/// SPDX-License-Identifier: GPL-3.0-or-later
/// SPDX-FileCopyrightText: Copyright © 2016-2024 Tony Garnock-Jones <tonyg@leastfixedpoint.com>

import { Bytes, underlying } from '@preserves/core';
import * as node_crypto from 'crypto';
import { makeHMAC, BLAKE2s } from 'salty-crypto';

export const KEY_LENGTH = 16; // 128 bits

export const newKey: () => Promise<Bytes> =
    (typeof crypto !== 'undefined' && 'getRandomValues' in crypto)
    ? (async () => {
        const bs = new Bytes(KEY_LENGTH);
        crypto.getRandomValues(underlying(bs));
        return bs;
    })
    : (async () => Bytes.from(node_crypto.randomBytes(KEY_LENGTH)));

const HMAC_BLAKE2s = makeHMAC(BLAKE2s);

export function mac(secretKey: Bytes, data: Bytes): Bytes {
    return Bytes.from(HMAC_BLAKE2s(underlying(secretKey), underlying(data))
        .subarray(0, KEY_LENGTH));
}