Add XLS-61d: 0061 XLS-61d: CrossCurrency NFTokenAcceptOffer

XLS-0061-cross-currency-nftokenacceptof/README.md

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+<pre>
+    XLS: XLS-61d
+    Title: 0061 XLS-61d: CrossCurrency NFTokenAcceptOffer
+    Author: tequ (tequdev)
+    Created: 2024-02-26
+    Status: Stagnant
+    Category: Amendment
+</pre>
+
+# Abstract
+
+XRPL's NFToken functionality, currently implemented as XLS-20, only allows the use of a single currency for transactions.
+
+This proposal allows cross-currency NFToken transactions using multiple currencies.
+
+Creators and marketplaces will be able to sell NFTs without being tied to a currency, and users will be able to buy NFTs without being tied to a currency.
+
+This will increase revenue opportunities for creators and marketplaces and create significant tokenomics.
+
+# Specification
+
+## `NFTokenAcceptOffer` Transaction
+
+Add the following field:
+
+| Field Name | Required? |      JSON Type       | Internal Type |
+| ---------- | :-------: | :------------------: | :-----------: |
+| `Amount`   |           | `object` or `string` |   `AMOUNT`    |
+
+### `Amount` Field
+
+When accepting an NFTokenOffer with the tfSellOffer flag set, the `Amount` field acts like the `SendMax` field, and when accepting an NFTokenOffer without tfSellOffer set, the `DeliverMin` field acts like the `Amount` field.
+
+It doesn't have to match the `Amount` of the Offeror specified in `NFTokenSellOffer` or `NFTokenBuyOffer`.
+
+In broker mode, the `Amount` field must not be present.
+
+### `NFTokenBrokerFee` Field
+
+The existing `NFTokenBrokerFee` field can be any currency amount.
+
+### CrossCurrency Accept
+
+The currency of `Amount` can be different from the currency of the BuyOffer / SellOffer.
+The currency of `NFTokenBrokerFee` can be different from the currency of the BuyOffer / SellOffer.
+
+Buyer must specify a sufficient amount that can be transferred to Seller, nftoken issuer(nftoken transfer fee), broker(broker fee), token issuer(token transfer fee).
+
+NFToken transfer fees are sent in the buyer's currency.
+NFToken with the tfOnlyXRP flag set will be paid in XRP.
+
+If there was insufficient amount or liquidity, the transaction will fail.
+
+## `NFTokenCreateOffer` Transaction
+
+No change in fields.
+
+Change to only check if the NFToken issuer has a trustline for the currenfy of `Amount` field when creating a BuyOffer for an NFToken with royalties.
+
+## The `NFTokenPage` Object
+
+No changes.
+
+## The `NFTokenOffer` Object
+
+No changes.
+
+# Cases
+
+## `Amount` Field not specified in `NFTokenAcceptOffer` Transaction
+
+According to XLS-20 specifications. Except for NFTs with royalties, issuer's trust line [must be checked](https://github.com/XRPLF/rippled/issues/4925).
+
+## `Amount` Field specified and equal to `Amount` in `NFTokenOffer`
+
+DEX liquidity will not be used and existing transfer processing will be used.
+If the quantity in the `Amount` cannot be sent to the seller, the transaction will fail.
+
+## `Amount` Field specified and not same as `Amount` in `NFTokenOffer`
+
+DEX liquidity will be used and other transfer processing (used in Payment/CheckCash) will be used.
+If the quantity in `Amount` cannot be sent to the seller, the transaction will fail.
+
+If the buyer's `Amount` can send more than the specified amount of the seller's `Amount`, the amount will be sent up to the maximum amount of the buyer's `Amount`.
+
+## `NFTokenBrokerFee` Field specified
+
+Convert and send the amount from the buyer's `Amount` to satisfy the `NFTokenBrokerFee`.
+
+## Accept NFToken with TransferFee
+
+Paid in the same currency as the buyer's `Amount`.
+If no trustline is set, the transaction will fail.
+
+## Accept NFToken with TransferFee, `tfOnlyXRP`, `Amount` Field specified, `NFTokenBrokerFee` Field specified
+
+Up to 3 times currency will be converted and up to 3 times token transfer fees will be charged.
+
+1. From Buyer to Broker (`NFTokenBrokerFee` currency, Buyer's `Amount` currency fee)
+1. From Buyer to Issuer (`TransferFee` currency or XRP, Buyer's `Amount` currency fee)
+1. From Buyer to Seller (`Amount` currency, Buyer's `Amount` currency fee)
+
+# Concern
+
+## Transaction load
+
+Processing load is expected to increase due to up to three cross-currency remittance processes (flows) within a single transaction.
+
+However, instead of merely being concerned about the increased load of a single transaction, it should be noted that in the current, similar processing would have to be spread over two or more transactions, NFTokenAccept and CrossCurrency Payment.
+
+## Royalty for NFToken with tfOnlyFlag
+
+The royalty is sent by converting a portion of the buyer's Amount (TransferFee %) into XRP, so if there is not enough liquidity, the royalty might be almost zero.
+
+# Note
+
+The process used by Payment is used for currency conversion and remittance processing.
+Path cannot be specified, and only direct AAA->BBB pairs are used at this time.
+
+If auto-bridge is enabled by default by XLS-60d, the auto-bridge path will also be used for the currency conversion process in this proposal.