const cron = require('node-cron');
const AbonemmentRepository = require('../../repositories/abonemments/AbonemmentRepository');
const InvoiceRepository = require('../../repositories/invoice/InvoiceRepository');
const InvoiceService = require('../invoice/InvoiceService');
const MailService = require('../email/MailService');
const { logger } = require('../../middleware/logger');

class RenewalCronService {
  constructor() {
    this.repo = new AbonemmentRepository();
    this.invoiceRepo = new InvoiceRepository();
    this.invoiceService = new InvoiceService();
  }

  addInterval(date, interval, count) {
    const d = new Date(date);
    if (interval === 'day') d.setDate(d.getDate() + count);
    if (interval === 'week') d.setDate(d.getDate() + 7 * count);
    if (interval === 'month') d.setMonth(d.getMonth() + count);
    if (interval === 'year') d.setFullYear(d.getFullYear() + count);
    return d;
  }

  /**
   * Get the latest invoice for a subscription.
   */
  async getLatestInvoice(abonementId) {
    const invoices = await this.invoiceRepo.findByAbonement(abonementId);
    return invoices.length ? invoices[0] : null; // already sorted DESC
  }

  // ──────────────────────────────────────────────
  //  PHASE 1 — Process active subscriptions due for renewal
  // ──────────────────────────────────────────────

  async processActiveRenewals(now) {
    let dueAbonements;
    try {
      dueAbonements = await this.repo.listDueForBilling(now);
    } catch (err) {
      logger.error('RenewalCron:fetch_due_error', { message: err?.message });
      return;
    }

    if (!dueAbonements.length) {
      logger.info('RenewalCron:no_due_subscriptions');
      return;
    }

    logger.info('RenewalCron:found_due', { count: dueAbonements.length });
    const results = { renewed: 0, skipped: 0, paused: 0, reminded: 0, errors: [] };

    for (const abon of dueAbonements) {
      try {
        // Re-check status (race-condition protection)
        const fresh = await this.repo.getAbonementById(abon.id);
        if (!fresh || fresh.status !== 'active') {
          results.skipped++;
          continue;
        }

        // Gift-abo where recipient hasn't registered yet → pause
        if (!fresh.user_id) {
          await this.pauseAbonement(fresh, 'no_registered_user');
          results.paused++;
          continue;
        }

        // Check last invoice payment status
        const lastInvoice = await this.getLatestInvoice(fresh.id);

        if (!lastInvoice) {
          // First cycle, no invoice yet → renew
          await this.renewSingleAbonement(fresh);
          results.renewed++;
          continue;
        }

        if (lastInvoice.status === 'paid') {
          // Previous invoice paid → renew
          await this.renewSingleAbonement(fresh);
          results.renewed++;
          continue;
        }

        // Previous invoice NOT paid — do NOT renew, do NOT shift next_billing_at
        // Check how overdue it is
        const issuedAt = lastInvoice.issued_at ? new Date(lastInvoice.issued_at) : new Date(lastInvoice.created_at);
        const daysSinceIssued = Math.floor((now - issuedAt) / (1000 * 60 * 60 * 24));

        if (daysSinceIssued >= 30) {
          // 30+ days unpaid → pause subscription
          if (lastInvoice.status !== 'overdue') {
            await this.invoiceRepo.updateStatus(lastInvoice.id, 'overdue');
          }
          await this.pauseAbonement(fresh, 'unpaid_30_days');
          results.paused++;
        } else if (daysSinceIssued >= 7) {
          // 7+ days → mark overdue + send reminder
          if (lastInvoice.status !== 'overdue') {
            await this.invoiceRepo.updateStatus(lastInvoice.id, 'overdue');
          }
          await this.sendPaymentReminder(fresh, lastInvoice, daysSinceIssued);
          results.reminded++;
        } else {
          // < 7 days — just skip, wait longer
          results.skipped++;
        }
      } catch (err) {
        results.errors.push({ abonementId: abon.id, message: err?.message });
        logger.error('RenewalCron:renewal_failed', {
          abonementId: abon.id,
          message: err?.message,
          stack: err?.stack,
        });
      }
    }

