From 22ab4657d65a883b19bbc5613c18c0c4ae195a37 Mon Sep 17 00:00:00 2001
From: Jonas Gunz <himself@jonasgunz.de>
Date: Thu, 7 May 2020 20:17:50 +0200
Subject: MC-126244 Hackfix: Cartographer map trade crash

Replaced structure map trade with dummy map around (0,0) to mitigate server crash on large worlds due to poor locateStructure implementation.
---
 Readme.md                                          |  6 +++
 .../re/jag/parquet/mixin/SellMapFactoryMixin.java  | 49 ++++++++++++++++++++++
 src/main/resources/parquet.mixins.json             |  3 +-
 3 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 src/main/java/re/jag/parquet/mixin/SellMapFactoryMixin.java

diff --git a/Readme.md b/Readme.md
index aae5531..6c5576b 100644
--- a/Readme.md
+++ b/Readme.md
@@ -50,3 +50,9 @@ A dispenser pointing into an undyed Shulker Box can apply a color.
 ### [MC-111534](https://bugs.mojang.com/browse/MC-111534)
 
 Stat `minecraft.used:minecraft.firework_rocket` is only incremented, when the rocket is used on the ground, not during elytra flight.
+
+## "Fixes"
+
+### [MC-126244](https://bugs.mojang.com/browse/MC-126244)
+
+Cartographer map trade replaced with dummy map around (0,0) to mitigate server crash in large worlds due to poor implementation of locateStructure.
diff --git a/src/main/java/re/jag/parquet/mixin/SellMapFactoryMixin.java b/src/main/java/re/jag/parquet/mixin/SellMapFactoryMixin.java
new file mode 100644
index 0000000..7dc536b
--- /dev/null
+++ b/src/main/java/re/jag/parquet/mixin/SellMapFactoryMixin.java
@@ -0,0 +1,49 @@
+package re.jag.parquet.mixin;
+
+import net.minecraft.entity.Entity;
+import net.minecraft.item.FilledMapItem;
+import net.minecraft.item.ItemStack;
+import net.minecraft.item.Items;
+import net.minecraft.item.map.MapIcon;
+import net.minecraft.item.map.MapState;
+import net.minecraft.server.world.ServerWorld;
+import net.minecraft.text.LiteralText;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.village.TradeOffer;
+import net.minecraft.village.TradeOffers;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Overwrite;
+import org.spongepowered.asm.mixin.Shadow;
+
+import java.util.Random;
+
+@Mixin(targets="net.minecraft.village.TradeOffers$SellMapFactory")
+public class SellMapFactoryMixin implements TradeOffers.Factory {
+    @Shadow
+    private int price;
+    @Shadow
+    private String structure;
+    @Shadow
+    private MapIcon.Type iconType;
+    @Shadow
+    private int maxUses;
+    @Shadow
+    private int experience;
+
+    @Overwrite
+    public TradeOffer create(Entity entity, Random random) {
+        if (!(entity.world instanceof ServerWorld)) {
+            return null;
+        } else {
+            ServerWorld serverWorld = (ServerWorld) entity.world;
+            BlockPos blockPos = new BlockPos(0,0,0);
+            ItemStack itemStack = FilledMapItem.createMap(serverWorld, blockPos.getX(), blockPos.getZ(), (byte)2, true, true);
+            FilledMapItem.fillExplorationMap(serverWorld, itemStack);
+            MapState.addDecorationsTag(itemStack, blockPos, "+", this.iconType);
+            itemStack.setCustomName(new LiteralText("You shall not crash"));
+            return new TradeOffer(new ItemStack(Items.EMERALD, this.price), new ItemStack(Items.COMPASS), itemStack, this.maxUses, this.experience, 0.2F);
+        }
+    }
+}
+
diff --git a/src/main/resources/parquet.mixins.json b/src/main/resources/parquet.mixins.json
index 93d9905..5d809a4 100644
--- a/src/main/resources/parquet.mixins.json
+++ b/src/main/resources/parquet.mixins.json
@@ -10,7 +10,8 @@
     "CommandManagerMixin",
     "ServerPlayerEntityMixin",
     "BootstrapMixin",
-    "FireWorkItemMixin"
+    "FireWorkItemMixin",
+    "SellMapFactoryMixin"
   ],
   "client": [
   ],
-- 
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