Haketilo

/**

 * This file is part of Haketilo.

 *

 * Function: Facilitate broadcasting messages between different execution

 *           contexts of the extension

 *

 * 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/message_server.js IMPORT listen_for_connection

let next_id = 1;

const listeners_by_channel = new Map();

function new_broadcast_listener(port)

{

    const listener_ctx = {port, id: ++next_id, channels: new Set()};

    port.onMessage.addListener(msg => listener_command(msg, listener_ctx));

    const on_disconnect = () => remove_broadcast_listener(listener_ctx);

    port.onDisconnect.addListener(on_disconnect);

}

function listener_command(msg, listener_ctx)

{

    const [disposition, name] = msg;

    if (disposition === "subscribe")

	subscribe_channel(name, listener_ctx);

    else if (disposition === "unsubscribe")

	unsubscribe_channel(name, listener_ctx);

    else

	throw `bad broadcast listener disposition '${disposition}'`;

}

function subscribe_channel(channel_name, listener_ctx)

{

    if (!listeners_by_channel.has(channel_name))

	listeners_by_channel.set(channel_name, new Map());

    listeners_by_channel.get(channel_name).set(listener_ctx.id, listener_ctx);

    listener_ctx.channels.add(channel_name);

}

function unsubscribe_channel(channel_name, listener_ctx)

{

    const channel_listeners =

	  listeners_by_channel.get(channel_name) || new Map();

    channel_listeners.delete(listener_ctx.id);

    if (channel_listeners.size == 0)

	listeners_by_channel.delete(channel_name);

    listener_ctx.channels.delete(channel_name);

}

function remove_broadcast_listener(listener_ctx)

{

    for (const channel_name of [...listener_ctx.channels.keys()])

	unsubscribe_channel(channel_name, listener_ctx);

}

function new_broadcast_sender(port)

{

    const sender_ctx = {prepared_broadcasts: new Set()};

    port.onMessage.addListener(msg => sender_command(msg, sender_ctx));

    port.onDisconnect.addListener(msg => flush(sender_ctx));

}

function sender_command(msg, sender_ctx)

{

    const [disposition, name, value, timeout] = msg;

    if (disposition === "prepare")

	prepare(sender_ctx, name, value, timeout)

    else if (disposition === "discard")

	sender_ctx.prepared_broadcasts = new Set();

    else if (disposition === "flush")

	flush(sender_ctx);

    else if (disposition === "broadcast")

	broadcast(name, value);

    else

	throw `bad broadcast sender disposition '${disposition}'`;

}

function prepare(sender_ctx, channel_name, value, timeout)

{

    const broadcast_data = [channel_name, value];

    sender_ctx.prepared_broadcasts.add(broadcast_data);

    if (timeout === 0)

	return;

    setTimeout(() => prepare_timeout_cb(sender_ctx, broadcast_data), timeout);

}

function prepare_timeout_cb(sender_ctx, broadcast_data)

{

    if (sender_ctx.prepared_broadcasts.has(broadcast_data)) {

	sender_ctx.prepared_broadcasts.delete(broadcast_data);

	broadcast(...broadcast_data);

    }

}

function flush(sender_ctx)

{

    sender_ctx.prepared_broadcasts.forEach(nv => broadcast(...nv));

    sender_ctx.prepared_broadcasts = new Set();

}

function broadcast(channel_name, value)

{

    const listeners = listeners_by_channel.get(channel_name);

    if (listeners == undefined)

	return;

    for (const listener_ctx of [...listeners.values()]) {

	try {

	    listener_ctx.port.postMessage([channel_name, value]);

	} catch (e) {

	    console.error(e);

	    remove_broadcast_listener(listener_ctx);

	}

    }

}

function remove_broadcast_sender(sender_ctx)

{

    sender_ctx.prepared_broadcasts.forEach(nv => broadcast(...nv));

}

function start()

{

    listen_for_connection("broadcast_send", new_broadcast_sender);

    listen_for_connection("broadcast_listen", new_broadcast_listener);

}

#EXPORT start