/**
 * 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("Haketilo:", 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