Send explosions only to nearby players

src/main/java/net/minestom/server/ServerFlag.java

@@ -27,6 +27,7 @@ public final class ServerFlag {
     public static final int POOLED_BUFFER_SIZE = intProperty("minestom.pooled-buffer-size", 262_143);
     public static final int SEND_LIGHT_AFTER_BLOCK_PLACEMENT_DELAY = intProperty("minestom.send-light-after-block-placement-delay", 100);
     public static final long LOGIN_PLUGIN_MESSAGE_TIMEOUT = longProperty("minestom.login-plugin-message-timeout", 5_000);
+    public static final int EXPLOSION_SEND_DISTANCE = intProperty("minestom.explosion-send-distance", 100);
     public static final int SERVER_LINK_AMOUNT = intProperty("minestom.server-link-amount", 100);
 
     // Network rate limiting

src/main/java/net/minestom/server/instance/Explosion.java

@@ -1,6 +1,9 @@
 package net.minestom.server.instance;
 
+import net.minestom.server.ServerFlag;
 import net.minestom.server.coordinate.Point;
+import net.minestom.server.coordinate.Pos;
+import net.minestom.server.entity.Player;
 import net.minestom.server.instance.block.Block;
 import net.minestom.server.network.packet.server.play.ExplosionPacket;
 import net.minestom.server.utils.PacketUtils;
@@ -69,11 +72,14 @@ public void apply(@NotNull Instance instance) {
             records[i * 3 + 2] = z;
         }
 
-        // TODO send only to close players
         ExplosionPacket packet = new ExplosionPacket(centerX, centerY, centerZ, strength,
                 records, 0, 0, 0);
         postExplosion(instance, blocks, packet);
-        PacketUtils.sendGroupedPacket(instance.getPlayers(), packet);
+        List<Player> players = instance.getNearbyEntities(new Pos(centerX, centerY, centerZ), ServerFlag.EXPLOSION_SEND_DISTANCE)
+                .stream()
+                .filter(Player.class::isInstance)
+                .map(Player.class::cast).toList();
+        PacketUtils.sendGroupedPacket(players, packet);
 
         postSend(instance, blocks);
     }

src/test/java/net/minestom/server/instance/ExplosionIntegrationTest.java

@@ -0,0 +1,62 @@
+package net.minestom.server.instance;
+
+import net.kyori.adventure.nbt.CompoundBinaryTag;
+import net.minestom.server.coordinate.Point;
+import net.minestom.server.coordinate.Pos;
+import net.minestom.server.network.packet.server.play.ExplosionPacket;
+import net.minestom.testing.Env;
+import net.minestom.testing.extension.MicrotusExtension;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import java.util.List;
+
+
+@ExtendWith(MicrotusExtension.class)
+class ExplosionIntegrationTest {
+
+    // Checks that only nearby players actually receive the packet from the server
+    @Test
+    void sendToNearbyPlayers(Env env) {
+        var instance = env.createFlatInstance();
+        instance.setExplosionSupplier(new TestExplosionSupplierImpl());
+
+        var connection1 = env.createConnection();
+        var connection2 = env.createConnection();
+        var connection3 = env.createConnection();
+
+        // Assumes that the default ServerFlag.EXPLOSION_SEND_DISTANCE is set to 100 blocks
+        var player1 = connection1.connect(instance, new Pos(0, 41, 0));
+        var player2 = connection2.connect(instance, new Pos(50, 41, 0));
+        var player3 = connection3.connect(instance, new Pos(0, 41, 110));
+
+        var packetTracker1 = connection1.trackIncoming(ExplosionPacket.class);
+        var packetTracker2 = connection2.trackIncoming(ExplosionPacket.class);
+        var packetTracker3 = connection3.trackIncoming(ExplosionPacket.class);
+
+        instance.explode(0, 41, 0, 1);
+        packetTracker1.assertSingle();
+        packetTracker2.assertSingle();
+        packetTracker3.assertEmpty();
+        env.destroyInstance(instance, true);
+    }
+
+
+    class TestExplosionSupplierImpl implements ExplosionSupplier {
+        @Override
+        public Explosion createExplosion(float centerX, float centerY, float centerZ, float strength, CompoundBinaryTag additionalData) {
+            return new TestExplosionImpl(centerX, centerY, centerZ, strength);
+        }
+
+        class TestExplosionImpl extends Explosion {
+
+            TestExplosionImpl(float centerX, float centerY, float centerZ, float strength) {
+                super(centerX, centerY, centerZ, strength);
+            }
+            @Override
+            protected List<Point> prepare(Instance instance) {
+                return List.of(new Pos(getCenterX(), getCenterY(), getCenterZ()));
+            }
+        }
+    }
+
+}