p2tr_tapscript.ts

import * as bitcoin from 'bitcoinjs-lib';
import { randomBytes } from 'crypto';
import { ECPairFactory } from 'ecpair';
import * as curve from 'tiny-secp256k1';
import {
    bech32toScriptPubKey,
    createTaprootOutput,
    decodeRawTransaction,
    fundOutputScript,
    getnewaddress,
    negateIfOddPubkey,
    OP_CHECKSIGADD,
    send,
    tapBranch,
    tapLeaf,
} from './btc';

const ECPair = ECPairFactory(curve);

const network = bitcoin.networks.testnet;
const hashtype = bitcoin.Transaction.SIGHASH_DEFAULT;

const internalKey = ECPair.fromPrivateKey(negateIfOddPubkey(randomBytes(32)), { network });

const ecpair2 = ECPair.makeRandom({ network });

// build taptree
const leaf1script = bitcoin.script.compile([
    ecpair2.publicKey.subarray(1, 33),
    bitcoin.opcodes.OP_CHECKSIG,
    ecpair2.publicKey.subarray(1, 33),
    OP_CHECKSIGADD,
    bitcoin.opcodes.OP_2,
    bitcoin.opcodes.OP_EQUAL,
]);

const leaf1 = tapLeaf(leaf1script);

const leaf2 = Buffer.alloc(32); // all zeros

const branch = tapBranch(leaf1, leaf2);

const tr = createTaprootOutput(internalKey.publicKey, branch);

const fee_sat = 162;
const input_sat = 1000;

console.log(tr.address);

fundOutputScript(tr.scriptPubKey, input_sat).then(async outpoint => {
    const tx = new bitcoin.Transaction();

    tx.version = 2;
    tx.addInput(Buffer.from(outpoint.txid, 'hex').reverse(), outpoint.vout);

    tx.addOutput(bech32toScriptPubKey(await getnewaddress()), input_sat - fee_sat);

    const sighash = tx.hashForWitnessV1(
        0, // which input
        [tr.scriptPubKey], // All previous outputs of all inputs
        [input_sat], // All previous values of all inputs
        hashtype, // sighash flag, DEFAULT is schnorr-only (DEFAULT == ALL)
        leaf1,
    );

    const signature = ecpair2.signSchnorr(sighash);
    const pub = internalKey.publicKey;
    pub.writeUint8(0xc0 | tr.parity);
    const ctrl = Buffer.concat([pub, leaf2]);
    tx.setWitness(0, [signature, signature, leaf1script, ctrl]);

    const decoded = await decodeRawTransaction(tx.toHex());
    console.log(JSON.stringify(decoded, null, 2));
    console.log(tx.toHex());

    await send(tx.toHex());
    console.log('sendrawtransaction successful');
});