feat: add markdown divider encoder parser

lib/src/plugins/markdown/document_markdown.dart

@@ -6,7 +6,6 @@ import 'package:appflowy_editor/src/core/document/document.dart';
 import 'package:appflowy_editor/src/plugins/markdown/decoder/document_markdown_decoder.dart';
 import 'package:appflowy_editor/src/plugins/markdown/decoder/parser/custom_node_parser.dart';
 import 'package:appflowy_editor/src/plugins/markdown/encoder/document_markdown_encoder.dart';
-import 'package:appflowy_editor/src/plugins/markdown/encoder/parser/image_node_parser.dart';
 import 'package:appflowy_editor/src/plugins/markdown/encoder/parser/parser.dart';
 import 'package:markdown/markdown.dart' as md;
 
@@ -43,6 +42,7 @@ String documentToMarkdown(
       const HeadingNodeParser(),
       const ImageNodeParser(),
       const TableNodeParser(),
+      const DividerNodeParser(),
     ],
   ).encode(document);
 }

lib/src/plugins/markdown/encoder/parser/divider_node_parser.dart

@@ -0,0 +1,13 @@
+import 'package:appflowy_editor/appflowy_editor.dart';
+
+class DividerNodeParser extends NodeParser {
+  const DividerNodeParser();
+
+  @override
+  String get id => DividerBlockKeys.type;
+
+  @override
+  String transform(Node node, DocumentMarkdownEncoder? encoder) {
+    return '---\n';
+  }
+}

lib/src/plugins/markdown/encoder/parser/parser.dart

@@ -1,9 +1,11 @@
 export 'bulleted_list_node_parser.dart';
+export 'code_block_node_parser.dart';
+export 'divider_node_parser.dart';
 export 'heading_node_parser.dart';
+export 'image_node_parser.dart';
 export 'node_parser.dart';
-export 'quote_node_parser.dart';
 export 'numbered_list_node_parser.dart';
-export 'todo_list_node_parser.dart';
-export 'text_node_parser.dart';
-export 'code_block_node_parser.dart';
+export 'quote_node_parser.dart';
 export 'table_node_parser.dart';
+export 'text_node_parser.dart';
+export 'todo_list_node_parser.dart';

lib/src/plugins/plugins.dart

@@ -7,7 +7,5 @@ export 'markdown/decoder/delta_markdown_decoder.dart';
 export 'markdown/document_markdown.dart';
 export 'markdown/encoder/delta_markdown_encoder.dart';
 export 'markdown/encoder/document_markdown_encoder.dart';
-export 'markdown/encoder/parser/image_node_parser.dart';
-export 'markdown/encoder/parser/node_parser.dart';
-export 'markdown/encoder/parser/text_node_parser.dart';
+export 'markdown/encoder/parser/parser.dart';
 export 'quill_delta/quill_delta_encoder.dart';

test/plugins/markdown/document_markdown_test.dart

@@ -98,4 +98,5 @@ const markdownDocumentEncoded = """# Heading 1
 ## Heading 2
 ### Heading 3
 
+---
 """;

test/plugins/markdown/encoder/document_markdown_encoder_test.dart

@@ -1,7 +1,6 @@
 import 'dart:convert';
 
 import 'package:appflowy_editor/appflowy_editor.dart';
-import 'package:appflowy_editor/src/plugins/markdown/encoder/parser/parser.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() async {

test/plugins/markdown/encoder/parser/divider_node_parser_test.dart

@@ -0,0 +1,20 @@
+import 'package:appflowy_editor/appflowy_editor.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() async {
+  group('divider_node_parser.dart', () {
+    test('parser divider node', () {
+      final node = Node(
+        type: DividerBlockKeys.type,
+      );
+
+      final result = const DividerNodeParser().transform(node, null);
+      expect(result, '---\n');
+    });
+
+    test('DividerNodeParser id getter', () {
+      const imageNodeParser = DividerNodeParser();
+      expect(imageNodeParser.id, 'divider');
+    });
+  });
+}

test/plugins/markdown/encoder/parser/text_node_parser_test.dart

@@ -1,5 +1,4 @@
 import 'package:appflowy_editor/appflowy_editor.dart';
-import 'package:appflowy_editor/src/plugins/markdown/encoder/parser/parser.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() async {