[B+C] Add Merchant Trade API - Adds BUKKIT-5663

src/main/java/org/bukkit/configuration/serialization/ConfigurationSerialization.java

@@ -14,6 +14,7 @@
 import org.bukkit.FireworkEffect;
 import org.bukkit.configuration.Configuration;
 import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.TradeOffer;
 import org.bukkit.potion.PotionEffect;
 import org.bukkit.util.BlockVector;
 import org.bukkit.util.Vector;
@@ -33,6 +34,7 @@ public class ConfigurationSerialization {
         registerClass(Color.class);
         registerClass(PotionEffect.class);
         registerClass(FireworkEffect.class);
+        registerClass(TradeOffer.class);
     }
 
     protected ConfigurationSerialization(Class<? extends ConfigurationSerializable> clazz) {

src/main/java/org/bukkit/entity/HumanEntity.java

@@ -1,12 +1,16 @@
 package org.bukkit.entity;
 
+import java.util.Collection;
+
 import org.bukkit.GameMode;
 import org.bukkit.Location;
 import org.bukkit.inventory.Inventory;
 import org.bukkit.inventory.InventoryHolder;
 import org.bukkit.inventory.InventoryView;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.inventory.PlayerInventory;
+import org.bukkit.inventory.TradeOffer;
+import org.bukkit.merchant.Merchant;
 import org.bukkit.permissions.Permissible;
 
 /**
@@ -89,6 +93,28 @@ public interface HumanEntity extends LivingEntity, AnimalTamer, Permissible, Inv
      */
     public InventoryView openEnchanting(Location location, boolean force);
 
+    /**
+     * Opens a trade inventory window with the player's inventory on the bottom
+     * and the respective offers from the {@link org.bukkit.inventory.MerchantInventory#getOffers()}.
+     *
+     * @param merchant the merchant to trade with
+     * @param force if false, and the merchant is too far away from the player, the
+     *     inventory will be closed if this player is too far
+     * @return the newly opened inventory view, or null if it could not be opened
+     */
+    public InventoryView openTrade(Merchant merchant, boolean force);
+
+    /**
+     * Opens a trade inventory window with the player's inventory on the bottom and
+     * the specified offers listed in said trade inventory window.
+     *
+     * @param offers the offers to send to the player
+     * @param customName The custom name to label the trade window
+     * @return the newly opened inventory view, or null if it could not be opened
+     * @throws IllegalArgumentException if the offers are null
+     */
+    public InventoryView openTrade(Collection<TradeOffer> offers, String customName);
+
     /**
      * Opens an inventory window to the specified inventory view.
      *

src/main/java/org/bukkit/entity/Villager.java

@@ -1,9 +1,11 @@
 package org.bukkit.entity;
 
+import org.bukkit.merchant.Merchant;
+
 /**
  * Represents a villager NPC
  */
-public interface Villager extends Ageable, NPC {
+public interface Villager extends Ageable, NPC, Merchant {
 
     /**
      * Gets the current profession of this villager.

src/main/java/org/bukkit/event/merchant/MerchantAddOfferEvent.java

@@ -0,0 +1,66 @@
+package org.bukkit.event.merchant;
+
+import java.util.List;
+
+import org.apache.commons.lang.Validate;
+
+import org.bukkit.merchant.Merchant;
+import org.bukkit.event.Cancellable;
+import org.bukkit.event.HandlerList;
+import org.bukkit.inventory.TradeOffer;
+
+/**
+ * This event is called whenever a TradeOffer is being added to a Merchant's
+ * list of offers. If cancelled, the TradeOffer will not be added to the list.
+ */
+public class MerchantAddOfferEvent extends MerchantEvent implements Cancellable {
+    private static final HandlerList handlers = new HandlerList();
+
+    private List<TradeOffer> offers;
+    private TradeOffer offerToAdd;
+    private boolean cancelled = false;
+
+    public MerchantAddOfferEvent(Merchant merchant, TradeOffer toAdd) {
+        super(merchant);
+        Validate.notNull(toAdd, "Cannot add a null TradeOffer!");
+        this.offers = merchant.getInventory().getOffers();
+        this.offerToAdd = toAdd;
+    }
+
+    /**
+     * Gets an immutable copy of the list of TradeOffers the merchant currently has.
+     *
+     * @return a copy of the current offers from the merchant
+     */
+    public List<TradeOffer> getCurrentOffers() {
+        return offers;
+    }
+
+    /**
+     * Gets the immutable TradeOffer being added to the Merchant's current offers.
+     *
+     * @return the offer to add
+     */
+    public TradeOffer getOfferToAdd() {
+        return offerToAdd;
+    }
+
+    @Override
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+
+    @Override
+    public boolean isCancelled() {
+        return this.cancelled;
+    }
+
+    @Override
+    public void setCancelled(boolean cancel) {
+        this.cancelled = cancel;
+    }
+}

src/main/java/org/bukkit/event/merchant/MerchantEvent.java

@@ -0,0 +1,28 @@
+package org.bukkit.event.merchant;
+
+import org.apache.commons.lang.Validate;
+
+import org.bukkit.event.Event;
+import org.bukkit.merchant.Merchant;
+
+/**
+ * Represents a Merchant related event.
+ */
+public abstract class MerchantEvent extends Event {
+
+    protected Merchant merchant;
+
+    MerchantEvent(Merchant merchant) {
+        Validate.notNull(merchant, "Cannot have a null Merchant!");
+        this.merchant = merchant;
+    }
+
+    /**
+     * Gets the merchant involved with this event.
+     *
+     * @return The merchant
+     */
+    public Merchant getMerchant() {
+        return this.merchant;
+    }
+}

src/main/java/org/bukkit/inventory/MerchantInventory.java

@@ -1,4 +1,41 @@
 package org.bukkit.inventory;
 
+import java.util.List;
+
+import org.bukkit.merchant.Merchant;
+
+/**
+ * Represents the inventory of a merchant which contains a list of {@link TradeOffer}s.
+ */
 public interface MerchantInventory extends Inventory {
+
+    /**
+     * Gets the merchant belonging to this inventory
+     *
+     * @return the merchant
+     */
+    public Merchant getMerchant();
+
+    /**
+     * Gets a copy of the offers presented to a Player.
+     *
+     * @return a copied list of TradeOffers being given to the Player
+     */
+    public List<TradeOffer> getOffers();
+
+    /**
+     * Adds the given TradeOffer to this Inventory's list of trade
+     * offers.
+     *
+     * @param offer to add
+     */
+    public void addOffer(TradeOffer offer);
+
+    /**
+     * Removes the specified offer if it is contained within the list of
+     * offers by this inventory.
+     *
+     * @param offer to remove
+     */
+    public void removeOffer(TradeOffer offer);
 }