From 673b1a60aa173cb3e0dcfce506a473618a852c17 Mon Sep 17 00:00:00 2001
From: Richard Maw <richard.maw@gmail.com>
Date: Tue, 3 Dec 2024 19:27:09 +0000
Subject: [PATCH] Turn Server into a sealed interface

Sealed interfaces are useful in switch exprs to enumerate possible values
so that it becomes a compile error to introduce a new server type
without implementing an appropriate arm for the switch block.
---
 .../net/rptools/clientserver/simple/server/AbstractServer.java  | 2 +-
 .../java/net/rptools/clientserver/simple/server/NilServer.java  | 2 +-
 .../java/net/rptools/clientserver/simple/server/Server.java     | 2 +-
 .../net/rptools/clientserver/simple/server/SocketServer.java    | 2 +-
 .../net/rptools/clientserver/simple/server/WebRTCServer.java    | 2 +-
 5 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/clientserver/src/main/java/net/rptools/clientserver/simple/server/AbstractServer.java b/clientserver/src/main/java/net/rptools/clientserver/simple/server/AbstractServer.java
index 7186d6c0ef..2f45ec8389 100644
--- a/clientserver/src/main/java/net/rptools/clientserver/simple/server/AbstractServer.java
+++ b/clientserver/src/main/java/net/rptools/clientserver/simple/server/AbstractServer.java
@@ -20,7 +20,7 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
-public abstract class AbstractServer implements Server {
+public abstract class AbstractServer {
 
   private static final Logger log = LogManager.getLogger(AbstractServer.class);
 
diff --git a/clientserver/src/main/java/net/rptools/clientserver/simple/server/NilServer.java b/clientserver/src/main/java/net/rptools/clientserver/simple/server/NilServer.java
index ad9b76bec3..9aacaaa8b0 100644
--- a/clientserver/src/main/java/net/rptools/clientserver/simple/server/NilServer.java
+++ b/clientserver/src/main/java/net/rptools/clientserver/simple/server/NilServer.java
@@ -15,7 +15,7 @@
 package net.rptools.clientserver.simple.server;
 
 /** A server implementation that never receives connections */
-public class NilServer extends AbstractServer {
+public final class NilServer extends AbstractServer implements Server {
   @Override
   public void start() {}
 
diff --git a/clientserver/src/main/java/net/rptools/clientserver/simple/server/Server.java b/clientserver/src/main/java/net/rptools/clientserver/simple/server/Server.java
index 00b379a7d9..9f92b9926e 100644
--- a/clientserver/src/main/java/net/rptools/clientserver/simple/server/Server.java
+++ b/clientserver/src/main/java/net/rptools/clientserver/simple/server/Server.java
@@ -16,7 +16,7 @@
 
 import java.io.IOException;
 
-public interface Server extends AutoCloseable {
+public sealed interface Server extends AutoCloseable permits NilServer, SocketServer, WebRTCServer {
   void start() throws IOException;
 
   void close();
diff --git a/clientserver/src/main/java/net/rptools/clientserver/simple/server/SocketServer.java b/clientserver/src/main/java/net/rptools/clientserver/simple/server/SocketServer.java
index 2b4c0ac9c5..c7341d169f 100644
--- a/clientserver/src/main/java/net/rptools/clientserver/simple/server/SocketServer.java
+++ b/clientserver/src/main/java/net/rptools/clientserver/simple/server/SocketServer.java
@@ -25,7 +25,7 @@
 /**
  * @author drice
  */
-public class SocketServer extends AbstractServer {
+public final class SocketServer extends AbstractServer implements Server {
 
   private static final Logger log = LogManager.getLogger(SocketServer.class);
   private final int port;
diff --git a/clientserver/src/main/java/net/rptools/clientserver/simple/server/WebRTCServer.java b/clientserver/src/main/java/net/rptools/clientserver/simple/server/WebRTCServer.java
index 32ad0b8c7b..880424ef2a 100644
--- a/clientserver/src/main/java/net/rptools/clientserver/simple/server/WebRTCServer.java
+++ b/clientserver/src/main/java/net/rptools/clientserver/simple/server/WebRTCServer.java
@@ -29,7 +29,7 @@
 import org.java_websocket.client.WebSocketClient;
 import org.java_websocket.handshake.ServerHandshake;
 
-public class WebRTCServer extends AbstractServer {
+public final class WebRTCServer extends AbstractServer implements Server {
   private static final Logger log = LogManager.getLogger(WebRTCServer.class);
 
   public interface Listener {