Show proxy-wide online players in server ping (#811)

* Show proxy-wide online players in server ping

* Reflow arguments in VelocityConfiguration constructor

api/src/main/java/com/velocitypowered/api/proxy/server/ServerPing.java

@@ -516,6 +516,10 @@ public final class ServerPing {
    */
   public static final class SamplePlayer {
 
+    public static final SamplePlayer ANONYMOUS = new SamplePlayer(
+        "Anonymous Player",
+        new UUID(0L, 0L)
+    );
     private final String name;
     private final UUID id;
 

proxy/src/main/java/com/velocitypowered/proxy/config/VelocityConfiguration.java

@@ -78,6 +78,8 @@ public class VelocityConfiguration implements ProxyConfig {
   private boolean onlineModeKickExistingPlayers = false;
   @Expose
   private PingPassthroughMode pingPassthrough = PingPassthroughMode.DISABLED;
+  @Expose
+  private boolean samplePlayersInPing = false;
   private final Servers servers;
   private final ForcedHosts forcedHosts;
   @Expose
@@ -105,8 +107,9 @@ public class VelocityConfiguration implements ProxyConfig {
       boolean preventClientProxyConnections, boolean announceForge,
       PlayerInfoForwarding playerInfoForwardingMode, byte[] forwardingSecret,
       boolean onlineModeKickExistingPlayers, PingPassthroughMode pingPassthrough,
-      boolean enablePlayerAddressLogging, Servers servers, ForcedHosts forcedHosts,
-      Advanced advanced, Query query, Metrics metrics, boolean forceKeyAuthentication) {
+      boolean samplePlayersInPing, boolean enablePlayerAddressLogging, Servers servers,
+      ForcedHosts forcedHosts, Advanced advanced, Query query, Metrics metrics,
+      boolean forceKeyAuthentication) {
     this.bind = bind;
     this.motd = motd;
     this.showMaxPlayers = showMaxPlayers;
@@ -117,6 +120,7 @@ public class VelocityConfiguration implements ProxyConfig {
     this.forwardingSecret = forwardingSecret;
     this.onlineModeKickExistingPlayers = onlineModeKickExistingPlayers;
     this.pingPassthrough = pingPassthrough;
+    this.samplePlayersInPing = samplePlayersInPing;
     this.enablePlayerAddressLogging = enablePlayerAddressLogging;
     this.servers = servers;
     this.forcedHosts = forcedHosts;
@@ -371,6 +375,10 @@ public class VelocityConfiguration implements ProxyConfig {
     return pingPassthrough;
   }
 
+  public boolean getSamplePlayersInPing() {
+    return samplePlayersInPing;
+  }
+
   public boolean isPlayerAddressLoggingEnabled() {
     return enablePlayerAddressLogging;
   }
@@ -507,6 +515,8 @@ public class VelocityConfiguration implements ProxyConfig {
       final PingPassthroughMode pingPassthroughMode = config.getEnumOrElse("ping-passthrough",
               PingPassthroughMode.DISABLED);
 
+      final boolean samplePlayersInPing = config.getOrElse("sample-players-in-ping", false);
+
       final String bind = config.getOrElse("bind", "0.0.0.0:25565");
       final int maxPlayers = config.getIntOrElse("show-max-players", 500);
       final boolean onlineMode = config.getOrElse("online-mode", true);
@@ -537,6 +547,7 @@ public class VelocityConfiguration implements ProxyConfig {
               forwardingSecret,
               kickExisting,
               pingPassthroughMode,
+              samplePlayersInPing,
               enablePlayerAddressLogging,
               new Servers(serversConfig),
               new ForcedHosts(forcedHostsConfig),

proxy/src/main/java/com/velocitypowered/proxy/connection/util/ServerListPingHandler.java

@@ -30,10 +30,12 @@ import com.velocitypowered.proxy.config.VelocityConfiguration;
 import com.velocitypowered.proxy.server.VelocityRegisteredServer;
 import java.net.InetSocketAddress;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
 import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
+import java.util.stream.Collectors;
 
 /**
  * Common utilities for handling server list ping results.
@@ -51,11 +53,27 @@ public class ServerListPingHandler {
       version = ProtocolVersion.MAXIMUM_VERSION;
     }
     VelocityConfiguration configuration = server.getConfiguration();
+    List<ServerPing.SamplePlayer> samplePlayers;
+    if (configuration.getSamplePlayersInPing()) {
+      List<ServerPing.SamplePlayer> unshuffledPlayers = server.getAllPlayers().stream()
+              .map(p -> {
+                if (p.getPlayerSettings().isClientListingAllowed()) {
+                  return new ServerPing.SamplePlayer(p.getUsername(), p.getUniqueId());
+                } else {
+                  return ServerPing.SamplePlayer.ANONYMOUS;
+                }
+              })
+              .collect(Collectors.toList());
+      Collections.shuffle(unshuffledPlayers);
+      samplePlayers = unshuffledPlayers.subList(0, Math.min(12, server.getPlayerCount()));
+    } else {
+      samplePlayers = ImmutableList.of();
+    }
     return new ServerPing(
         new ServerPing.Version(version.getProtocol(),
             "Velocity " + ProtocolVersion.SUPPORTED_VERSION_STRING),
         new ServerPing.Players(server.getPlayerCount(), configuration.getShowMaxPlayers(),
-            ImmutableList.of()),
+            samplePlayers),
         configuration.getMotd(),
         configuration.getFavicon().orElse(null),
         configuration.isAnnounceForge() ? ModInfo.DEFAULT : null

proxy/src/main/resources/default-velocity.toml

@@ -66,6 +66,11 @@ kick-existing-players = false
 #                  configuration is used if no servers could be contacted.
 ping-passthrough = "DISABLED"
 
+# If enabled (default is false), then a sample of the online players on the proxy will be visible
+# when hovering over the player count in the server list.
+# This doesn't have any effect when ping passthrough is set to either "description" or "all".
+sample-players-in-ping = false
+
 # If not enabled (default is true) player IP addresses will be replaced by <ip address withheld> in logs
 enable-player-address-logging = true