// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0

import { KEY_TYPE_IDENTIFIER, SIGNATURE_IDENTIFIER } from '../constants';

import { getHashedData } from './dataHashHelpers';

/**
 * Returns a signing key to be used for signing requests.
 *
 * @param secretAccessKey AWS secret access key from credentials.
 * @param date Current date in the format 'YYYYMMDD'.
 * @param region AWS region in which the service resides.
 * @param service Service to which the signed request is being sent.
 *
 * @returns `Uint8Array` calculated from its composite parts.
 *
 * @internal
 */
export const getSigningKey = (
	secretAccessKey: string,
	date: string,
	region: string,
	service: string,
): Uint8Array => {
	const key = `${SIGNATURE_IDENTIFIER}${secretAccessKey}`;
	const dateKey = getHashedData(key, date);
	const regionKey = getHashedData(dateKey, region);
	const serviceKey = getHashedData(regionKey, service);
	const signingKey = getHashedData(serviceKey, KEY_TYPE_IDENTIFIER);

	return signingKey;
};