    logger.info('RenewalCron:active_phase_complete', results);
  }

  // ──────────────────────────────────────────────
  //  PHASE 2 — Reactivate paused subscriptions that have been paid
  // ──────────────────────────────────────────────

  async processPausedReactivations(now) {
    let pausedAbonements;
    try {
      pausedAbonements = await this.repo.listPausedAutoRenew();
    } catch (err) {
      logger.error('RenewalCron:fetch_paused_error', { message: err?.message });
      return;
    }

    if (!pausedAbonements.length) {
      logger.info('RenewalCron:no_paused_to_reactivate');
      return;
    }

    logger.info('RenewalCron:found_paused', { count: pausedAbonements.length });
    const dayOfMonth = now.getDate();
    const results = { reactivated: 0, deferred: 0, skipped: 0 };

    for (const abon of pausedAbonements) {
      try {
        // Gift-abo still without user → skip
        if (!abon.user_id) {
          results.skipped++;
          continue;
        }

        const lastInvoice = await this.getLatestInvoice(abon.id);
        if (!lastInvoice || lastInvoice.status !== 'paid') {
          results.skipped++;
          continue;
        }

        // Invoice is paid — check if before 11th of current month
        if (dayOfMonth <= 10) {
          // Before the 11th → reactivate for this cycle
          const nextBilling = this.addInterval(
            now,
            abon.billing_interval || 'month',
            abon.interval_count || 1,
          );
          await this.reactivateAbonement(abon, nextBilling);
          results.reactivated++;
        } else {
          // On or after the 11th → defer to next month
          const nextMonth = new Date(now.getFullYear(), now.getMonth() + 1, 1);
          const nextBilling = this.addInterval(
            nextMonth,
            abon.billing_interval || 'month',
            abon.interval_count || 1,
          );
          await this.reactivateAbonement(abon, nextBilling);
          results.deferred++;
        }
      } catch (err) {
        logger.error('RenewalCron:reactivation_failed', {
          abonementId: abon.id,
          message: err?.message,
        });
      }
    }

    logger.info('RenewalCron:paused_phase_complete', results);
  }

  // ──────────────────────────────────────────────
  //  Helpers
  // ──────────────────────────────────────────────

  async renewSingleAbonement(abon) {
    const abonId = abon.id;
    const oldNextBilling = new Date(abon.next_billing_at);
    const newNextBilling = this.addInterval(
      oldNextBilling,
      abon.billing_interval || 'month',
      abon.interval_count || 1,
    );

    logger.info('RenewalCron:renewing', {
      abonementId: abonId,
      oldNextBilling: oldNextBilling.toISOString(),
      newNextBilling: newNextBilling.toISOString(),
    });

    // Update billing date + history
    const renewed = await this.repo.transitionBilling(abonId, newNextBilling, {
      event_type: 'renewed',
      actor_user_id: null,
      details: {
        pack_group: abon.pack_group,
        trigger: 'auto_renewal_cron',
        previous_next_billing_at: oldNextBilling.toISOString(),
      },
    });

    // Issue new invoice
    let invoice = null;
    try {
      const lang = abon.language || abon.lang || 'de';
      invoice = await this.invoiceService.issueForAbonement(
        renewed,
        oldNextBilling,
        newNextBilling,
        { actorUserId: null, lang },
      );

      logger.info('RenewalCron:invoice_issued', {
        abonementId: abonId,
        invoiceId: invoice?.id,
        invoiceNumber: invoice?.invoice_number,
      });

      await this.repo.appendHistory(abonId, 'invoice_issued', null, {
        pack_group: renewed.pack_group,
        invoiceId: invoice.id,
        trigger: 'auto_renewal_cron',
      }, new Date());
    } catch (invoiceErr) {
      logger.error('RenewalCron:invoice_error', {
        abonementId: abonId,
        message: invoiceErr?.message,
      });
    }

