نمط Saga

إنشاء طلب ✓ → حجز مخزون ✓ → دفع ✗
              ← إرجاع المخزون ← إلغاء الطلب

import { InventoryInsufficientError, PaymentFailedError, OrderNotFoundError } from './lib/base_repository';
import { generateIdempotencyKey, IdempotencyRepository } from './lib/base_repository';

// 1. خدمة الطلبات — تنشئ طلباً عبر Repository
class CreateOrderStep {
  constructor(
    private readonly orderRepo: OrderRepositoryProtocol,
    private readonly idemRepo: IdempotencyRepository,
  ) {}

  async execute(data: OrderData): Promise<void> {
    const idemKey = data.idempotencyKey;   // يأتي مع الطلب من العميل، لا يُولَّد هنا
    const existing = await this.idemRepo.findByIdempotencyKey(idemKey);
    if (existing) return; // Idempotency — طلب مكرر

    const order = await this.orderRepo.save({
      id: data.orderId,
      userId: data.userId,
      items: data.items,
      total: data.total,
      status: 'PENDING',
      createdAt: new Date(),
    });

    await this.idemRepo.saveIdempotencyRecord({ key: idemKey, result: order, createdAt: new Date() });
    await eventBus.publish('order.created', { orderId: order.id, ...data });
  }
}

// 2. خدمة المخزون — تحجز المنتجات عبر Repository
class ReserveInventoryStep {
  constructor(private readonly productRepo: ProductRepositoryProtocol) {}

  async handle(event: OrderCreatedEvent): Promise<void> {
    try {
      for (const item of event.items) {
        const product = await this.productRepo.findById(item.productId);
        if (!product || product.stock < item.quantity) {
          throw new InventoryInsufficientError(item.productId, product?.stock ?? 0, item.quantity);
        }
        product.stock -= item.quantity;
        await this.productRepo.save(product);
      }
      await eventBus.publish('inventory.reserved', { orderId: event.orderId });
    } catch (err) {
      await eventBus.publish('inventory.failed', { orderId: event.orderId, reason: (err as Error).message });
    }
  }
}

// 3. خدمة المدفوعات — تخصم المبلغ
class ChargePaymentStep {
  constructor(private readonly paymentRepo: PaymentRepositoryProtocol) {}

  async handle(event: InventoryReservedEvent): Promise<void> {
    try {
      await this.paymentRepo.charge(event.orderId, event.amount);
      await eventBus.publish('payment.completed', { orderId: event.orderId });
    } catch (err) {
      await eventBus.publish('payment.failed', {
        orderId: event.orderId,
        reason: (err as Error).message,
      });
    }
  }
}

class CompensationHandler {
  constructor(
    private readonly orderRepo: OrderRepositoryProtocol,
    private readonly productRepo: ProductRepositoryProtocol,
    private readonly paymentRepo: PaymentRepositoryProtocol,
  ) {}

  // إرجاع المخزون إذا فشلت المدفوعات
  async onPaymentFailed(event: PaymentFailedEvent): Promise<void> {
    const order = await this.orderRepo.findById(event.orderId);
    if (!order) throw new OrderNotFoundError(event.orderId);

    for (const item of order.items) {
      const product = await this.productRepo.findById(item.productId);
      if (product) {
        product.stock += item.quantity;
        await this.productRepo.save(product);
      }
    }

    // Refund عبر Repository
    await this.paymentRepo.refund(event.orderId);
    order.status = 'CANCELLED';
    await this.orderRepo.save(order);
  }
}

import {
  SagaRepositoryProtocol, SagaEntity, SagaExecutionError,
  IdempotencyRepository, generateIdempotencyKey,
} from './lib/base_repository';

class OrderSagaOrchestrator {
  constructor(
    private readonly sagaRepo: SagaRepositoryProtocol,
    private readonly orderRepo: OrderRepositoryProtocol,
    private readonly productRepo: ProductRepositoryProtocol,
    private readonly paymentRepo: PaymentRepositoryProtocol,
    private readonly idemRepo: IdempotencyRepository,
  ) {}

