flags.js

/*  *************************************************************************************
 *   copyright: Copyright (c) 2021 Lowell D. Thomas, all rights reserved
 *     license: BSD-2-Clause (https://opensource.org/licenses/BSD-2-Clause)
 *   ********************************************************************************* */

module.exports = function exportFlags(obj, flags) {
  'use strict;';

  const errorName = 'apg-exp: constructor: flags: ';
  let error = null;
  const readonly = {
    writable: false,
    enumerable: false,
    configurable: true,
  };
  /* defaults - all flags default to false */
  /* set to true only if they appear in the input flags string */
  obj.flags = '';
  obj.global = false;
  obj.sticky = false;
  obj.unicode = false;
  obj.debug = false;
  const TRUE = true;
  while (TRUE) {
    /* validation */
    if (typeof flags === 'undefined' || flags === null) {
      break;
    }
    if (typeof flags !== 'string') {
      error = `${errorName}Invalid flags supplied to constructor: must be null, undefined or string: '${typeof flags}'`;
      break;
    }
    if (flags === '') {
      break;
    }
    /* set the flags */
    const f = flags.toLowerCase().split('');
    for (let i = 0; i < f.length; i += 1) {
      switch (f[i]) {
        case 'd':
          obj.debug = true;
          break;
        case 'g':
          obj.global = true;
          break;
        case 'u':
          obj.unicode = true;
          break;
        case 'y':
          obj.sticky = true;
          break;
        default:
          error = `${errorName}Invalid flags supplied to constructor: '${flags}'`;
          return error;
      }
    }
    /* alphabetize the existing flags */
    if (obj.debug) {
      obj.flags += 'd';
    }
    if (obj.global) {
      obj.flags += 'g';
    }
    if (obj.unicode) {
      obj.flags += 'u';
    }
    if (obj.sticky) {
      obj.flags += 'y';
    }
    break;
  }
  /* make flag properties read-only */
  Object.defineProperty(obj, 'flags', readonly);
  Object.defineProperty(obj, 'global', readonly);
  Object.defineProperty(obj, 'debug', readonly);
  Object.defineProperty(obj, 'unicode', readonly);
  Object.defineProperty(obj, 'sticky', readonly);
  return error;
};