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
174
175

//! This module implements full networking stack. The stack is implemented as a
//! set of asynchronous tasks communicating via channels.
//!
//! Bellow, `--->` lines represent channels and `* * >` represent task
//! cancellation tokens.
//!
//! ```text
//!                         +-------------+
//!                         |             |
//!           +-----------+ |   usender   | * * *
//!           |             |             |     *
//!           |             +-------------+     *
//!           v                                 *
//! +-------------+         +-------------+     *
//! |             |         |             | < * *
//! |   dsender   | <-----+ |   resender  |
//! |             |         |             | * * * *
//! +-------------+         +-------------+       *
//!           ^                                   *
//!           |             +-------------+       *
//!           |             |             |       *
//!           +-----------+ |  confirmer  | < *   *
//!                         |             |   *   *
//!                         +-------------+   *   *
//!                                           *   *
//! +-------------+         +-------------+   *   *
//! |             |         |             |   *   *
//! |  dreceiver  | +-----> |  ureceiver  | * *   *
//! |             |         |             |       *
//! +-------------+         +-------------+       *
//!           +                                   *
//!           |             +-------------+       *
//!           |             |             |       *
//!           +-----------> |  sreceiver  | < * * *
//!                         |             |
//!                         +-------------+
//! ```
//!
//! `dsender` and `dreceiver` are responsible for sending and receiving UDP
//! datagrams. Both are terminated soon after all their channels are closed.
//!
//! `resender` is responsible for redelivery of reliably sent datagrams whose
//! confirmation was not received within a time limit. If all attempts fail,
//! the user is informed via [`ConnErrorReceiver`].
//!
//! `sreceiver` is responsible for processing of system / protocol datagrams.
//! These include delivery confirmations.
//!
//! `confirmer` is responsible for sending of datagram delivery confirmations.
//!
//! `resender`, `sreceiver`, and `confirmer` are terminated soon after their
//! cancellation token is canceled.
//!
//! `usender` and `ureceiver` are responsible for sending and reception of user
//! data. The user communicates with these via [`PackageSender`] and
//! [`PackageReceiver`] respectively.

use async_std::channel::bounded;
pub use communicator::{
    ConnErrorReceiver, ConnectionError, InPackage, MessageDecoder, OutPackage, PackageBuilder,
    PackageIterator, PackageReceiver, PackageSender,
};
pub(crate) use dsender::OutDatagram;
use futures::future::BoxFuture;
use tracing::info;

use crate::{
    connection::{DeliveryHandler, DispatchHandler},
    protocol::ProtocolSocket,
    tasks::cancellation::cancellation,
    Socket,
};

mod cancellation;
mod communicator;
mod confirmer;
mod dreceiver;
mod dsender;
mod resender;
mod sreceiver;
mod ureceiver;
mod usender;

const CHANNEL_CAPACITY: usize = 1024;

/// Setups and starts communication stack tasks and returns communication
/// channels for data sending, data retrieval, and error retrieval.
///
/// All tasks in the network stack keep running until the returned channels are
/// closed. Once the [`PackageSender`], [`PackageReceiver`], and
/// [`ConnErrorReceiver`] are all dropped, the networking stack will terminate
/// completely.
///
/// # Arguments
///
/// * `spawn` - async task spawner.
///
/// * `socket` - network communication will happen over this socket.
pub fn startup<S>(spawn: S, socket: Socket) -> (PackageSender, PackageReceiver, ConnErrorReceiver)
where
    S: Fn(BoxFuture<'static, ()>),
{
    let port = socket.port();
    info!("Starting up network stack on port {port}...");

    let protocol_socket = ProtocolSocket::new(socket);

    let (out_datagrams_sender, out_datagrams_receiver) = bounded(16);
    spawn(Box::pin(dsender::run(
        port,
        out_datagrams_receiver,
        protocol_socket.clone(),
    )));

    let (in_system_datagrams_sender, in_system_datagrams_receiver) = bounded(16);
    let (in_user_datagrams_sender, in_user_datagrams_receiver) = bounded(16);
    spawn(Box::pin(dreceiver::run(
        port,
        in_system_datagrams_sender,
        in_user_datagrams_sender,
        protocol_socket,
    )));

    let dispatch_handler = DispatchHandler::new();
    let (sreceiver_cancellation_sender, sreceiver_cancellation_receiver) = cancellation();
    spawn(Box::pin(sreceiver::run(
        port,
        sreceiver_cancellation_receiver,
        in_system_datagrams_receiver,
        dispatch_handler.clone(),
    )));

    let (inputs_sender, inputs_receiver) = bounded(CHANNEL_CAPACITY);
    let (confirmer_cancellation_sender, confirmer_cancellation_receiver) = cancellation();
    let delivery_handler = DeliveryHandler::new();
    spawn(Box::pin(ureceiver::run(
        port,
        confirmer_cancellation_sender,
        in_user_datagrams_receiver,
        inputs_sender,
        delivery_handler.clone(),
    )));

    let (outputs_sender, outputs_receiver) = bounded(CHANNEL_CAPACITY);
    let (errors_sender, errors_receiver) = bounded(CHANNEL_CAPACITY);
    let (resender_cancellation_sender, resender_cancellation_receiver) = cancellation();
    spawn(Box::pin(resender::run(
        port,
        resender_cancellation_receiver,
        sreceiver_cancellation_sender,
        out_datagrams_sender.clone(),
        errors_sender,
        dispatch_handler.clone(),
    )));

    spawn(Box::pin(confirmer::run(
        port,
        confirmer_cancellation_receiver,
        out_datagrams_sender.clone(),
        delivery_handler,
    )));
    spawn(Box::pin(usender::run(
        port,
        resender_cancellation_sender,
        out_datagrams_sender,
        outputs_receiver,
        dispatch_handler,
    )));

    (
        PackageSender(outputs_sender),
        PackageReceiver(inputs_receiver),
        ConnErrorReceiver(errors_receiver),
    )
}