Split `iced_futures` into different `backend` implementations

10 files changed, 266 insertions, 12 deletions

diff --git a/futures/src/backend.rs b/futures/src/backend.rs
new file mode 100644
index 00000000..1cc4af80
--- /dev/null
+++ b/futures/src/backend.rs
@@ -0,0 +1,10 @@
+//! The underlying implementations of the `iced_futures` contract!
+pub mod null;
+
+#[cfg(not(target_arch = "wasm32"))]
+pub mod native;
+
+#[cfg(target_arch = "wasm32")]
+pub mod wasm;
+
+pub mod default;
diff --git a/futures/src/backend/default.rs b/futures/src/backend/default.rs
new file mode 100644
index 00000000..76264f55
--- /dev/null
+++ b/futures/src/backend/default.rs
@@ -0,0 +1,38 @@
+//! A default, cross-platform backend.
+//!
+//! - On native platforms, it will use:
+//!   - `backend::native::tokio` when the `tokio` feature is enabled.
+//!   - `backend::native::async-std` when the `async-std` feature is
+//!     enabled.
+//!   - `backend::native::smol` when the `smol` feature is enabled.
+//!   - `backend::native::thread_pool` otherwise.
+//!
+//! - On Wasm, it will use `backend::wasm::wasm_bindgen`.
+#[cfg(not(target_arch = "wasm32"))]
+mod platform {
+    #[cfg(feature = "tokio")]
+    pub use crate::backend::native::tokio::*;
+
+    #[cfg(all(feature = "async-std", not(feature = "tokio"),))]
+    pub use crate::backend::native::async_std::*;
+
+    #[cfg(all(
+        feature = "smol",
+        not(any(feature = "tokio", feature = "async-std")),
+    ))]
+    pub use crate::backend::native::smol::*;
+
+    #[cfg(not(any(
+        feature = "tokio",
+        feature = "async-std",
+        feature = "smol",
+    )))]
+    pub use crate::backend::native::thread_pool::*;
+}
+
+#[cfg(target_arch = "wasm32")]
+mod platform {
+    pub use crate::backend::wasm::wasm_bindgen::*;
+}
+
+pub use platform::*;
diff --git a/futures/src/backend/native.rs b/futures/src/backend/native.rs
new file mode 100644
index 00000000..4199ad16
--- /dev/null
+++ b/futures/src/backend/native.rs
@@ -0,0 +1,16 @@
+//! Backends that are only available in native platforms: Windows, macOS, or Linux.
+#[cfg_attr(docsrs, doc(cfg(feature = "tokio",)))]
+#[cfg(feature = "tokio")]
+pub mod tokio;
+
+#[cfg_attr(docsrs, doc(cfg(feature = "async-std",)))]
+#[cfg(feature = "async-std")]
+pub mod async_std;
+
+#[cfg_attr(docsrs, doc(cfg(feature = "smol",)))]
+#[cfg(feature = "smol")]
+pub mod smol;
+
+#[cfg_attr(docsrs, doc(cfg(feature = "thread-pool",)))]
+#[cfg(feature = "thread-pool")]
+pub mod thread_pool;
diff --git a/futures/src/backend/native/async_std.rs b/futures/src/backend/native/async_std.rs
new file mode 100644
index 00000000..e8641626
--- /dev/null
+++ b/futures/src/backend/native/async_std.rs
@@ -0,0 +1,59 @@
+//! An `async-std` backend.
+use futures::Future;
+
+/// An `async-std` executor.
+#[derive(Debug)]
+pub struct Executor;
+
+impl crate::Executor for Executor {
+    fn new() -> Result<Self, futures::io::Error> {
+        Ok(Self)
+    }
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static) {
+        let _ = async_std::task::spawn(future);
+    }
+}
+
+pub mod time {
+    //! Listen and react to time.
+    use crate::subscription::{self, Subscription};
+
+    /// Returns a [`Subscription`] that produces messages at a set interval.
