chore(toc): attempt to read using CKEditor API

apps/client/src/widgets/sidebar/TableOfContents.tsx

@@ -1,15 +1,62 @@
+import { CKTextEditor, ModelElement } from "@triliumnext/ckeditor5";
+import { useEffect, useState } from "preact/hooks";
+
 import FNote from "../../entities/fnote";
 import { t } from "../../services/i18n";
-import { useNoteSavedData } from "../react/hooks";
+import { useActiveNoteContext, useNoteSavedData, useTriliumEvent } from "../react/hooks";
 import RightPanelWidget from "./RightPanelWidget";
 
-export default function TableOfContents({ note }: { note: FNote }) {
-    const content = useNoteSavedData(note.noteId);
+interface CKHeading {
+    level: number;
+    text: string;
+    element: ModelElement;
+}
+
+export default function TableOfContents() {
+    const { ntxId } = useActiveNoteContext();
+    const [ textEditor, setTextEditor ] = useState<CKTextEditor | null>(null);
+    const [ headings, setHeadings ] = useState<CKHeading[]>([]);
+
+    // Populate the cache with the toolbar of every note context.
+    useTriliumEvent("textEditorRefreshed", ({ ntxId: eventNtxId, editor }) => {
+        if (eventNtxId !== ntxId) return;
+        setTextEditor(editor);
+    });
+
+    useEffect(() => {
+        if (!textEditor) return;
+        const headings  = extractTocFromTextEditor(textEditor);
+        setHeadings(headings);
+    }, [ textEditor ]);
+
+    console.log("Render with ", headings);
 
     return (
         <RightPanelWidget title={t("toc.table_of_contents")}>
-            {content?.length}
+            {headings.map(heading => (
+                <li>{heading.text}</li>
+            ))}
         </RightPanelWidget>
     );
 
 }
+
+function extractTocFromTextEditor(editor: CKTextEditor) {
+    const headings: CKHeading[] = [];
+
+    const root = editor.model.document.getRoot();
+    if (!root) return [];
+
+    for (const { type, item } of editor.model.createRangeIn(root).getWalker()) {
+        if (type !== "elementStart" || !item.is('element') || !item.name.startsWith('heading')) continue;
+
+        const level = Number(item.name.replace( 'heading', '' ));
+        const text = Array.from( item.getChildren() )
+            .map( c => c.is( '$text' ) ? c.data : '' )
+            .join( '' );
+
+        headings.push({ level, text, element: item });
+    }
+
+    return headings;
+}