generate-iso-contract-id-checksum

generate-iso-contract-id-checksum.ts

const P1 = [
  [0, 1, 1, 1],
  [1, 1, 1, 0],
  [1, 0, 0, 1],
  [0, 1, 1, 1],
  [1, 1, 1, 0],
  [1, 0, 0, 1],
  [0, 1, 1, 1],
  [1, 1, 1, 0],
  [1, 0, 0, 1],
  [0, 1, 1, 1],
  [1, 1, 1, 0],
  [1, 0, 0, 1],
  [0, 1, 1, 1],
  [1, 1, 1, 0],
  [1, 0, 0, 1],
];
const P2 = [
  [0, 1, 1, 2],
  [1, 2, 2, 2],
  [2, 2, 2, 0],
  [2, 0, 0, 2],
  [0, 2, 2, 1],
  [2, 1, 1, 1],
  [1, 1, 1, 0],
  [1, 0, 0, 1],
  [0, 1, 1, 2],
  [1, 2, 2, 2],
  [2, 2, 2, 0],
  [2, 0, 0, 2],
  [0, 2, 2, 1],
  [2, 1, 1, 1],
  [1, 1, 1, 0],
];
const listAlphaNumeric = {
  '0': [0, 0, 0, 0, 0],
  '1': [0, 0, 0, 1, 16],
  '2': [0, 0, 0, 2, 32],
  '3': [0, 0, 1, 0, 4],
  '4': [0, 0, 1, 1, 20],
  '5': [0, 0, 1, 2, 36],
  '6': [0, 0, 2, 0, 8],
  '7': [0, 0, 2, 1, 24],
  '8': [0, 0, 2, 2, 40],
  '9': [0, 1, 0, 0, 2],
  A: [0, 1, 0, 1, 18],
  B: [0, 1, 0, 2, 34],
  C: [0, 1, 1, 0, 6],
  D: [0, 1, 1, 1, 22],
  E: [0, 1, 1, 2, 38],
  F: [0, 1, 2, 0, 10],
  G: [0, 1, 2, 1, 26],
  H: [0, 1, 2, 2, 42],
  I: [1, 0, 0, 0, 1],
  J: [1, 0, 0, 1, 17],
  K: [1, 0, 0, 2, 33],
  L: [1, 0, 1, 0, 5],
  M: [1, 0, 1, 1, 21],
  N: [1, 0, 1, 2, 37],
  O: [1, 0, 2, 0, 9],
  P: [1, 0, 2, 1, 25],
  Q: [1, 0, 2, 2, 41],
  R: [1, 1, 0, 0, 3],
  S: [1, 1, 0, 1, 19],
  T: [1, 1, 0, 2, 35],
  U: [1, 1, 1, 0, 7],
  V: [1, 1, 1, 1, 23],
  W: [1, 1, 1, 2, 39],
  X: [1, 1, 2, 0, 11],
  Y: [1, 1, 2, 1, 27],
  Z: [1, 1, 2, 2, 43],
};

/**
 * Generates the checksum of an ISO contract id
 * @param contractId
 */
export const generateISOContractIdChecksum = (contractId: string): string => {
  contractId = contractId.replace(/[-\*]?/g, '').toUpperCase();
  // validate contract id
  const pattern =
    /^([A-Za-z]{2})([A-Za-z0-9]{3})([A-Za-z0-9]{9})([A-Za-z0-9])?(?=$)/g;
  if (!pattern.test(contractId)) {
    throw new Error(
      `Contract ID ${contractId} does not fit in validation pattern`,
    );
  }
  if (contractId.length > 14) {
    throw new Error(
      `Checksum is already included in contract id ${contractId}`,
    );
  }
  const calc = [];
  // Digisto Matrix
  let counter = 0;
  for (let letter = 0; letter < 14; letter++) {
    for (let i = 0; i < 4; i++) {
      calc[counter] = listAlphaNumeric[contractId[letter]][i];
      counter++;
    }
  }
  // Check Equation
  let c1 = 0;
  let c2 = 0;
  let c3 = 0;
  let c4 = 0;
  for (let i = 0; i < 14; i += 1) {
    c1 += calc[i * 4] * P1[i][0] + calc[i * 4 + 1] * P1[i][2];
    c2 += calc[i * 4] * P1[i][1] + calc[i * 4 + 1] * P1[i][3];
    c3 += calc[i * 4 + 2] * P2[i][0] + calc[i * 4 + 3] * P2[i][2];
    c4 += calc[i * 4 + 2] * P2[i][1] + calc[i * 4 + 3] * P2[i][3];
  }
  c1 = c1 % 2;
  c2 = c2 % 2;
  c3 = c3 % 3;
  c4 = c4 % 3;
  const q1 = c1;
  const q2 = c2;
  let r1, r2;
  if (c4 == 0) r1 = 0;
  if (c4 == 1) r1 = 2;
  if (c4 == 2) r1 = 1;
  if (c3 + r1 == 0) r2 = 0;
  if (c3 + r1 == 1) r2 = 2;
  if (c3 + r1 == 2) r2 = 1;
  if (c3 + r1 == 3) r2 = 0;
  if (c3 + r1 == 4) r2 = 2;
  const revDigit = q1 + q2 * 2 + r1 * 4 + r2 * 16;
  // Get Checksum
  let k;
  for (k in listAlphaNumeric) {
    if (listAlphaNumeric.hasOwnProperty(k)) {
      if (revDigit == listAlphaNumeric[k][4]) {
        break;
      }
    }
  }
  return k;
};