Add PlayerTradeEvent and PlayerPurchaseEvent

Co-authored-by: Alexander <protonull@protonmail.com>

paper-server/patches/sources/net/minecraft/world/entity/npc/AbstractVillager.java.patch

@@ -45,7 +45,35 @@
      @Override
      public MerchantOffers getOffers() {
          if (this.level().isClientSide) {
-@@ -179,7 +199,7 @@
+@@ -121,11 +141,24 @@
+     @Override
+     public void overrideXp(int experience) {}
+ 
++    // Paper start - Add PlayerTradeEvent and PlayerPurchaseEvent
+     @Override
+-    public void notifyTrade(MerchantOffer offer) {
+-        offer.increaseUses();
++    public void processTrade(MerchantOffer recipe, @Nullable io.papermc.paper.event.player.PlayerPurchaseEvent event) { // The MerchantRecipe passed in here is the one set by the PlayerPurchaseEvent
++        if (event == null || event.willIncreaseTradeUses()) {
++            recipe.increaseUses();
++        }
++        if (event == null || event.isRewardingExp()) {
++            this.rewardTradeXp(recipe);
++        }
++        this.notifyTrade(recipe);
++    }
++    // Paper end - Add PlayerTradeEvent and PlayerPurchaseEvent
++
++    @Override
++    public void notifyTrade(MerchantOffer offer) {
++        // offer.increaseUses(); // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent
+         this.ambientSoundTime = -this.getAmbientSoundInterval();
+-        this.rewardTradeXp(offer);
++        // this.rewardTradeXp(offer); // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent
+         if (this.tradingPlayer instanceof ServerPlayer) {
+             CriteriaTriggers.TRADE.trigger((ServerPlayer) this.tradingPlayer, this, offer.getResult());
+         }
+@@ -179,7 +212,7 @@
      public void readAdditionalSaveData(CompoundTag nbt) {
          super.readAdditionalSaveData(nbt);
          if (nbt.contains("Offers")) {
@@ -54,7 +82,7 @@
              Logger logger = AbstractVillager.LOGGER;
  
              Objects.requireNonNull(logger);
-@@ -246,7 +266,20 @@
+@@ -246,7 +279,20 @@
              MerchantOffer merchantrecipe = ((VillagerTrades.ItemListing) arraylist.remove(this.random.nextInt(arraylist.size()))).getOffer(this, this.random);
  
              if (merchantrecipe != null) {

paper-server/patches/sources/net/minecraft/world/inventory/AbstractContainerMenu.java.patch

@@ -214,7 +214,73 @@
              }
  
          }
-@@ -893,6 +995,11 @@
+@@ -729,6 +831,14 @@
+     public abstract boolean stillValid(Player player);
+ 
+     protected boolean moveItemStackTo(ItemStack stack, int startIndex, int endIndex, boolean fromLast) {
++        // Paper start - Add PlayerTradeEvent and PlayerPurchaseEvent
++        return this.moveItemStackTo(stack, startIndex, endIndex, fromLast, false);
++    }
++    protected boolean moveItemStackTo(ItemStack stack, int startIndex, int endIndex, boolean fromLast, boolean isCheck) {
++        if (isCheck) {
++            stack = stack.copy();
++        }
++        // Paper end - Add PlayerTradeEvent and PlayerPurchaseEvent
+         boolean flag1 = false;
+         int k = startIndex;
+ 
+@@ -752,6 +862,11 @@
+ 
+                 slot = (Slot) this.slots.get(k);
+                 itemstack1 = slot.getItem();
++                // Paper start - Add PlayerTradeEvent and PlayerPurchaseEvent; clone if only a check
++                if (isCheck) {
++                    itemstack1 = itemstack1.copy();
++                }
++                // Paper end - Add PlayerTradeEvent and PlayerPurchaseEvent
+                 if (!itemstack1.isEmpty() && ItemStack.isSameItemSameComponents(stack, itemstack1)) {
+                     l = itemstack1.getCount() + stack.getCount();
+                     int i1 = slot.getMaxStackSize(itemstack1);
+@@ -759,12 +874,16 @@
+                     if (l <= i1) {
+                         stack.setCount(0);
+                         itemstack1.setCount(l);
++                        if (!isCheck) { // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent
+                         slot.setChanged();
++                        } // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent
+                         flag1 = true;
+                     } else if (itemstack1.getCount() < i1) {
+                         stack.shrink(i1 - itemstack1.getCount());
+                         itemstack1.setCount(i1);
++                        if (!isCheck) { // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent
+                         slot.setChanged();
++                        } // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent
+                         flag1 = true;
+                     }
+                 }
+@@ -795,10 +914,21 @@
+ 
+                 slot = (Slot) this.slots.get(k);
+                 itemstack1 = slot.getItem();
++                // Paper start - Add PlayerTradeEvent and PlayerPurchaseEvent
++                if (isCheck) {
++                    itemstack1 = itemstack1.copy();
++                }
++                // Paper end - Add PlayerTradeEvent and PlayerPurchaseEvent
+                 if (itemstack1.isEmpty() && slot.mayPlace(stack)) {
+                     l = slot.getMaxStackSize(stack);
++                    // Paper start - Add PlayerTradeEvent and PlayerPurchaseEvent
++                    if (isCheck) {
++                        stack.shrink(Math.min(stack.getCount(), l));
++                    } else {
++                    // Paper end - Add PlayerTradeEvent and PlayerPurchaseEvent
+                     slot.setByPlayer(stack.split(Math.min(stack.getCount(), l)));
+                     slot.setChanged();
++                    } // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent
+                     flag1 = true;
+                     break;
+                 }
+@@ -893,6 +1023,11 @@
      }
  
