feat: add game metrics

src/main/java/dev/emortal/minestom/gamesdk/game/Game.java

@@ -3,6 +3,9 @@
 import dev.emortal.minestom.gamesdk.config.GameCreationInfo;
 import dev.emortal.minestom.gamesdk.internal.GameManager;
 import dev.emortal.minestom.gamesdk.util.GameEventPredicates;
+import io.micrometer.core.instrument.Gauge;
+import io.micrometer.core.instrument.Meter;
+import io.micrometer.core.instrument.Metrics;
 import net.minestom.server.MinecraftServer;
 import net.minestom.server.adventure.audience.PacketGroupingAudience;
 import net.minestom.server.entity.Player;
@@ -15,11 +18,13 @@
 import java.time.Instant;
 import java.util.Collections;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 public abstract class Game implements PacketGroupingAudience, TrackableGame {
+    protected final @NotNull Set<Meter> meters = new HashSet<>();
 
     private final @NotNull GameCreationInfo creationInfo;
     private final @NotNull EventNode<Event> eventNode;
@@ -33,6 +38,11 @@ public abstract class Game implements PacketGroupingAudience, TrackableGame {
     protected Game(@NotNull GameCreationInfo creationInfo) {
         this.creationInfo = creationInfo;
         this.eventNode = this.createEventNode();
+
+        this.meters.add(Gauge.builder("gamesdk.game_player_count", this, game -> game.getPlayers().size())
+                .tag("gameId", this.creationInfo.id())
+                .description("The amount of players currently in the game")
+                .register(Metrics.globalRegistry));
     }
 
     /**
@@ -64,6 +74,10 @@ protected Game(@NotNull GameCreationInfo creationInfo) {
      */
     public abstract void onLeave(@NotNull Player player);
 
+    public @NotNull Set<Meter> getMeters() {
+        return this.meters;
+    }
+
     public abstract @NotNull Instance getSpawningInstance(@NotNull Player player);
 
     public final @NotNull EventNode<Event> getEventNode() {

src/main/java/dev/emortal/minestom/gamesdk/internal/GameManager.java

@@ -8,6 +8,10 @@
 import dev.emortal.minestom.gamesdk.game.GameFinishedEvent;
 import dev.emortal.minestom.gamesdk.game.GameProvider;
 import dev.emortal.minestom.gamesdk.internal.listener.GameStatusListener;
+import io.micrometer.core.instrument.Counter;
+import io.micrometer.core.instrument.Gauge;
+import io.micrometer.core.instrument.Meter;
+import io.micrometer.core.instrument.Metrics;
 import net.kyori.adventure.text.Component;
 import net.kyori.adventure.text.format.NamedTextColor;
 import net.minestom.server.entity.Player;
@@ -40,6 +44,10 @@ public GameManager(@NotNull GameSdkConfig config) {
         }
 
         GameEventNodes.GAME_MANAGER.addListener(GameFinishedEvent.class, this::onGameFinish);
+
+        Gauge.builder("gamesdk.game_count", this.games, Set::size)
+                .description("The amount of games currently running")
+                .register(Metrics.globalRegistry);
     }
 
     private void initTestMode() {
@@ -73,6 +81,11 @@ public void startGame(@NotNull Game game) {
         for (GameStatusListener listener : this.statusListeners) {
             listener.onGameStart(game);
         }
+
+        game.getMeters().add(Gauge.builder("gamesdk.game_start_time", System.currentTimeMillis(), Long::doubleValue)
+                .tag("gameId", game.getCreationInfo().id())
+                .description("The time the game started")
+                .register(Metrics.globalRegistry));
     }
 
     private void removeGame(@NotNull Game game) {
@@ -109,6 +122,7 @@ private void onGameFinish(@NotNull GameFinishedEvent event) {
     private void cleanUpGame(@NotNull Game game) {
         this.kickAllRemainingPlayers(game);
         game.cleanUp();
+        game.getMeters().forEach(Meter::close);
 
         // We call this here to ensure all the game's players are disconnected and the game is unregistered, so the check for the
         // player count will actually see the new player count after the players are disconnected.

src/main/java/dev/emortal/minestom/gamesdk/internal/PreGameInitializer.java

@@ -22,6 +22,8 @@
 final class PreGameInitializer {
     private static final Logger LOGGER = LoggerFactory.getLogger(PreGameInitializer.class);
 
+    private final @NotNull GameManager gameManager;
+
     private final @NotNull GameSdkConfig config;
     private final @NotNull Game game;
 
@@ -32,6 +34,7 @@ final class PreGameInitializer {
     private final AtomicInteger playerCount = new AtomicInteger();
 
     PreGameInitializer(@NotNull GameManager gameManager, @NotNull GameSdkConfig config, @NotNull Game game) {
+        this.gameManager = gameManager;
         this.config = config;
         this.game = game;
 
@@ -61,7 +64,7 @@ private void timeOut() {
         int actualPlayerCount = this.game.getPlayers().size();
         if (actualPlayerCount >= this.config.minPlayers()) {
             this.cleanUpPreGame();
-            this.game.start();
+            this.gameManager.startGame(this.game);
         } else {
             // TODO: This isn't a normal finish. We should inform players that the game couldn't start and send them back to the lobby.
             this.game.finish();