createDescriptors.ts

import { bip32 } from '@bitgo/wasm-utxo';

import { createNamedDescriptorWithSignature, NamedDescriptor } from '../NamedDescriptor.js';
import { getDescriptorFromBuilder, DescriptorBuilder } from '../builder/index.js';

export type DescriptorFromKeys = (
  userKey: bip32.BIP32Interface,
  cosigners: bip32.BIP32Interface[]
) => NamedDescriptor[];

/**
 * Create a pair of external and internal descriptors for a 2-of-3 multisig wallet.
 * Overrides the path of the builder to use the external and internal derivation paths (0/* and 1/*).
 *
 * @param builder
 * @param userKey
 */
function createExternalInternalPair(
  builder: DescriptorBuilder,
  userKey: bip32.BIP32Interface
): [NamedDescriptor, NamedDescriptor] {
  if (userKey.isNeutered()) {
    throw new Error('User key must be private');
  }
  const external = createNamedDescriptorWithSignature(
    builder.name + '/external',
    getDescriptorFromBuilder({ ...builder, path: '0/*' }),
    userKey
  );
  const internal = createNamedDescriptorWithSignature(
    builder.name + '/internal',
    getDescriptorFromBuilder({ ...builder, path: '1/*' }),
    userKey
  );
  if (external.value === internal.value) {
    throw new Error('External and internal descriptors must be different. Make to use the path in descriptor.');
  }
  return [external, internal];
}

/**
 * Create a pair of external and internal descriptors for a 2-of-3 multisig wallet.
 *
 * @param userKey
 * @param cosigners
 * @constructor
 */
export const DefaultWsh2Of3: DescriptorFromKeys = (userKey, cosigners) =>
  createExternalInternalPair({ name: 'Wsh2Of3', keys: [userKey.neutered(), ...cosigners], path: '' }, userKey);