Python Saga Compensating Steps Mock

from datetime import datetime


def make_payment(user_id, amount):
    print(f"[{datetime.now():%H:%M:%S}] Payment of ${amount} processed for user {user_id}")
    return {"step": "payment", "status": "ok", "details": f"${amount} charged"}


def deduct_inventory(order_id, items):
    print(f"[{datetime.now():%H:%M:%S}] Inventory deducted for order {order_id}: {items}")
    return {"step": "inventory", "status": "ok", "details": f"{len(items)} items reserved"}


def notify_user(user_id, order_id):
    print(f"[{datetime.now():%H:%M:%S}] Notification sent to user {user_id} for order {order_id}")
    return {"step": "notify", "status": "ok", "details": f"Order {order_id} confirmed"}


def compensate_payment(transaction_id):
    print(f"[{datetime.now():%H:%M:%S}] COMPENSATION: Refund issued for transaction {transaction_id}")
    return "refunded"


def compensate_inventory(order_id, items):
    print(f"[{datetime.now():%H:%M:%S}] COMPENSATION: Inventory restored for order {order_id}: {items}")
    return "restored"


def compensate_notify(user_id, order_id):
    print(f"[{datetime.now():%H:%M:%S}] COMPENSATION: Cancel notification for order {order_id}")
    return "cancelled"


def run_saga(user_id, order_id, items, amount, fail_at="notify"):
    steps = [
        ("payment", make_payment, lambda: compensate_payment(transaction_id)),
        ("inventory", deduct_inventory, lambda: compensate_inventory(order_id, items)),
        ("notify", notify_user, lambda: compensate_notify(user_id, order_id)),
    ]
    # Simulate a transaction ID for compensation demo
    global transaction_id
    transaction_id = f"TXN-{order_id}"

    executed = []
    for name, forward, compensate in steps:
        if name == fail_at:
            print(f"[{datetime.now():%H:%M:%S}] FAILURE at step '{name}' — simulating outage")
            raise RuntimeError(f"{name} step failed")
        result = forward(*(user_id, amount) if name == "payment" else
                          (order_id, items) if name == "inventory" else
                          (user_id, order_id))
        executed.append((name, result, compensate))

    print("Saga completed — all steps succeeded. No compensation needed.")
    return True


if __name__ == "__main__":
    try:
        run_saga(user_id=42, order_id=1001, items=["laptop", "mouse"], amount=1299.99, fail_at="inventory")
    except RuntimeError as e:
        print(f"Saga aborted: {e}")
    finally:
        print("--- Compensation sequence finished ---")