
      }
    }
  }
  return { resolved };
}

/**
 * Trennt die gespeicherte Zahlungsmethode, sobald keine Rate mehr offen ist
 * (vollstaendig bezahlt oder storniert). Danach ist technisch keine weitere
 * Abbuchung mehr moeglich.
 */
export async function detachFinishedPaymentMethods(db: Db, gateway: PaymentGateway, bookingIds?: string[]) {
  const candidates = await db.booking.findMany({
    where: {
      stripePaymentMethodId: { not: null },
      paymentMethodDetachedAt: null,
      livemode: gateway.mode === "live",
      ...(bookingIds ? { id: { in: bookingIds } } : {}),
      installments: { none: { status: { in: ["PENDING", "PROCESSING", "FAILED", "REQUIRES_ACTION"] } } },
      // Stornierte Buchungen mit Stripe-Ratenplan: erst den Plan beenden
      // (stopCanceledInstallmentPlans), sonst zoege Stripe weiter ein.
      NOT: { status: "CANCELED", stripeScheduleId: { not: null } },
    },
    take: 50,
  });
  for (const booking of candidates) {
    await gateway.detachPaymentMethod(booking.stripePaymentMethodId!);
    await db.booking.update({ where: { id: booking.id }, data: { paymentMethodDetachedAt: new Date() } });
    await audit(db, WORKER, "payment_method.detached", "Booking", booking.id, { paymentMethodId: booking.stripePaymentMethodId });
  }
  return { detached: candidates.length };
}

export async function runWorker(db: Db, gateway: PaymentGateway, ctx: HandlerContext) {
  const reservations = await releaseExpiredReservations(db, gateway, ctx);
  const reconcile = await reconcileStuck(db, gateway, ctx);
  const held = await holdSchedulesInReview(db, gateway);
  const schedules = await createMissingSchedules(db, gateway, ctx);
  const installments = await reconcileInstallmentInvoices(db, gateway, ctx);
  const stopped = await stopCanceledInstallmentPlans(db, gateway);
  const detach = await detachFinishedPaymentMethods(db, gateway);
  const emails = await flushEmails(db, { limit: 200 });
  const purged = await purgeRateLimits(db);
  return { reservations, reconcile, held, schedules, installments, stopped, detach, emails, purgedRateLimits: purged };
}