summaryrefslogtreecommitdiff
path: root/background/broadcast_broker.js
blob: d8a0e28ab8769125a8442c967c39e7ace8e12d68 (about) (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
/**
 * 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