1 files changed, 41 insertions, 17 deletions

diff --git a/rprt-engine/src/monad.rs b/rprt-engine/src/monad.rs
index ae0df3e..34ff46b 100644
--- a/rprt-engine/src/monad.rs
+++ b/rprt-engine/src/monad.rs
@@ -1,6 +1,6 @@
 use crate::{
-    selection::Selection,
-    state::{EditorState, EvaluationResult},
+    selection::{Selection, SelectionError},
+    state::{EditorState, EvaluationResult, GroupedChangeError},
 };
 
 pub enum EvaluationStrategy {
@@ -8,43 +8,67 @@ pub enum EvaluationStrategy {
     Grouped,
 }
 
-pub type MonadicState = (EditorState, EvaluationResult);
+#[derive(Debug)]
+pub enum EvaluationError {
+    Selection(SelectionError),
+    GroupedChange(GroupedChangeError),
+}
+
+impl From<SelectionError> for EvaluationError {
+    fn from(err: SelectionError) -> Self {
+        EvaluationError::Selection(err)
+    }
+}
+
+impl From<GroupedChangeError> for EvaluationError {
+    fn from(err: GroupedChangeError) -> Self {
+        EvaluationError::GroupedChange(err)
+    }
+}
 
 pub struct EditorStateMonad {
-    func: Box<dyn Fn(EditorState) -> MonadicState>,
+    func: Box<dyn Fn(&EditorState) -> EvaluationResult>,
 }
 
 impl EditorStateMonad {
-    pub fn new(f: impl Fn(EditorState) -> MonadicState + 'static) -> Self {
+    pub fn new(f: impl Fn(&EditorState) -> EvaluationResult + 'static) -> Self {
         Self { func: Box::new(f) }
     }
 
-    pub fn run(&self, initial_state: EditorState) -> MonadicState {
-        (self.func)(initial_state)
+    pub fn run(&self, state: &EditorState) -> EvaluationResult {
+        (self.func)(state)
     }
 
-    pub fn run_with_strategy<E>(
+    pub fn run_with_strategy(
         monads: Vec<EditorStateMonad>,
         strategy: EvaluationStrategy,
-        initial_state: EditorState,
-    ) -> Result<MonadicState, E> {
+        state: &mut EditorState,
+    ) -> Result<Selection, EvaluationError> {
         match strategy {
             EvaluationStrategy::Sequential => {
-                let mut state_changes = Vec::new();
                 let mut last_selection = Selection::empty();
-                let mut current_state = initial_state;
 
                 for monad in monads {
-                    let (new_state, (sel, st_ch)) = monad.run(current_state);
-                    current_state = new_state;
+                    let (sel, state_changes) = monad.run(state);
+                    state.commit_changes(state_changes);
                     last_selection = sel;
-                    state_changes.extend(st_ch);
                 }
 
-                Ok((current_state, (last_selection, state_changes)))
+                Ok(last_selection)
             }
             EvaluationStrategy::Grouped => {
-                panic!("TODO")
+                let mut arms = Vec::new();
+                let mut all_selections = Vec::new();
+
+                for monad in monads {
+                    let (sel, state_changes) = monad.run(state);
+                    all_selections.push(sel);
+                    arms.push(state_changes);
+                }
+
+                state.commit_changes_grouped(arms)?;
+
+                Ok(Selection::union(all_selections)?)
             }
         }
     }