From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
Date: Fri, 13 Sep 2024 14:32:32 -0700
Subject: [PATCH] PaperPR: Add ticket on player join to avoid chunk
 load-unload-load cycle

Original license: GPLv3
Original project: https://github.com/PaperMC/Paper
Paper pull request: https://github.com/PaperMC/Paper/pull/11398

Adding the entity will add and then immediately remove an entity load ticket, which would result in the chunk loading and then unloading before being loaded again once the player chunk loader reacts (delay can vary based on rate limit configs)
By adding a ticket with a short removal delay we attempt to keep the chunk loaded until the player chunk loader reacts, but this is not a guarantee due to the aforementioned rate limit configs. Plugins should still handle load/unload events as normal, however this will reduce redundant calls.
The delay is currently set to 2 seconds, however, we may want to adjust this before merging (for example the player chunk unload delay is 5 seconds)

fixes Paper#9581

diff --git a/ca/spottedleaf/moonrise/patches/chunk_system/player/RegionizedPlayerChunkLoader.java b/ca/spottedleaf/moonrise/patches/chunk_system/player/RegionizedPlayerChunkLoader.java
index 3a78e7512772fd3f7cf8f221e3a72474def14bea..ba52af914e9e231caa0ac50562e9a6925908c615 100644
--- a/ca/spottedleaf/moonrise/patches/chunk_system/player/RegionizedPlayerChunkLoader.java
+++ b/ca/spottedleaf/moonrise/patches/chunk_system/player/RegionizedPlayerChunkLoader.java
@@ -48,6 +48,7 @@ public final class RegionizedPlayerChunkLoader {
 
     public static final TicketType PLAYER_TICKET         = ChunkSystemTicketType.create("chunk_system:player_ticket", Long::compareTo);
     public static final TicketType PLAYER_TICKET_DELAYED = ChunkSystemTicketType.create("chunk_system:player_ticket_delayed", Long::compareTo, 5L * 20L);
+    public static final TicketType PLAYER_JOIN           = ChunkSystemTicketType.create("chunk_system:player_join", (a, b) -> 0, 5 * 20); // Paper - Add ticket on player join to avoid chunk load-unload-load cycle
 
     public static final int GENERATED_TICKET_LEVEL = ChunkHolderManager.FULL_LOADED_TICKET_LEVEL;
     public static final int LOADED_TICKET_LEVEL = ChunkTaskScheduler.getTicketLevel(ChunkStatus.EMPTY);
diff --git a/net/minecraft/server/players/PlayerList.java b/net/minecraft/server/players/PlayerList.java
index 96202ffdb73cb9d8c63351b4538c64645b91d21c..65857e4799186b7166fb0023694dc2749a492546 100644
--- a/net/minecraft/server/players/PlayerList.java
+++ b/net/minecraft/server/players/PlayerList.java
@@ -434,6 +434,13 @@ public abstract class PlayerList {
         // this.broadcastAll(ClientboundPlayerInfoUpdatePacket.createPlayerInitializing(List.of(player))); // CraftBukkit - replaced with loop below
         // Paper start - Fire PlayerJoinEvent when Player is actually ready; correctly register player BEFORE PlayerJoinEvent, so the entity is valid and doesn't require tick delay hacks
         player.supressTrackerForLogin = true;
+        // Paper start - Add ticket on player join to avoid chunk load-unload-load cycle
+        serverLevel.moonrise$getChunkTaskScheduler().chunkHolderManager.addTicketAtLevel(
+            ca.spottedleaf.moonrise.patches.chunk_system.player.RegionizedPlayerChunkLoader.PLAYER_JOIN,
+            player.chunkPosition(),
+            ca.spottedleaf.moonrise.patches.chunk_system.player.RegionizedPlayerChunkLoader.TICK_TICKET_LEVEL,
+            net.minecraft.util.Unit.INSTANCE);
+        // Paper end - Add ticket on player join to avoid chunk load-unload-load cycle
         serverLevel.addNewPlayer(player);
         this.server.getCustomBossEvents().onPlayerConnect(player); // see commented out section below serverLevel.addPlayerJoin(player);
         // Paper end - Fire PlayerJoinEvent when Player is actually ready