    // Send renewal confirmation email
    try {
      const recipientEmail = abon.email || invoice?.buyer_email;
      if (recipientEmail) {
        const lang = abon.language || abon.lang || 'de';
        const customerName = [abon.first_name, abon.last_name].filter(Boolean).join(' ') || recipientEmail;

        await MailService.sendRenewalEmail({
          email: recipientEmail,
          customerName,
          invoiceNumber: invoice?.invoice_number || '-',
          totalGross: invoice?.total_gross
            ? `${Number(invoice.total_gross).toFixed(2)} ${invoice.currency || abon.currency || 'EUR'}`
            : '-',
          nextBillingDate: newNextBilling.toISOString().slice(0, 10),
          lang,
        });
      }
    } catch (mailErr) {
      logger.error('RenewalCron:renewal_email_error', {
        abonementId: abonId,
        message: mailErr?.message,
      });
    }

    return { abonementId: abonId, invoiceId: invoice?.id || null };
  }

  async pauseAbonement(abon, reason) {
    logger.info('RenewalCron:pausing', { abonementId: abon.id, reason });

    await this.repo.transitionStatus(abon.id, 'paused', {
      event_type: 'paused',
      actor_user_id: null,
      details: {
        pack_group: abon.pack_group,
        trigger: 'auto_renewal_cron',
        reason,
      },
    });

    // Notify the subscriber (or purchaser)
    try {
      const recipientEmail = abon.email;
      if (recipientEmail) {
        const lang = abon.language || abon.lang || 'de';
        const customerName = [abon.first_name, abon.last_name].filter(Boolean).join(' ') || recipientEmail;
        await MailService.sendSubscriptionPausedEmail({ email: recipientEmail, customerName, reason, lang });
      }
    } catch (mailErr) {
      logger.error('RenewalCron:pause_email_error', {
        abonementId: abon.id,
        message: mailErr?.message,
      });
    }
  }

  async reactivateAbonement(abon, nextBillingAt) {
    logger.info('RenewalCron:reactivating', {
      abonementId: abon.id,
      nextBillingAt: nextBillingAt.toISOString(),
    });

    // Set status back to active + update billing date
    await this.repo.transitionStatus(abon.id, 'active', {
      event_type: 'resumed',
      actor_user_id: null,
      details: {
        pack_group: abon.pack_group,
        trigger: 'auto_renewal_cron',
        reason: 'payment_received',
        next_billing_at: nextBillingAt.toISOString(),
      },
    });

    await this.repo.updateBilling(abon.id, nextBillingAt);
  }

  async sendPaymentReminder(abon, invoice, daysSinceIssued) {
    const recipientEmail = abon.email || invoice.buyer_email;
    if (!recipientEmail) return;

    const lang = abon.language || abon.lang || 'de';
    const customerName = [abon.first_name, abon.last_name].filter(Boolean).join(' ') || recipientEmail;

    try {
      await MailService.sendPaymentReminderEmail({
        email: recipientEmail,
        customerName,
        invoiceNumber: invoice.invoice_number || '-',
        totalGross: invoice.total_gross
          ? `${Number(invoice.total_gross).toFixed(2)} ${invoice.currency || abon.currency || 'EUR'}`
          : '-',
        daysOverdue: daysSinceIssued,
        lang,
      });

      logger.info('RenewalCron:payment_reminder_sent', {
        abonementId: abon.id,
        invoiceId: invoice.id,
        daysOverdue: daysSinceIssued,
      });
    } catch (mailErr) {
      logger.error('RenewalCron:payment_reminder_error', {
        abonementId: abon.id,
        message: mailErr?.message,
      });
    }
  }

  // ──────────────────────────────────────────────
  //  Main entry point
  // ──────────────────────────────────────────────

  async processDueRenewals() {
    const now = new Date();
    logger.info('RenewalCron:tick_start', { now: now.toISOString() });

    await this.processActiveRenewals(now);
    await this.processPausedReactivations(now);

    logger.info('RenewalCron:tick_end', { now: now.toISOString() });
  }

  /**
   * Start the cron schedule.
   * Runs every day at 02:00 AM.
   */
  start() {
    cron.schedule('0 2 * * *', async () => {
      try {
        await this.processDueRenewals();
      } catch (err) {
        logger.error('RenewalCron:unhandled_error', {
          message: err?.message,
          stack: err?.stack,
        });
      }
    });

    logger.info('RenewalCron:scheduled', { schedule: '0 2 * * * (daily at 02:00)' });
  }
}

module.exports = RenewalCronService;