Add TradeSelectEvent

By: Coleman Yantis <diamonddagger590@gmail.com>

paper-api/src/main/java/org/bukkit/event/inventory/TradeSelectEvent.java

@@ -0,0 +1,62 @@
+package org.bukkit.event.inventory;
+
+import org.bukkit.event.HandlerList;
+import org.bukkit.inventory.InventoryView;
+import org.bukkit.inventory.Merchant;
+import org.bukkit.inventory.MerchantInventory;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * This event is called whenever a player clicks a new trade on the trades
+ * sidebar.
+ * <p>
+ * This event allows the user to get the index of the trade, letting them get
+ * the MerchantRecipe via the Merchant.
+ */
+public class TradeSelectEvent extends InventoryInteractEvent {
+
+    private static final HandlerList handlers = new HandlerList();
+    //
+    private final int index;
+
+    public TradeSelectEvent(@NotNull InventoryView transaction, int newIndex) {
+        super(transaction);
+        this.index = newIndex;
+    }
+
+    /**
+     * Used to get the index of the trade the player clicked on.
+     *
+     * @return The index of the trade clicked by the player
+     */
+    public int getIndex() {
+        return index;
+    }
+
+    @NotNull
+    @Override
+    public MerchantInventory getInventory() {
+        return (MerchantInventory) super.getInventory();
+    }
+
+    /**
+     * Get the Merchant involved.
+     *
+     * @return the Merchant
+     */
+    @NotNull
+    public Merchant getMerchant() {
+        return getInventory().getMerchant();
+    }
+
+    @NotNull
+    @Override
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    @NotNull
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+}

paper-api/src/main/java/org/bukkit/inventory/MerchantInventory.java

@@ -1,5 +1,6 @@
 package org.bukkit.inventory;
 
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 /**
@@ -30,4 +31,12 @@ public interface MerchantInventory extends Inventory {
      */
     @Nullable
     MerchantRecipe getSelectedRecipe();
+
+    /**
+     * Gets the Merchant associated with this inventory.
+     *
+     * @return merchant
+     */
+    @NotNull
+    Merchant getMerchant();
 }