1 files changed, 124 insertions, 0 deletions
diff --git a/futures/src/runtime.rs b/futures/src/runtime.rs
new file mode 100644
index 00000000..d204670b
--- /dev/null
+++ b/futures/src/runtime.rs
@@ -0,0 +1,124 @@
+//! Run commands and keep track of subscriptions.
+use crate::{subscription, Command, Executor, Subscription};
+
+use futures::{channel::mpsc, Sink};
+use std::marker::PhantomData;
+
+/// A batteries-included runtime of commands and subscriptions.
+///
+/// If you have an [`Executor`], a [`Runtime`] can be leveraged to run any
+/// [`Command`] or [`Subscription`] and get notified of the results!
+///
+/// [`Runtime`]: struct.Runtime.html
+/// [`Executor`]: executor/trait.Executor.html
+/// [`Command`]: struct.Command.html
+/// [`Subscription`]: subscription/struct.Subscription.html
+#[derive(Debug)]
+pub struct Runtime<Hasher, Event, Executor, Sender, Message> {
+    executor: Executor,
+    sender: Sender,
+    subscriptions: subscription::Tracker<Hasher, Event>,
+    _message: PhantomData<Message>,
+}
+
+impl<Hasher, Event, Executor, Sender, Message>
+    Runtime<Hasher, Event, Executor, Sender, Message>
+where
+    Hasher: std::hash::Hasher + Default,
+    Event: Send + Clone + 'static,
+    Executor: self::Executor,
+    Sender:
+        Sink<Message, Error = mpsc::SendError> + Unpin + Send + Clone + 'static,
+    Message: Send + 'static,
+{
+    /// Creates a new empty [`Runtime`].
+    ///
+    /// You need to provide:
+    /// - an [`Executor`] to spawn futures
+    /// - a `Sender` implementing `Sink` to receive the results
+    ///
+    /// [`Runtime`]: struct.Runtime.html
+    pub fn new(executor: Executor, sender: Sender) -> Self {
+        Self {
+            executor,
+            sender,
+            subscriptions: subscription::Tracker::new(),
+            _message: PhantomData,
+        }
+    }
+
+    /// Runs the given closure inside the [`Executor`] of the [`Runtime`].
+    ///
+    /// See [`Executor::enter`] to learn more.
+    ///
+    /// [`Executor`]: executor/trait.Executor.html
+    /// [`Runtime`]: struct.Runtime.html
+    /// [`Executor::enter`]: executor/trait.Executor.html#method.enter
+    pub fn enter<R>(&self, f: impl FnOnce() -> R) -> R {
+        self.executor.enter(f)
+    }
+
+    /// Spawns a [`Command`] in the [`Runtime`].
+    ///
+    /// The resulting `Message` will be forwarded to the `Sender` of the
+    /// [`Runtime`].
+    ///
+    /// [`Command`]: struct.Command.html
+    /// [`Runtime`]: struct.Runtime.html
+    pub fn spawn(&mut self, command: Command<Message>) {
+        use futures::{FutureExt, SinkExt};
+
+        let futures = command.futures();
+
+        for future in futures {
+            let mut sender = self.sender.clone();
+
+            let future = future.then(|message| async move {
+                let _ = sender.send(message).await;
+
+                ()
+            });
+
+            self.executor.spawn(future);
+        }
+    }
+
+    /// Tracks a [`Subscription`] in the [`Runtime`].
+    ///
+    /// It will spawn new streams or close old ones as necessary! See
+    /// [`Tracker::update`] to learn more about this!
+    ///
+    /// [`Subscription`]: subscription/struct.Subscription.html
+    /// [`Runtime`]: struct.Runtime.html
+    /// [`Tracker::update`]: subscription/struct.Tracker.html#method.update
+    pub fn track(
+        &mut self,
+        subscription: Subscription<Hasher, Event, Message>,
+    ) {
+        let Runtime {
+            executor,
+            subscriptions,
+            sender,
+            ..
+        } = self;
+
+        let futures = executor
+            .enter(|| subscriptions.update(subscription, sender.clone()));
+
+        for future in futures {
+            executor.spawn(future);
+        }
+    }
+
+    /// Broadcasts an event to all the subscriptions currently alive in the
+    /// [`Runtime`].
+    ///
+    /// See [`Tracker::broadcast`] to learn more.
+    ///
+    /// [`Runtime`]: struct.Runtime.html
+    /// [`Tracker::broadcast`]:
+    /// subscription/struct.Tracker.html#method.broadcast
+    pub fn broadcast(&mut self, event: Event) {
+        self.subscriptions.broadcast(event);
+    }
+}