1 files changed, 70 insertions, 0 deletions
diff --git a/components/script/routed_promise.rs b/components/script/routed_promise.rs
new file mode 100644
index 00000000000..5a68287f450
--- /dev/null
+++ b/components/script/routed_promise.rs
@@ -0,0 +1,70 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use std::rc::Rc;
+
+use ipc_channel::ipc::{self, IpcSender};
+use ipc_channel::router::ROUTER;
+use serde::Serialize;
+use serde::de::DeserializeOwned;
+
+use crate::dom::bindings::refcounted::{Trusted, TrustedPromise};
+use crate::dom::bindings::reflector::{DomGlobal, DomObject};
+use crate::dom::promise::Promise;
+use crate::script_runtime::CanGc;
+
+pub(crate) trait RoutedPromiseListener {
+    type Response: Serialize + DeserializeOwned + Send;
+
+    fn handle_response(&self, response: Self::Response, promise: &Rc<Promise>, can_gc: CanGc);
+}
+
+pub(crate) struct RoutedPromiseContext<T: RoutedPromiseListener + DomObject> {
+    trusted: TrustedPromise,
+    receiver: Trusted<T>,
+}
+
+impl<T: RoutedPromiseListener + DomObject> RoutedPromiseContext<T> {
+    #[cfg_attr(crown, allow(crown::unrooted_must_root))]
+    fn response(self, response: T::Response, can_gc: CanGc) {
+        let promise = self.trusted.root();
+        self.receiver
+            .root()
+            .handle_response(response, &promise, can_gc);
+    }
+}
+
+pub(crate) fn route_promise<T: RoutedPromiseListener + DomObject + 'static>(
+    promise: &Rc<Promise>,
+    receiver: &T,
+) -> IpcSender<T::Response> {
+    let (action_sender, action_receiver) = ipc::channel().unwrap();
+    let task_source = receiver
+        .global()
+        .task_manager()
+        .dom_manipulation_task_source()
+        .to_sendable();
+    let mut trusted: Option<TrustedPromise> = Some(TrustedPromise::new(promise.clone()));
+    let trusted_receiver = Trusted::new(receiver);
+    ROUTER.add_typed_route(
+        action_receiver,
+        Box::new(move |message| {
+            let trusted = if let Some(trusted) = trusted.take() {
+                trusted
+            } else {
+                error!("RoutedPromiseListener callback called twice!");
+                return;
+            };
+
+            let context = RoutedPromiseContext {
+                trusted,
+                receiver: trusted_receiver.clone(),
+            };
+            task_source.queue(task!(routed_promise_task: move|| {
+                context.response(message.unwrap(), CanGc::note());
+            }));
+        }),
+    );
+    action_sender
+}