swc/crates/swc_bundler/tests/.cache/deno/3a3f8c7742754003bcc33fe80a730f2687e2953d.ts

// Loaded from https://deno.land/x/segno@v1.1.0/lib/validations/isEAN.ts


/**
 * The most commonly used EAN standard is
 * the thirteen-digit EAN-13, while the
 * less commonly used 8-digit EAN-8 barcode was
 * introduced for use on small packages.
 * EAN consists of:
 * GS1 prefix, manufacturer code, product code and check digit
 * Reference: https://en.wikipedia.org/wiki/International_Article_Number
 */

// @ts-ignore allowing typedoc to build
import { assertString } from '../helpers/assertString.ts';

/**
 * Define EAN Lenghts; 8 for EAN-8; 13 for EAN-13
 * and Regular Expression for valid EANs (EAN-8, EAN-13),
 * with exact numberic matching of 8 or 13 digits [0-9]
 */
/**
 * @ignore
 */
const LENGTH_EAN_8 = 8;
/**
 * @ignore
 */
const validEanRegex = /^(\d{8}|\d{13})$/;

/**
 * Get position weight given:
 * EAN length and digit index/position
 *
 * @param {number} length
 * @param {number} index
 * @return {number}
 */
/**
 * @ignore
 */
const getPositionWeightThroughLengthAndIndex = (
  length: number,
  index: number
) => {
  if (length === LENGTH_EAN_8) {
    return index % 2 === 0 ? 3 : 1;
  }

  return index % 2 === 0 ? 1 : 3;
};

/**
 * Calculate EAN Check Digit
 * Reference: https://en.wikipedia.org/wiki/International_Article_Number#Calculation_of_checksum_digit
 *
 * @param {string} ean
 * @return {number}
 */
/**
 * @ignore
 */
const calculateCheckDigit = (ean: string) => {
  const checksum = ean
    .slice(0, -1)
    .split('')
    .map(
      (char, index) =>
        Number(char) * getPositionWeightThroughLengthAndIndex(ean.length, index)
    )
    .reduce((acc, partialSum) => acc + partialSum, 0);

  const remainder = 10 - (checksum % 10);

  return remainder < 10 ? remainder : 0;
};

/**
 * Check if string is valid EAN:
 * Matches EAN-8/EAN-13 regex
 * Has valid check digit.
 *
 * @param {string} str
 * @return {boolean}
 */
export const isEAN = (str: string) => {
  assertString(str);
  const actualCheckDigit = Number(str.slice(-1));

  return (
    validEanRegex.test(str) && actualCheckDigit === calculateCheckDigit(str)
  );
};