Haketilo

/**

 * This file is part of Haketilo.

 *

 * Function: Message server.

 *

 * Copyright (C) 2021 Wojtek Kosior

 *

 * This program is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * This program 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 General Public License for more details.

 *

 * As additional permission under GNU GPL version 3 section 7, you

 * may distribute forms of that code without the copy of the GNU

 * GPL normally required by section 4, provided you include this

 * license notice and, in case of non-source distribution, a URL

 * through which recipients can access the Corresponding Source.

 * If you modify file(s) with this exception, you may extend this

 * exception to your version of the file(s), but you are not

 * obligated to do so. If you do not wish to do so, delete this

 * exception statement from your version.

 *

 * As a special exception to the GPL, any HTML file which merely

 * makes function calls to this code, and for that purpose

 * includes it by reference shall be deemed a separate work for

 * copyright law purposes. If you modify this code, you may extend

 * this exception to your version of the code, but you are not

 * obligated to do so. If you do not wish to do so, delete this

 * exception statement from your version.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <https://www.gnu.org/licenses/>.

 *

 * I, Wojtek Kosior, thereby promise not to sue for violation of this file's

 * license. Although I request that you do not make use of this code in a

 * proprietary program, I am not going to enforce this in court.

 */

#FROM common/browser.js IMPORT browser

let listeners = {};

let listening = false;

function raw_listen(port)

{

    if (listeners[port.name] === undefined)

	return;

    listeners[port.name](port);

}

/* magic should be one of the constants from /common/connection_types.js */

function listen_for_connection(magic, cb)

{

    if (!listening) {

	listening = true;

	browser.runtime.onConnect.addListener(raw_listen);

    }

    listeners[magic] = cb;

}

#EXPORT listen_for_connection

/*

 * Messaging background page from itself might result in messages being silently

 * discarded. Here we implement an interface (somewhat) compatible with the one

 * provided by the browser, but which allows for background page to communicate

 * with itself.

 */

function EvTarget()

{

    this.listeners = new Set();

    this.addListener    = cb => this.listeners.add(cb);

    this.removeListener = cb => this.listeners.delete(cb);

    this.dispatch       = msg => this.listeners.forEach(l => l(msg));

}

function Port(magic)

{

    this.name = magic;

    this.onDisconnect = new EvTarget();

    this.onMessage    = new EvTarget();

    this.postMessage  = msg => this.other.onMessage.dispatch(msg);

    this.disconnect   = () => this.other.onDisconnect.dispatch(this.other);

}

let bg_page_url;

function connect_to_background(magic)

{

    if (bg_page_url === undefined)

	bg_page_url = browser.runtime.getURL("_generated_background_page.html");

    if (typeof document === "undefined" || document.URL !== bg_page_url)

	return browser.runtime.connect({name: magic});

    if (!(magic in listeners))

	throw `no listener for '${magic}'`;

    const ports = [new Port(magic), new Port(magic)];

    ports[0].other = ports[1];

    ports[1].other = ports[0];

    listeners[magic](ports[0]);

    return ports[1];

}

#EXPORT connect_to_background