feat: open html decoder for custom parser (#1145)

lib/src/plugins/html/html_document.dart

@@ -9,9 +9,16 @@ import 'package:appflowy_editor/src/plugins/html/html_document_encoder.dart';
 
 import 'encoder/parser/html_parser.dart';
 
+export 'html_document_decoder.dart' show ElementParser;
+
 /// Converts a html to [Document].
-Document htmlToDocument(String html) {
-  return const AppFlowyEditorHTMLCodec().decode(html);
+Document htmlToDocument(
+  String html, {
+  Map<String, ElementParser> customDecoders = const {},
+}) {
+  return AppFlowyEditorHTMLCodec(
+    customDecoders: customDecoders,
+  ).decode(html);
 }
 
 /// Converts a [Document] to html.
@@ -38,12 +45,16 @@ String documentToHTML(
 class AppFlowyEditorHTMLCodec extends Codec<Document, String> {
   const AppFlowyEditorHTMLCodec({
     this.encodeParsers = const [],
+    this.customDecoders = const {},
   });
 
   final List<HTMLNodeParser> encodeParsers;
+  final Map<String, ElementParser> customDecoders;
 
   @override
-  Converter<String, Document> get decoder => DocumentHTMLDecoder();
+  Converter<String, Document> get decoder => DocumentHTMLDecoder(
+        customDecoders: customDecoders,
+      );
 
   @override
   Converter<Document, String> get encoder => DocumentHTMLEncoder(

lib/src/plugins/html/html_document_decoder.dart

@@ -5,9 +5,20 @@ import 'package:appflowy_editor/appflowy_editor.dart';
 import 'package:html/dom.dart' as dom;
 import 'package:html/parser.dart' show parse;
 
-class DocumentHTMLDecoder extends Converter<String, Document> {
-  DocumentHTMLDecoder();
+typedef ElementParser = Iterable<Node> Function(
+  dom.Element element,
+  (Delta, Iterable<Node>) Function(
+    dom.Element element, {
+    String? type,
+  }) parseDeltaElement,
+);
 
+class DocumentHTMLDecoder extends Converter<String, Document> {
+  DocumentHTMLDecoder({
+    this.customDecoders = const {},
+  });
+
+  final Map<String, ElementParser> customDecoders;
   // Set to true to enable parsing color from HTML
   static bool enableColorParse = true;
 
@@ -67,6 +78,13 @@ class DocumentHTMLDecoder extends Converter<String, Document> {
               type: type ?? ParagraphBlockKeys.type,
             ),
           );
+        } else if (customDecoders.containsKey(localName)) {
+          if (delta.isNotEmpty) {
+            nodes.add(paragraphNode(delta: delta));
+          }
+          nodes.addAll(
+            customDecoders[localName]!(domNode, _parseDeltaElement),
+          );
         }
       } else if (domNode is dom.Text) {
         // skip the empty text node
@@ -395,6 +413,10 @@ class DocumentHTMLDecoder extends Converter<String, Document> {
                 type: ParagraphBlockKeys.type,
               ),
             );
+          } else if (customDecoders.containsKey(child.localName)) {
+            nodes.addAll(
+              customDecoders[child.localName]!(child, _parseDeltaElement),
+            );
           } else {
             final attributes = _parserFormattingElementAttributes(child);
             delta.insert(