generalize some of the command logic

engine/src/edn.rs

@@ -1 +0,0 @@
-use crate::*;

engine/src/input.rs

@@ -1,6 +1,8 @@
 use crate::*;
 
 mod handle; pub use self::handle::*;
+mod command; pub use self::command::*;
+mod event_map; pub use self::event_map::*;
 
 /// Current input state
 pub trait Input<E: Engine> {

engine/src/input/command.rs

@@ -0,0 +1,45 @@
+use crate::*;
+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> {
+        Ok(self.execute(state)?.map(wrap))
+    }
+}
+#[macro_export] macro_rules! input_to_command {
+    (<$($l:lifetime),+> $Command:ty: |$state:ident:$State:ty, $input:ident:$Input:ty| $handler:expr) => {
+        impl<$($l),+> InputToCommand<$Input, $State> for $Command {
+            fn input_to_command ($state: &$State, $input: &$Input) -> Option<Self> {
+                Some($handler)
+            }
+        }
+    };
+    ($Command:ty: |$state:ident:$State:ty, $input:ident:$Input:ty| $handler:expr) => {
+        impl InputToCommand<$Input, $State> for $Command {
+            fn input_to_command ($state: &$State, $input: &$Input) -> Option<Self> {
+                Some($handler)
+            }
+        }
+    }
+}
+
+pub trait InputToCommand<I, S>: Command<S> + Sized {
+    fn input_to_command (state: &S, input: &I) -> Option<Self>;
+    fn execute_with_state (state: &mut S, input: &I) -> Perhaps<bool> {
+        Ok(if let Some(command) = Self::input_to_command(state, input) {
+            let _undo = command.execute(state)?;
+            Some(true)
+        } else {
+            None
+        })
+    }
+}
+
+#[macro_export] macro_rules! command {
+    ($(<$($l:lifetime),+>)?|$self:ident:$Command:ty,$state:ident:$State:ty|$handler:expr) => {
+        impl$(<$($l),+>)? Command<$State> for $Command {
+            fn execute ($self, $state: &mut $State) -> Perhaps<Self> {
+                Ok($handler)
+            }
+        }
+    };
+}

engine/src/input/event_map.rs

@@ -0,0 +1,43 @@
+use crate::*;
+
+pub struct EventMap<'a, S, I: PartialEq, C> {
+    pub bindings: &'a [(I, &'a dyn Fn(&S) -> Option<C>)],
+    pub fallback: Option<&'a dyn Fn(&S, &I) -> Option<C>>
+}
+impl<'a, S, I: PartialEq, C> EventMap<'a, S, I, C> {
+    pub fn handle (&self, state: &S, input: &I) -> Option<C> {
+        for (binding, handler) in self.bindings.iter() {
+            if input == binding {
+                return handler(state)
+            }
+        }
+        if let Some(fallback) = self.fallback {
+            fallback(state, input)
+        } else {
+            None
+        }
+    }
+}
+
+#[macro_export] macro_rules! keymap {
+    (
+        $(<$lt:lifetime>)? $KEYS:ident = |$state:ident: $State:ty, $input:ident: $Input:ty| $Command:ty
+        { $($key:expr => $handler:expr),* $(,)? } $(,)?
+    ) => {
+        pub const $KEYS: EventMap<'static, $State, $Input, $Command> = EventMap {
+            fallback: None,
+            bindings: &[ $(($key, &|$state|Some($handler)),)* ]
+        };
+        input_to_command!($(<$lt>)? $Command: |$state: $State, input: $Input|$KEYS.handle($state, input)?);
+    };
+    (
+        $(<$lt:lifetime>)? $KEYS:ident = |$state:ident: $State:ty, $input:ident: $Input:ty| $Command:ty
+        { $($key:expr => $handler:expr),* $(,)? }, $default:expr
+    ) => {
+        pub const $KEYS: EventMap<'static, $State, $Input, $Command> = EventMap {
+            fallback: Some(&|$state, $input|Some($default)),
+            bindings: &[ $(($key, &|$state|Some($handler)),)* ]
+        };
+        input_to_command!($(<$lt>)? $Command: |$state: $State, input: $Input|$KEYS.handle($state, input)?);
+    };
+}