  async execute(orderData: OrderData): Promise<SagaResult> {
    // Idempotency على مستوى الـ Saga بأكمله — المفتاح من الطلب نفسه
    const sagaIdemKey = orderData.idempotencyKey;
    const existingSaga = await this.idemRepo.findByIdempotencyKey(sagaIdemKey);
    if (existingSaga) return existingSaga.result as SagaResult;

    const saga = await this.sagaRepo.save({
      id: crypto.randomUUID(),
      state: 'STARTED',
      data: orderData as unknown as Record<string, unknown>,
      steps: [],
      createdAt: new Date(),
      updatedAt: new Date(),
    });

    try {
      // الخطوة 1: إنشاء طلب — مع Idempotency Key
      const step1Key = generateIdempotencyKey();
      const order = await this.orderRepo.save({
        id: saga.id,
        userId: orderData.userId,
        items: orderData.items,
        total: orderData.total,
        status: 'PENDING',
        createdAt: new Date(),
      });
      await this.recordStep(saga.id, 'ORDER_CREATED', step1Key);

      // الخطوة 2: حجز المخزون — مع Idempotency Key
      const step2Key = generateIdempotencyKey();
      for (const item of orderData.items) {
        const product = await this.productRepo.findById(item.productId);
        if (!product || product.stock < item.quantity) {
          throw new SagaExecutionError(saga.id, 'RESERVE_INVENTORY',
            `Insufficient stock for ${item.productId}`);
        }
        product.stock -= item.quantity;
        await this.productRepo.save(product);
      }
      await this.recordStep(saga.id, 'INVENTORY_RESERVED', step2Key);

      // الخطوة 3: المدفوعات — مع Idempotency Key
      const step3Key = generateIdempotencyKey();
      await this.paymentRepo.charge(saga.id, orderData.total, step3Key);
      await this.recordStep(saga.id, 'PAYMENT_COMPLETED', step3Key);

      await this.updateSaga(saga.id, 'COMPLETED');
      const result = { success: true, orderId: saga.id };

      await this.idemRepo.saveIdempotencyRecord({
        key: sagaIdemKey, result, createdAt: new Date(),
      });
      return result;

    } catch (error) {
      await this.compensate(saga.id);
      return { success: false, error: (error as Error).message };
    }
  }

  private async recordStep(sagaId: string, name: string, idemKey: string): Promise<void> {
    const saga = await this.sagaRepo.findById(sagaId);
    if (!saga) return;
    saga.steps.push({ name, status: 'COMPLETED', idempotencyKey: idemKey });
    saga.updatedAt = new Date();
    await this.sagaRepo.save(saga);
  }

  private async compensate(sagaId: string): Promise<void> {
    const saga = await this.sagaRepo.findById(sagaId);
    if (!saga) return;

    for (const step of [...saga.steps].reverse()) {
      switch (step.name) {
        case 'PAYMENT_COMPLETED':
          await this.paymentRepo.refund(saga.id);
          break;
        case 'INVENTORY_RESERVED':
          for (const item of (saga.data as OrderData).items) {
            const product = await this.productRepo.findById(item.productId);
            if (product) {
              product.stock += item.quantity;
              await this.productRepo.save(product);
            }
          }
          break;
        case 'ORDER_CREATED': {
          const order = await this.orderRepo.findById(saga.id);
          if (order) {
            order.status = 'CANCELLED';
            await this.orderRepo.save(order);
          }
          break;
        }
      }
      step.status = 'COMPENSATED';
    }

    saga.state = 'COMPENSATED';
    saga.updatedAt = new Date();
    await this.sagaRepo.save(saga);
  }

  private async updateSaga(sagaId: string, state: string): Promise<void> {
    const saga = await this.sagaRepo.findById(sagaId);
    if (!saga) return;
    saga.state = state;
    saga.updatedAt = new Date();
    await this.sagaRepo.save(saga);
  }
}