Implement server state handling in ChatController and ChatService, add ServerStateMapper utility, and create/update server state unit tests.

backend/src/main/java/com/alttd/altitudeweb/controllers/chat/ChatController.java

@@ -28,7 +28,7 @@ public class ChatController implements ChatApi {
 
     @Override
     public ResponseEntity<Void> updateServerStates(ServerStateDto serverStateDto) {
-        //TODO [Stijn] [2026-07-18]: Implement handling server state updates (push to listeners)
+        chatService.updateServerState(serverStateDto);
-        throw new UnsupportedOperationException("Not implemented");
+        return new ResponseEntity<>(HttpStatus.ACCEPTED);
     }
 }

backend/src/main/java/com/alttd/altitudeweb/controllers/chat/ServerStateMapper.java

@@ -0,0 +1,24 @@
+package com.alttd.altitudeweb.controllers.chat;
+
+import com.alttd.altitudeweb.model.ServerStateDto;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import lombok.experimental.UtilityClass;
+
+@UtilityClass
+public class ServerStateMapper {
+    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper()
+            .registerModule(new JavaTimeModule())
+            .enable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+            .disable(SerializationFeature.WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS);
+
+    public static String toJson(ServerStateDto serverStateDto) {
+        try {
+            return OBJECT_MAPPER.writeValueAsString(serverStateDto);
+        } catch (JsonProcessingException e) {
+            throw new IllegalStateException("Failed to serialize ServerStateDto to JSON", e);
+        }
+    }
+}

backend/src/main/java/com/alttd/altitudeweb/services/chat/ChatService.java

@@ -2,11 +2,14 @@ package com.alttd.altitudeweb.services.chat;
 
 import com.alttd.altitudeweb.controllers.chat.ChatMessage;
 import com.alttd.altitudeweb.controllers.chat.ChatMessageMapper;
+import com.alttd.altitudeweb.controllers.chat.ServerStateMapper;
 import com.alttd.altitudeweb.database.Databases;
 import com.alttd.altitudeweb.database.chat.ChatLogMapper;
 import com.alttd.altitudeweb.database.web_db.chat_session.ChatSession;
 import com.alttd.altitudeweb.database.web_db.chat_session.ChatSessionMapper;
 import com.alttd.altitudeweb.model.PermissionClaimDto;
+import com.alttd.altitudeweb.model.ServerDto;
+import com.alttd.altitudeweb.model.ServerStateDto;
 import com.alttd.altitudeweb.services.chat.event_publisher.EventPublisher;
 import com.alttd.altitudeweb.services.chat.event_publisher.EventUser;
 import com.alttd.altitudeweb.services.chat.event_publisher.MessageForUser;
@@ -121,6 +124,20 @@ public class ChatService {
         sendMessagesToListeners(chatMessageList);
     }
 
+    public void updateServerState(ServerStateDto serverStateDto) {
+        sendToUsers("server-state", (eventUser) -> {
+            if (eventUser.hasPermission(PermissionClaimDto.HEAD_MOD)) {
+                return ServerStateMapper.toJson(serverStateDto);
+            }
+
+            List<ServerDto> filteredServers = serverStateDto.getServers().stream()
+                    .filter(serverDto -> Arrays.asList(allowedServers).contains(serverDto.getName()))
+                    .toList();
+
+            return ServerStateMapper.toJson(new ServerStateDto().servers(filteredServers));
+        });
+    }
+
     private void sendMessagesToListeners(List<ChatMessage> chatMessageList) {
         Map<ChatMessage, String> jsonCache = new HashMap<>();
         for (ChatMessage message : chatMessageList) {

backend/src/test/java/com/alttd/altitudeweb/controllers/chat/ChatControllerTest.java

@@ -0,0 +1,34 @@
+package com.alttd.altitudeweb.controllers.chat;
+
+import com.alttd.altitudeweb.model.ServerStateDto;
+import com.alttd.altitudeweb.services.chat.ChatService;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.verify;
+
+@ExtendWith(MockitoExtension.class)
+class ChatControllerTest {
+
+    @Mock
+    private ChatService chatService;
+
+    @InjectMocks
+    private ChatController chatController;
+
+    @Test
+    void testUpdateServerStatesDelegatesToService() {
+        ServerStateDto serverStateDto = new ServerStateDto();
+        
+        ResponseEntity<Void> response = chatController.updateServerStates(serverStateDto);
+        
+        verify(chatService).updateServerState(serverStateDto);
+        assertEquals(HttpStatus.ACCEPTED, response.getStatusCode());
+    }
+}

backend/src/test/java/com/alttd/altitudeweb/services/chat/ChatServiceTest.java

@@ -3,6 +3,8 @@ package com.alttd.altitudeweb.services.chat;
 import com.alttd.altitudeweb.controllers.chat.ChatMessage;
 import com.alttd.altitudeweb.controllers.chat.ChatMessageType;
 import com.alttd.altitudeweb.model.PermissionClaimDto;
+import com.alttd.altitudeweb.model.ServerDto;
+import com.alttd.altitudeweb.model.ServerStateDto;
 import com.alttd.altitudeweb.services.chat.event_publisher.EventPublisher;
 import com.alttd.altitudeweb.services.chat.event_publisher.EventUser;
 import com.alttd.altitudeweb.services.chat.event_publisher.MessageForUser;
@@ -18,6 +20,7 @@ import java.util.UUID;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.*;
 
 class ChatServiceTest {
@@ -152,4 +155,28 @@ class ChatServiceTest {
         assertFalse(messageForUser.get(regularUser).contains("blocked message"));
         assertTrue(messageForUser.get(headModUser).contains("blocked message"));
     }
+
+    @Test
+    void testUpdateServerStateFiltering() {
+        ServerStateDto serverStateDto = new ServerStateDto()
+                .addServersItem(new ServerDto().name("server1"))
+                .addServersItem(new ServerDto().name("server2"));
+
+        chatService.updateServerState(serverStateDto);
+
+        ArgumentCaptor<MessageForUser> captor = ArgumentCaptor.forClass(MessageForUser.class);
+        verify(chatService).sendToUsers(eq("server-state"), captor.capture());
+
+        MessageForUser messageForUser = captor.getValue();
+
+        EventUser regularUser = new EventUser(UUID.randomUUID(), List.of(), null);
+        String regularResult = messageForUser.get(regularUser);
+        assertTrue(regularResult.contains("server1"), "Regular user should see allowed server");
+        assertFalse(regularResult.contains("server2"), "Regular user should NOT see non-allowed server");
+
+        EventUser headModUser = new EventUser(UUID.randomUUID(), List.of(PermissionClaimDto.HEAD_MOD.getValue()), null);
+        String headModResult = messageForUser.get(headModUser);
+        assertTrue(headModResult.contains("server1"), "HEAD_MOD should see allowed server");
+        assertTrue(headModResult.contains("server2"), "HEAD_MOD should see non-allowed server");
+    }
 }

open_api/src/main/resources/chat-api.yml

@@ -53,6 +53,7 @@ components:
         - uuid
         - name
         - styledName
+      # TODO [Stijn] [2026-07-19]: Add who they ignore and who they are ignored by
 
       properties:
         uuid:
@@ -140,11 +141,3 @@ components:
           type: array
           items:
             $ref: "#/components/schemas/Server"
-  parameters:
-    From:
-      name: from
-      in: path
-      required: true
-      schema:
-        type: string
-        format: date-time