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
// Take a look at the license at the top of the repository in the LICENSE file.

use std::{
    ops::Deref,
    pin::Pin,
    ptr,
    task::{Context, Poll},
};

use glib::translate::*;

use crate::{PromiseResult, Structure, StructureRef};

glib::wrapper! {
    #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
    #[doc(alias = "GstPromise")]
    pub struct Promise(Shared<ffi::GstPromise>);

    match fn {
        ref => |ptr| ffi::gst_mini_object_ref(ptr as *mut _),
        unref => |ptr| ffi::gst_mini_object_unref(ptr as *mut _),
        type_ => || ffi::gst_promise_get_type(),
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub enum PromiseError {
    Interrupted,
    Expired,
    Other(PromiseResult),
}

impl Promise {
    #[doc(alias = "gst_promise_new")]
    pub fn new() -> Promise {
        assert_initialized_main_thread!();
        unsafe { from_glib_full(ffi::gst_promise_new()) }
    }

    #[doc(alias = "gst_promise_new_with_change_func")]
    pub fn with_change_func<F>(func: F) -> Promise
    where
        F: FnOnce(Result<Option<&StructureRef>, PromiseError>) + Send + 'static,
    {
        assert_initialized_main_thread!();
        let user_data: Box<Option<F>> = Box::new(Some(func));

        unsafe extern "C" fn trampoline<
            F: FnOnce(Result<Option<&StructureRef>, PromiseError>) + Send + 'static,
        >(
            promise: *mut ffi::GstPromise,
            user_data: glib::ffi::gpointer,
        ) {
            let user_data: &mut Option<F> = &mut *(user_data as *mut _);
            let callback = user_data.take().unwrap();

            let promise: Borrowed<Promise> = from_glib_borrow(promise);

            let res = match promise.wait() {
                PromiseResult::Replied => Ok(promise.get_reply()),
                PromiseResult::Interrupted => Err(PromiseError::Interrupted),
                PromiseResult::Expired => Err(PromiseError::Expired),
                PromiseResult::Pending => {
                    panic!("Promise resolved but returned Pending");
                }
                err => Err(PromiseError::Other(err)),
            };

            callback(res);
        }

        unsafe extern "C" fn free_user_data<
            F: FnOnce(Result<Option<&StructureRef>, PromiseError>) + Send + 'static,
        >(
            user_data: glib::ffi::gpointer,
        ) {
            let _: Box<Option<F>> = Box::from_raw(user_data as *mut _);
        }

        unsafe {
            from_glib_full(ffi::gst_promise_new_with_change_func(
                Some(trampoline::<F>),
                Box::into_raw(user_data) as *mut _,
                Some(free_user_data::<F>),
            ))
        }
    }

    pub fn new_future() -> (Self, PromiseFuture) {
        use futures_channel::oneshot;

        // We only use the channel as a convenient waker
        let (sender, receiver) = oneshot::channel();
        let promise = Self::with_change_func(move |_res| {
            let _ = sender.send(());
        });

        (promise.clone(), PromiseFuture(promise, receiver))
    }

    #[doc(alias = "gst_promise_expire")]
    pub fn expire(&self) {
        unsafe {
            ffi::gst_promise_expire(self.to_glib_none().0);
        }
    }

    #[doc(alias = "gst_promise_get_reply")]
    pub fn get_reply(&self) -> Option<&StructureRef> {
        unsafe {
            let s = ffi::gst_promise_get_reply(self.to_glib_none().0);
            if s.is_null() {
                None
            } else {
                Some(StructureRef::from_glib_borrow(s))
            }
        }
    }

    #[doc(alias = "gst_promise_interrupt")]
    pub fn interrupt(&self) {
        unsafe {
            ffi::gst_promise_interrupt(self.to_glib_none().0);
        }
    }

    #[doc(alias = "gst_promise_reply")]
    pub fn reply(&self, s: Option<Structure>) {
        unsafe {
            ffi::gst_promise_reply(
                self.to_glib_none().0,
                s.map(|s| s.into_glib_ptr()).unwrap_or(ptr::null_mut()),
            );
        }
    }

    #[doc(alias = "gst_promise_wait")]
    pub fn wait(&self) -> PromiseResult {
        unsafe { from_glib(ffi::gst_promise_wait(self.to_glib_none().0)) }
    }
}

impl Default for Promise {
    fn default() -> Self {
        Self::new()
    }
}

unsafe impl Send for Promise {}
unsafe impl Sync for Promise {}

#[derive(Debug)]
pub struct PromiseFuture(Promise, futures_channel::oneshot::Receiver<()>);

pub struct PromiseReply(Promise);

impl std::future::Future for PromiseFuture {
    type Output = Result<Option<PromiseReply>, PromiseError>;

    fn poll(mut self: Pin<&mut Self>, context: &mut Context) -> Poll<Self::Output> {
        match Pin::new(&mut self.1).poll(context) {
            Poll::Ready(Err(_)) => panic!("Sender dropped before callback was called"),
            Poll::Ready(Ok(())) => {
                let res = match self.0.wait() {
                    PromiseResult::Replied => {
                        if self.0.get_reply().is_none() {
                            Ok(None)
                        } else {
                            Ok(Some(PromiseReply(self.0.clone())))
                        }
                    }
                    PromiseResult::Interrupted => Err(PromiseError::Interrupted),
                    PromiseResult::Expired => Err(PromiseError::Expired),
                    PromiseResult::Pending => {
                        panic!("Promise resolved but returned Pending");
                    }
                    err => Err(PromiseError::Other(err)),
                };
                Poll::Ready(res)
            }
            Poll::Pending => Poll::Pending,
        }
    }
}

impl futures_core::future::FusedFuture for PromiseFuture {
    fn is_terminated(&self) -> bool {
        self.1.is_terminated()
    }
}

impl Deref for PromiseReply {
    type Target = StructureRef;

    #[inline]
    fn deref(&self) -> &StructureRef {
        self.0.get_reply().expect("Promise without reply")
    }
}

impl std::fmt::Debug for PromiseReply {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let mut debug = f.debug_tuple("PromiseReply");

        match self.0.get_reply() {
            Some(reply) => debug.field(reply),
            None => debug.field(&"<no reply>"),
        }
        .finish()
    }
}

#[cfg(test)]
mod tests {
    use std::{sync::mpsc::channel, thread};

    use super::*;

    #[test]
    fn test_change_func() {
        crate::init().unwrap();

        let (sender, receiver) = channel();
        let promise = Promise::with_change_func(move |res| {
            sender.send(res.map(|s| s.map(ToOwned::to_owned))).unwrap();
        });

        thread::spawn(move || {
            promise.reply(Some(crate::Structure::new_empty("foo/bar")));
        });

        let res = receiver.recv().unwrap();
        let res = res.expect("promise failed").expect("promise returned None");
        assert_eq!(res.name(), "foo/bar");
    }
}