fix: Correctly generate reply fallbacks

lib/src/room.dart

@@ -17,6 +17,7 @@
  */
 
 import 'dart:async';
+import 'dart:convert';
 
 import 'package:html_unescape/html_unescape.dart';
 import 'package:matrix_file_e2ee/matrix_file_e2ee.dart';
@@ -583,7 +584,8 @@ class Room {
     if (parseMarkdown) {
       final html = markdown(event['body'], emotePacks ?? this.emotePacks);
       // if the decoded html is the same as the body, there is no need in sending a formatted message
-      if (HtmlUnescape().convert(html) != event['body']) {
+      if (HtmlUnescape().convert(html.replaceAll(RegExp(r'<br />\n?'), '\n')) !=
+          event['body']) {
         event['format'] = 'org.matrix.custom.html';
         event['formatted_body'] = html;
       }
@@ -754,9 +756,22 @@ class Room {
       }
       replyText = replyTextLines.join('\n');
       content['format'] = 'org.matrix.custom.html';
+      // be sure that we strip any previous reply fallbacks
+      final replyHtml = (inReplyTo.formattedText.isNotEmpty
+              ? inReplyTo.formattedText
+              : htmlEscape.convert(inReplyTo.body).replaceAll('\n', '<br>'))
+          .replaceAll(
+              RegExp(r'<mx-reply>.*<\/mx-reply>',
+                  caseSensitive: false, multiLine: false, dotAll: true),
+              '');
+      final repliedHtml = content.tryGet<String>(
+          'formatted_body',
+          htmlEscape
+              .convert(content.tryGet<String>('body', ''))
+              .replaceAll('\n', '<br>'));
       content['formatted_body'] =
-          '<mx-reply><blockquote><a href="https://matrix.to/#/${inReplyTo.room.id}/${inReplyTo.eventId}">In reply to</a> <a href="https://matrix.to/#/${inReplyTo.senderId}">${inReplyTo.senderId}</a><br>${inReplyTo.body}</blockquote></mx-reply>${content["formatted_body"] ?? content["body"]}';
+          '<mx-reply><blockquote><a href="https://matrix.to/#/${inReplyTo.room.id}/${inReplyTo.eventId}">In reply to</a> <a href="https://matrix.to/#/${inReplyTo.senderId}">${inReplyTo.senderId}</a><br>$replyHtml</blockquote></mx-reply>$repliedHtml';
-      content['body'] = replyText + "\n\n${content["body"] ?? ""}";
+      content['body'] = replyText + "\n\n${content.tryGet<String>('body', '')}";
       content['m.relates_to'] = {
         'm.in_reply_to': {
           'event_id': inReplyTo.eventId,

test/room_test.dart

@@ -420,12 +420,12 @@ void main() {
         'sender': '@alice:example.org',
       }, room);
       FakeMatrixApi.calledEndpoints.clear();
-      final dynamic resp = await room.sendTextEvent('Hello world',
+      var resp = await room.sendTextEvent('Hello world',
           txid: 'testtxid', inReplyTo: event);
       expect(resp.startsWith('\$event'), true);
-      final entry = FakeMatrixApi.calledEndpoints.entries
+      var entry = FakeMatrixApi.calledEndpoints.entries
           .firstWhere((p) => p.key.contains('/send/m.room.message/'));
-      final content = json.decode(entry.value.first);
+      var content = json.decode(entry.value.first);
       expect(content, {
         'body': '> <@alice:example.org> Blah\n\nHello world',
         'msgtype': 'm.text',
@@ -438,6 +438,67 @@ void main() {
           },
         },
       });
+
+      event = Event.fromJson({
+        'event_id': '\$replyEvent',
+        'content': {
+          'body': '<b>Blah</b>\nbeep',
+          'msgtype': 'm.text',
+        },
+        'type': 'm.room.message',
+        'sender': '@alice:example.org',
+      }, room);
+      FakeMatrixApi.calledEndpoints.clear();
+      resp = await room.sendTextEvent('Hello world\nfox',
+          txid: 'testtxid', inReplyTo: event);
+      expect(resp.startsWith('\$event'), true);
+      entry = FakeMatrixApi.calledEndpoints.entries
+          .firstWhere((p) => p.key.contains('/send/m.room.message/'));
+      content = json.decode(entry.value.first);
+      expect(content, {
+        'body':
+            '> <@alice:example.org> <b>Blah</b>\n> beep\n\nHello world\nfox',
+        'msgtype': 'm.text',
+        'format': 'org.matrix.custom.html',
+        'formatted_body':
+            '<mx-reply><blockquote><a href="https://matrix.to/#/!localpart:server.abc/\$replyEvent">In reply to</a> <a href="https://matrix.to/#/@alice:example.org">@alice:example.org</a><br>&lt;b&gt;Blah&lt;&#47;b&gt;<br>beep</blockquote></mx-reply>Hello world<br>fox',
+        'm.relates_to': {
+          'm.in_reply_to': {
+            'event_id': '\$replyEvent',
+          },
+        },
+      });
+
+      event = Event.fromJson({
+        'event_id': '\$replyEvent',
+        'content': {
+          'format': 'org.matrix.custom.html',
+          'formatted_body': '<mx-reply>heya</mx-reply>meow',
+          'body': 'plaintext meow',
+          'msgtype': 'm.text',
+        },
+        'type': 'm.room.message',
+        'sender': '@alice:example.org',
+      }, room);
+      FakeMatrixApi.calledEndpoints.clear();
+      resp = await room.sendTextEvent('Hello world',
+          txid: 'testtxid', inReplyTo: event);
+      expect(resp.startsWith('\$event'), true);
+      entry = FakeMatrixApi.calledEndpoints.entries
+          .firstWhere((p) => p.key.contains('/send/m.room.message/'));
+      content = json.decode(entry.value.first);
+      expect(content, {
+        'body': '> <@alice:example.org> plaintext meow\n\nHello world',
+        'msgtype': 'm.text',
+        'format': 'org.matrix.custom.html',
+        'formatted_body':
+            '<mx-reply><blockquote><a href="https://matrix.to/#/!localpart:server.abc/\$replyEvent">In reply to</a> <a href="https://matrix.to/#/@alice:example.org">@alice:example.org</a><br>meow</blockquote></mx-reply>Hello world',
+        'm.relates_to': {
+          'm.in_reply_to': {
+            'event_id': '\$replyEvent',
+          },
+        },
+      });
     });
 
     test('send reaction', () async {