measure/src/main/scala/org/apache/griffin/measure/step/builder/dsl/expr/TreeNode.scala

/*
 * 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 org.apache.griffin.measure.step.builder.dsl.expr

import scala.reflect.ClassTag

trait TreeNode extends Serializable {

  var children: Seq[TreeNode] = Seq[TreeNode]()

  def addChild(expr: TreeNode): Unit = { children :+= expr }
  def addChildren(exprs: Seq[TreeNode]): Unit = { children ++= exprs }

  def preOrderTraverseDepthFirst[T, A <: TreeNode](z: T)(seqOp: (A, T) => T, combOp: (T, T) => T)(
      implicit tag: ClassTag[A]): T = {

    val clazz = tag.runtimeClass
    if (clazz.isAssignableFrom(this.getClass)) {
      val tv = seqOp(this.asInstanceOf[A], z)
      children.foldLeft(combOp(z, tv)) { (ov, tn) =>
        combOp(ov, tn.preOrderTraverseDepthFirst(z)(seqOp, combOp))
      }
    } else {
      z
    }

  }
  def postOrderTraverseDepthFirst[T, A <: TreeNode](
      z: T)(seqOp: (A, T) => T, combOp: (T, T) => T)(implicit tag: ClassTag[A]): T = {

    val clazz = tag.runtimeClass
    if (clazz.isAssignableFrom(this.getClass)) {
      val cv = children.foldLeft(z) { (ov, tn) =>
        combOp(ov, tn.postOrderTraverseDepthFirst(z)(seqOp, combOp))
      }
      combOp(z, seqOp(this.asInstanceOf[A], cv))
    } else {
      z
    }
  }

}