/*
 * 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.
var lookup = new Uint8Array(256);
for (var i = 0; i < chars.length; i++) {
    lookup[chars.charCodeAt(i)] = i;
}

export const encode = function(arraybuffer) {
    var bytes = new Uint8Array(arraybuffer),
    i, len = bytes.length, base64 = "";

    for (i = 0; i < len; i+=3) {
        base64 += chars[bytes[i] >> 2];
        base64 += chars[((bytes[i] & 3) << 4) | (bytes[i + 1] >> 4)];
        base64 += chars[((bytes[i + 1] & 15) << 2) | (bytes[i + 2] >> 6)];
        base64 += chars[bytes[i + 2] & 63];
    }

    if ((len % 3) === 2) {
        base64 = base64.substring(0, base64.length - 1);
    } else if (len % 3 === 1) {
        base64 = base64.substring(0, base64.length - 2);
    }

    return base64;
};

export const decode = function(base64) {
    var bufferLength = base64.length * 0.75,
    len = base64.length, i, p = 0,
    encoded1, encoded2, encoded3, encoded4;

    var arraybuffer = new ArrayBuffer(bufferLength),
    bytes = new Uint8Array(arraybuffer);

    for (i = 0; i < len; i+=4) {
        encoded1 = lookup[base64.charCodeAt(i)];
        encoded2 = lookup[base64.charCodeAt(i+1)];
        encoded3 = lookup[base64.charCodeAt(i+2)];
        encoded4 = lookup[base64.charCodeAt(i+3)];

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

    return arraybuffer;
};