/*
 * 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.iotdb.db.engine.storagegroup;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.FileAlreadyExistsException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Objects;
import java.util.Random;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.iotdb.db.conf.IoTDBConstant;
import org.apache.iotdb.db.engine.StorageEngine;
import org.apache.iotdb.db.engine.modification.ModificationFile;
import org.apache.iotdb.db.engine.querycontext.ReadOnlyMemChunk;
import org.apache.iotdb.db.engine.storagegroup.StorageGroupProcessor.UpgradeTsFileResourceCallBack;
import org.apache.iotdb.db.engine.upgrade.UpgradeTask;
import org.apache.iotdb.db.exception.PartitionViolationException;
import org.apache.iotdb.db.rescon.CachedStringPool;
import org.apache.iotdb.db.service.UpgradeSevice;
import org.apache.iotdb.db.utils.FilePathUtils;
import org.apache.iotdb.db.utils.UpgradeUtils;
import org.apache.iotdb.tsfile.common.constant.TsFileConstant;
import org.apache.iotdb.tsfile.file.metadata.ChunkMetadata;
import org.apache.iotdb.tsfile.file.metadata.TimeseriesMetadata;
import org.apache.iotdb.tsfile.file.metadata.enums.TSDataType;
import org.apache.iotdb.tsfile.file.metadata.statistics.Statistics;
import org.apache.iotdb.tsfile.fileSystem.FSFactoryProducer;
import org.apache.iotdb.tsfile.fileSystem.fsFactory.FSFactory;
import org.apache.iotdb.tsfile.utils.RamUsageEstimator;
import org.apache.iotdb.tsfile.utils.ReadWriteIOUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class TsFileResource {

  private static final Logger logger = LoggerFactory.getLogger(TsFileResource.class);
  private static Map<String, String> cachedDevicePool = CachedStringPool.getInstance()
      .getCachedPool();

  // tsfile
  private File file;

  public static final String RESOURCE_SUFFIX = ".resource";
  static final String TEMP_SUFFIX = ".temp";
  private static final String CLOSING_SUFFIX = ".closing";
  protected static final int INIT_ARRAY_SIZE = 64;

  /**
   * start times array.
   */
  protected long[] startTimes;

  /**
   * end times array. The values in this array are Long.MIN_VALUE if it's an unsealed sequence
   * tsfile
   */
  protected long[] endTimes;

  /**
   * device -> index of start times array and end times array
   */
  protected Map<String, Integer> deviceToIndex;

  public TsFileProcessor getProcessor() {
    return processor;
  }

  private TsFileProcessor processor;

  private ModificationFile modFile;

  private volatile boolean closed = false;
  private volatile boolean deleted = false;
  private volatile boolean isMerging = false;

  // historicalVersions are used to track the merge history of a TsFile. For a TsFile generated
  // by flush, this field only contains its own version number. For a TsFile generated by merge,
  // its historicalVersions are the union of all TsFiles' historicalVersions that joined this merge.
  // This field helps us compare the files that are generated by different IoTDBs that share the
  // same file generation policy but have their own merge policies.
  // https://issues.apache.org/jira/browse/IOTDB-702 for improve this field.
  private Set<Long> historicalVersions = new HashSet<>();

  private TsFileLock tsFileLock = new TsFileLock();

  private Random random = new Random();

  /**
   * Chunk metadata list of unsealed tsfile. Only be set in a temporal TsFileResource in a query
   * process.
   */
  private List<ChunkMetadata> chunkMetadataList;

  /**
   * Mem chunk data. Only be set in a temporal TsFileResource in a query process.
   */
  private List<ReadOnlyMemChunk> readOnlyMemChunk;

  /**
   * used for unsealed file to get TimeseriesMetadata
   */
  private TimeseriesMetadata timeSeriesMetadata;

  private FSFactory fsFactory = FSFactoryProducer.getFSFactory();

  /**
   * generated upgraded TsFile ResourceList used for upgrading v0.9.x/v1 -> 0.10/v2
   */
  private List<TsFileResource> upgradedResources;

  /**
   * load upgraded TsFile Resources to storage group processor used for upgrading v0.9.x/v1 ->
   * 0.10/v2
   */
  private UpgradeTsFileResourceCallBack upgradeTsFileResourceCallBack;

  /**
   * indicate if this tsfile resource belongs to a sequence tsfile or not used for upgrading
   * v0.9.x/v1 -> 0.10/v2
   */
  private boolean isSeq;

