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/* Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.flowable.engine.debug;

import java.util.Iterator;
import java.util.LinkedList;

/**
 * Iterates over an {@link ExecutionTree} using breadth-first search
 * 
 * @author Joram Barrez
 */
public class ExecutionTreeBfsIterator implements Iterator {

    protected ExecutionTreeNode rootNode;
    protected boolean reverseOrder;

    protected LinkedList flattenedList;
    protected Iterator flattenedListIterator;

    public ExecutionTreeBfsIterator(ExecutionTreeNode executionTree) {
        this(executionTree, false);
    }

    public ExecutionTreeBfsIterator(ExecutionTreeNode rootNode, boolean reverseOrder) {
        this.rootNode = rootNode;
        this.reverseOrder = reverseOrder;
    }

    protected void flattenTree() {
        flattenedList = new LinkedList<>();

        LinkedList nodesToHandle = new LinkedList<>();
        nodesToHandle.add(rootNode);
        while (!nodesToHandle.isEmpty()) {

            ExecutionTreeNode currentNode = nodesToHandle.pop();
            if (reverseOrder) {
                flattenedList.addFirst(currentNode);
            } else {
                flattenedList.add(currentNode);
            }

            if (currentNode.getChildren() != null && currentNode.getChildren().size() > 0) {
                nodesToHandle.addAll(currentNode.getChildren());
            }
        }

        flattenedListIterator = flattenedList.iterator();
    }

    @Override
    public boolean hasNext() {
        if (flattenedList == null) {
            flattenTree();
        }
        return flattenedListIterator.hasNext();
    }

    @Override
    public ExecutionTreeNode next() {
        if (flattenedList == null) {
            flattenTree();
        }
        return flattenedListIterator.next();
    }

    @Override
    public void remove() {
        if (flattenedList == null) {
            flattenTree();
        }
        flattenedListIterator.remove();
    }

}