/*
 *
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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 com.dlink.explainer.sqllineage;

import java.util.Iterator;

public class TreeNodeIterator<T> implements Iterator<TreeNode<T>> {

    private ProcessStages doNext;
    private TreeNode<T> next;
    private Iterator<TreeNode<T>> childrenCurNodeIter;
    private Iterator<TreeNode<T>> childrenSubNodeIter;
    private TreeNode<T> treeNode;

    public TreeNodeIterator(TreeNode<T> treeNode) {
        this.treeNode = treeNode;
        this.doNext = ProcessStages.ProcessParent;
        this.childrenCurNodeIter = treeNode.children.iterator();
    }

    public boolean hasNext() {
        if (this.doNext == ProcessStages.ProcessParent) {
            this.next = this.treeNode;
            this.doNext = ProcessStages.ProcessChildCurNode;
            return true;
        }

        if (this.doNext == ProcessStages.ProcessChildCurNode) {
            if (childrenCurNodeIter.hasNext()) {
                TreeNode<T> childDirect = childrenCurNodeIter.next();
                childrenSubNodeIter = childDirect.iterator();
                this.doNext = ProcessStages.ProcessChildSubNode;
                return hasNext();
            } else {
                this.doNext = null;
                return false;
            }
        }

        if (this.doNext == ProcessStages.ProcessChildSubNode) {
            if (childrenSubNodeIter.hasNext()) {
                this.next = childrenSubNodeIter.next();
                return true;
            } else {
                this.next = null;
                this.doNext = ProcessStages.ProcessChildCurNode;
                return hasNext();
            }
        }

        return false;
    }

    public TreeNode<T> next() {
        return this.next;
    }

    /**
     * 目前不支持删除节点
     */
    public void remove() {
        throw new UnsupportedOperationException();
    }

    enum ProcessStages {
        ProcessParent, ProcessChildCurNode, ProcessChildSubNode
    }
}

