From 18156579a68f274c92794b01393397770251ce2b Mon Sep 17 00:00:00 2001
From: ishland <ishlandmc@yeah.net>
Date: Thu, 13 Jul 2023 17:21:14 +0800
Subject: [PATCH] perf: improve chunk transition speed

---
 .../access/IThreadedAnvilChunkStorage.java    |  4 ++
 .../worldgen/mixin/MixinChunkHolder.java      | 43 +++++++++++++++++++
 .../c2me-threading-worldgen.mixins.json       |  1 +
 3 files changed, 48 insertions(+)
 create mode 100644 c2me-threading-worldgen/src/main/java/com/ishland/c2me/threading/worldgen/mixin/MixinChunkHolder.java

diff --git a/c2me-base/src/main/java/com/ishland/c2me/base/mixin/access/IThreadedAnvilChunkStorage.java b/c2me-base/src/main/java/com/ishland/c2me/base/mixin/access/IThreadedAnvilChunkStorage.java
index 74315c06..edbe2aa3 100644
--- a/c2me-base/src/main/java/com/ishland/c2me/base/mixin/access/IThreadedAnvilChunkStorage.java
+++ b/c2me-base/src/main/java/com/ishland/c2me/base/mixin/access/IThreadedAnvilChunkStorage.java
@@ -5,6 +5,7 @@
 import net.minecraft.server.world.ServerWorld;
 import net.minecraft.server.world.ThreadedAnvilChunkStorage;
 import net.minecraft.util.math.ChunkPos;
+import net.minecraft.util.thread.ThreadExecutor;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.gen.Accessor;
 import org.spongepowered.asm.mixin.gen.Invoker;
@@ -30,4 +31,7 @@ public interface IThreadedAnvilChunkStorage {
     @Invoker
     void invokeReleaseLightTicket(ChunkPos pos);
 
+    @Accessor
+    ThreadExecutor<Runnable> getMainThreadExecutor();
+
 }
diff --git a/c2me-threading-worldgen/src/main/java/com/ishland/c2me/threading/worldgen/mixin/MixinChunkHolder.java b/c2me-threading-worldgen/src/main/java/com/ishland/c2me/threading/worldgen/mixin/MixinChunkHolder.java
new file mode 100644
index 00000000..aac6b667
--- /dev/null
+++ b/c2me-threading-worldgen/src/main/java/com/ishland/c2me/threading/worldgen/mixin/MixinChunkHolder.java
@@ -0,0 +1,43 @@
+package com.ishland.c2me.threading.worldgen.mixin;
+
+import com.ishland.c2me.base.mixin.access.IThreadedAnvilChunkStorage;
+import com.ishland.c2me.threading.worldgen.common.Config;
+import com.mojang.datafixers.util.Either;
+import net.minecraft.server.world.ChunkHolder;
+import net.minecraft.server.world.ThreadedAnvilChunkStorage;
+import net.minecraft.util.thread.ThreadExecutor;
+import net.minecraft.world.chunk.Chunk;
+import net.minecraft.world.chunk.ChunkStatus;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+import java.util.concurrent.CompletableFuture;
+
+@Mixin(value = ChunkHolder.class, priority = 1110)
+public abstract class MixinChunkHolder {
+
+    @Shadow public abstract CompletableFuture<Either<Chunk, ChunkHolder.Unloaded>> getChunkAt(ChunkStatus targetStatus, ThreadedAnvilChunkStorage chunkStorage);
+
+    @Redirect(method = "getChunkAt", at = @At(value = "INVOKE", target = "Lnet/minecraft/server/world/ThreadedAnvilChunkStorage;getChunk(Lnet/minecraft/server/world/ChunkHolder;Lnet/minecraft/world/chunk/ChunkStatus;)Ljava/util/concurrent/CompletableFuture;"))
+    private CompletableFuture<Either<Chunk, ChunkHolder.Unloaded>> redirectGetChunk(ThreadedAnvilChunkStorage instance, ChunkHolder holder, ChunkStatus requiredStatus) {
+        if (requiredStatus == ChunkStatus.EMPTY) {
+            return instance.getChunk(holder, requiredStatus);
+        } else {
+            return this.getChunkAt(requiredStatus.getPrevious(), instance)
+                    .thenComposeAsync(
+                            unused -> instance.getChunk(holder, requiredStatus),
+                            Config.asyncScheduling ? Runnable::run : r -> {
+                                final ThreadExecutor<Runnable> executor = ((IThreadedAnvilChunkStorage) instance).getMainThreadExecutor();
+                                if (executor.isOnThread()) {
+                                    r.run();
+                                } else {
+                                    executor.execute(r);
+                                }
+                            }
+                    );
+        }
+    }
+
+}
diff --git a/c2me-threading-worldgen/src/main/resources/c2me-threading-worldgen.mixins.json b/c2me-threading-worldgen/src/main/resources/c2me-threading-worldgen.mixins.json
index 51e88e73..c4605ca9 100644
--- a/c2me-threading-worldgen/src/main/resources/c2me-threading-worldgen.mixins.json
+++ b/c2me-threading-worldgen/src/main/resources/c2me-threading-worldgen.mixins.json
@@ -5,6 +5,7 @@
   "plugin": "com.ishland.c2me.base.common.ModuleMixinPlugin",
   "mixins": [
     "MixinChunkGenerator",
+    "MixinChunkHolder",
     "MixinChunkRegion",
     "MixinChunkStatus",
     "MixinNoiseChunkGenerator",