Gossip: Zaps

Gossip is a desktop nostr client. This post is about the code that lets users send lightning zaps to each other (NIP-57).

Gossip implemented Zaps initially on 20th of June, 2023.

Gossip maintains a state of where zapping is at, one of: None, CheckingLnurl, SeekingAmount, LoadingInvoice, and ReadyToPay.

When you click the zap lightning bolt icon, Gossip moves to the CheckingLnurl state while it looks up the LN URL of the user.

If this is successful, it moves to the SeekingAmount state and presents amount options to the user.

Once a user chooses an amount, it moves to the LoadingInvoice state where it interacts with the lightning node and receives and checks an invoice.

Once that is complete, it moves to the ReadyToPay state, where it presents the invoice as a QR code for the user to scan with their phone. There is also a copy button so they can pay it from their desktop computer too.

Gossip also loads zap receipt events and associates them with the event that was zapped, tallying a zap total on that event. Gossip is unfortunately not validating these receipts very well currently, so fake zap receipts can cause an incorrect total to show. This remains an open issue.

Another open issue is the implementation of NIP-46 Nostr Connect and NIP-47 Wallet Connect.