  /**
   * If it is not null, it indicates that the current tsfile resource is a snapshot of the
   * originTsFileResource, and if so, when we want to used the lock, we should try to acquire the
   * lock of originTsFileResource
   */
  private TsFileResource originTsFileResource;

  /**
   * Maximum index of plans executed within this TsFile.
   */
  private long maxPlanIndex = Long.MIN_VALUE;

  /**
   * Minimum index of plans executed within this TsFile.
   */
  private long minPlanIndex = Long.MAX_VALUE;

  public TsFileResource() {
  }

  public TsFileResource(TsFileResource other) throws IOException {
    this.file = other.file;
    this.deviceToIndex = other.deviceToIndex;
    this.startTimes = other.startTimes;
    this.endTimes = other.endTimes;
    this.processor = other.processor;
    this.modFile = other.modFile;
    this.closed = other.closed;
    this.deleted = other.deleted;
    this.isMerging = other.isMerging;
    this.chunkMetadataList = other.chunkMetadataList;
    this.readOnlyMemChunk = other.readOnlyMemChunk;
    generateTimeSeriesMetadata();
    this.tsFileLock = other.tsFileLock;
    this.fsFactory = other.fsFactory;
    this.historicalVersions = other.historicalVersions;
  }

  /**
   * for sealed TsFile, call setClosed to close TsFileResource
   */
  public TsFileResource(File file) {
    this.file = file;
    this.deviceToIndex = new ConcurrentHashMap<>();
    this.startTimes = new long[INIT_ARRAY_SIZE];
    this.endTimes = new long[INIT_ARRAY_SIZE];
    initTimes(startTimes, Long.MAX_VALUE);
    initTimes(endTimes, Long.MIN_VALUE);
  }

  /**
   * unsealed TsFile
   */
  public TsFileResource(File file, TsFileProcessor processor) {
    this.file = file;
    this.deviceToIndex = new ConcurrentHashMap<>();
    this.startTimes = new long[INIT_ARRAY_SIZE];
    this.endTimes = new long[INIT_ARRAY_SIZE];
    initTimes(startTimes, Long.MAX_VALUE);
    initTimes(endTimes, Long.MIN_VALUE);
    this.processor = processor;
  }

  /**
   * unsealed TsFile
   */
  public TsFileResource(File file, Map<String, Integer> deviceToIndex, long[] startTimes,
      long[] endTimes, List<ReadOnlyMemChunk> readOnlyMemChunk,
      List<ChunkMetadata> chunkMetadataList, TsFileResource originTsFileResource)
      throws IOException {
    this.file = file;
    this.deviceToIndex = deviceToIndex;
    this.startTimes = startTimes;
    this.endTimes = endTimes;
    this.chunkMetadataList = chunkMetadataList;
    this.readOnlyMemChunk = readOnlyMemChunk;
    this.originTsFileResource = originTsFileResource;
    generateTimeSeriesMetadata();
  }

  private void generateTimeSeriesMetadata() throws IOException {
    timeSeriesMetadata = new TimeseriesMetadata();
    timeSeriesMetadata.setOffsetOfChunkMetaDataList(-1);
    timeSeriesMetadata.setDataSizeOfChunkMetaDataList(-1);

    if (!(chunkMetadataList == null || chunkMetadataList.isEmpty())) {
      timeSeriesMetadata.setMeasurementId(chunkMetadataList.get(0).getMeasurementUid());
      TSDataType dataType = chunkMetadataList.get(0).getDataType();
      timeSeriesMetadata.setTSDataType(dataType);
    } else if (!(readOnlyMemChunk == null || readOnlyMemChunk.isEmpty())) {
      timeSeriesMetadata.setMeasurementId(readOnlyMemChunk.get(0).getMeasurementUid());
      TSDataType dataType = readOnlyMemChunk.get(0).getDataType();
      timeSeriesMetadata.setTSDataType(dataType);
    }
    if (timeSeriesMetadata.getTSDataType() != null) {
      Statistics seriesStatistics = Statistics.getStatsByType(timeSeriesMetadata.getTSDataType());
      // flush chunkMetadataList one by one
      for (ChunkMetadata chunkMetadata : chunkMetadataList) {
        seriesStatistics.mergeStatistics(chunkMetadata.getStatistics());
      }

      for (ReadOnlyMemChunk memChunk : readOnlyMemChunk) {
        if (!memChunk.isEmpty()) {
          seriesStatistics.mergeStatistics(memChunk.getChunkMetaData().getStatistics());
        }
      }
      timeSeriesMetadata.setStatistics(seriesStatistics);
    } else {
      timeSeriesMetadata = null;
    }
  }

