Missing ReputationChanged event on successful sales creates inconsistency in tracking reputation

Description

• In Cyfrin_Hub.vy the sell_to_customer function updates the company's reputation in two places:

  • When a sale succeeds and reputation < 100, the code increases reputation but currently does not emit ReputationChanged.

  • When a sale fails due to insufficient inventory, the function decreases reputation and emits ReputationChanged(new_reputation=...).

  This asymmetry means successful reputation changes are not recorded in events, reducing on-chain observability and making it harder for off-chain indexers, UIs, and auditors to track reputation history.

Risk

Likelihood: High

• Occurs under normal, expected circumstances

Impact: Low

• Events are the canonical way to track state changes on-chain. Not emitting an event on a successful reputation increase makes the protocol harder to monitor and debug.

Proof of Concept

This is an low impact issue (missing event), so PoC is simply observing transaction traces where a successful sale increases reputation but no ReputationChanged event is emitted. Example steps:

1. Ensure reputation is below 100 (e.g., set to 98 in test setup).

2. Call sell_to_customer via the CustomerEngine with requested small enough to succeed.

3. Observe the transaction receipt: the Sold event should be present, the reputation state variable should have increased, but no ReputationChanged event is emitted.

Recommended Mitigation

Add an event as shown