import { supported } from './lib';

/**
 *
 * @param value String ISBN
 * @description How to check if the ISBN-10 is valid:
 * 1. Starting from the left, calculate 10 times the first number
 * 2. Starting from the right, sum every digit in even positions
 * 3. Multiply the result by 3
 * 4. Starting from the right, sum every digit in odd positions
 * 5. Add the results of the last two steps together
 * 6. Sum the check digit value with the result
 * 7. Use the modulo function
 * @description How to check if the ISBN-13 is valid:
 * 1. Starting from the left, alternately multiplied by 1 or 3
 * 2. Starting from the right, sum every digit in even positions
 * 3. Sum the results of the last two steps together
 * 7. Use the modulo function
 * @return A boolean of weather the ISBN is valid or not
 */
export const isbn = (value: number | string): boolean | TypeError => {
  if (!supported.includes(typeof value)) return new TypeError(`The ISBN is a of a type not supported`);
  const str_isbn = String(value).replace(/-/g, '');

  const length = str_isbn.length;

  let sum = 0;
  const list = str_isbn.split('');
  const checksum = Number(list[length - 1]);

  if (length === 10) {
    for (let i = length + 1; i >= 1; i--) {
      const number = Number(list[i]);
      sum += number * i;
    }
    return sum % 11 === 0;
  } else if (length === 13) {
    for (let i = 0; i < length - 1; i++) {
      const number = Number(list[i]);
      if (i % 2 !== 0) {
        sum += number * 3;
      } else {
        sum += number * 1;
      }
    }

    return (sum % 10 !== 0 ? 10 : 0) - (sum % 10) === checksum;
  }
  return false;
};