chat implemented, testing needed

backend/social/chat/serializers.py

@@ -1,5 +1,6 @@
 from rest_framework import serializers
-from .models import Chat, Message, MessageFile, MessageHistory, MessageReaction
+from drf_spectacular.utils import extend_schema_field
+from .models import Chat, ChatReadStatus, Message, MessageFile, MessageHistory, MessageReaction
 
 
 class MessageFileSerializer(serializers.ModelSerializer):
@@ -60,14 +61,28 @@ class MessageSendSerializer(serializers.Serializer):
 
 
 class ChatSerializer(serializers.ModelSerializer):
+    unread_count = serializers.SerializerMethodField(read_only=True)
+
+    @extend_schema_field(serializers.IntegerField())
+    def get_unread_count(self, obj):
+        request = self.context.get('request')
+        if not request or not request.user.is_authenticated:
+            return 0
+        last_read = ChatReadStatus.objects.filter(
+            user=request.user, chat=obj
+        ).values_list('last_read_at', flat=True).first()
+        if last_read is None:
+            return obj.messages.filter(is_deleted=False).count()
+        return obj.messages.filter(created_at__gt=last_read, is_deleted=False).count()
+
     class Meta:
         model = Chat
         fields = [
             'id', 'chat_type', 'owner', 'name',
             'icon', 'banner', 'members', 'moderators',
-            'hub', 'created_at', 'updated_at',
+            'hub', 'created_at', 'updated_at', 'unread_count',
         ]
-        read_only_fields = ['owner', 'created_at', 'updated_at']
+        read_only_fields = ['owner', 'created_at', 'updated_at', 'unread_count']
 
 
 class ChatMemberSerializer(serializers.Serializer):