Feat: Add SessionDispatcher to send responses by username

src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/network/protocol/response/dispatcher/SessionDispatcher.java

@@ -0,0 +1,47 @@
+package ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.response.dispatcher;
+
+import ch.unibas.dmi.dbis.cs108.casono.server.domain.lobby.Lobby;
+import ch.unibas.dmi.dbis.cs108.casono.server.domain.user.User;
+import ch.unibas.dmi.dbis.cs108.casono.server.domain.user.UserRegistry;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.request.RequestContext;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.response.SuccessResponse;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.protocol.response.builder.ResponseBody;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.sessions.SessionId;
+import java.util.Optional;
+
+/** Helper to send responses to sessions identified by usernames. */
+public class SessionDispatcher {
+    private final ResponseDispatcher responseDispatcher;
+    private final UserRegistry userRegistry;
+
+    public SessionDispatcher(ResponseDispatcher responseDispatcher, UserRegistry userRegistry) {
+        this.responseDispatcher = responseDispatcher;
+        this.userRegistry = userRegistry;
+    }
+
+    /**
+     * Dispatch a success response built from {@code body} to the user with {@code username}. If the
+     * user is disconnected or unknown, the call is a no-op.
+     */
+    public void dispatchToUser(String username, ResponseBody body) {
+        Optional<User> opt = userRegistry.getByUsername(username);
+        if (opt.isEmpty()) {
+            return;
+        }
+        User user = opt.get();
+        Optional<SessionId> sid = user.getSessionId();
+        if (sid.isEmpty()) {
+            return;
+        }
+        RequestContext ctx = new RequestContext(sid.get(), 0);
+        SuccessResponse resp = new SuccessResponse(ctx, body) {};
+        responseDispatcher.dispatch(resp);
+    }
+
+    /** Broadcast the provided {@code body} to every player in the given lobby. */
+    public void broadcastToLobby(Lobby lobby, ResponseBody body) {
+        for (String username : lobby.getPlayerNames()) {
+            dispatchToUser(username, body);
+        }
+    }
+}