Convert PlayerChooseInitialServerEvent into a resulted event

api/src/main/java/com/velocitypowered/api/event/player/PlayerChooseInitialServerEvent.java

@@ -8,11 +8,17 @@
 package com.velocitypowered.api.event.player;
 
 import com.google.common.base.Preconditions;
+import com.velocitypowered.api.event.ResultedEvent;
 import com.velocitypowered.api.event.annotation.AwaitingEvent;
 import com.velocitypowered.api.proxy.Player;
 import com.velocitypowered.api.proxy.server.RegisteredServer;
+
 import java.util.Optional;
+
+import net.kyori.adventure.text.Component;
 import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.NonNull;
 
 /**
  * Fired when a player has finished the login process, and we need to choose the first server
@@ -21,10 +27,10 @@ import org.checkerframework.checker.nullness.qual.Nullable;
  * {@link KickedFromServerEvent} as normal.
  */
 @AwaitingEvent
-public class PlayerChooseInitialServerEvent {
+public class PlayerChooseInitialServerEvent implements ResultedEvent<PlayerChooseInitialServerEvent.Result> {
 
   private final Player player;
-  private @Nullable RegisteredServer initialServer;
+  private @NotNull Result result;
 
   /**
    * Constructs a PlayerChooseInitialServerEvent.
@@ -34,7 +40,7 @@ public class PlayerChooseInitialServerEvent {
    */
   public PlayerChooseInitialServerEvent(Player player, @Nullable RegisteredServer initialServer) {
     this.player = Preconditions.checkNotNull(player, "player");
-    this.initialServer = initialServer;
+    this.result = Allowed.of(initialServer);
   }
 
   public Player getPlayer() {
@@ -42,8 +48,11 @@ public class PlayerChooseInitialServerEvent {
   }
 
   public Optional<RegisteredServer> getInitialServer() {
+    if (result instanceof Allowed(RegisteredServer initialServer)) {
       return Optional.ofNullable(initialServer);
     }
+    return Optional.empty();
+  }
 
   /**
    * Sets the new initial server.
@@ -51,14 +60,62 @@ public class PlayerChooseInitialServerEvent {
    * @param server the initial server the player should connect to
    */
   public void setInitialServer(@Nullable RegisteredServer server) {
-    this.initialServer = server;
+    if (server == null) {
+      this.result = Denied.of();
+      return;
+    }
+    this.result = Allowed.of(server);
   }
 
   @Override
   public String toString() {
     return "PlayerChooseInitialServerEvent{"
       + "player=" + player
-        + ", initialServer=" + initialServer
+      + ", result=" + result
       + '}';
   }
+
+  @Override
+  public @NonNull Result getResult() {
+    return this.result;
+  }
+
+  @Override
+  public void setResult(final Result result) {
+    this.result = Preconditions.checkNotNull(result, "result");
+  }
+
+  public sealed interface Result extends ResultedEvent.Result permits Allowed, Denied {
+  }
+
+  public record Allowed(@NotNull RegisteredServer initialServer) implements Result {
+
+    public Allowed {
+      Preconditions.checkNotNull(initialServer, "initialServer");
+    }
+
+    public static @NotNull Result of(final RegisteredServer initialServer) {
+      return new Allowed(initialServer);
+    }
+
+    @Override
+    public boolean isAllowed() {
+      return true;
+    }
+  }
+
+  public record Denied(@Nullable Component reason) implements Result {
+    public static @NotNull Result of(@Nullable Component reason) {
+      return new Denied(reason);
+    }
+
+    public static @NotNull Result of() {
+      return new Denied(null);
+    }
+
+    @Override
+    public boolean isAllowed() {
+      return false;
+    }
+  }
 }

proxy/src/main/java/com/velocitypowered/proxy/connection/client/AuthSessionHandler.java

@@ -262,14 +262,16 @@ public class AuthSessionHandler implements MinecraftSessionHandler {
         new PlayerChooseInitialServerEvent(player, initialFromConfig.orElse(null));
 
     return server.getEventManager().fire(event).thenRunAsync(() -> {
-      Optional<RegisteredServer> toTry = event.getInitialServer();
-      if (toTry.isEmpty()) {
-        player.disconnect0(
-            Component.translatable("velocity.error.no-available-servers", NamedTextColor.RED),
+      final PlayerChooseInitialServerEvent.Result result = event.getResult();
+      if (event.getResult() instanceof PlayerChooseInitialServerEvent.Denied(Component reason)) {
+        player.disconnect0(Objects.requireNonNullElse(reason,
+          Component.translatable("velocity.error.no-available-servers", NamedTextColor.RED)),
           true);
+        //noinspection UnnecessaryReturnStatement
         return;
+      } else if (result instanceof PlayerChooseInitialServerEvent.Allowed(RegisteredServer initialServer)) {
+        player.createConnectionRequest(initialServer).fireAndForget();
       }
-      player.createConnectionRequest(toTry.get()).fireAndForget();
     }, mcConnection.eventLoop());
   }