Undo and redo!

src/cg/06-textEditor.cg

@@ -12,6 +12,33 @@ textEditor = name \
 
     { state = state.{ lines = newLines, cursorCol = state.cursorCol + 1 }, emit = [] };
 
+  insertMode = state \
+    stateSnapshot = { lines = state.lines, cursorRow = state.cursorRow, cursorCol = state.cursorCol };
+    newUndoStack = [stateSnapshot, ...state.undoStack];
+    {
+      state = state.{
+        undoStack = newUndoStack,
+        mode = Insert
+      },
+      emit = []
+    };
+
+  escape = state \ { state = state.{ mode = Normal }, emit = [] };
+
+  undo = state \ state.undoStack
+    | [] \ { state = state, emit = [] }
+    | [prev, ...rest] \ (
+      stateSnapshot = { lines = state.lines, cursorRow = state.cursorRow, cursorCol = state.cursorCol };
+
+      { state = state.{ lines = prev.lines, cursorCol = prev.cursorCol, cursorRow = prev.cursorRow, undoStack = rest, redoStack = [stateSnapshot, ...state.redoStack] }, emit = [] });
+
+  redo = state \ state.redoStack
+    | [] \ { state = state, emit = [] }
+    | [prev, ...rest] \ (
+      stateSnapshot = { lines = state.lines, cursorRow = state.cursorRow, cursorCol = state.cursorCol };
+
+      { state = state.{ lines = prev.lines, cursorCol = prev.cursorCol, cursorRow = prev.cursorRow, undoStack = [stateSnapshot, ...state.undoStack], redoStack = rest }, emit = [] });
+
   backspace = state \
     state.cursorCol == 0
     | True \ (
@@ -84,6 +111,8 @@ textEditor = name \
         cursorCol = 0,
         scrollX = 0,
         scrollY = 0,
+        undoStack = [],
+        redoStack = [],
         mode = Normal # Normal | Insert | Visual
       },
 
@@ -110,9 +139,17 @@ textEditor = name \
 
         | Key { key = "i" } \ (state.mode
           | Insert \ insertChar "i" state
-          | Normal \ { state = state.{ mode = state.mode | Normal \ Insert | _ \ Insert } })
+          | Normal \ insertMode state)
 
-        | Key { key = "Escape" } \ { state = state.{ mode = state.mode | Insert \ Normal | _ \ Normal } }
+        | Key { key = "u" } \ (state.mode
+          | Insert \ insertChar "u" state
+          | Normal \ undo state)
+
+        | Key { key = "r", ctrl = True } \ (state.mode
+          | Insert \ insertChar "R" state
+          | Normal \ redo state)
+
+        | Key { key = "Escape" } \ escape state
 
         | Key { key = "Backspace" } \ (state.mode
           | Insert \ backspace state
@@ -130,8 +167,6 @@ textEditor = name \
         | _ \ { state = state, emit = [] },
 
       view = state emit \
-        _ = debug! "view" state;
-
         buffer = map (l \ text l) state.lines;
 
         scale = 2;