Bangun Account aggregate dengan event sourcing.

createAccount(events), return aggregate object. events adalah array event awal (bisa kosong). State direkonstruksi dengan apply semua event.

Event types:

• { type: "Deposited", amount }: tambah ke balance
• { type: "Withdrew", amount }: kurangi balance

Aggregate punya method:

• balance(): return balance saat ini
• deposit(amount): jika amount <= 0 throw. Push event { type: "Deposited", amount } dan apply.
• withdraw(amount): jika amount > balance throw "Insufficient funds". Push event dan apply.
• getEvents(): return array semua event (termasuk yang awal).
• replay(events): static reset, rebuild state dari events baru. Disediakan lewat rebuild(events) top-level function yang return aggregate baru.

Hint

• Event sourcing: state = hasil replay semua event. createAccount(events): iterasi events, apply tiap event ke state awal.
• Apply event: "deposit" tambah balance, "withdraw" kurangi (tapi validasi: throw "Insufficient funds" kalau > balance).
• Validasi input event: deposit amount harus > 0 (throw "invalid deposit"). Balance akhir = hasil replay; events count = events.length.