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
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
/*!
# Trillium tools for server sent events

This primarily provides [`SseConnExt`](crate::SseConnExt), an
extension trait for [`trillium::Conn`] that has a
[`with_sse_stream`](crate::SseConnExt::with_sse_stream) chainable
method that takes a [`Stream`](futures_lite::Stream) where the `Item`
implements [`Eventable`].

Often, you will want this stream to be something like a channel, but
the specifics of that are dependent on the event fanout
characteristics of your application.

This crate implements [`Eventable`] for an [`Event`] type that you can
use in your application, for `String`, and for `&'static str`. You can
also implement [`Eventable`] for any type in your application.

## Example usage

```
use broadcaster::BroadcastChannel;
use trillium::{conn_try, conn_unwrap, log_error, Conn, Method, State};
use trillium_sse::SseConnExt;
use trillium_static_compiled::static_compiled;

type Channel = BroadcastChannel<String>;

fn get_sse(mut conn: Conn) -> Conn {
    let broadcaster = conn_unwrap!(conn.take_state::<Channel>(), conn);
    conn.with_sse_stream(broadcaster)
}

async fn post_broadcast(mut conn: Conn) -> Conn {
    let broadcaster = conn_unwrap!(conn.take_state::<Channel>(), conn);
    let body = conn_try!(conn.request_body_string().await, conn);
    log_error!(broadcaster.send(&body).await);
    conn.ok("sent")
}

fn main() {
    let handler = (
        static_compiled!("examples/static").with_index_file("index.html"),
        State::new(Channel::new()),
        |conn: Conn| async move {
            match (conn.method(), conn.path()) {
                (Method::Get, "/sse") => get_sse(conn),
                (Method::Post, "/broadcast") => post_broadcast(conn).await,
                _ => conn,
            }
        },
    );

    // trillium_smol::run(handler);
}

```
*/
#![forbid(unsafe_code)]
#![deny(
    missing_copy_implementations,
    rustdoc::missing_crate_level_docs,
    missing_debug_implementations,
    nonstandard_style,
    unused_qualifications
)]
#![warn(missing_docs)]

use futures_lite::{stream::Stream, AsyncRead};
use std::{
    borrow::Cow,
    fmt::Write,
    io,
    marker::PhantomData,
    pin::Pin,
    task::{Context, Poll},
};
use trillium::{Body, Conn, KnownHeaderName, Status};

struct SseBody<S, E> {
    stream: S,
    buffer: Vec<u8>,
    event: PhantomData<E>,
}

impl<S, E> SseBody<S, E>
where
    S: Stream<Item = E> + Unpin + Send + Sync + 'static,
    E: Eventable,
{
    pub fn new(stream: S) -> Self {
        Self {
            stream,
            buffer: Vec::new(),
            event: PhantomData,
        }
    }
}

fn encode(event: impl Eventable) -> String {
    let mut output = String::new();
    if let Some(event_type) = event.event_type() {
        writeln!(&mut output, "event: {event_type}").unwrap();
    }

    if let Some(id) = event.id() {
        writeln!(&mut output, "id: {id}").unwrap();
    }

    for part in event.data().lines() {
        writeln!(&mut output, "data: {part}").unwrap();
    }

    writeln!(output).unwrap();

    output
}

impl<S, E> AsyncRead for SseBody<S, E>
where
    S: Stream<Item = E> + Unpin + Send + Sync + 'static,
    E: Eventable,
{
    fn poll_read(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &mut [u8],
    ) -> Poll<io::Result<usize>> {
        let Self { buffer, stream, .. } = self.get_mut();

        let buffer_read = buffer.len().min(buf.len());
        if buffer_read > 0 {
            buf[0..buffer_read].copy_from_slice(&buffer[0..buffer_read]);
            buffer.drain(0..buffer_read);
            return Poll::Ready(Ok(buffer_read));
        }

        match Pin::new(stream).poll_next(cx) {
            Poll::Pending => Poll::Pending,
            Poll::Ready(Some(item)) => {
                let data = encode(item).into_bytes();
                let writable_len = data.len().min(buf.len());
                buf[0..writable_len].copy_from_slice(&data[0..writable_len]);
                if writable_len < data.len() {
                    buffer.extend_from_slice(&data[writable_len..]);
                }
                Poll::Ready(Ok(writable_len))
            }