+    ///
+    /// The first message is produced after a `duration`, and then continues to
+    /// produce more messages every `duration` after that.
+    pub fn every<H: std::hash::Hasher, E>(
+        duration: std::time::Duration,
+    ) -> Subscription<H, E, std::time::Instant> {
+        Subscription::from_recipe(Every(duration))
+    }
+
+    #[derive(Debug)]
+    struct Every(std::time::Duration);
+
+    impl<H, E> subscription::Recipe<H, E> for Every
+    where
+        H: std::hash::Hasher,
+    {
+        type Output = std::time::Instant;
+
+        fn hash(&self, state: &mut H) {
+            use std::hash::Hash;
+
+            std::any::TypeId::of::<Self>().hash(state);
+            self.0.hash(state);
+        }
+
+        fn stream(
+            self: Box<Self>,
+            _input: futures::stream::BoxStream<'static, E>,
+        ) -> futures::stream::BoxStream<'static, Self::Output> {
+            use futures::stream::StreamExt;
+
+            async_std::stream::interval(self.0)
+                .map(|_| std::time::Instant::now())
+                .boxed()
+        }
+    }
+}
diff --git a/futures/src/backend/native/smol.rs b/futures/src/backend/native/smol.rs
new file mode 100644
index 00000000..d5201cde
--- /dev/null
+++ b/futures/src/backend/native/smol.rs
@@ -0,0 +1,59 @@
+//! A `smol` backend.
+
+use futures::Future;
+
+/// A `smol` executor.
+#[cfg_attr(docsrs, doc(cfg(feature = "smol")))]
+#[derive(Debug)]
+pub struct Executor;
+
+impl crate::Executor for Executor {
+    fn new() -> Result<Self, futures::io::Error> {
+        Ok(Self)
+    }
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static) {
+        smol::spawn(future).detach();
+    }
+}
+
+pub mod time {
+    //! Listen and react to time.
+    use crate::subscription::{self, Subscription};
+
+    /// Returns a [`Subscription`] that produces messages at a set interval.
+    ///
+    /// The first message is produced after a `duration`, and then continues to
+    /// produce more messages every `duration` after that.
+    pub fn every<H: std::hash::Hasher, E>(
+        duration: std::time::Duration,
+    ) -> Subscription<H, E, std::time::Instant> {
+        Subscription::from_recipe(Every(duration))
+    }
+
+    #[derive(Debug)]
+    struct Every(std::time::Duration);
+
+    impl<H, E> subscription::Recipe<H, E> for Every
+    where
+        H: std::hash::Hasher,
+    {
+        type Output = std::time::Instant;
+
+        fn hash(&self, state: &mut H) {
+            use std::hash::Hash;
+
+            std::any::TypeId::of::<Self>().hash(state);
+            self.0.hash(state);
+        }
+
+        fn stream(
+            self: Box<Self>,
+            _input: futures::stream::BoxStream<'static, E>,
+        ) -> futures::stream::BoxStream<'static, Self::Output> {
+            use futures::stream::StreamExt;
+
+            smol::Timer::interval(self.0).boxed()
+        }
+    }
+}
diff --git a/futures/src/executor/thread_pool.rs b/futures/src/backend/native/thread_pool.rs
index a6c6168e..6e791533 100644
--- a/futures/src/executor/thread_pool.rs
+++ b/futures/src/backend/native/thread_pool.rs
@@ -1,12 +1,11 @@
-use crate::Executor;
-
+//! A `ThreadPool` backend.
 use futures::Future;
 
