feat(history): add undo redo stack

commands/dispatcher.ts

@@ -1,5 +1,6 @@
-import type { AppState } from "@editor/state";
+import type { AppState, HistorySnapshot } from "@editor/state";
 import type { CommandContext } from "./command";
+import { commandIds } from "./ids";
 import type { CommandId, CommandPayloads } from "./payloads";
 import type { CommandRegistry } from "./registry";
 
@@ -21,10 +22,31 @@ export function createCommandDispatcher(options: {
         throw new Error(`Unknown command: ${commandId}`);
       }
 
-      const context: CommandContext = { state: options.getState() };
-      const nextState = command.execute(context, payload);
+      const currentState = options.getState();
+      const context: CommandContext = { state: currentState };
+      const executedState = command.execute(context, payload);
+      const nextState = shouldRecordHistory(commandId, currentState, executedState) ? recordHistory(currentState, executedState) : executedState;
       options.setState(nextState);
       return nextState;
     },
   };
 }
+
+function shouldRecordHistory(commandId: CommandId, currentState: AppState, nextState: AppState) {
+  if (commandId === commandIds.historyUndo || commandId === commandIds.historyRedo) return false;
+  return currentState.document !== nextState.document;
+}
+
+function recordHistory(currentState: AppState, nextState: AppState): AppState {
+  return {
+    ...nextState,
+    history: {
+      past: [...currentState.history.past, snapshot(currentState)].slice(-100),
+      future: [],
+    },
+  };
+}
+
+function snapshot(state: AppState): HistorySnapshot {
+  return { document: state.document, editor: state.editor };
+}