Add basic undo functionality

This adds very basic undo functionality.
It works very well in a non collaborative environment, however undoing
your local changes when other remote changes occured can have unexpected consequences.

frontend/package.json

@@ -73,6 +73,7 @@
     "reconnecting-websocket": "^4.4.0",
     "slate": "^0.94.0",
     "slate-automerge-doc": "github:bugbakery/slate-automerge-doc",
+    "slate-history": "^0.93.0",
     "slate-react": "^0.94.0",
     "swr": "^2.1.0",
     "tailwindcss": "^3.2.7",

frontend/src/editor/automerge_websocket_editor.ts

@@ -1,6 +1,7 @@
 import { useLocation } from 'wouter';
 import { useEffect, useRef, useState } from 'react';
 import { Editor, createEditor } from 'slate';
+import { withHistory, HistoryEditor } from 'slate-history';
 import { withReact } from 'slate-react';
 import { withAutomergeDoc } from 'slate-automerge-doc';
 import { unstable as Automerge } from '@automerge/automerge';
@@ -53,7 +54,7 @@ export function useAutomergeWebsocketEditor(
     const createNewEditor = (doc: Automerge.Doc<Document>) => {
       const baseEditor = createEditor();
       const editorWithReact = withReact(baseEditor);
-      const editor = withAutomergeDoc(editorWithReact, Automerge.init());
+      const editor = withHistory(withAutomergeDoc(editorWithReact, Automerge.init()));
       editor.addDocChangeListener(sendDocChange);
 
       const migratedDoc = migrateDocument(doc as Automerge.Doc<Document>);
@@ -83,7 +84,9 @@ export function useAutomergeWebsocketEditor(
         const [newDoc] = Automerge.applyChanges(editorRef.current.doc, [msg]);
         console.timeEnd('automerge');
         console.time('setDoc');
-        editorRef.current?.setDoc(newDoc);
+        HistoryEditor.withoutSaving(editorRef.current, () => {
+          editorRef.current?.setDoc(newDoc);
+        });
         console.timeEnd('setDoc');
       } else if (msg_type === MessageSyncType.ChangeBacklogComplete) {
         console.info('backlog complete');

frontend/src/editor/slate_types.d.ts

@@ -1,11 +1,12 @@
 import { BaseEditor } from 'slate';
 import { ReactEditor } from 'slate-react';
+import { HistoryEditor } from 'slate-history';
 import { Paragraph, Text, Document } from './types';
 import { AutomergeEditor } from 'slate-automerge-doc';
 
 declare module 'slate' {
   interface CustomTypes {
-    Editor: BaseEditor & ReactEditor & AutomergeEditor<Document>;
+    Editor: BaseEditor & ReactEditor & HistoryEditor & AutomergeEditor<Document>;
     Element: Paragraph;
     Text: Text;
   }