      public ItemStack getCarried() {
@@ -226,7 +292,7 @@
          return this.carried;
      }
  
-@@ -947,4 +1054,15 @@
+@@ -947,4 +1082,15 @@
          this.stateId = this.stateId + 1 & 32767;
          return this.stateId;
      }

paper-server/patches/sources/net/minecraft/world/inventory/MerchantMenu.java.patch

@@ -36,7 +36,52 @@
          this.addStandardInventorySlots(playerInventory, 108, 84);
      }
  
-@@ -143,7 +158,7 @@
+@@ -108,12 +123,12 @@
+ 
+             itemstack = itemstack1.copy();
+             if (slot == 2) {
+-                if (!this.moveItemStackTo(itemstack1, 3, 39, true)) {
++                if (!this.moveItemStackTo(itemstack1, 3, 39, true, true)) { // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent
+                     return ItemStack.EMPTY;
+                 }
+ 
+-                slot1.onQuickCraft(itemstack1, itemstack);
+-                this.playTradeSound();
++                //  slot1.onQuickCraft(itemstack1, itemstack); // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent; moved to after the non-check moveItemStackTo call
++                // this.playTradeSound();
+             } else if (slot != 0 && slot != 1) {
+                 if (slot >= 3 && slot < 30) {
+                     if (!this.moveItemStackTo(itemstack1, 30, 39, false)) {
+@@ -126,6 +141,7 @@
+                 return ItemStack.EMPTY;
+             }
+ 
++            if (slot != 2) { // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent; moved down for slot 2
+             if (itemstack1.isEmpty()) {
+                 slot1.setByPlayer(ItemStack.EMPTY);
+             } else {
+@@ -137,13 +153,28 @@
+             }
+ 
+             slot1.onTake(player, itemstack1);
++            } // Paper start - Add PlayerTradeEvent and PlayerPurchaseEvent; handle slot 2
++            if (slot == 2) { // is merchant result slot
++                slot1.onTake(player, itemstack1);
++                if (itemstack1.isEmpty()) {
++                    slot1.set(ItemStack.EMPTY);
++                    return ItemStack.EMPTY;
++                }
++
++                this.moveItemStackTo(itemstack1, 3, 39, true, false); // This should always succeed because it's checked above
++
++                slot1.onQuickCraft(itemstack1, itemstack);
++                this.playTradeSound();
++                slot1.set(ItemStack.EMPTY); // itemstack1 should ALWAYS be empty
++            }
++            // Paper end - Add PlayerTradeEvent and PlayerPurchaseEvent
+         }
+ 
+         return itemstack;
      }
  
      private void playTradeSound() {

paper-server/patches/sources/net/minecraft/world/inventory/MerchantResultSlot.java.patch