  protected void initTimes(long[] times, long defaultTime) {
    Arrays.fill(times, defaultTime);
  }

  public void serialize() throws IOException {
    try (OutputStream outputStream = fsFactory.getBufferedOutputStream(
        file + RESOURCE_SUFFIX + TEMP_SUFFIX)) {
      ReadWriteIOUtils.write(this.deviceToIndex.size(), outputStream);
      for (Entry<String, Integer> entry : this.deviceToIndex.entrySet()) {
        ReadWriteIOUtils.write(entry.getKey(), outputStream);
        ReadWriteIOUtils.write(startTimes[entry.getValue()], outputStream);
      }
      ReadWriteIOUtils.write(this.deviceToIndex.size(), outputStream);
      for (Entry<String, Integer> entry : this.deviceToIndex.entrySet()) {
        ReadWriteIOUtils.write(entry.getKey(), outputStream);
        ReadWriteIOUtils.write(endTimes[entry.getValue()], outputStream);
      }

      if (historicalVersions != null) {
        ReadWriteIOUtils.write(this.historicalVersions.size(), outputStream);
        for (Long historicalVersion : historicalVersions) {
          ReadWriteIOUtils.write(historicalVersion, outputStream);
        }
      }
    }
    File src = fsFactory.getFile(file + RESOURCE_SUFFIX + TEMP_SUFFIX);
    File dest = fsFactory.getFile(file + RESOURCE_SUFFIX);
    dest.delete();
    fsFactory.moveFile(src, dest);
  }

  public void deserialize() throws IOException {
    try (InputStream inputStream = fsFactory.getBufferedInputStream(
        file + RESOURCE_SUFFIX)) {
      int size = ReadWriteIOUtils.readInt(inputStream);
      Map<String, Integer> deviceMap = new HashMap<>();
      long[] startTimesArray = new long[size];
      long[] endTimesArray = new long[size];
      for (int i = 0; i < size; i++) {
        String path = ReadWriteIOUtils.readString(inputStream);
        long time = ReadWriteIOUtils.readLong(inputStream);
        // To reduce the String number in memory,
        // use the deviceId from memory instead of the deviceId read from disk
        String cachedPath = cachedDevicePool.computeIfAbsent(path, k -> k);
        deviceMap.put(cachedPath, i);
        startTimesArray[i] = time;
      }
      size = ReadWriteIOUtils.readInt(inputStream);
      for (int i = 0; i < size; i++) {
        ReadWriteIOUtils.readString(inputStream); // String path
        long time = ReadWriteIOUtils.readLong(inputStream);
        endTimesArray[i] = time;
      }
      this.startTimes = startTimesArray;
      this.endTimes = endTimesArray;
      this.deviceToIndex = deviceMap;

      if (inputStream.available() > 0) {
        int versionSize = ReadWriteIOUtils.readInt(inputStream);
        historicalVersions = new HashSet<>();
        for (int i = 0; i < versionSize; i++) {
          historicalVersions.add(ReadWriteIOUtils.readLong(inputStream));
        }
      } else {
        // use the version in file name as the historical version for files of old versions
        long version = Long.parseLong(file.getName().split(IoTDBConstant.FILE_NAME_SEPARATOR)[1]);
        historicalVersions = Collections.singleton(version);
      }
    }
  }

  public void updateStartTime(String device, long time) {
    long startTime = getStartTime(device);
    if (time < startTime) {
      putStartTime(device, time);
    }
  }

  public void updateEndTime(String device, long time) {
    long endTime = getEndTime(device);
    if (time > endTime) {
      putEndTime(device, time);
    }
  }

  public boolean resourceFileExists() {
    return fsFactory.getFile(file + RESOURCE_SUFFIX).exists();
  }

  void forceUpdateEndTime(String device, long time) {
    putEndTime(device, time);
  }

  public List<ChunkMetadata> getChunkMetadataList() {
    return new ArrayList<>(chunkMetadataList);
  }

  public List<ReadOnlyMemChunk> getReadOnlyMemChunk() {
    return readOnlyMemChunk;
  }

  public synchronized ModificationFile getModFile() {
    if (modFile == null) {
      modFile = new ModificationFile(file.getPath() + ModificationFile.FILE_SUFFIX);
    }
    return modFile;
  }

