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

use std::marker::PhantomData;

use bevy::{ecs::system::SystemParam, prelude::*};
use de_lobby_client::{LobbyRequest, RequestEvent, ResponseEvent, Result};

use crate::MenuState;

pub(super) struct RequestsPlugin<T>
where
    T: LobbyRequest,
{
    _marker: PhantomData<fn() -> T>,
}

impl<T> RequestsPlugin<T>
where
    T: LobbyRequest,
{
    pub(super) fn new() -> Self {
        Self {
            _marker: PhantomData,
        }
    }
}

impl<T> Plugin for RequestsPlugin<T>
where
    T: LobbyRequest,
{
    fn build(&self, app: &mut App) {
        app.add_systems(OnEnter(MenuState::Multiplayer), setup::<T>)
            .add_systems(OnExit(MenuState::Multiplayer), cleanup::<T>);
    }
}

#[derive(SystemParam)]
pub(super) struct Sender<'w, T>
where
    T: LobbyRequest,
{
    counter: ResMut<'w, Counter<T>>,
    requests: EventWriter<'w, RequestEvent<T>>,
}

impl<'w, T> Sender<'w, T>
where
    T: LobbyRequest,
{
    pub(super) fn send(&mut self, request: T) {
        self.requests
            .send(RequestEvent::new(self.counter.increment(), request));
    }
}

#[derive(SystemParam)]
pub(super) struct Receiver<'w, 's, T>
where
    T: LobbyRequest,
{
    counter: Res<'w, Counter<T>>,
    responses: EventReader<'w, 's, ResponseEvent<T>>,
}

impl<'w, 's, T> Receiver<'w, 's, T>
where
    T: LobbyRequest,
{
    /// Returns the response result corresponding the ID of the last request.
    /// Responses to earlier requests or requests not made via Sender are
    /// ignored.
    pub(super) fn receive(&mut self) -> Option<&Result<T::Response>> {
        self.responses
            .read()
            .filter_map(|e| {
                if self.counter.compare(e.id()) {
                    Some(e.result())
                } else {
                    None
                }
            })
            .last()
    }
}

#[derive(Resource)]
pub(super) struct Counter<T>
where
    T: LobbyRequest,
{
    counter: u64,
    _marker: PhantomData<fn() -> T>,
}

impl<T> Counter<T>
where
    T: LobbyRequest,
{
    fn new(initial_value: u64) -> Self {
        Self {
            counter: initial_value,
            _marker: PhantomData,
        }
    }

    fn increment(&mut self) -> u64 {
        self.counter = self.counter.wrapping_add(1);
        self.counter
    }

    fn compare(&self, id: &str) -> bool {
        self.counter.to_string() == id
    }
}

fn setup<T>(mut commands: Commands, time: Res<Time>)
where
    T: LobbyRequest,
{
    let init = time.elapsed().as_secs().wrapping_mul(1024);
    commands.insert_resource(Counter::<T>::new(init));
}

fn cleanup<T>(mut commands: Commands)
where
    T: LobbyRequest,
{
    commands.remove_resource::<Counter<T>>();
}