Implement `Runtime` and `Executor` in `iced_core`

They can be leveraged by shells to easily execute commands
and track subscriptions.

5 files changed, 97 insertions, 4 deletions

diff --git a/core/Cargo.toml b/core/Cargo.toml
index 4e019ba9..5e1a5532 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -12,6 +12,8 @@ repository = "https://github.com/hecrj/iced"
 command = ["futures"]
 # Exposes a future-based `Subscription` type
 subscription = ["futures", "log"]
+# Exposes a `runtime` module meant to abstract over different future executors
+runtime = ["command", "subscription"]
 
 [dependencies]
 futures = { version = "0.3", optional = true }
diff --git a/core/src/lib.rs b/core/src/lib.rs
index 6f13c310..760acefe 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -44,3 +44,9 @@ pub mod subscription;
 
 #[cfg(feature = "subscription")]
 pub use subscription::Subscription;
+
+#[cfg(feature = "runtime")]
+mod runtime;
+
+#[cfg(feature = "runtime")]
+pub use runtime::Runtime;
diff --git a/core/src/runtime.rs b/core/src/runtime.rs
new file mode 100644
index 00000000..31234d11
--- /dev/null
+++ b/core/src/runtime.rs
@@ -0,0 +1,74 @@
+mod executor;
+
+pub use executor::Executor;
+
+use crate::{subscription, Command, Subscription};
+
+use futures::Sink;
+use std::marker::PhantomData;
+
+#[derive(Debug)]
+pub struct Runtime<Hasher, Event, Executor, Receiver, Message> {
+    executor: Executor,
+    subscriptions: subscription::Tracker<Hasher, Event>,
+    receiver: Receiver,
+    _message: PhantomData<Message>,
+}
+
+impl<Hasher, Event, Executor, Receiver, Message>
+    Runtime<Hasher, Event, Executor, Receiver, Message>
+where
+    Hasher: std::hash::Hasher + Default,
+    Event: Send + Clone + 'static,
+    Executor: self::Executor,
+    Receiver: Sink<Message, Error = core::convert::Infallible>
+        + Unpin
+        + Send
+        + Clone
+        + 'static,
+    Message: Send + 'static,
+{
+    pub fn new(receiver: Receiver) -> Self {
+        Self {
+            executor: Executor::new(),
+            subscriptions: subscription::Tracker::new(),
+            receiver,
+            _message: PhantomData,
+        }
+    }
+
+    pub fn spawn(&mut self, command: Command<Message>) {
+        use futures::{FutureExt, SinkExt};
+
+        let futures = command.futures();
+
+        for future in futures {
+            let mut receiver = self.receiver.clone();
+
+            self.executor.spawn(future.then(|message| {
+                async move {
+                    let _ = receiver.send(message).await;
+
+                    ()
+                }
+            }));
+        }
+    }
+
+    pub fn track(
+        &mut self,
+        subscription: Subscription<Hasher, Event, Message>,
+    ) {
+        let futures = self
+            .subscriptions
+            .update(subscription, self.receiver.clone());
+
+        for future in futures {
+            self.executor.spawn(future);
+        }
+    }
+
+    pub fn broadcast(&mut self, event: Event) {
+        self.subscriptions.broadcast(event);
+    }
+}
diff --git a/core/src/runtime/executor.rs b/core/src/runtime/executor.rs
new file mode 100644
index 00000000..d171c6d5
--- /dev/null
+++ b/core/src/runtime/executor.rs
@@ -0,0 +1,11 @@
+use futures::Future;
+
+pub trait Executor {
+    fn new() -> Self;
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static);
+
+    fn enter<R>(&self, f: impl FnOnce() -> R) -> R {
+        f()
+    }
+}
diff --git a/core/src/subscription/tracker.rs b/core/src/subscription/tracker.rs
index 826f60c0..a942b619 100644
--- a/core/src/subscription/tracker.rs
+++ b/core/src/subscription/tracker.rs
@@ -28,14 +28,14 @@ where
         }
     }
 
-    pub fn update<Message, S>(
+    pub fn update<Message, Receiver>(
         &mut self,
         subscription: Subscription<Hasher, Event, Message>,
-        sink: S,
+        receiver: Receiver,
     ) -> Vec<BoxFuture<'static, ()>>
     where
         Message: 'static + Send,
-        S: 'static
+        Receiver: 'static
             + Sink<Message, Error = core::convert::Infallible>
             + Unpin
             + Send
@@ -72,7 +72,7 @@ where
 
             let future = futures::future::select(
                 cancelled,
-                stream.map(Ok).forward(sink.clone()),
+                stream.map(Ok).forward(receiver.clone()),
             )
             .map(|_| ());