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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.hadoop.hbase.regionserver;

import com.google.errorprone.annotations.RestrictedApi;
import java.io.IOException;
import java.util.Collection;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Optional;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.KeyValue;
import org.apache.yetus.audience.InterfaceAudience;

import org.apache.hbase.thirdparty.com.google.common.collect.ImmutableCollection;

/**
 * Manages the store files and basic metadata about that that determines the logical structure (e.g.
 * what files to return for scan, how to determine split point, and such). Does NOT affect the
 * physical structure of files in HDFS. Example alternative structures - the default list of files
 * by seqNum; levelDB one sorted by level and seqNum.
 * 
 * Notice that, all the states are only in memory, we do not persist anything here. The only place
 * where we throw an {@link IOException} is the {@link #getSplitPoint()} method, where we need to
 * read startKey, endKey etc, which may lead to an {@link IOException}.
 * 
 * Implementations are assumed to be not thread safe.
 */
@InterfaceAudience.Private
public interface StoreFileManager {
  /**
   * Loads the initial store files into empty StoreFileManager.
   * @param storeFiles The files to load.
   */
  @RestrictedApi(explanation = "Should only be called in StoreEngine", link = "",
      allowedOnPath = ".*(/org/apache/hadoop/hbase/regionserver/StoreEngine.java|/src/test/.*)")
  void loadFiles(List storeFiles);

  /**
   * Adds new files, either for from MemStore flush or bulk insert, into the structure.
   * @param sfs New store files.
   */
  @RestrictedApi(explanation = "Should only be called in StoreEngine", link = "",
      allowedOnPath = ".*(/org/apache/hadoop/hbase/regionserver/StoreEngine.java|/src/test/.*)")
  void insertNewFiles(Collection sfs);

  /**
   * Adds only the new compaction results into the structure.
   * @param compactedFiles The input files for the compaction.
   * @param results        The resulting files for the compaction.
   */
  @RestrictedApi(explanation = "Should only be called in StoreEngine", link = "",
      allowedOnPath = ".*(/org/apache/hadoop/hbase/regionserver/StoreEngine.java|/src/test/.*)")
  void addCompactionResults(Collection compactedFiles, Collection results);

  /**
   * Remove the compacted files
   * @param compactedFiles the list of compacted files
   */
  @RestrictedApi(explanation = "Should only be called in StoreEngine", link = "",
      allowedOnPath = ".*(/org/apache/hadoop/hbase/regionserver/StoreEngine.java|/src/test/.*)")
  void removeCompactedFiles(Collection compactedFiles);

  /**
   * Clears all the files currently in use and returns them.
   * @return The files previously in use.
   */
  ImmutableCollection clearFiles();

  /**
   * Clears all the compacted files and returns them. This method is expected to be accessed single
   * threaded.
   * @return The files compacted previously.
   */
  Collection clearCompactedFiles();

  /**
   * Gets the snapshot of the store files currently in use. Can be used for things like metrics and
   * checks; should not assume anything about relations between store files in the list.
   * @return The list of StoreFiles.
   */
  Collection getStorefiles();

  /**
   * List of compacted files inside this store that needs to be excluded in reads because further
   * new reads will be using only the newly created files out of compaction. These compacted files
   * will be deleted/cleared once all the existing readers on these compacted files are done.
   * @return the list of compacted files
   */
  Collection getCompactedfiles();

  /**
   * Returns the number of files currently in use.
   * @return The number of files.
   */
  int getStorefileCount();

  /**
   * Returns the number of compacted files.
   * @return The number of files.
   */
  int getCompactedFilesCount();

  /**
   * Gets the store files to scan for a Scan or Get request.
   * @param startRow Start row of the request.
   * @param stopRow  Stop row of the request.
   * @return The list of files that are to be read for this request.
   */
  Collection getFilesForScan(byte[] startRow, boolean includeStartRow, byte[] stopRow,
    boolean includeStopRow);

  /**
   * Gets initial, full list of candidate store files to check for row-key-before.
   * @param targetKey The key that is the basis of the search.
   * @return The files that may have the key less than or equal to targetKey, in reverse order of
   *         new-ness, and preference for target key.
   */
  Iterator getCandidateFilesForRowKeyBefore(KeyValue targetKey);

  /**
   * Updates the candidate list for finding row key before. Based on the list of candidates
   * remaining to check from getCandidateFilesForRowKeyBefore, targetKey and current candidate, may
   * trim and reorder the list to remove the files where a better candidate cannot be found.
   * @param candidateFiles The candidate files not yet checked for better candidates - return value
   *                       from {@link #getCandidateFilesForRowKeyBefore(KeyValue)}, with some files
   *                       already removed.
   * @param targetKey      The key to search for.
   * @param candidate      The current best candidate found.
   * @return The list to replace candidateFiles.
   */
  Iterator updateCandidateFilesForRowKeyBefore(Iterator candidateFiles,
    KeyValue targetKey, Cell candidate);

  /**
   * Gets the split point for the split of this set of store files (approx. middle).
   * @return The mid-point if possible.
   */
  Optional getSplitPoint() throws IOException;

  /** Returns The store compaction priority. */
  int getStoreCompactionPriority();

  /**
   * @param maxTs           Maximum expired timestamp.
   * @param filesCompacting Files that are currently compacting.
   * @return The files which don't have any necessary data according to TTL and other criteria.
   */
  Collection getUnneededFiles(long maxTs, List filesCompacting);

  /**
   * @return the compaction pressure used for compaction throughput tuning.
   * @see HStore#getCompactionPressure()
   */
  double getCompactionPressure();

  /**
   * @return the comparator used to sort storefiles. Usually, the
   *         {@link HStoreFile#getMaxSequenceId()} is the first priority.
   */
  Comparator getStoreFileComparator();
}