text: const crypto = require('crypto');
  const base64url = require('base64url');
  const MerkleTools = require('merkle-tools');
  
  const merkleTools = new MerkleTools({
    hashType: 'sha256', // optional, defaults to 'sha256'
  });
  
  module.exports = ({ receipt, merkleRoot, operation }) => {
    const hash = crypto
      .createHash('sha256')
      .update(operation)
      .digest();
  
    const proof = JSON.parse(base64url.decode(receipt));
    return merkleTools.validateProof(proof, hash, merkleRoot);
  };
  