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] Paper PR: 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)

This patch fixes PaperMC/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 8697528095ebed543ee1bb3b6b617a26a800bd5d..4fc29f7aae32180f86af971f7f80a37aa6e797e4 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, 0L, TicketType.FLAG_LOADING | TicketType.FLAG_SIMULATION | TicketType.FLAG_KEEP_DIMENSION_ACTIVE);
     public static final TicketType PLAYER_TICKET_DELAYED = ChunkSystemTicketType.create("chunk_system:player_ticket_delayed", Long::compareTo, 1L, TicketType.FLAG_LOADING | TicketType.FLAG_SIMULATION | TicketType.FLAG_KEEP_DIMENSION_ACTIVE);
+    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 561165ccc8c4d66ef590fb8deb65782a214d9611..79210997e56ec6798d249608049e108724670cde 100644
--- a/net/minecraft/server/players/PlayerList.java
+++ b/net/minecraft/server/players/PlayerList.java
@@ -220,6 +220,13 @@ 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.suppressTrackerForLogin = 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
         this.sendLevelInfo(player, serverLevel);
         serverLevel.addNewPlayer(player);
         this.server.getCustomBossEvents().onPlayerConnect(player); // see commented out section below serverLevel.addPlayerJoin(player);