            Poll::Ready(None) => Poll::Ready(Ok(0)),
        }
    }
}

impl<S, E> From<SseBody<S, E>> for Body
where
    S: Stream<Item = E> + Unpin + Send + Sync + 'static,
    E: Eventable,
{
    fn from(sse_body: SseBody<S, E>) -> Self {
        Body::new_streaming(sse_body, None)
    }
}

/**
Extension trait for server sent events
*/
pub trait SseConnExt {
    /**
    builds and sets a streaming response body that conforms to the
    [server-sent-events
    spec](https://html.spec.whatwg.org/multipage/server-sent-events.html#server-sent-events)
    from a Stream of any [`Eventable`](crate::Eventable) type (such as
    [`Event`](crate::Event), as well as setting appropiate headers for
    this response.
    */
    fn with_sse_stream<S, E>(self, sse_stream: S) -> Self
    where
        S: Stream<Item = E> + Unpin + Send + Sync + 'static,
        E: Eventable;
}

impl SseConnExt for Conn {
    fn with_sse_stream<S, E>(self, sse_stream: S) -> Self
    where
        S: Stream<Item = E> + Unpin + Send + Sync + 'static,
        E: Eventable,
    {
        let body = SseBody::new(self.inner().stopper().stop_stream(sse_stream));
        self.with_response_header(KnownHeaderName::ContentType, "text/event-stream")
            .with_response_header(KnownHeaderName::CacheControl, "no-cache")
            .with_body(body)
            .with_status(Status::Ok)
            .halt()
    }
}

/**
A trait that allows any Unpin + Send + Sync type to act as an event.

For a concrete implementation of this trait, you can use [`Event`],
but it is also implemented for [`String`] and [`&'static str`].
*/

pub trait Eventable: Unpin + Send + Sync + 'static {
    /// return the data for this event. non-optional.
    fn data(&self) -> &str;

    /// return the event type, optionally
    fn event_type(&self) -> Option<&str> {
        None
    }

    /// return a unique event id, optionally
    fn id(&self) -> Option<&str> {
        None
    }
}

impl Eventable for Event {
    fn data(&self) -> &str {
        Event::data(self)
    }

    fn event_type(&self) -> Option<&str> {
        Event::event_type(self)
    }
}

impl Eventable for &'static str {
    fn data(&self) -> &str {
        self
    }
}

impl Eventable for String {
    fn data(&self) -> &str {
        self
    }
}

/**
Events are a concrete implementation of the [`Eventable`] trait.
*/
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct Event {
    data: Cow<'static, str>,
    event_type: Option<Cow<'static, str>>,
}

impl From<&'static str> for Event {
    fn from(s: &'static str) -> Self {
        Self::from(Cow::Borrowed(s))
    }
}

impl From<String> for Event {
    fn from(s: String) -> Self {
        Self::from(Cow::Owned(s))
    }
}

impl From<Cow<'static, str>> for Event {
    fn from(data: Cow<'static, str>) -> Self {
        Event {
            data,
            event_type: None,
        }
    }
}

impl Event {
    /**
    builds a new [`Event`]

    by default, this event has no event type. to set an event type,
    use [`Event::with_type`] or [`Event::set_type`]
    */
    pub fn new(data: impl Into<Cow<'static, str>>) -> Self {
        Self::from(data.into())
    }

    /**
    chainable constructor to set the type on an event

    ```
    let event = trillium_sse::Event::new("event data").with_type("userdata");
    assert_eq!(event.event_type(), Some("userdata"));
    assert_eq!(event.data(), "event data");
    ```
    */
    pub fn with_type(mut self, event_type: impl Into<Cow<'static, str>>) -> Self {
        self.set_type(event_type);
        self
    }

    /**
    set the event type for this Event. The default is None.

    ```
    let mut event = trillium_sse::Event::new("event data");
    assert_eq!(event.event_type(), None);
    event.set_type("userdata");
    assert_eq!(event.event_type(), Some("userdata"));
    ```
     */
    pub fn set_type(&mut self, event_type: impl Into<Cow<'static, str>>) {
        self.event_type = Some(event_type.into());
    }

    /// returns this Event's data as a &str
    pub fn data(&self) -> &str {
        &self.data
    }

    /// returns this Event's type as a str, if set
    pub fn event_type(&self) -> Option<&str> {
        self.event_type.as_deref()
    }
}