Bitcoin Cash Covenant with Spedn

covenant.ts

import { BITBOX } from "bitbox-sdk";
import { SigHash, Spedn, TxBuilder } from "spedn";

async function main() {
  // BITBOX boilerplace
  const bitbox = new BITBOX();
  const mnemonic = "draw parade crater busy book swim soldier tragic exit feel top civil";
  const wallet = bitbox.HDNode.fromSeed(bitbox.Mnemonic.toSeed(mnemonic));
  const alice = bitbox.HDNode.derivePath(wallet, "m/44'/145'/0'/0/0");

  // Compile a contract that checks that the provided preimage matches the tx preimage.
  const compiler = new Spedn();
  const Covenant = await compiler.compileCode(`
    contract Covenant(Ripemd160 alice) {
      challenge spend(Sig sig, PubKey pubKey, bin preimage) {
          verify hash160(pubKey) == alice;
          verify checkSig(sig, pubKey);
          verify checkDataSig(toDataSig(sig), sha256(preimage), pubKey);
          // here go the actual covenant conditions...
      }
    }
  `);
  compiler.dispose();

  //  Instantiate the contract for Alice's key.
  const covenant = new Covenant({
    alice: alice.getIdentifier()
  });

  // Find Alice's coins
  const coins = await covenant.findCoins("mainnet");

  // Spend all Alice's coint to a new address (500000 sat) and the change back to the covenant.
  const txid = await new TxBuilder("mainnet")
    .from(coins, (input, context) =>
      input.spend({
        sig: context.sign(alice.keyPair, SigHash.SIGHASH_ALL),
        pubKey: alice.getPublicKeyBuffer(),
        preimage: context.preimage(SigHash.SIGHASH_ALL)
      })
    )
    .to("bitcoincash:qrc2jhalczuka8q3dvk0g8mnkqx79wxp9gvvqvg7qt", 500000)
    .to(covenant.getAddress("mainnet"))
    .broadcast();

  console.log(txid);
}

main();

package.json

{
  "name": "bitbox-example",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "private": true,
  "dependencies": {
    "bitbox-sdk": "^8.5.1",
    "spedn": "^0.1.2"
  }
}