A historical BlockCypher transaction-signing client

require('dotenv').config();

import { ECPairFactory } from 'ecpair';
import * as ecc from 'tiny-secp256k1';
import * as bitcoin from 'bitcoinjs-lib';

const axios = require('axios').default;
const ECPair = ECPairFactory(ecc);
bitcoin.initEccLib(ecc);

const env = {
  ['development']: {
    network: bitcoin.networks.testnet,
    blockCypherApi: 'https://api.blockcypher.com/v1/btc/test3',
    explorer: 'https://live.blockcypher.com/btc-testnet/tx',
  },
  ['production']: {
    network: bitcoin.networks.bitcoin,
    blockCypherApi: 'https://api.blockcypher.com/v1/btc/main',
    explorer: 'https://live.blockcypher.com/btc/tx',
  },
};
const { network, blockCypherApi, explorer } = env[process.env.NODE_ENV || 'development'];

/**
 * Prepare wallet from a Wallet Import Format (WIF) private key
 * Each network -> Each address has own private key.
 */
export const initKeyPair = (WIF = process.env.WALLET_PRIVATE_KEY) => {
  if (!WIF) throw new Error('WALLET_PRIVATE_KEY is not set');
  // Decode WIF private key
  const keyPair = ECPair.fromWIF(WIF, network);
  return {
    keyPair,
    publicKey: keyPair.publicKey,
  };
};

// Native Segwit P2WPKH, bech32 address type with 42 chars. Start with tb1q or bc1q
// Ex: tb1q2fzh9f7ss8eu56fnv2zhr56a0wd3g64xp7d4xk
export const getNativeSegwitP2WPKH = (publicKeyBuffer: Buffer) => {
  return bitcoin.payments.p2wpkh({
    pubkey: publicKeyBuffer,
    network: network,
  });
};

// P2PKH type with 34 chars
// Ex: mo1xu79z1354YicBa5EXwMh7HrCAfRdPSW
export const getLegacyP2PKH = (publicKeyBuffer: Buffer) => {
  return bitcoin.payments.p2pkh({ pubkey: publicKeyBuffer, network: network });
};

/**
 * Send BTC with BlockCypher.
 * Support 2 address types: Native Segwit P2WPKH, Legacy P2PKH
 * https://www.blockcypher.com/dev/bitcoin/data/samples/create-tx.html
 * https://gist.github.com/matthieu/b07c5ba27bc99188a15f
 * https://www.blockcypher.com/dev/bitcoin/#restful-resources
 * Usage:
 * ** For Legacy P2PKH address type
 * await sendBitcoinWithBlockCypher(true, 'tb1qpcvt26nnu4s75p2ur5nflvwcqq3p38yh2ny438', 1000);
 * Res: From (Legacy P2PKH) mo1xu79z1354YicBa5EXwMh7HrCAfRdPSW to tb1qpcvt26nnu4s75p2ur5nflvwcqq3p38yh2ny438 amount 0.00001 BTC
 * Transaction hash: https://live.blockcypher.com/btc-testnet/tx/dd6f9246e9e8d62739cdc2708680da9f010956692bd5a0792036183371b8bd70
 *
 * ** For Native Segwit P2WPKH address type
 * await sendBitcoinWithBlockCypher(false, 'tb1qpcvt26nnu4s75p2ur5nflvwcqq3p38yh2ny438', 1000);
 * From (Native Segwit P2WPKH) tb1q2fzh9f7ss8eu56fnv2zhr56a0wd3g64xp7d4xk to tb1qpcvt26nnu4s75p2ur5nflvwcqq3p38yh2ny438 amount 0.00001 BTC
 * Transaction hash: https://live.blockcypher.com/btc-testnet/tx/742baa3da4e1b9968755e4be43745f3e5039b8be373dc512485b4be12154ace9
 */
export const sendBitcoinWithBlockCypher = async (useLegacyP2PKH: boolean, to: string, amount = 1000) => {
  const { keyPair, publicKey } = initKeyPair();
  let senderPayment = getLegacyP2PKH(publicKey);
  let senderType = 'Legacy P2PKH';
  if (!useLegacyP2PKH) {
    senderPayment = getNativeSegwitP2WPKH(publicKey);
    senderType = 'Native Segwit P2WPKH';
  }
  const sender = senderPayment.address;
  console.log(`From (${senderType}) ${sender} to ${to} amount ${(amount / 1e8).toFixed(8)} BTC `);

  // Init config
  const txInOut = {
    inputs: [{ addresses: [sender] }],
    outputs: [{ addresses: [to], value: amount }],
  };

  try {
    // Generate tx input, output for signing
    const txInfo = (await axios.post(`${blockCypherApi}/txs/new`, txInOut)).data;

    // Sign tx
    txInfo.pubkeys = [];
    txInfo.signatures = txInfo.tosign.map((tosign: string) => {
      // Public key in Hex format with 66 chars
      txInfo.pubkeys.push(publicKey.toString('hex'));
      const signature = keyPair.sign(Buffer.from(tosign, 'hex'));
      // Legacy P2PKH Signature: SIGHASH_NONE with 142 chars
      let finalSig = bitcoin.script.signature
        .encode(signature, bitcoin.Transaction.SIGHASH_NONE)
        .toString('hex')
        .slice(0, -2);
      if (!useLegacyP2PKH) {
        // Native Segwit P2WPKH Signature: SIGHASH_ALL with 144 chars end with '01'
        finalSig = bitcoin.script.signature.encode(signature, bitcoin.Transaction.SIGHASH_ALL).toString('hex');
      }
      return finalSig;
    });

    try {
      const res = await axios.post(`${blockCypherApi}/txs/send`, txInfo);
      if (res.data) {
        console.log('Transaction hash:', `${explorer}/${res.data.tx.hash}`);
      }
    } catch (e) {
      console.error('Broadcast tx error:', e.message, e.response?.data.errors);
    }
  } catch (e) {
    console.error('Create tx error:', e.message, e.response?.data.errors);
  }
};