Implementing the given methods in the Wallet class

wallet.js

/*

Mnemoics used -
  quality armor buddy double food laugh tunnel marine lizard west cup what basket lumber walnut link frog rice pigeon abstract nurse volcano curve twice

Generated tpub from iancoleman.io/bip32
  tpubDC93eCC1ySXoBp7AKVv9M9uRi4evZjwgd8LbmYuhXs6NnarvhHsNFPcrzwPqsrUa3y5E5FjnbGE4Li55Y5G96aaPJsb2DKagQC8zgpcRcMQ

Generated Account extended private key from iancoleman.io/bip32
  tprv8fT1Vn9mq4r8JM5NRrFYwkFK938zQQkn3pjpV2sQ7bHyx6cA4u3n4tzzpn9vJysFzvbLW2VSUDgG9bPQhxGKhfxvyc8wVMahKNFVPL8aMqv

*/

const bjl = require('bitcoinjs-lib')
const axios = require('axios').default
const BIP32Factory = require('bip32').default
const coinselect = require('coinselect')

const BLOCKCYPHER_API_ROOT = 'https://api.blockcypher.com'
const feeRate = 55

class Wallet {
  constructor(network) {
    this.network = network
    this.token = 'd6c3025e283c468e8b7c5268cd5b550f'
  }

  // Generate bitcoin testnet addresses using "xpub" for "chain" index = 0 or 1 from range index "start" to "end".
  async address_list(xpub, chain = null, start = 0, end = 1) {
    const ecc = await import('tiny-secp256k1')
    const bip32 = await BIP32Factory(ecc)
    let node = bip32.fromBase58(xpub, this.network)
    const { address } = bjl.payments.p2pkh({
      pubkey: node.derive(start).derive(end).publicKey,
      network: this.network,
    })
    return address
  }

  // Add the "addresses" list on blockcypher database. This list is recognised by the "name" argument.
  async add_wallet(name, addresses) {
    const endpoint = new URL('/v1/btc/test3/wallets', BLOCKCYPHER_API_ROOT)
    endpoint.searchParams.set('token', this.token)
    try {
      const response = await axios.post(endpoint.href, { name, addresses })
      return response.data
    } catch (e) {
      throw new Error(e.message)
    }
  }

  // Add the "addresses" on blockcypher database to an already existing wallet recognised by the "name" argument.
  add_addresses(name, addresses) {
    const endpoint = new URL(
      `/v1/btc/test3/wallets/${name}/addresses`,
      BLOCKCYPHER_API_ROOT,
    )
    endpoint.searchParams.set('token', this.token)
    axios
      .post(endpoint.href)
      .then(({ data }) => {
        console.log('Added', data['addresses'], 'to wallet', name)
      })
      .catch((e) => {
        console.error(e.message)
      })
  }

  // Fetch the "addresses" from blockcypher database of an already existing wallet recognised by the "name" argument.
  async fetch_wallet(name) {
    const endpoint = new URL(
      `/v1/btc/test3/wallets/${name}`,
      BLOCKCYPHER_API_ROOT,
    )
    endpoint.searchParams.set('token', this.token)
    try {
      const response = await axios.get(endpoint.href)
      return response.data.addresses
    } catch (e) {
      throw new Error(e.message)
    }
  }

  // Fetch "UTXOs" using wallet name provided in "receive" and "change" argumnets using blockcypher APIs
  async fetch_utxo(walletName, receive, change) {
    const addresses = await this.fetch_wallet(walletName)

    const utxos = []
    for (let addr of addresses) {
      const endpoint = new URL(
        `/v1/btc/test3/addrs/${addr}`,
        BLOCKCYPHER_API_ROOT,
      )
      endpoint.searchParams.set('unspentOnly', true)
      const response = await axios.get(endpoint.href)
      utxos.push(response.data)
    }
    return utxos
  }

  // Generate unsigned txn using "xpub" to send "amount" to "output_address"
  async generate_unsigned_transaction(
    xpub,
    outputAddress,
    amount,
    config = { index: 1 },
  ) {
    const inputAddress = await this.address_list(xpub, null, config['index'])
    const endpoint = new URL(
      '/v1/btc/test3/txs/new',
      'https://api.blockcypher.com',
    )
    const txPayload = {
      inputs: [{ addresses: [inputAddress] }],
      outputs: [
        {
          addresses: [outputAddress],
          value: amount,
        },
      ],
    }
    const response = await axios.post(endpoint.href, JSON.stringify(txPayload))
    const txResponse = response.data
    let txId = txResponse['tx']['hash']
    const tx = new bjl.Psbt({ network: bjl.networks.testnet })
    const txInput = {
      hash: txId,
      index: txResponse['tx']['inputs'][0]['output_index'],
    }
    const txOutput = {
      address: outputAddress,
      value: amount,
    }

    let { inputs, outputs, fee } = coinselect([txInput], [txOutput], feeRate)

    // Remove below condition to create raw unsigned TX
    if (!inputs || !outputs) throw new Error('Inputs or outputs not generated')

    tx.addInput(txInput)
    tx.addOutput(txOutput)
    return tx.toHex()
  }
}

async function main() {
  const w = new Wallet(bjl.networks.testnet)
  // const tx = await w.generate_unsigned_transaction(
  //   'tpubDC93eCC1ySXoBp7AKVv9M9uRi4evZjwgd8LbmYuhXs6NnarvhHsNFPcrzwPqsrUa3y5E5FjnbGE4Li55Y5G96aaPJsb2DKagQC8zgpcRcMQ',
  //   'n1oAxbBijCqVDYhfmxkW6CzR7abTx6zoud',
  //   50000,
  //   { index: 1 },
  // )
  // console.log('[OK] Created TX', tx)
  const utxo = await w.fetch_utxo('rosh0', 'n1oAxbBijCqVDYhfmxkW6CzR7abTx6zoud')
  console.log(utxo)
}

main().catch((e) => {
  console.error('[FAILED]', e.response ? e.response.data : e.message)
})