/**
 * 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