const crypto = require('crypto');

// Function to create a hash (MD5)
function createHash(value) {
  return crypto.createHash('sha256').update(value).digest('hex');
}

// Function to make Base64 URL-safe
function base64UrlEncode(value) {
  return Buffer.from(value, 'hex') // Convert hex to buffer
    .toString('base64')            // Base64 encode
    .replace(/\+/g, '-')           // Replace '+' with '-'
    .replace(/\//g, '_')           // Replace '/' with '_'
    .replace(/=+$/, '');           // Remove trailing '='
}

// Function to decode Base64 URL-safe encoding
function base64UrlDecode(value) {
  value = value
    .replace(/-/g, '+')            // Replace '-' with '+'
    .replace(/_/g, '/');           // Replace '_' with '/'

  // Add padding if necessary
  const padLength = (4 - (value.length % 4)) % 4;
  value += '='.repeat(padLength);

  return Buffer.from(value, 'base64').toString('hex'); // Decode Base64 to hex
}

// Function to isolate the three hashes (MD5 hashes are 32 characters long)
function isolateHashes(decodedHash) {
  const hashLength = 64; // Each MD5 hash in hex is 32 characters long
  const hashA = decodedHash.slice(0, hashLength);
  const hashB = decodedHash.slice(hashLength, hashLength * 2);
  const hashC = decodedHash.slice(hashLength * 2, hashLength * 3);
  const extraDataHex = decodedHash.slice(hashLength * 3); // Remaining part as extraData

  return { hashA, hashB, hashC, extraDataHex };
}

var tenant_id = '1-NMVM';
var customerId = '1-NXHTP';
var extraData = {'saved_search_name': createHash('Default Search111')};

// Create unsubscribe hash and combine it with Base64-encoded extraData
var unsubscribeHash = createHash(tenant_id) + createHash(customerId) + createHash('saved_search');
var encodedExtraData = Buffer.from(JSON.stringify(extraData)).toString('hex');
var finalToken = base64UrlEncode(unsubscribeHash + encodedExtraData);

console.log('Final Token:', finalToken);

// Decode the Base64 URL-safe encoded token back to original parts
const decodedHash = base64UrlDecode(finalToken);

// Isolate individual hashes and extraData
const { hashA: isolatedHashA, hashB: isolatedHashB, hashC: isolatedHashC, extraDataHex } = isolateHashes(decodedHash);

// Decode and parse extraData
const decodedExtraData = JSON.parse(Buffer.from(extraDataHex, 'hex').toString('utf8'));

// Output isolated hashes and decoded extraData
console.log('Isolated Hash A:', isolatedHashA);
console.log('Isolated Hash B:', isolatedHashB);
console.log('Isolated Hash C:', isolatedHashC);
console.log('Decoded ExtraData:', decodedExtraData);

// Verify that isolated hashes match the original ones
console.log('Verification:');
console.log('Hash A matches:', isolatedHashA === createHash(tenant_id));
console.log('Hash B matches:', isolatedHashB === createHash(customerId));
console.log('Hash C matches:', isolatedHashC === createHash('saved_search'));