content-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, window, document, CustomEvent */

const FETCH_SUPPORTED_REQUEST_EVENT = "single-file-request-fetch-supported";
const FETCH_SUPPORTED_RESPONSE_EVENT = "single-file-response-fetch-supported";
const FETCH_REQUEST_EVENT = "single-file-request-fetch";
const FETCH_RESPONSE_EVENT = "single-file-response-fetch";
const ERR_HOST_FETCH = "Host fetch error (SingleFile)";
const USE_HOST_FETCH = Boolean(window.wrappedJSObject);

const fetch = (url, options) => {
	options.cache = "force-cache";
	options.referrerPolicy = "strict-origin-when-cross-origin";
	return window.fetch(url, options);
};

let requestId = 0, pendingResponses = new Map(), hostFetchSupported;

browser.runtime.onMessage.addListener(message => {
	if (message.method == "singlefile.fetchFrame" && window.frameId && window.frameId == message.frameId) {
		return onFetchFrame(message);
	}
	if (message.method == "singlefile.fetchResponse") {
		return onFetchResponse(message);
	}
});

async function onFetchFrame(message) {
	try {
		const response = await fetch(message.url, { cache: "force-cache", headers: message.headers, referrerPolicy: "strict-origin-when-cross-origin" });
		return {
			status: response.status,
			headers: [...response.headers],
			array: Array.from(new Uint8Array(await response.arrayBuffer()))
		};
	} catch (error) {
		return {
			error: error && error.toString()
		};
	}
}

async function onFetchResponse(message) {
	const pendingResponse = pendingResponses.get(message.requestId);
	if (pendingResponse) {
		if (message.error) {
			pendingResponse.reject(new Error(message.error));
			pendingResponses.delete(message.requestId);
		} else {
			if (message.truncated) {
				if (pendingResponse.array) {
					pendingResponse.array = pendingResponse.array.concat(message.array);
				} else {
					pendingResponse.array = message.array;
					pendingResponses.set(message.requestId, pendingResponse);
				}
				if (message.finished) {
					message.array = pendingResponse.array;
				}
			}
			if (!message.truncated || message.finished) {
				pendingResponse.resolve({
					status: message.status,
					headers: { get: headerName => message.headers && message.headers[headerName] },
					arrayBuffer: async () => new Uint8Array(message.array).buffer
				});
				pendingResponses.delete(message.requestId);
			}
		}
	}
	return {};
}

async function hostFetch(url, options) {
	if (hostFetchSupported === undefined) {
		hostFetchSupported = false;
		document.addEventListener(FETCH_SUPPORTED_RESPONSE_EVENT, () => hostFetchSupported = true, false);
		document.dispatchEvent(new CustomEvent(FETCH_SUPPORTED_REQUEST_EVENT));
	}
	if (hostFetchSupported) {
		const result = new Promise((resolve, reject) => {
			document.dispatchEvent(new CustomEvent(FETCH_REQUEST_EVENT, { detail: JSON.stringify({ url, options }) }));
			document.addEventListener(FETCH_RESPONSE_EVENT, onResponseFetch, false);

			function onResponseFetch(event) {
				if (event.detail) {
					if (event.detail.url == url) {
						document.removeEventListener(FETCH_RESPONSE_EVENT, onResponseFetch, false);
						if (event.detail.response) {
							resolve({
								status: event.detail.status,
								headers: new Map(event.detail.headers),
								arrayBuffer: async () => event.detail.response
							});
						} else {
							reject(event.detail.error);
						}
					}
				} else {
					reject();
				}
			}
		});
		try {
			return await result;
		} catch (error) {
			if (error && error.message == ERR_HOST_FETCH) {
				return fetch(url, options);
			} else {
				throw error;
			}
		}
	} else {
		return fetch(url, options);
	}
}

export {
	fetchResource as fetch,
	frameFetch
};

async function fetchResource(url, options = {}) {
	try {
		const fetchOptions = { cache: "force-cache", headers: options.headers, referrerPolicy: "strict-origin-when-cross-origin" };
		let response;
		try {
			if (options.referrer && !USE_HOST_FETCH) {
				response = await fetch(url, fetchOptions);
			} else {
				response = await hostFetch(url, fetchOptions);
			}
		} catch (error) {
			if (error && error.message == ERR_HOST_FETCH) {
				response = await fetch(url, fetchOptions);
			} else {
				throw error;
			}
		}
		return response;
	}
	catch (error) {
		requestId++;
		const promise = new Promise((resolve, reject) => pendingResponses.set(requestId, { resolve, reject }));
		await sendMessage({ method: "singlefile.fetch", url, requestId, referrer: options.referrer, headers: options.headers });
		return promise;
	}
}

async function frameFetch(url, options) {
	const response = await sendMessage({ method: "singlefile.fetchFrame", url, frameId: options.frameId, referrer: options.referrer, headers: options.headers });
	return {
		status: response.status,
		headers: new Map(response.headers),
		arrayBuffer: async () => new Uint8Array(response.array).buffer
	};
}

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