Merkel Proof

const CryptoJS = require('crypto-js');

// Create an array of data items
const data = ['data1', 'data2', 'data3', 'data4'];

// Function to generate Merkle tree
function generateMerkleTree(data) {
  if (data.length === 0) return [];

  if (data.length === 1) {
    return [CryptoJS.SHA256(data[0]).toString()];
  }

  const newData = [];
  for (let i = 0; i < data.length; i += 2) {
    const left = CryptoJS.SHA256(data[i]).toString();
    const right = (i + 1 < data.length) ? CryptoJS.SHA256(data[i + 1]).toString() : left;
    newData.push(CryptoJS.SHA256(left + right).toString());
  }

  return generateMerkleTree(newData);
}

// Generate the Merkle tree
const merkleTree = generateMerkleTree(data);

// Function to generate Merkle proof for a specific data item
function generateMerkleProof(dataItem, merkleTree) {
  const proof = [];
  let index = data.indexOf(dataItem);
  if (index === -1) {
    throw new Error('Data item not found in the Merkle tree');
  }

  for (let i = 0; i < merkleTree.length; i++) {
    const isRightNode = index % 2 === 0;
    const siblingIndex = isRightNode ? index + 1 : index - 1;

    if (siblingIndex < merkleTree.length) {
      proof.push({
        data: merkleTree[siblingIndex],
        isLeftNode: !isRightNode
      });
    }

    index = Math.floor(index / 2);
  }

  return proof;
}

// Generate the Merkle proof for 'data2'
const proof = generateMerkleProof('data2', merkleTree);

// Print the proof
console.log(proof);