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/*
 * Copyright © 2017 camunda services GmbH ([email protected])
 *
 * Licensed 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 io.zeebe.logstreams.state;

import io.zeebe.logstreams.impl.Loggers;
import java.util.Objects;
import org.slf4j.Logger;

public class StateSnapshotMetadata implements Comparable {
  public static final long INITIAL_LAST_PROCESSED_EVENT_POSITION = -1;
  public static final long INITIAL_LAST_WRITTEN_EVENT_POSITION = -1;
  private static final Logger LOG = Loggers.ROCKSDB_LOGGER;

  private final long lastSuccessfulProcessedEventPosition;
  private final long lastWrittenEventPosition;
  private final int lastWrittenEventTerm;
  private final boolean exists;

  /**
   * @param term the current term
   * @return a snapshot metadata based on nothing but the term
   */
  public static StateSnapshotMetadata createInitial(int term) {
    return new StateSnapshotMetadata(
        INITIAL_LAST_PROCESSED_EVENT_POSITION, INITIAL_LAST_WRITTEN_EVENT_POSITION, term, false);
  }

  public StateSnapshotMetadata(long lastWrittenEventPosition) {
    this(0, lastWrittenEventPosition, 0, true);
  }

  public StateSnapshotMetadata(
      long lastSuccessfulProcessedEventPosition,
      long lastWrittenEventPosition,
      int lastWrittenEventTerm,
      boolean exists) {
    this.lastSuccessfulProcessedEventPosition = lastSuccessfulProcessedEventPosition;
    this.lastWrittenEventPosition = lastWrittenEventPosition;
    this.lastWrittenEventTerm = lastWrittenEventTerm;
    this.exists = exists;
  }

  /**
   * Returns the last successful processed event position when the state was last updated.
   *
   * @return last successful processed event position
   */
  public long getLastSuccessfulProcessedEventPosition() {
    return lastSuccessfulProcessedEventPosition;
  }

  /**
   * Returns the last written event position when the state was last updated.
   *
   * @return last written event position
   */
  public long getLastWrittenEventPosition() {
    return lastWrittenEventPosition;
  }

  /**
   * Returns the term of the last written event
   *
   * @return term of the last written event
   */
  public int getLastWrittenEventTerm() {
    return lastWrittenEventTerm;
  }

  /** @return true if there is a state associated to it, false otherwise */
  public boolean exists() {
    return exists;
  }

  public boolean isInitial() {
    return getLastSuccessfulProcessedEventPosition() == INITIAL_LAST_PROCESSED_EVENT_POSITION
        && getLastWrittenEventPosition() == INITIAL_LAST_WRITTEN_EVENT_POSITION;
  }

  @Override
  public boolean equals(Object obj) {
    if (!(obj instanceof StateSnapshotMetadata)) {
      return false;
    }

    final StateSnapshotMetadata other = (StateSnapshotMetadata) obj;

    return getLastSuccessfulProcessedEventPosition()
            == other.getLastSuccessfulProcessedEventPosition()
        && getLastWrittenEventPosition() == other.getLastWrittenEventPosition()
        && getLastWrittenEventTerm() == other.getLastWrittenEventTerm();
  }

  @Override
  public int hashCode() {
    return Objects.hash(
        getLastSuccessfulProcessedEventPosition(),
        getLastWrittenEventPosition(),
        getLastWrittenEventTerm(),
        exists());
  }

  @Override
  public String toString() {
    return "StateSnapshotMetadata{"
        + "lastSuccessfulProcessedEventPosition="
        + getLastSuccessfulProcessedEventPosition()
        + ", lastWrittenEventPosition="
        + getLastWrittenEventPosition()
        + ", lastWrittenEventTerm="
        + getLastWrittenEventTerm()
        + ", exists="
        + exists()
        + '}';
  }

  @Override
  public int compareTo(StateSnapshotMetadata o) {
    int result =
        Long.compare(
            getLastSuccessfulProcessedEventPosition(), o.getLastSuccessfulProcessedEventPosition());

    if (result == 0) {
      result = Integer.compare(getLastWrittenEventTerm(), o.getLastWrittenEventTerm());
      if (result == 0) {
        result = Long.compare(getLastWrittenEventPosition(), o.getLastWrittenEventPosition());
      }
    }

    return result;
  }
}