Fix horse inventories indices (#11139)

patches/server/1031-fix-horse-inventories.patch

@@ -23,10 +23,10 @@ index 9bcc0931510607b8fbd01233e2b3c346369b214d..467693a60786688b753cebac3b0a8889
  
      // Paper start - Horse API
 diff --git a/src/main/java/org/bukkit/craftbukkit/inventory/CraftInventoryAbstractHorse.java b/src/main/java/org/bukkit/craftbukkit/inventory/CraftInventoryAbstractHorse.java
-index 4946da593713f4d11d88ac1bb68a089f2f6d5ae0..bae0db99a8159bdea71182485b22cce9fc61e00a 100644
+index 4946da593713f4d11d88ac1bb68a089f2f6d5ae0..abef7f23361e6c5d18243dd18439ffd13ac787ae 100644
 --- a/src/main/java/org/bukkit/craftbukkit/inventory/CraftInventoryAbstractHorse.java
 +++ b/src/main/java/org/bukkit/craftbukkit/inventory/CraftInventoryAbstractHorse.java
-@@ -6,17 +6,64 @@ import org.bukkit.inventory.ItemStack;
+@@ -6,17 +6,73 @@ import org.bukkit.inventory.ItemStack;
  
  public class CraftInventoryAbstractHorse extends CraftInventory implements AbstractHorseInventory {
  
@@ -76,10 +76,15 @@ index 4946da593713f4d11d88ac1bb68a089f2f6d5ae0..bae0db99a8159bdea71182485b22cce9
 +    @Override
 +    public ItemStack getItem(final int index) {
 +        if (index == net.minecraft.world.inventory.HorseInventoryMenu.SLOT_BODY_ARMOR) {
-+            final net.minecraft.world.item.ItemStack item = this.getArmorInventory().getItem(index);
++            final net.minecraft.world.item.ItemStack item = this.getArmorInventory().getItem(0);
 +            return item.isEmpty() ? null : CraftItemStack.asCraftMirror(item);
 +        } else {
-+            final net.minecraft.world.item.ItemStack item = this.getMainInventory().getItem(index);
++            int shiftedIndex = index;
++            if (index > net.minecraft.world.inventory.HorseInventoryMenu.SLOT_BODY_ARMOR) {
++                shiftedIndex--;
++            }
++
++            final net.minecraft.world.item.ItemStack item = this.getMainInventory().getItem(shiftedIndex);
 +            return item.isEmpty() ? null : CraftItemStack.asCraftMirror(item);
 +        }
 +    }
@@ -87,9 +92,13 @@ index 4946da593713f4d11d88ac1bb68a089f2f6d5ae0..bae0db99a8159bdea71182485b22cce9
 +    @Override
 +    public void setItem(final int index, final ItemStack item) {
 +        if (index == net.minecraft.world.inventory.HorseInventoryMenu.SLOT_BODY_ARMOR) {
-+            this.getArmorInventory().setItem(index, CraftItemStack.asNMSCopy(item));
++            this.getArmorInventory().setItem(0, CraftItemStack.asNMSCopy(item));
 +        } else {
-+            this.getMainInventory().setItem(index, CraftItemStack.asNMSCopy(item));
++            int shiftedIndex = index;
++            if (index > net.minecraft.world.inventory.HorseInventoryMenu.SLOT_BODY_ARMOR) {
++                shiftedIndex--;
++            }
++            this.getMainInventory().setItem(shiftedIndex, CraftItemStack.asNMSCopy(item));
 +        }
 +    }
 +    // Paper end - combine both horse inventories