Added OperationQueue to execute multiple operations sequentially.

src/main/java/com/sk89q/worldedit/function/operation/OperationQueue.java

@@ -0,0 +1,103 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.function.operation;
+
+import com.sk89q.worldedit.WorldEditException;
+
+import java.util.ArrayDeque;
+import java.util.Collection;
+import java.util.Deque;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * Executes multiple queues in order.
+ */
+public class OperationQueue implements Operation {
+
+    private final Deque<Operation> queue = new ArrayDeque<Operation>();
+    private Operation current;
+
+    /**
+     * Create a new queue containing no operations.
+     */
+    public OperationQueue() {
+    }
+
+    /**
+     * Create a new queue with operations from the given collection.
+     *
+     * @param operations a collection of operations
+     */
+    public OperationQueue(Collection<Operation> operations) {
+        checkNotNull(operations);
+        for (Operation operation : operations) {
+            offer(operation);
+        }
+    }
+
+    /**
+     * Create a new queue with operations from the given array.
+     *
+     * @param operation an array of operations
+     */
+    public OperationQueue(Operation... operation) {
+        checkNotNull(operation);
+        for (Operation o : operation) {
+            offer(o);
+        }
+    }
+
+    /**
+     * Add a new operation to the queue.
+     *
+     * @param operation the operation
+     */
+    public void offer(Operation operation) {
+        checkNotNull(operation);
+        queue.offer(operation);
+    }
+
+    @Override
+    public Operation resume() throws WorldEditException {
+        if (current == null && queue.size() > 0) {
+            current = queue.poll();
+        }
+
+        if (current != null) {
+            current = current.resume();
+
+            if (current == null) {
+                current = queue.poll();
+            }
+        }
+
+        return current != null ? this : null;
+    }
+
+    @Override
+    public void cancel() {
+        for (Operation operation : queue) {
+            operation.cancel();
+        }
+        queue.clear();
+    }
+
+}