feat(xep): Allow ignoring the discussion history

Also allow specifying the amount of stanzas of discussion history we
want.

examples_dart/bin/muc_client.dart

@@ -58,7 +58,11 @@ void main(List<String> args) async {
   Logger.root.info('Connected.');
 
   // Join room
-  await connection.getManagerById<MUCManager>(mucManager)!.joinRoom(muc, nick);
+  await connection.getManagerById<MUCManager>(mucManager)!.joinRoom(
+    muc,
+    nick,
+    maxHistoryStanzas: 0,
+  );
 
   final repl = Repl(prompt: '> ');
   await for (final line in repl.runAsync()) {

packages/moxxmpp/lib/src/xeps/xep_0045/types.dart

@@ -34,10 +34,25 @@ class RoomInformation {
 }
 
 class RoomState {
-  RoomState({
-    required this.roomJid,
-    this.nick,
-  });
+  RoomState({required this.roomJid, this.nick, required this.joined});
+
+  /// The JID of the room.
   final JID roomJid;
+
+  /// The nick we're joined with.
   String? nick;
+
+  /// Flag whether we're joined and can process messages
+  bool joined;
+
+  RoomState copyWith({
+    bool? joined,
+    String? nick,
+  }) {
+    return RoomState(
+      roomJid: roomJid,
+      joined: joined ?? this.joined,
+      nick: nick ?? this.nick,
+    );
+  }
 }

packages/moxxmpp/lib/src/xeps/xep_0045/xep_0045.dart

@@ -1,6 +1,8 @@
 import 'package:moxlib/moxlib.dart';
 import 'package:moxxmpp/src/jid.dart';
 import 'package:moxxmpp/src/managers/base.dart';
+import 'package:moxxmpp/src/managers/data.dart';
+import 'package:moxxmpp/src/managers/handlers.dart';
 import 'package:moxxmpp/src/managers/namespaces.dart';
 import 'package:moxxmpp/src/namespaces.dart';
 import 'package:moxxmpp/src/stanza.dart';
@@ -9,6 +11,7 @@ import 'package:moxxmpp/src/xeps/xep_0030/types.dart';
 import 'package:moxxmpp/src/xeps/xep_0030/xep_0030.dart';
 import 'package:moxxmpp/src/xeps/xep_0045/errors.dart';
 import 'package:moxxmpp/src/xeps/xep_0045/types.dart';
+import 'package:synchronized/extension.dart';
 import 'package:synchronized/synchronized.dart';
 
 class MUCManager extends XmppManagerBase {
@@ -23,6 +26,16 @@ class MUCManager extends XmppManagerBase {
   /// Cache lock
   final Lock _cacheLock = Lock();
 
+  @override
+  List<StanzaHandler> getIncomingStanzaHandlers() => [
+        StanzaHandler(
+          stanzaTag: 'message',
+          callback: _onMessage,
+          // Before the message handler
+          priority: -99,
+        )
+      ];
+
   /// Queries the information of a Multi-User Chat room.
   ///
   /// Retrieves the information about the specified MUC room by performing a
@@ -55,11 +68,23 @@ class MUCManager extends XmppManagerBase {
   /// if applicable.
   Future<Result<bool, MUCError>> joinRoom(
     JID roomJid,
-    String nick,
-  ) async {
+    String nick, {
+    int? maxHistoryStanzas,
+  }) async {
     if (nick.isEmpty) {
       return Result(NoNicknameSpecified());
     }
+
+    await _cacheLock.synchronized(
+      () {
+        _mucRoomCache[roomJid] = RoomState(
+          roomJid: roomJid,
+          nick: nick,
+          joined: false,
+        );
+      },
+    );
+
     await getAttributes().sendStanza(
       StanzaDetails(
         Stanza.presence(
@@ -68,16 +93,20 @@ class MUCManager extends XmppManagerBase {
             XMLNode.xmlns(
               tag: 'x',
               xmlns: mucXmlns,
-            )
+              children: [
+                if (maxHistoryStanzas != null)
+                  XMLNode(
+                    tag: 'history',
+                    attributes: {
+                      'maxstanzas': maxHistoryStanzas.toString(),
+                    },
+                  ),
+              ],
+            ),
           ],
         ),
       ),
     );
-    await _cacheLock.synchronized(
-      () {
-        _mucRoomCache[roomJid] = RoomState(roomJid: roomJid, nick: nick);
-      },
-    );
     return const Result(true);
   }
 
@@ -108,4 +137,48 @@ class MUCManager extends XmppManagerBase {
     );
     return const Result(true);
   }
+
+  Future<StanzaHandlerData> _onMessage(
+    Stanza message,
+    StanzaHandlerData state,
+  ) async {
+    final roomJid = JID.fromString(message.from!).toBare();
+    return _mucRoomCache.synchronized(() {
+      final roomState = _mucRoomCache[roomJid];
+      if (roomState == null) {
+        return state;
+      }
+
+      if (message.type == 'groupchat' && message.firstTag('subject') != null) {
+        // The room subject marks the end of the join flow.
+        if (!roomState.joined) {
+          // Mark the room as joined.
+          _mucRoomCache[roomJid] = roomState.copyWith(joined: true);
+          logger.finest('$roomJid is now joined');
+        }
+
+        // TODO(Unknown): Signal the subject?
+
+        return StanzaHandlerData(
+          true,
+          false,
+          message,
+          state.extensions,
+        );
+      } else {
+        if (!roomState.joined) {
+          // Ignore the discussion history.
+          // TODO: Implement a copyWith method
+          return StanzaHandlerData(
+            true,
+            false,
+            message,
+            state.extensions,
+          );
+        }
+      }
+
+      return state;
+    });
+  }
 }