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

import { StorageUploadDataPayload } from '../../../types';
import { getDataChunker } from '../apis/internal/uploadData/multipart/getDataChunker';

import { calculateContentCRC32 } from './crc32';

/**
 * Calculates a combined CRC32 checksum for the given data.
 *
 * This function chunks the input data, calculates CRC32 for each chunk,
 * and then combines these checksums into a single value.
 *
 * @async
 * @param {StorageUploadDataPayload} data - The data to calculate the checksum for.
 * @param {number | undefined} size - The size of each chunk. If undefined, a default chunk size will be used.
 * @returns {Promise<string>} A promise that resolves to a string containing the combined CRC32 checksum
 *                            and the number of chunks, separated by a hyphen.
 */
export const getCombinedCrc32 = async (
	data: StorageUploadDataPayload,
	size: number | undefined,
) => {
	const crc32List: Uint8Array[] = [];
	const dataChunker = getDataChunker(data, size);

	let totalLength = 0;
	for (const { data: checkData } of dataChunker) {
		const checksum = new Uint8Array(
			(await calculateContentCRC32(checkData)).checksumArrayBuffer,
		);
		totalLength += checksum.length;
		crc32List.push(checksum);
	}

	// Combine all Uint8Arrays into a single Uint8Array
	const combinedArray = new Uint8Array(totalLength);
	let offset = 0;
	for (const crc32Hash of crc32List) {
		combinedArray.set(crc32Hash, offset);
		offset += crc32Hash.length;
	}

	return `${(await calculateContentCRC32(combinedArray.buffer)).checksum}-${crc32List.length}`;
};