fix: unable to accpet 'make it longer'

frontend/appflowy_flutter/lib/plugins/document/presentation/editor_plugins/base/markdown_text_robot.dart

@@ -320,6 +320,12 @@ class MarkdownTextRobot {
     required Selection selection,
     required String markdownText,
   }) async {
+    if (markdownText.isEmpty) {
+      assert(false, 'Expected non-empty markdown text');
+      Log.error('Expected non-empty markdown text');
+      return;
+    }
+
     selection = selection.normalized;
 
     // If the selection is not a single node, do nothing.
@@ -372,15 +378,42 @@ class MarkdownTextRobot {
     //   }
     // ]
     final document = customMarkdownToDocument(markdownText);
+    final nodes = document.root.children;
     final decoder = DeltaMarkdownDecoder();
     final markdownDelta =
-        document.nodeAtPath([0])?.delta ?? decoder.convert(markdownText);
+        nodes.firstOrNull?.delta ?? decoder.convert(markdownText);
+
+    if (markdownDelta.isEmpty) {
+      assert(false, 'Expected non-empty markdown delta');
+      Log.error('Expected non-empty markdown delta');
+      return;
+    }
 
     // Replace the delta of the selected node.
     final transaction = editorState.transaction;
-    transaction
-      ..deleteText(node, startIndex, length)
-      ..insertTextDelta(node, startIndex, markdownDelta);
+
+    // it means the user selected the entire sentence, we just replace the node
+    if (startIndex == 0 && length == node.delta?.length) {
+      transaction
+        ..insertNodes(node.path.next, nodes)
+        ..deleteNode(node);
+    } else {
+      // it means the user selected a part of the sentence, we need to delete the
+      // selected part and insert the new delta.
+      transaction
+        ..deleteText(node, startIndex, length)
+        ..insertTextDelta(node, startIndex, markdownDelta);
+
+      // Add the remaining nodes to the document.
+      final remainingNodes = nodes.skip(1);
+      if (remainingNodes.isNotEmpty) {
+        transaction.insertNodes(
+          node.path.next,
+          remainingNodes,
+        );
+      }
+    }
+
     await editorState.apply(transaction);
   }
 

frontend/appflowy_flutter/test/unit_test/document/text_robot/markdown_text_robot_test.dart

@@ -487,6 +487,63 @@ void main() {
       );
       expect(d7.attributes, null);
     });
+
+    test('replace markdown text with selection from start to end', () async {
+      final document = Document(
+        root: pageNode(
+          children: [
+            paragraphNode(delta: Delta()..insert(text1)),
+            paragraphNode(delta: Delta()..insert(text2)),
+            paragraphNode(delta: Delta()..insert(text3)),
+          ],
+        ),
+      );
+      final editorState = EditorState(document: document);
+
+      editorState.selection = Selection(
+        start: Position(path: [0]),
+        end: Position(path: [0], offset: text1.length),
+      );
+
+      final markdownText = '''1. $text1
+
+2. $text1
+
+3. $text1''';
+      final markdownTextRobot = MarkdownTextRobot(
+        editorState: editorState,
+      );
+      await markdownTextRobot.replace(
+        selection: editorState.selection!,
+        markdownText: markdownText,
+      );
+
+      final nodes = editorState.document.root.children;
+      expect(nodes.length, 5);
+
+      final d1 = nodes[0].delta!.toList()[0] as TextInsert;
+      expect(d1.text, text1);
+      expect(d1.attributes, null);
+      expect(nodes[0].type, NumberedListBlockKeys.type);
+
+      final d2 = nodes[1].delta!.toList()[1] as TextInsert;
+      expect(d2.text, text1);
+      expect(d2.attributes, null);
+      expect(nodes[1].type, NumberedListBlockKeys.type);
+
+      final d3 = nodes[2].delta!.toList()[2] as TextInsert;
+      expect(d3.text, text1);
+      expect(d3.attributes, null);
+      expect(nodes[2].type, NumberedListBlockKeys.type);
+
+      final d4 = nodes[3].delta!.toList()[3] as TextInsert;
+      expect(d4.text, text2);
+      expect(d4.attributes, null);
+
+      final d5 = nodes[4].delta!.toList()[4] as TextInsert;
+      expect(d5.text, text3);
+      expect(d5.attributes, null);
+    });
   });
 
   group('markdown text robot - replace in multiple lines:', () {