export default class Base32 {
  static charmap: any =     null;
  static alphabet: string = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567';

  static encode(data: any[]): string {
    let encoded: string = '';
    let shift: number = 3;
    let carry: number = 0;
    let symbol: number;
    let byte: number;

    for (let i = 0; i < data.length; i++) {
      byte = data[i];
      symbol = carry | (byte >> shift);
      encoded += Base32.alphabet[symbol & 0x1f];

      if (shift > 5) {
        shift -= 5;
        symbol = byte >> shift;
        encoded += Base32.alphabet[symbol & 0x1f];
      }

      shift = 5 - shift;
      carry = byte << shift;
      shift = 8 - shift;
    }

    if (shift !== 3) encoded += Base32.alphabet[carry & 0x1f];
    return encoded;
  }

  static decode(data: string): Buffer | void {
    Base32._charmap();
    let shift: number = 8;
    let carry: number = 0;
    const chunks: number[] = [];

    for (const char of data.toUpperCase().split('')) {
      if (char === '') return;
      const symbol: number = Base32.charmap[char] & 0xff;

      shift -= 5;
      if (shift > 0) carry |= symbol << shift;
      else if (shift < 0) {
        chunks.push(carry | (symbol >> -shift));
        shift += 8;
        carry = (symbol << shift) & 0xff;
      } else {
        chunks.push(carry | symbol);
        shift = 8;
        carry = 0;
      }
    }

    if (shift !== 8 && carry !== 0) chunks.push(carry);
    return Buffer.from(chunks);
  }

  private static _charmap() {
    if (!Base32.charmap) {
      const mappings: object = { 0: 14, 1: 8 };
      const alphabet: string[] = Base32.alphabet.split('');
      for (const i in alphabet) if (!(alphabet[i] in mappings)) mappings[alphabet[i]] = i;
      Base32.charmap = mappings;
    }
  }
}