export const fetchHeaders = Object.freeze({
	Accept: 'text/html',
	'Content-Type': 'text/html',
	'X-Requested-With': 'XMLHttpRequest',
	'Cache-Control': 'no-cache',
	Pragma: 'no-cache',
	Expires: '0',
});

/**
 * Creates an abortable AJAX request.
 *
 * @param {string} url Request endpoint.
 * @param {RequestInit} options Fetch options.
 * @returns {{fetchPromise: () => Promise<unknown>, abort: () => void}} Request controls.
 * @sideEffects Starts a network request.
 */
export function AjaxReq(url, options = {}) {
	const controller = new AbortController();
	const headers = { ...fetchHeaders, ...options.headers };
	if (options.body instanceof FormData) {
		delete headers['Content-Type'];
	}

	const requestOptions = { ...options, headers, signal: controller.signal };
	const fetchPromise = fetch(url, requestOptions).then(parseJsonResponse);

	return {
		fetchPromise: () => fetchPromise,
		abort: () => controller.abort(),
	};
}

/**
 * Returns the JSON body of a successful HTTP response.
 *
 * @param {Response} response Fetch response.
 * @returns {Promise<unknown>} Parsed response body.
 * @throws {Response} When the response status is not successful.
 */
function parseJsonResponse(response) {
	if (!response.ok) {
		return Promise.reject(response);
	}

	return response.json();
}