Handling Edge Cases

1) Underpaid (received < requested)

What happens: Customer sends less than amount.

Recommended rules (pick one):

• A. Top-up flow (recommended): Mark pending_underpaid; display/paylink to send the difference. Auto-confirm when total ≥ requested.
• B. Partial credit: Mark partial_paid; create a balance/credit for the shortfall and let customer continue with a scaled service (e.g., lower deposit).

2) Overpaid (received > requested)

What happens: Customer sends more than amount.

Recommended rules (order of preference):

• A. Auto-credit difference (recommended): Confirm invoice, credit {received - amount} to customer account.

3) No payment / Timeout / Expired

What happens: Session created, no valid on-chain payment within window.

Recommended rules:

• Mark expired.

4) Late payment after expiry

What happens: Funds arrive after you marked the session expired.

Recommended rules:

• Auto-reconcile: Detect late arrival → create a new transaction record linked to the expired invoice; notify merchant via callback as late_confirmed.

5) Multiple payments to the same invoice

What happens: Customer sends multiple transfers for one invoice.

Recommended rules:

• Aggregate totals within the active window.
• If total ≥ requested → confirm; if > requested → follow Overpaid rules.
• After confirm, additional funds become extra deposit/credit.