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/*
 * 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.druid.indexing.seekablestream.common;

import java.util.Objects;

/**
 * Represents a Kafka/Kinesis stream sequence number. Mainly used to do
 * comparison and indicate whether the sequence number is exclusive.
 * 
 * isExclusive is used to indicate if this sequence number is the starting
 * sequence of some Kinesis partition and should be discarded because some
 * previous task has already read this sequence number
 *
 * @param  type of sequence number
 */
public abstract class OrderedSequenceNumber
    implements Comparable>
{
  private final SequenceOffsetType sequenceNumber;
  private final boolean isExclusive;

  protected OrderedSequenceNumber(SequenceOffsetType sequenceNumber, boolean isExclusive)
  {
    this.sequenceNumber = sequenceNumber;
    this.isExclusive = isExclusive;
  }

  public SequenceOffsetType get()
  {
    return sequenceNumber;
  }

  public boolean isExclusive()
  {
    return isExclusive;
  }

  @Override
  public boolean equals(Object o)
  {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    OrderedSequenceNumber that = (OrderedSequenceNumber) o;
    return isExclusive == that.isExclusive &&
           Objects.equals(sequenceNumber, that.sequenceNumber);
  }

  @Override
  public int hashCode()
  {
    return Objects.hash(sequenceNumber, isExclusive);
  }

  @Override
  public String toString()
  {
    return getClass().getSimpleName() + "{" +
           "sequenceNumber=" + sequenceNumber +
           ", isExclusive=" + isExclusive +
           '}';
  }

  public boolean isAvailableWithEarliest(OrderedSequenceNumber earliest)
  {
    return earliest.compareTo(this) <= 0;
  }

  /**
   * Returns true if, given that we want to start reading from this sequence number and stop at the sequence number end,
   * there is more left to read. Used in pre-read checks to determine if there is anything left to read.
   *
   * @param end the end offset of the partition for a given task
   * @param isEndOffsetExclusive indicates if the TaskRunner considers the end offsets to be exclusive
   * @return true if more records need to be read given that this is the current sequence number
   */
  public boolean isMoreToReadBeforeReadingRecord(OrderedSequenceNumber end,
                                                 boolean isEndOffsetExclusive)
  {
    final int compareToEnd = this.compareTo(end);
    return isEndOffsetExclusive ? compareToEnd < 0 : compareToEnd <= 0;
  }
}