/*
 * 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.intersect

import org.apache.texera.amber.core.executor.OperatorExecutor
import org.apache.texera.amber.core.tuple.{Tuple, TupleLike}

import scala.collection.mutable

class IntersectOpExec extends OperatorExecutor {
  private var leftSet: mutable.HashSet[Tuple] = _
  private var rightSet: mutable.HashSet[Tuple] = _
  private var exhaustedCounter: Int = _

  override def open(): Unit = {
    leftSet = new mutable.HashSet[Tuple]()
    rightSet = new mutable.HashSet[Tuple]()
    exhaustedCounter = 0
  }

  override def close(): Unit = {
    leftSet.clear()
    rightSet.clear()
  }

  override def processTuple(tuple: Tuple, port: Int): Iterator[TupleLike] = {

    // add the tuple to corresponding set
    if (port == 0) leftSet += tuple else rightSet += tuple
    Iterator()

  }

  override def onFinish(port: Int): Iterator[TupleLike] = {
    exhaustedCounter += 1
    if (exhaustedCounter == 2) {
      // both streams are exhausted, take the intersect and return the results
      leftSet.intersect(rightSet).iterator
    } else {
      // only one of the stream is exhausted, continue accepting tuples
      Iterator()
    }
  }
}