-/// A thread pool runtime for futures.
+/// A thread pool executor for futures.
 #[cfg_attr(docsrs, doc(cfg(feature = "thread-pool")))]
 pub type ThreadPool = futures::executor::ThreadPool;
 
-impl Executor for futures::executor::ThreadPool {
+impl crate::Executor for futures::executor::ThreadPool {
     fn new() -> Result<Self, futures::io::Error> {
         futures::executor::ThreadPool::new()
     }
diff --git a/futures/src/backend/native/tokio.rs b/futures/src/backend/native/tokio.rs
new file mode 100644
index 00000000..f86b0ea3
--- /dev/null
+++ b/futures/src/backend/native/tokio.rs
@@ -0,0 +1,72 @@
+//! A `tokio` backend.
+use futures::Future;
+
+/// A `tokio` executor.
+pub type Executor = tokio::runtime::Runtime;
+
+impl crate::Executor for Executor {
+    fn new() -> Result<Self, futures::io::Error> {
+        tokio::runtime::Runtime::new()
+    }
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static) {
+        let _ = tokio::runtime::Runtime::spawn(self, future);
+    }
+
+    fn enter<R>(&self, f: impl FnOnce() -> R) -> R {
+        let _guard = tokio::runtime::Runtime::enter(self);
+        f()
+    }
+}
+
+pub mod time {
+    //! Listen and react to time.
+    use crate::subscription::{self, Subscription};
+
+    /// Returns a [`Subscription`] that produces messages at a set interval.
+    ///
+    /// The first message is produced after a `duration`, and then continues to
+    /// produce more messages every `duration` after that.
+    pub fn every<H: std::hash::Hasher, E>(
+        duration: std::time::Duration,
+    ) -> Subscription<H, E, std::time::Instant> {
+        Subscription::from_recipe(Every(duration))
+    }
+
+    #[derive(Debug)]
+    struct Every(std::time::Duration);
+
+    impl<H, E> subscription::Recipe<H, E> for Every
+    where
+        H: std::hash::Hasher,
+    {
+        type Output = std::time::Instant;
+
+        fn hash(&self, state: &mut H) {
+            use std::hash::Hash;
+
+            std::any::TypeId::of::<Self>().hash(state);
+            self.0.hash(state);
+        }
+
+        fn stream(
+            self: Box<Self>,
+            _input: futures::stream::BoxStream<'static, E>,
+        ) -> futures::stream::BoxStream<'static, Self::Output> {
+            use futures::stream::StreamExt;
+
+            let start = tokio::time::Instant::now() + self.0;
+
+            let stream = {
+                futures::stream::unfold(
+                    tokio::time::interval_at(start, self.0),
+                    |mut interval| async move {
+                        Some((interval.tick().await, interval))
+                    },
+                )
+            };
+
+            stream.map(tokio::time::Instant::into_std).boxed()
+        }
+    }
+}
diff --git a/futures/src/executor/null.rs b/futures/src/backend/null.rs
index 65e2e2df..e22e7921 100644
--- a/futures/src/executor/null.rs
+++ b/futures/src/backend/null.rs
@@ -1,12 +1,11 @@
-use crate::Executor;
-
+//! A backend that does nothing!
 use futures::Future;
 
 /// An executor that drops all the futures, instead of spawning them.
 #[derive(Debug)]
-pub struct Null;
+pub struct Executor;
 
-impl Executor for Null {
+impl crate::Executor for Executor {
     fn new() -> Result<Self, futures::io::Error> {
         Ok(Self)
     }
diff --git a/futures/src/backend/wasm.rs b/futures/src/backend/wasm.rs
new file mode 100644
index 00000000..a49d9e55
--- /dev/null
+++ b/futures/src/backend/wasm.rs
@@ -0,0 +1,2 @@
+//! Backends that are only available on Wasm targets.
+pub mod wasm_bindgen;
diff --git a/futures/src/executor/wasm_bindgen.rs b/futures/src/backend/wasm/wasm_bindgen.rs
index 94d694c8..e914aeba 100644
--- a/futures/src/executor/wasm_bindgen.rs
+++ b/futures/src/backend/wasm/wasm_bindgen.rs
@@ -1,10 +1,10 @@
-use crate::Executor;
+//! A `wasm-bindgein-futures` backend.
 
-/// A `wasm-bindgen-futures` runtime.
+/// A `wasm-bindgen-futures` executor.
 #[derive(Debug)]
-pub struct WasmBindgen;
+pub struct Executor;
 
-impl Executor for WasmBindgen {
+impl crate::Executor for Executor {
     fn new() -> Result<Self, futures::io::Error> {
         Ok(Self)
     }