@@ -0,0 +1,37 @@
+--- a/net/minecraft/world/inventory/MerchantResultSlot.java
++++ b/net/minecraft/world/inventory/MerchantResultSlot.java
+@@ -47,13 +47,32 @@
+ 
+     @Override
+     public void onTake(Player player, ItemStack stack) {
+-        this.checkTakeAchievements(stack);
++        // this.checkTakeAchievements(stack); // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent; move to after event is called and not cancelled
+         MerchantOffer merchantOffer = this.slots.getActiveOffer();
++        // Paper start - Add PlayerTradeEvent and PlayerPurchaseEvent
++        io.papermc.paper.event.player.PlayerPurchaseEvent event = null;
++        if (merchantOffer != null && player instanceof net.minecraft.server.level.ServerPlayer serverPlayer) {
++            if (this.merchant instanceof net.minecraft.world.entity.npc.AbstractVillager abstractVillager) {
++                event = new io.papermc.paper.event.player.PlayerTradeEvent(serverPlayer.getBukkitEntity(), (org.bukkit.entity.AbstractVillager) abstractVillager.getBukkitEntity(), merchantOffer.asBukkit(), true, true);
++            } else if (this.merchant instanceof org.bukkit.craftbukkit.inventory.CraftMerchantCustom.MinecraftMerchant) {
++                event = new io.papermc.paper.event.player.PlayerPurchaseEvent(serverPlayer.getBukkitEntity(), merchantOffer.asBukkit(), false, true);
++            }
++            if (event != null) {
++                if (!event.callEvent()) {
++                    stack.setCount(0);
++                    event.getPlayer().updateInventory();
++                    return;
++                }
++                merchantOffer = org.bukkit.craftbukkit.inventory.CraftMerchantRecipe.fromBukkit(event.getTrade()).toMinecraft();
++            }
++        }
++        this.checkTakeAchievements(stack);
++        // Paper end - Add PlayerTradeEvent and PlayerPurchaseEvent
+         if (merchantOffer != null) {
+             ItemStack itemStack = this.slots.getItem(0);
+             ItemStack itemStack2 = this.slots.getItem(1);
+             if (merchantOffer.take(itemStack, itemStack2) || merchantOffer.take(itemStack2, itemStack)) {
+-                this.merchant.notifyTrade(merchantOffer);
++                this.merchant.processTrade(merchantOffer, event); // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent
+                 player.awardStat(Stats.TRADED_WITH_VILLAGER);
+                 this.slots.setItem(0, itemStack);
+                 this.slots.setItem(1, itemStack2);

paper-server/patches/sources/net/minecraft/world/item/trading/Merchant.java.patch

@@ -1,6 +1,14 @@
 --- a/net/minecraft/world/item/trading/Merchant.java
 +++ b/net/minecraft/world/item/trading/Merchant.java
-@@ -54,4 +54,6 @@
+@@ -20,6 +20,7 @@
+ 
+     void overrideOffers(MerchantOffers offers);
+ 
++    default void processTrade(MerchantOffer merchantRecipe, @Nullable io.papermc.paper.event.player.PlayerPurchaseEvent event) { this.notifyTrade(merchantRecipe); } // Paper
+     void notifyTrade(MerchantOffer offer);
+ 
+     void notifyTradeUpdated(ItemStack stack);
+@@ -54,4 +55,6 @@
      boolean isClientSide();
  
      boolean stillValid(Player player);

paper-server/src/main/java/org/bukkit/craftbukkit/inventory/CraftMerchantCustom.java

@@ -76,10 +76,25 @@ public class CraftMerchantCustom implements CraftMerchant {
             return this.trades;
         }
 
+        // Paper start - Add PlayerTradeEvent and PlayerPurchaseEvent
+        @Override
+        public void processTrade(MerchantOffer merchantRecipe, @javax.annotation.Nullable io.papermc.paper.event.player.PlayerPurchaseEvent event) { // The MerchantRecipe passed in here is the one set by the PlayerPurchaseEvent
+            /** Based on {@link net.minecraft.world.entity.npc.AbstractVillager#processTrade(MerchantOffer, io.papermc.paper.event.player.PlayerPurchaseEvent)} */
+            if (getTradingPlayer() instanceof net.minecraft.server.level.ServerPlayer) {
+                if (event == null || event.willIncreaseTradeUses()) {
+                    merchantRecipe.increaseUses();
+                }
+                if (event == null || event.isRewardingExp()) {
+                    this.tradingPlayer.level().addFreshEntity(new net.minecraft.world.entity.ExperienceOrb(this.tradingPlayer.level(), this.tradingPlayer.getX(), this.tradingPlayer.getY(), this.tradingPlayer.getZ(), merchantRecipe.getXp(), org.bukkit.entity.ExperienceOrb.SpawnReason.VILLAGER_TRADE, this.tradingPlayer, null));
+                }
+            }
+            this.notifyTrade(merchantRecipe);
+        }
+        // Paper end - Add PlayerTradeEvent and PlayerPurchaseEvent
         @Override
         public void notifyTrade(MerchantOffer offer) {
             // increase recipe's uses
-            offer.increaseUses();
+            // offer.increaseUses(); // Paper - Add PlayerTradeEvent and PlayerPurchaseEvent; handled above in processTrade
         }
 
         @Override