Start designing the inventory transaction system

game/src/main/org/apollo/game/model/inv/transaction/ItemTransaction.java

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+package org.apollo.game.model.inv.transaction;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Queue;
+import java.util.Set;
+
+import org.apollo.game.model.inv.Inventory;
+
+public final class ItemTransaction {
+
+	private final Queue<TransactionBlock> queuedBlocks = new ArrayDeque<>();
+	private final List<TransactionBlock> committedBlocks = new ArrayList<>();
+	private final Set<Inventory> inventories = new HashSet<>();
+	private TransactionListener listener;
+
+	public void setListener(TransactionListener listener) {
+		this.listener = listener;
+	}
+
+	public void sync(Inventory inventory) {
+		inventories.add(inventory);
+	}
+
+	public void append(TransactionBlock block) {
+		queuedBlocks.add(block);
+	}
+
+	public void refresh() {
+		inventories.forEach(Inventory::forceRefresh);
+	}
+
+	public void rollback() {
+		committedBlocks.forEach(TransactionBlock::revert);
+		listener.alertFailure();
+	}
+
+	public boolean commit() {
+		for (TransactionBlock change : queuedBlocks) {
+			if (!change.commit()) {
+				rollback();
+				return false;
+			}
+			committedBlocks.add(change);
+		}
+		refresh();
+		return true;
+	}
+
+}

game/src/main/org/apollo/game/model/inv/transaction/TransactionBlock.java

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+package org.apollo.game.model.inv.transaction;
+
+public interface TransactionBlock {
+
+	boolean commit();
+
+	void revert();
+
+}

game/src/main/org/apollo/game/model/inv/transaction/TransactionBuilder.java

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+package org.apollo.game.model.inv.transaction;
+
+import org.apollo.game.model.Item;
+import org.apollo.game.model.entity.Player;
+import org.apollo.game.model.inv.Inventory;
+
+public final class TransactionBuilder {
+
+	private final ItemTransaction transaction = new ItemTransaction();
+	private final Inventory inventory;
+
+	private TransactionBuilder(Inventory inventory) {
+		transaction.sync(inventory);
+		this.inventory = inventory;
+	}
+
+	public TransactionBuilder failureMessage(Player player, String message) {
+		return listener(new TransactionFailureListener(player, message));
+	}
+
+	public TransactionBuilder listener(TransactionListener listener) {
+		transaction.setListener(listener);
+		return this;
+	}
+
+	public TransactionBuilder swap(Inventory source, int fromSlot, int toSlot) {
+		// TODO: Swap item block
+		transaction.sync(source);
+		return this;
+	}
+
+	public TransactionBuilder add(Item item) {
+		// TODO: Add item block
+		return this;
+	}
+
+	public TransactionBuilder remove(Item item) {
+		// TODO: Remove item block
+		return this;
+	}
+
+	public TransactionBuilder move(Inventory source, Item item) {
+		// TODO: Move item block
+		transaction.sync(source);
+		return this;
+	}
+
+	public TransactionBuilder take(Inventory destination, Item item) {
+		// TODO: Move item block
+		transaction.sync(destination);
+		return this;
+	}
+
+	public ItemTransaction build() {
+		return transaction;
+	}
+
+	public static TransactionBuilder create(Inventory inventory) {
+		return new TransactionBuilder(inventory);
+	}
+
+}

game/src/main/org/apollo/game/model/inv/transaction/TransactionFailureListener.java

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+package org.apollo.game.model.inv.transaction;
+
+import org.apollo.game.model.entity.Player;
+
+public final class TransactionFailureListener implements TransactionListener {
+
+	private final Player player;
+	private final String message;
+
+	public TransactionFailureListener(Player player, String message) {
+		this.player = player;
+		this.message = message;
+	}
+
+	@Override
+	public void alertFailure() {
+		player.sendMessage(message);
+	}
+
+}

game/src/main/org/apollo/game/model/inv/transaction/TransactionItem.java

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+package org.apollo.game.model.inv.transaction;
+
+import org.apollo.game.model.Item;
+import org.apollo.game.model.inv.Inventory;
+
+public abstract class TransactionItem {
+
+	protected final Inventory inventory;
+
+	protected TransactionItem(Inventory inventory) {
+		this.inventory = inventory;
+	}
+
+	public abstract Item delete();
+
+	public abstract boolean deleteSuccessful();
+
+	public abstract void revert();
+
+}

game/src/main/org/apollo/game/model/inv/transaction/TransactionListener.java

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+package org.apollo.game.model.inv.transaction;
+
+public interface TransactionListener {
+
+	void alertFailure();
+
+}