Server side partition syncing and packets

src/main/java/net/xevianlight/aphelion/network/PartitionSync.java

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+package net.xevianlight.aphelion.network;
+
+
+import net.minecraft.server.level.ServerPlayer;
+import net.neoforged.bus.api.SubscribeEvent;
+import net.neoforged.fml.common.EventBusSubscriber;
+import net.neoforged.neoforge.event.entity.player.PlayerEvent;
+import net.neoforged.neoforge.event.tick.ServerTickEvent;
+import net.neoforged.neoforge.network.PacketDistributor;
+import net.xevianlight.aphelion.Aphelion;
+import net.xevianlight.aphelion.core.space.SpacePartitionSavedData;
+import net.xevianlight.aphelion.network.packet.PartitionData;
+import net.xevianlight.aphelion.util.SpacePartitionHelper;
+
+import java.util.HashSet;
+import java.util.Objects;
+import java.util.Set;
+import java.util.UUID;
+
+@EventBusSubscriber(modid = Aphelion.MOD_ID)
+public final class PartitionSync {
+
+    // send once right after join (safe: delayed to next server tick)
+    private static final Set<UUID> PENDING_JOIN_SEND = new HashSet<>();
+
+    @SubscribeEvent
+    public static void onLogin(PlayerEvent.PlayerLoggedInEvent e) {
+        if (e.getEntity() instanceof ServerPlayer sp) {
+            PENDING_JOIN_SEND.add(sp.getUUID());
+        }
+    }
+
+    private static final java.util.Map<UUID, PartitionData> LAST_SENT = new java.util.HashMap<>();
+
+    @SubscribeEvent
+    public static void onServerTick(ServerTickEvent.Post e) {
+        var server = e.getServer();
+
+//        Aphelion.LOGGER.info("WORKS!!!");
+
+        for (ServerPlayer sp : server.getPlayerList().getPlayers()) {
+            PartitionData now = computePartitionFor(sp); // your logic
+            PartitionData prev = LAST_SENT.get(sp.getUUID());
+
+            if (prev == null || !prev.equals(now)) {
+                PacketDistributor.sendToPlayer(sp, now);
+                LAST_SENT.put(sp.getUUID(), now);
+            }
+        }
+    }
+
+    private static PartitionData computePartitionFor(ServerPlayer sp) {
+        // Example: convert player position to partition coords
+        int px = (int)Math.floor(sp.getX() / SpacePartitionHelper.SIZE);
+        int pz = (int)Math.floor(sp.getZ() / SpacePartitionHelper.SIZE);
+
+        var orbit = SpacePartitionSavedData.get(sp.serverLevel()).getOrbitForPartition(px, pz);
+        String orbitId = (orbit != null) ? orbit.toString() : "aphelion:orbit/default";
+
+        return new PartitionData(orbitId);
+    }
+}

src/main/java/net/xevianlight/aphelion/network/ServerPayloadHandler.java

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+package net.xevianlight.aphelion.network;
+
+import net.neoforged.neoforge.network.handling.IPayloadContext;
+import net.xevianlight.aphelion.Aphelion;
+import net.xevianlight.aphelion.client.PartitionClientState;
+import net.xevianlight.aphelion.network.packet.PartitionData;
+
+// Handle packets TO the client FROM the server
+public class ServerPayloadHandler {
+
+    public static void handleDataOnMain(PartitionData data, IPayloadContext context) {
+        PartitionClientState.set(data);
+        Aphelion.LOGGER.info("Partition packet received! id={}", data.id());
+    }
+}

src/main/java/net/xevianlight/aphelion/network/packet/PartitionData.java

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+package net.xevianlight.aphelion.network.packet;
+
+import io.netty.buffer.ByteBuf;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.minecraft.resources.ResourceLocation;
+import net.xevianlight.aphelion.Aphelion;
+
+public record PartitionData (String id) implements CustomPacketPayload {
+    public static final Type<PartitionData> TYPE = new CustomPacketPayload.Type<>(ResourceLocation.fromNamespaceAndPath(Aphelion.MOD_ID, "partition_data"));
+
+    public static final StreamCodec<ByteBuf, PartitionData> STREAM_CODEC = StreamCodec.composite(
+            ByteBufCodecs.STRING_UTF8,
+            PartitionData::id,
+
+            PartitionData::new
+    );
+
+    @Override
+    public Type<? extends CustomPacketPayload> type() {
+        return TYPE;
+    }
+}