From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Wed, 20 Dec 2017 17:36:49 -0500
Subject: [PATCH] Ability to apply mending to XP API

This allows plugins that give players the ability to apply the experience
points to the Item Mending formula, which will repair an item instead
of giving the player experience points.

Both an API To standalone mend, and apply mending logic to .giveExp has been added.

== AT ==
public net.minecraft.world.entity.ExperienceOrb durabilityToXp(I)I
public net.minecraft.world.entity.ExperienceOrb xpToDurability(I)I

diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
index 6dd5deecd404a3b9858e63da6837caf2d5d382f0..a08c03bb984d27ded2979353f207693fb79d4256 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
@@ -1444,7 +1444,37 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
     }
 
     @Override
-    public void giveExp(int exp) {
+    // Paper start
+    public int applyMending(int amount) {
+        ServerPlayer handle = this.getHandle();
+        // Logic copied from EntityExperienceOrb and remapped to unobfuscated methods/properties
+        final var stackEntry = net.minecraft.world.item.enchantment.EnchantmentHelper
+            .getRandomItemWith(net.minecraft.world.item.enchantment.Enchantments.MENDING, handle);
+        final net.minecraft.world.item.ItemStack itemstack = stackEntry != null ? stackEntry.getValue() : net.minecraft.world.item.ItemStack.EMPTY;
+        if (!itemstack.isEmpty() && itemstack.getItem().canBeDepleted()) {
+            net.minecraft.world.entity.ExperienceOrb orb = net.minecraft.world.entity.EntityType.EXPERIENCE_ORB.create(handle.level);
+            orb.value = amount;
+            orb.spawnReason = org.bukkit.entity.ExperienceOrb.SpawnReason.CUSTOM;
+            orb.setPosRaw(handle.getX(), handle.getY(), handle.getZ());
+
+            int i = Math.min(orb.xpToDurability(amount), itemstack.getDamageValue());
+            org.bukkit.event.player.PlayerItemMendEvent event = org.bukkit.craftbukkit.event.CraftEventFactory.callPlayerItemMendEvent(handle, orb, itemstack, stackEntry.getKey(), i);
+            i = event.getRepairAmount();
+            orb.discard();
+            if (!event.isCancelled()) {
+                amount -= orb.durabilityToXp(i);
+                itemstack.setDamageValue(itemstack.getDamageValue() - i);
+            }
+        }
+        return amount;
+    }
+
+    @Override
+    public void giveExp(int exp, boolean applyMending) {
+        if (applyMending) {
+            exp = this.applyMending(exp);
+        }
+        // Paper end
         this.getHandle().giveExperiencePoints(exp);
     }