/* eslint-disable no-useless-escape */
/* eslint-disable no-nested-ternary */
/* eslint-disable no-mixed-operators */
/* eslint-disable no-plusplus */
/* eslint-disable no-cond-assign */
/**
 * This file is based on https://github.com/MaxArt2501/base64-js/
 * MIT licensed: https://github.com/MaxArt2501/base64-js/blob/master/LICENSE
 */

// base64 character set, plus padding character (=)
const b64 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
// Regular expression to check formal correctness of base64 encoded strings
const b64re = /^(?:[A-Za-z\d+\/]{4})*?(?:[A-Za-z\d+\/]{2}(?:==)?|[A-Za-z\d+\/]{3}=?)?$/;

declare function atob(string: string): string;
declare function btoa(string: string): string;

export const btoa_polyfill = typeof btoa === 'function' ? btoa : function btoa(string: string) {
  string = String(string);
  let bitmap; let a; let b; let c;
  let result = ''; let i = 0;
  const rest = string.length % 3; // To determine the final padding

  for (; i < string.length;) {
    if ((a = string.charCodeAt(i++)) > 255
        || (b = string.charCodeAt(i++)) > 255
        || (c = string.charCodeAt(i++)) > 255) throw new TypeError("Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range.");

    bitmap = (a << 16) | (b << 8) | c;
    result += b64.charAt(bitmap >> 18 & 63) + b64.charAt(bitmap >> 12 & 63)
            + b64.charAt(bitmap >> 6 & 63) + b64.charAt(bitmap & 63);
  }

  // If there's need of padding, replace the last 'A's with equal signs
  return rest ? result.slice(0, rest - 3) + '==='.substring(rest) : result;
};

export const atob_polyfill = typeof atob === 'function' ? atob : function atob(string: string) {
  // atob can work with strings with whitespaces, even inside the encoded part,
  // but only \t, \n, \f, \r and ' ', which can be stripped.
  string = String(string).replace(/[\t\n\f\r ]+/g, '');
  if (!b64re.test(string)) throw new TypeError("Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded.");

  // Adding the padding if missing, for semplicity
  string += '=='.slice(2 - (string.length & 3));
  let bitmap; let result = ''; let r1; let r2; let
    i = 0;
  for (; i < string.length;) {
    bitmap = b64.indexOf(string.charAt(i++)) << 18 | b64.indexOf(string.charAt(i++)) << 12
                    | (r1 = b64.indexOf(string.charAt(i++))) << 6 | (r2 = b64.indexOf(string.charAt(i++)));

    result += r1 === 64 ? String.fromCharCode(bitmap >> 16 & 255)
      : r2 === 64 ? String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255)
        : String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255, bitmap & 255);
  }
  return result;
};