// @flow
/* eslint-disable */

const CHARS =
  'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

export default {
  /**
   * window.btoa
   */
  btoa(input: string = ''): string {
    let map;
    let i = 0;
    let block = 0;
    let output = '';

    // eslint-disable-next-line
    for (
      block = 0, i = 0, map = CHARS;
      input.charAt(i | 0) || ((map = '='), i % 1);
      output += map.charAt(63 & (block >> (8 - (i % 1) * 8)))
    ) {
      const charCode = input.charCodeAt((i += 3 / 4));

      if (charCode > 0xff) {
        throw new Error(
          "'RNFirebase.utils.btoa' failed: The string to be encoded contains characters outside of the Latin1 range."
        );
      }

      block = (block << 8) | charCode;
    }

    return output;
  },

  /**
   * window.atob
   */
  atob(input: string = ''): string {
    let i = 0;
    let bc = 0;
    let bs = 0;
    let buffer;
    let output = '';

    const str = input.replace(/=+$/, '');

    if (str.length % 4 === 1) {
      throw new Error(
        "'RNFirebase.utils.atob' failed: The string to be decoded is not correctly encoded."
      );
    }

    // eslint-disable-next-line
    for (
      bc = 0, bs = 0, i = 0;
      (buffer = str.charAt(i++));
      ~buffer && ((bs = bc % 4 ? bs * 64 + buffer : buffer), bc++ % 4)
        ? (output += String.fromCharCode(255 & (bs >> ((-2 * bc) & 6))))
        : 0
    ) {
      buffer = CHARS.indexOf(buffer);
    }

    return output;
  },
};