index.js

const express = require('express')
const bcoin = require('bcoin')
const cors = require('cors')
const tbtcv2bitcoin = require("@keep-network/tbtc-v2.ts/dist/src/bitcoin")
const tbtcv2electrum = require("@keep-network/tbtc-v2.ts/dist/src/electrum")

bcoin.set("testnet")

const app = express()
app.use(cors())

const privateKeyWif = "cRJvyxtoggjAm9A94cB86hZ7Y62z2ei5VNJHLksFi2xdnz1GJ6xt"
const port = Number(process.env.PORT || "8080")
const electrumUrl = process.env.ELECTRUM_URL || "wss://electrumx-server.test.tbtc.network:8443"
const bitcoinClient = tbtcv2electrum.Client.fromUrl(electrumUrl)

app.get('/get-balance', async (req, res) => {
    const keyRing = tbtcv2bitcoin.createKeyRing(privateKeyWif)
    const address = keyRing.getAddress("string")

    const utxos = await bitcoinClient.findAllUnspentTransactionOutputs(
        address
    )

    let balance = 0

    for (let i = 0; i < utxos.length; i++) {
        balance += utxos[i].value.toNumber()
    }

    res.json({
        balance,
        address
    })
})

app.get('/send-transaction/:receiver/:amount', async (req, res) => {
    const keyRing = tbtcv2bitcoin.createKeyRing(privateKeyWif)
    const sender = keyRing.getAddress("string")

    const receiver = req.params.receiver
    const amount = Number(req.params.amount)

    const utxos = await bitcoinClient.findAllUnspentTransactionOutputs(
        sender
    )

    let inputSum = 0
    const utxosWithRaw= []
    for (const utxo of utxos) {
        if (inputSum > amount) {
            break
        }

        const utxoRawTransaction = await bitcoinClient.getRawTransaction(
            utxo.transactionHash
        )

        utxosWithRaw.push({
            ...utxo,
            transactionHex: utxoRawTransaction.transactionHex,
        })

        inputSum += utxo.value.toNumber()
    }

    const inputCoins = utxosWithRaw.map((utxo) =>
        bcoin.Coin.fromTX(
            bcoin.MTX.fromRaw(utxo.transactionHex, "hex"),
            utxo.outputIndex,
            -1
        )
    )

    const transaction = new bcoin.MTX()

    transaction.addOutput({
        script: bcoin.Script.fromAddress(receiver),
        value: amount,
    })

    await transaction.fund(inputCoins, {
        rate: null, // set null explicitly to always use the default value
        changeAddress: sender,
        subtractFee: false, // do not subtract the fee from outputs
    })

    transaction.sign(keyRing)

    const transactionHash = tbtcv2bitcoin.TransactionHash.from(transaction.txid())

    const rawTransaction = {
        transactionHex: transaction.toRaw().toString("hex"),
    }

    await bitcoinClient.broadcast(rawTransaction)

    res.json({
        transactionHash: transactionHash.toString(),
        transactionHex: rawTransaction.transactionHex
    })
})

app.get('*', (_, res) => {
    res.set('Content-Type', 'text/html');
    const content = "<p>Specify exact route</p>"
    res.send(Buffer.from(content));
})

app.listen(port, () => {
    console.log(`Listening on port ${port}`)
})

module.exports = {
    main: app
}