// adapted from https://gist.github.com/Juszczak/63e6d9e01decc850de03
/**
* base64 encoding/decoding
*/
export namespace base64 {
  const PADCHAR: string = '=';
  const ALPHA: string = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

  /**
  * Decode base64-encoded string and return a Uint8Array.
  * @param s Base64 encoded string.
  */
  export function decode (s: string): Uint8Array {
    let i: u32, b10: u32;
    let pads = 0,
    imax = s.length as u32;

    if (imax == 0) {
      return new Uint8Array(0);
    }

    if (s.charAt(imax - 1) == PADCHAR) {
      pads = 1;
      if (s.charAt(imax - 2) == PADCHAR) {
        pads = 2;
      }
      imax -= 4;
    }

    let main_chunk = imax % 4 == 0 ? imax / 4 * 3 : (imax / 4 + 1) * 3;
    let pad_size = pads > 0 ? 3 - pads : 0;
    let size = main_chunk + pad_size;

    let x = new Uint8Array(size),
    index = 0;

    for (i = 0; i < imax; i += 4) {
      b10 = (getByte64(s, i) << 18) | (getByte64(s, i + 1) << 12) | (getByte64(s, i + 2) << 6) | getByte64(s, i + 3);
      x[index++] = b10 >> 16;
      x[index++] = (b10 >> 8) & 255;
      x[index++] = b10 & 255;
    }
    switch (pads) {
      case 1:
      b10 = (getByte64(s, i) << 18) | (getByte64(s, i + 1) << 12) | (getByte64(s, i + 2) << 6);
      x[index++] = b10 >> 16;
      x[index++] = (b10 >> 8) & 255;
      break;
      case 2:
      b10 = (getByte64(s, i) << 18) | (getByte64(s, i + 1) << 12);
      x[index++] = b10 >> 16;
      break;
    }

    return x;
  }

  /**
  * Encode Uint8Array in base64.
  * @param bytes Byte array of type Uint8Array.
  */
  export function encode(bytes: Uint8Array): string {
    let i: i32, b10: u32;
    let x = new Array<string>(),
    imax = bytes.length - bytes.length % 3;

    if (bytes.length == 0) {
      return "";
    }

    for (i = 0; i < imax; i += 3) {
      b10 = ((bytes[i] as u32) << 16) | ((bytes[i+1] as u32) << 8) | bytes[i+2] as u32;
      x.push(ALPHA.charAt(b10 >> 18));
      x.push(ALPHA.charAt((b10 >> 12) & 63));
      x.push(ALPHA.charAt((b10 >> 6) & 63));
      x.push(ALPHA.charAt(b10 & 63));
    }

    switch (bytes.length - imax) {
      case 1:
      b10 = (bytes[i] as u32) << 16;
      x.push(ALPHA.charAt(b10 >> 18));
      x.push(ALPHA.charAt((b10 >> 12) & 63));
      x.push(PADCHAR);
      x.push(PADCHAR);
      break;
      case 2:
      b10 = ((bytes[i] as u32) << 16) | ((bytes[i+1] as u32) << 8);
      x.push(ALPHA.charAt(b10 >> 18));
      x.push(ALPHA.charAt((b10 >> 12) & 63));
      x.push(ALPHA.charAt((b10 >> 6) & 63));
      x.push(PADCHAR);
      break;
    }

    return x.join('');
  }

  function getByte64(s: string, i: u32): u32 {
    return ALPHA.indexOf(s.charAt(i));
  }
}