/*
   * Base64URL-ArrayBuffer
   * https://github.com/herrjemand/Base64URL-ArrayBuffer
   *
   * Copyright (c) 2017 Yuriy Ackermann <ackermann.yuriy@gmail.com>
   * Copyright (c) 2012 Niklas von Hertzen
   * Licensed under the MIT license.
   *
   */
const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_';

// Use a lookup table to find the index.
const lookup = new Uint8Array(256);
for (let i = 0; i < chars.length; i++) {
    lookup[chars.charCodeAt(i)] = i;
}

export default class Base64 {
    static encode(arraybuffer: ArrayBuffer) {
        const bytes = new Uint8Array(arraybuffer), len = bytes.length;
        let i: number, base64url = '';

        for (i = 0; i < len; i += 3) {
            base64url += chars[bytes[i] >> 2];
            base64url += chars[((bytes[i] & 3) << 4) | (bytes[i + 1] >> 4)];
            base64url += chars[((bytes[i + 1] & 15) << 2) | (bytes[i + 2] >> 6)];
            base64url += chars[bytes[i + 2] & 63];
        }

        if ((len % 3) === 2) {
            base64url = base64url.substring(0, base64url.length - 1);
        } else if (len % 3 === 1) {
            base64url = base64url.substring(0, base64url.length - 2);
        }

        return base64url;
    }

    static decode(base64string: string): ArrayBuffer {
        const bufferLength = base64string.length * 0.75, len = base64string.length;
        let i, p = 0, encoded1, encoded2, encoded3, encoded4;

        const bytes = new Uint8Array(bufferLength);

        for (i = 0; i < len; i += 4) {
            encoded1 = lookup[base64string.charCodeAt(i)];
            encoded2 = lookup[base64string.charCodeAt(i + 1)];
            encoded3 = lookup[base64string.charCodeAt(i + 2)];
            encoded4 = lookup[base64string.charCodeAt(i + 3)];

            bytes[p++] = (encoded1 << 2) | (encoded2 >> 4);
            bytes[p++] = ((encoded2 & 15) << 4) | (encoded3 >> 2);
            bytes[p++] = ((encoded3 & 3) << 6) | (encoded4 & 63);
        }

        return bytes.buffer
    }
}