/**
 * @module uid
 *
 * @description
 * Client side implementation of the DHIS2 code (uid) generator.
 * ({@link https://github.com/dhis2/dhis2-core/blob/ad2d5dea959aff3146d8fe5796cf0b75eb6ee5d8/dhis-2/dhis-api/src/main/java/org/hisp/dhis/common/CodeGenerator.java|CodeGenerator.java})
 *
 * This module is used to generate and validate DHIS2 uids. A valid DHIS2 uid is a 11 character string which starts with a letter from the ISO basic Latin alphabet.
 */

const abc = 'abcdefghijklmnopqrstuvwxyz';
const letters = abc.concat(abc.toUpperCase());

const ALLOWED_CHARS = `0123456789${letters}`;

const NUMBER_OF_CODEPOINTS = ALLOWED_CHARS.length;
const CODESIZE = 11;

const CODE_PATTERN = /^[a-zA-Z]{1}[a-zA-Z0-9]{10}$/;

function randomWithMax(max) {
  return Math.floor(Math.random() * max);
}
export function generateUid() {
  // First char should be a letter
  let randomChars = letters.charAt(randomWithMax(letters.length));

  for (let i = 1; i < CODESIZE; i += 1) {
    randomChars += ALLOWED_CHARS.charAt(randomWithMax(NUMBER_OF_CODEPOINTS));
  }

  // return new String( randomChars );
  return randomChars;
}

export function isValidUid(code) {
  if (code == null) {
    // eslint-disable-line eqeqeq
    return false;
  }

  return CODE_PATTERN.test(code);
}