Chapter 06 · Tabs

Flags are the payment policy

An invoice is not just an amount. It is a set of permissions — any amount, any destination, conversion, routing — encoded as flags.

FIGURE 6.1 · VerusPayInvoiceDetails, as wired by the form.

Signed or not — a real choice

Invoice is the only tab where signed is optional. An unsigned invoice is a payment request anyone can read; a signed one proves which identity asked. The route branches on it and only calls requireString(payload.signingId) when signing.

Building the details

destination = acceptsAnyDestination ? undefined :
  new TransferDestination({
    type: destinationType === "id" ? DEST_ID : DEST_PKH,
    destinationBytes: fromBase58Check(address).hash
  });

amount = acceptsAnyAmount ? undefined : new BN(amountString, 10);   // must be > 0

details.setFlags({
  acceptsAnyAmount, acceptsAnyDestination, acceptsConversion,
  expires, acceptsNonVerusSystems, isTestnet, isPreconvert, isTagged
});

setFlags() is where most invoice bugs live: the field is set from the flags, not the other way round. If you pass amount but forget acceptsAnyAmount: false (or the reverse), the serialised invoice will disagree with the form.

Flag meanings worth internalising

Flag	What it permits
`acceptsAnyAmount`	Payer chooses the amount — no amount field serialised
`acceptsAnyDestination`	Payer chooses where to send — no destination serialised
`acceptsConversion`	Payment may be converted through another currency, bounded by slippage
`acceptsNonVerusSystems`	Payment may route through listed PBaaS systems
`expires`	`expiryHeight` is enforced
`isPreconvert`	Pre-conversion semantics
`isTagged`	An invoice tag identifies the payment

Two flags are effectively permissions: "any amount" and "any destination". A wallet UI that shows them is telling the user they are handing over choice, not just convenience.

Reading the code

src/routes/requests/invoice.ts
  buildInvoiceRequest()   # destination, amount, flags, accepted systems
  generateInvoiceQr()     # signed branch + QR