/* The decoder is the original MPL one from Mozilla. The encoder is a faster MIT one
   from https://github.com/mitschabaude/fast-base64 */

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

// From: http://hg.mozilla.org/mozilla-central/raw-file/ec10630b1a54/js/src/devtools/jint/sunspider/string-base64.js

import * as Log from './util/logging.js';

const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
const encodeLookup = Object.fromEntries(Array.from(alphabet).map((a, i) => [i, a.charCodeAt(0)]));
const decoder = new TextDecoder();

export default {
    /* Convert data (an array of integers) to a Base64 string. */
    base64Pad: '=',

    encode(bytes) {
        let m = bytes.length;
        let k = m % 3;
        let n = Math.floor(m / 3) * 4 + (k && k + 1);
        let N = Math.ceil(m / 3) * 4;
        let encoded = new Uint8Array(N);

        for (let i = 0, j = 0; j < m; i += 4, j += 3) {
            let y = (bytes[j] << 16) + (bytes[j + 1] << 8) + (bytes[j + 2] | 0);
            encoded[i] = encodeLookup[y >> 18];
            encoded[i + 1] = encodeLookup[(y >> 12) & 0x3f];
            encoded[i + 2] = encodeLookup[(y >> 6) & 0x3f];
            encoded[i + 3] = encodeLookup[y & 0x3f];
        }

        let base64 = decoder.decode(new Uint8Array(encoded.buffer, 0, n));
        if (k === 1) base64 += '==';
        if (k === 2) base64 += '=';
        return base64;
    },

    /* Convert Base64 data to a string */
    /* eslint-disable comma-spacing */
    toBinaryTable: [
        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,62, -1,-1,-1,63,
        52,53,54,55, 56,57,58,59, 60,61,-1,-1, -1, 0,-1,-1,
        -1, 0, 1, 2,  3, 4, 5, 6,  7, 8, 9,10, 11,12,13,14,
        15,16,17,18, 19,20,21,22, 23,24,25,-1, -1,-1,-1,-1,
        -1,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
        41,42,43,44, 45,46,47,48, 49,50,51,-1, -1,-1,-1,-1
    ],
    /* eslint-enable comma-spacing */

    decode(data, offset = 0) {
        let dataLength = data.indexOf('=') - offset;
        if (dataLength < 0) { dataLength = data.length - offset; }

        /* Every four characters is 3 resulting numbers */
        const resultLength = (dataLength >> 2) * 3 + Math.floor((dataLength % 4) / 1.5);
        const result = new Array(resultLength);

        // Convert one by one.

        let leftbits = 0; // number of bits decoded, but yet to be appended
        let leftdata = 0; // bits decoded, but yet to be appended
        for (let idx = 0, i = offset; i < data.length; i++) {
            const c = this.toBinaryTable[data.charCodeAt(i) & 0x7f];
            const padding = (data.charAt(i) === this.base64Pad);
            // Skip illegal characters and whitespace
            if (c === -1) {
                Log.Error("Illegal character code " + data.charCodeAt(i) + " at position " + i);
                continue;
            }

            // Collect data into leftdata, update bitcount
            leftdata = (leftdata << 6) | c;
            leftbits += 6;

            // If we have 8 or more bits, append 8 bits to the result
            if (leftbits >= 8) {
                leftbits -= 8;
                // Append if not padding.
                if (!padding) {
                    result[idx++] = (leftdata >> leftbits) & 0xff;
                }
                leftdata &= (1 << leftbits) - 1;
            }
        }

        // If there are any bits left, the base64 string was corrupted
        if (leftbits) {
            const err = new Error('Corrupted base64 string');
            err.name = 'Base64-Error';
            throw err;
        }

        return result;
    }
}; /* End of Base64 namespace */
