/*
 * 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.texera.amber.operator.source.scan

/**
  * A wrapper around an Interator that automatically invokes a cleanup function
  * when the iterator is fully consumed (i.e. hasNext returns false)
  *
  * This is useful for lazily reading resources like InputStreams and ensuring
  * they are properly closed once no more data is available
  *
  * @param iter the underlying iterator to consume
  * @param onClose a function to call once the iterator is exhausted
  */
class AutoClosingIterator[T](iter: Iterator[T], onClose: () => Unit) extends Iterator[T] {
  private var alreadyClosed = false

  override def hasNext: Boolean = {
    val hn = iter.hasNext
    if (!hn && !alreadyClosed) {
      onClose()
      alreadyClosed = true
    }
    hn
  }

  override def next(): T = iter.next()
}
