1 files changed, 108 insertions, 0 deletions
diff --git a/runtime/src/command.rs b/runtime/src/command.rs
new file mode 100644
index 00000000..cd4c51ff
--- /dev/null
+++ b/runtime/src/command.rs
@@ -0,0 +1,108 @@
+//! Run asynchronous actions.
+mod action;
+
+pub use action::Action;
+
+use crate::core::widget;
+use crate::futures::MaybeSend;
+
+use std::fmt;
+use std::future::Future;
+
+/// A set of asynchronous actions to be performed by some runtime.
+#[must_use = "`Command` must be returned to runtime to take effect"]
+pub struct Command<T>(Internal<Action<T>>);
+
+#[derive(Debug)]
+enum Internal<T> {
+    None,
+    Single(T),
+    Batch(Vec<T>),
+}
+
+impl<T> Command<T> {
+    /// Creates an empty [`Command`].
+    ///
+    /// In other words, a [`Command`] that does nothing.
+    pub const fn none() -> Self {
+        Self(Internal::None)
+    }
+
+    /// Creates a [`Command`] that performs a single [`Action`].
+    pub const fn single(action: Action<T>) -> Self {
+        Self(Internal::Single(action))
+    }
+
+    /// Creates a [`Command`] that performs a [`widget::Operation`].
+    pub fn widget(operation: impl widget::Operation<T> + 'static) -> Self {
+        Self::single(Action::Widget(Box::new(operation)))
+    }
+
+    /// Creates a [`Command`] that performs the action of the given future.
+    pub fn perform<A>(
+        future: impl Future<Output = T> + 'static + MaybeSend,
+        f: impl FnOnce(T) -> A + 'static + MaybeSend,
+    ) -> Command<A> {
+        use iced_futures::futures::FutureExt;
+
+        Command::single(Action::Future(Box::pin(future.map(f))))
+    }
+
+    /// Creates a [`Command`] that performs the actions of all the given
+    /// commands.
+    ///
+    /// Once this command is run, all the commands will be executed at once.
+    pub fn batch(commands: impl IntoIterator<Item = Command<T>>) -> Self {
+        let mut batch = Vec::new();
+
+        for Command(command) in commands {
+            match command {
+                Internal::None => {}
+                Internal::Single(command) => batch.push(command),
+                Internal::Batch(commands) => batch.extend(commands),
+            }
+        }
+
+        Self(Internal::Batch(batch))
+    }
+
+    /// Applies a transformation to the result of a [`Command`].
+    pub fn map<A>(
+        self,
+        f: impl Fn(T) -> A + 'static + MaybeSend + Sync + Clone,
+    ) -> Command<A>
+    where
+        T: 'static,
+        A: 'static,
+    {
+        match self.0 {
+            Internal::None => Command::none(),
+            Internal::Single(action) => Command::single(action.map(f)),
+            Internal::Batch(batch) => Command(Internal::Batch(
+                batch
+                    .into_iter()
+                    .map(|action| action.map(f.clone()))
+                    .collect(),
+            )),
+        }
+    }
+
+    /// Returns all of the actions of the [`Command`].
+    pub fn actions(self) -> Vec<Action<T>> {
+        let Command(command) = self;
+
+        match command {
+            Internal::None => Vec::new(),
+            Internal::Single(action) => vec![action],
+            Internal::Batch(batch) => batch,
+        }
+    }
+}
+
+impl<T> fmt::Debug for Command<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Command(command) = self;
+
+        command.fmt(f)
+    }
+}