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

export const resolveHeaders = (
	headers?: Record<string, string>,
	body?: unknown,
) => {
	const normalizedHeaders: Record<string, string> = {};
	for (const key in headers) {
		normalizedHeaders[key.toLowerCase()] = headers[key];
	}
	if (body) {
		const contentType = normalizedHeaders['content-type'];
		const isJsonCompatible =
			contentType &&
			(contentType.startsWith('application/json') ||
				(contentType.startsWith('application/') &&
					contentType.includes('+json')));

		if (!isJsonCompatible) {
			normalizedHeaders['content-type'] = 'application/json; charset=UTF-8';
		}

		if (body instanceof FormData) {
			/**
			 * If body is a FormData we should not allow setting content-type.
			 * It's because runtime HTTP handlers(xhr, fetch, undici, node-fetch,
			 * etc.) will modify the content-type value when setting multipart
			 * boundary.
			 */
			delete normalizedHeaders['content-type'];
		}
	}

	return normalizedHeaders;
};