libswap - Fastspot Atomic Swap Library

A Typescript handler class to handle and process atomic swaps with Fastspot.

The library does not work only with Fastspot, but it uses the Fastspot API types.

Package

This package can be installed from NPM as

@nimiq/libswap

https://www.npmjs.com/package/@nimiq/libswap

API

import { SwapHandler } from '@nimiq/libswap'

// Setup for swaps from NIM to BTC

// This fulfills the `Swap` type from @nimiq/fastspot-api
const swap = {
    from: {
        asset: 'NIM',
        amount: 1000e5, // 1000 NIM
    },
    to: {
        asset: 'BTC',
        amount: 0.001e8, // 1 mBTC
    },
    hash: '<swap hash (hashRoot) as HEX>',
    contracts: {
        NIM: {
            htlc: {
                address: '<HTLC address>',
                data: '<HTLC creation data as HEX>',
            }
        },
        BTC: {
            htlc: {
                address: '<HTLC address>',
                script: '<HTLC script as HEX>',
            }
        },
        /* For EUR: */
        // EUR: {
        //     htlc: {
        //         address: '<HTLC ID>',
        //     }
        // },
    }
}

/**
 * Initialize a SwapHandler with the swap object, the client for
 * the FROM asset and the client for the TO asset:
 */
const swapHandler = new SwapHandler(swap, nimiqClient, electrumClient)

/****************************************
 ** General process for any swap pair: **
 ****************************************/

/**
 * 1. Wait for swap partner to create their HTLC
 *
 * This method validates the HTLC data against the swap object
 * and resolves when the HTLC is valid.
 *
 * The optional `onUpdate` callback receives the transaction/HTLC object:
 * @type {(tx: Transaction<ToAsset>) => any} onUpdate
 */
await swapHandler.awaitIncoming(onUpdate)

/**
 * 2.A Create our HTLC
 *
 * The optional `onPending` callback receives the transaction object:
 * @type {(tx: Transaction<FromAsset>) => any} onPending
 */
await swapHandler.createOutgoing(serializedFundingTx, onPending)

/**
 * 2.B Alternatively, await HTLC funding from external wallet
 *
 * The optional `onUpdate` callback receives the transaction object:
 * @type {(tx: Transaction<FromAsset>) => any} onUpdate
 */
await swapHandler.awaitOutgoing(onUpdate)

/**
 * 3. Wait for the swap secret to be published on-chain
 */
const secret = await swapHandler.awaitSecret()

/**
 * 4. Settle the incoming HTLC with the swap secret
 *
 * The `serializedSettlementTx` (HEX string) must have a string of 0s (zeros) in place of
 * the swap secret, which will be replaced with the secret automatically.
 */
await swapHandler.settleIncoming(serializedSettlementTx, secret)

/**
 * 5. Await confirmation of settled HTLC
 *
 * This is especially relevant for EUR contracts, as they may take a
 * few minutes to confirm after they were settled.
 *
 * The optional `onUpdate` callback receives the transaction object:
 * @type {(tx: Transaction<ToAsset>) => any} onUpdate
 */
await swapHandler.awaitIncomingConfirmation(onUpdate)

// Done!