core, input, output, dsl: factor away 'flexi' traits

input/src/input.rs

@@ -0,0 +1,41 @@
+use crate::*;
+
+/// Event source
+pub trait Input: Sized {
+    /// Type of input event
+    type Event;
+    /// Result of handling input
+    type Handled; // TODO: make this an Option<Box dyn Command<Self>> containing the undo
+    /// Currently handled event
+    fn event (&self) -> &Self::Event;
+    /// Whether component should exit
+    fn is_done (&self) -> bool;
+    /// Mark component as done
+    fn done (&self);
+}
+
+flex_trait_mut!(Handle <E: Input> {
+    fn handle (&mut self, _input: &E) -> Perhaps<E::Handled> {
+        Ok(None)
+    }
+});
+
+pub trait Command<S>: Send + Sync + Sized {
+    fn execute (self, state: &mut S) -> Perhaps<Self>;
+    fn delegate <T> (self, state: &mut S, wrap: impl Fn(Self)->T) -> Perhaps<T>
+        where Self: Sized
+    {
+        Ok(self.execute(state)?.map(wrap))
+    }
+}
+
+impl<S, T: Command<S>> Command<S> for Option<T> {
+    fn execute (self, _: &mut S) -> Perhaps<Self> {
+        Ok(None)
+    }
+    fn delegate <U> (self, _: &mut S, _: impl Fn(Self)->U) -> Perhaps<U>
+        where Self: Sized
+    {
+        Ok(None)
+    }
+}