SingleFile/extension/lib/single-file/fetch/bg/fetch.js

/*
 * Copyright 2010-2020 Gildas Lormeau
 * contact : gildas.lormeau <at> gmail.com
 * 
 * This file is part of SingleFile.
 *
 *   The code in this file is free software: you can redistribute it and/or 
 *   modify it under the terms of the GNU Affero General Public License 
 *   (GNU AGPL) as published by the Free Software Foundation, either version 3
 *   of the License, or (at your option) any later version.
 * 
 *   The code in this file 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 Affero 
 *   General Public License for more details.
 *
 *   As additional permission under GNU AGPL version 3 section 7, you may 
 *   distribute UNMODIFIED VERSIONS OF THIS file without the copy of the GNU 
 *   AGPL normally required by section 4, provided you include this license 
 *   notice and a URL through which recipients can access the Corresponding 
 *   Source.
 */

/* global browser, XMLHttpRequest */

(() => {

	const MAX_CONTENT_SIZE = 8 * (1024 * 1024);

	const pendingRequests = [];

	browser.runtime.onMessage.addListener((message, sender) => {
		if (message.method == "singlefile.fetchRequest"
			|| message.method == "singlefile.fetchFrameRequest"
			|| message.method == "singlefile.bgFetchFrameResponse") {
			return onMessage(message, sender);
		}
	});

	async function onMessage(message, sender) {
		if (message.method == "singlefile.fetchRequest") {
			return onRequest(message, sender);
		} else if (message.method == "singlefile.fetchFrameRequest") {
			message.bgId = pendingRequests.length;
			browser.tabs.sendMessage(sender.tab.id, message);
			pendingRequests.push({ tabId: sender.tab.id });
		} else if (message.method == "singlefile.bgFetchFrameResponse") {
			onFrameResponse(message);
		}
	}

	async function onRequest(message, sender) {
		if (message.method == "singlefile.fetchRequest") {
			try {
				const response = await fetchResource(message.url);
				const id = message.id;
				for (let blockIndex = 0; blockIndex * MAX_CONTENT_SIZE < response.array.length; blockIndex++) {
					const message = {
						method: "singlefile.fetchResponse",
						id
					};
					message.truncated = response.array.length > MAX_CONTENT_SIZE;
					if (message.truncated) {
						message.finished = (blockIndex + 1) * MAX_CONTENT_SIZE > response.array.length;
						message.array = Array.from(response.array.slice(blockIndex * MAX_CONTENT_SIZE, (blockIndex + 1) * MAX_CONTENT_SIZE));
					} else {
						message.array = Array.from(response.array);
					}
					if (!message.truncated || message.finished) {
						message.headers = response.headers;
						message.status = response.status;
					}
					browser.tabs.sendMessage(sender.tab.id, message);
				}
			} catch (error) {
				await browser.tabs.sendMessage(sender.tab.id, {
					method: "singlefile.fetchResponse",
					id: message.id,
					error: error.toString()
				});
			}
		}
	}

	function onFrameResponse(message) {
		const pendingRequest = pendingRequests[message.bgId];
		if (pendingRequest) {
			if (message.error) {
				browser.tabs.sendMessage(pendingRequest.tabId, message);
				pendingRequests[message.bgId] = null;
			} else {
				message.method = "singlefile.fetchFrameResponse";
				browser.tabs.sendMessage(pendingRequest.tabId, message);
				if (!message.truncated || message.finished) {
					pendingRequests[message.bgId] = null;
				}
			}
		}
	}

	function fetchResource(url) {
		return new Promise((resolve, reject) => {
			const xhrRequest = new XMLHttpRequest();
			xhrRequest.withCredentials = true;
			xhrRequest.responseType = "arraybuffer";
			xhrRequest.onerror = event => reject(new Error(event.detail));
			xhrRequest.onreadystatechange = () => {
				if (xhrRequest.readyState == XMLHttpRequest.DONE) {
					if (xhrRequest.status || xhrRequest.response.byteLength) {
						resolve({
							array: new Uint8Array(xhrRequest.response),
							headers: { "content-type": xhrRequest.getResponseHeader("Content-Type") },
							status: xhrRequest.status
						});
					} else {
						reject();
					}
				}
			};
			xhrRequest.open("GET", url, true);
			xhrRequest.send();
		});
	}

})();