Shop

The shop is the one place money flows the other way: from your wallet to the treasury. You pay with an ordinary Nimiq transaction carrying a memo, and the treasury's chain watcher decides whether that payment counts.

What is for sale

The price is the server's, not a number your phone sends. A client that asks to pay less is refused when the payment is inspected, not when the order is made.

How a purchase works

1. POST /api/shop/orders with the item id opens a pending order. You get back the treasury address, the price in luna and in NIM, a memo of the shape vettai:shop: followed by the first eight characters of the order id, and an expiry.
2. Your wallet sends a basic transaction with that memo attached. The payment goes straight to the treasury address. Vettai is not in the middle of it.
3. The treasury's watcher scans the treasury address for incoming transactions, matches the memo against pending orders, and decides.
4. Once the order is paid, the world sweeps paid orders every five seconds, applies the gear to the live room, pushes a gear event to your socket and only then marks the order as announced. If you are offline you get the gear at your next join, from your player row.

An order has half an hour to be paid before it is closed.

What the watcher checks

• The memo. Anything arriving at the treasury without the vettai:shop: prefix is refused and written down. The cursor moves past it, because it will never become an order.
• The amount. A payment below the order's price is refused and recorded as short.
• The sender. The address that paid must be the address that opened the order, compared in a normalised form so a space or a lowercase letter never decides it.
• The clock. Expiry is judged against the block the payment was mined in, not the moment the watcher got round to reading it. A payment that reached the chain inside the half hour is honoured even if the treasury was restarting while it landed.
• Doing it twice. The memo is unique, the transaction hash is unique, and the grant is a conditional update inside the same transaction as the gear write. Reading the same block twice is a no-op, not a second grant.

Nothing is thrown away

Every incoming transaction the watcher inspects is written to a received_payments row with its outcome: paid, short, expired, unknown_memo, sender_mismatch or already_paid, together with the sender, the value, the block, the block time and the order it named. The transaction hash is the primary key and a repeat insert keeps the first decision.

Money that arrived is money that arrived. A refusal is something a person can settle by hand, because the row is still there.

The local prove-it run, which is a testnet tool, pays a real 0.6 NIM shop order and, in the same pass, sends 0.01 NIM from the wrong wallet against a different order and shows it left pending. See check 10.