SingleFile/lib/fetch/content/fetch.js

/*
 * Copyright 2018 Gildas Lormeau
 * contact : gildas.lormeau <at> gmail.com
 * 
 * This file is part of SingleFile.
 *
 *   SingleFile is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   SingleFile is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public License
 *   along with SingleFile.  If not, see <http://www.gnu.org/licenses/>.
 */

/* global browser, XMLHttpRequest */

this.superFetch = this.superFetch || (() => {

	const superFetch = {
		fetch: async url => {
			const xhrPromise = new Promise((resolve, reject) => {
				const xhrRequest = new XMLHttpRequest();
				let receivedResponse, receivedError, resolveResponse = response => receivedResponse = response, rejectResponse = error => receivedError = error;
				xhrRequest.withCredentials = true;
				xhrRequest.responseType = "arraybuffer";
				xhrRequest.onerror = event => reject(new Error(event.details));
				xhrRequest.onreadystatechange = () => {
					if (xhrRequest.readyState == XMLHttpRequest.HEADERS_RECEIVED) {
						const headers = new Map();
						headers.set("content-type", xhrRequest.getResponseHeader("Content-Type"));
						resolve({
							headers, status: xhrRequest.status, arrayBuffer: () => new Promise((resolve, reject) => {
								if (receivedError) {
									reject(receivedError);
								} else if (receivedResponse) {
									resolve(receivedResponse);
								} else {
									[resolveResponse, rejectResponse] = [resolve, reject];
								}
							})
						});
					}
					if (xhrRequest.readyState == XMLHttpRequest.DONE) {
						resolveResponse(xhrRequest.response);
					}
				};
				xhrRequest.onerror = error => {
					reject(error);
					if (rejectResponse) {
						rejectResponse(error);
					}
				};
				xhrRequest.open("GET", url, true);
				xhrRequest.send();
			});
			return xhrPromise
				.catch(async () => {
					const responseFetch = await sendMessage({ method: "fetch", url });
					return {
						headers: { get: headerName => responseFetch.headers[headerName] },
						arrayBuffer: async () => {
							const response = await sendMessage({ method: "fetch.array", requestId: responseFetch.responseId });
							return new Uint8Array(response.array).buffer;
						}
					};
				});
		}
	};
	return superFetch;

	async function sendMessage(message) {
		const response = await browser.runtime.sendMessage(message);
		if (!response || response.error) {
			throw new Error(response && response.error.toString());
		} else {
			return response;
		}
	}

})();