Aggregates & Domain Events

1// Order Aggregate — racine d'agrégat
2class Order extends Entity<string> {
3  private _items: OrderItem[] = [];        // Entités internes à l'agrégat
4  private _status: OrderStatus = 'draft';
5  private _total: Money;
6  private _events: DomainEvent[] = [];
7
8  // ❌ On n'expose PAS les items directement
9  // Toutes les mutations passent par des méthodes de l'agrégat
10
11  addItem(productId: string, name: string, price: Money, qty: number): void {
12    if (this._status !== 'draft') {
13      throw new DomainError('Impossible de modifier une commande confirmée');
14    }
15    const existing = this._items.find((i) => i.productId === productId);
16    if (existing) {
17      existing.increaseQuantity(qty); // mutation interne autorisée
18    } else {
19      this._items.push(OrderItem.create({ productId, name, price, qty }));
20    }
21    this._total = this.calculateTotal();
22  }
23
24  confirm(): void {
25    if (this._items.length === 0) {
26      throw new DomainError('Impossible de confirmer une commande vide');
27    }
28    this._status = 'confirmed';
29    // Domain Event — d'autres parties du système peuvent réagir
30    this._events.push(
31      new OrderConfirmed({
32        orderId: this._id,
33        total: this._total,
34        confirmedAt: new Date(),
35      })
36    );
37  }
38
39  private calculateTotal(): Money {
40    return this._items.reduce(
41      (acc, item) => acc.add(item.subtotal),
42      Money.of(0, 'XOF')
43    );
44  }
45}
46
47// Domain Event — immutable, passé simple
48class OrderConfirmed implements DomainEvent {
49  readonly name = 'OrderConfirmed';
50  readonly occurredAt: Date;
51  readonly orderId: string;
52  readonly total: Money;
53
54  constructor(props: { orderId: string; total: Money; confirmedAt: Date }) {
55    this.orderId = props.orderId;
56    this.total = props.total;
57    this.occurredAt = props.confirmedAt;
58  }
59}