  public void setFile(File file) {
    this.file = file;
  }

  boolean containsDevice(String deviceId) {
    return deviceToIndex.containsKey(deviceId);
  }

  public File getTsFile() {
    return file;
  }

  public String getTsFilePath() {
    return file.getPath();
  }

  public long getTsFileSize() {
    return file.length();
  }

  public long getStartTime(String deviceId) {
    if (!deviceToIndex.containsKey(deviceId)) {
      return Long.MAX_VALUE;
    }
    return startTimes[deviceToIndex.get(deviceId)];
  }

  public long getStartTime(int index) {
    return startTimes[index];
  }

  public long getEndTime(String deviceId) {
    if (!deviceToIndex.containsKey(deviceId)) {
      return Long.MIN_VALUE;
    }
    return endTimes[deviceToIndex.get(deviceId)];
  }

  public long getEndTime(int index) {
    return endTimes[index];
  }

  public long getOrDefaultStartTime(String deviceId, long defaultTime) {
    long startTime = getStartTime(deviceId);
    return startTime != Long.MAX_VALUE ? startTime : defaultTime;
  }

  public long getOrDefaultEndTime(String deviceId, long defaultTime) {
    long endTime = getEndTime(deviceId);
    return endTime != Long.MIN_VALUE ? endTime : defaultTime;
  }

  public void putStartTime(String deviceId, long startTime) {
    int index;
    if (containsDevice(deviceId)) {
      index = deviceToIndex.get(deviceId);
    } else {
      index = deviceToIndex.size();
      deviceToIndex.put(deviceId, index);
      if (startTimes.length <= index) {
        startTimes = enLargeArray(startTimes, Long.MAX_VALUE);
        endTimes = enLargeArray(endTimes, Long.MIN_VALUE);
      }
    }
    startTimes[index] = startTime;
  }

  public void putEndTime(String deviceId, long endTime) {
    int index;
    if (containsDevice(deviceId)) {
      index = deviceToIndex.get(deviceId);
    } else {
      index = deviceToIndex.size();
      deviceToIndex.put(deviceId, index);
      if (endTimes.length <= index) {
        startTimes = enLargeArray(startTimes, Long.MAX_VALUE);
        endTimes = enLargeArray(endTimes, Long.MIN_VALUE);
      }
    }
    endTimes[index] = endTime;
  }

  private long[] enLargeArray(long[] array, long defaultValue) {
    long[] tmp = new long[(int) (array.length * 1.5)];
    initTimes(tmp, defaultValue);
    System.arraycopy(array, 0, tmp, 0, array.length);
    return tmp;
  }

  public Map<String, Integer> getDeviceToIndexMap() {
    return deviceToIndex;
  }

  public long[] getStartTimes() {
    return startTimes;
  }

  public long[] getEndTimes() {
    return endTimes;
  }

  public void clearEndTimes() {
    endTimes = new long[endTimes.length];
    initTimes(endTimes, Long.MIN_VALUE);
  }

  public boolean areEndTimesEmpty() {
    for (long endTime : endTimes) {
      if (endTime != -1) {
        return false;
      }
    }
    return true;
  }

  private void trimStartEndTimes() {
    startTimes = Arrays.copyOfRange(startTimes, 0, deviceToIndex.size());
    endTimes = Arrays.copyOfRange(endTimes, 0, deviceToIndex.size());
  }

  public boolean isClosed() {
    return closed;
  }

  public void close() throws IOException {
    closed = true;
    if (modFile != null) {
      modFile.close();
      modFile = null;
    }
    processor = null;
    chunkMetadataList = null;
    trimStartEndTimes();
  }

  TsFileProcessor getUnsealedFileProcessor() {
    return processor;
  }


  public void writeLock() {
    if (originTsFileResource == null) {
      tsFileLock.writeLock();
    } else {
      originTsFileResource.writeLock();
    }
  }

  public void writeUnlock() {
    if (originTsFileResource == null) {
      tsFileLock.writeUnlock();
    } else {
      originTsFileResource.writeUnlock();
    }
  }

  /**
   * If originTsFileResource is not null, we should acquire the read lock of originTsFileResource
   * before construct the current TsFileResource
   */
  public void readLock() {
    if (originTsFileResource == null) {
      tsFileLock.readLock();
    } else {
      originTsFileResource.readLock();
    }
  }

  public void readUnlock() {
    if (originTsFileResource == null) {
      tsFileLock.readUnlock();
    } else {
      originTsFileResource.readUnlock();
    }
  }

  public boolean tryReadLock() {
    return tsFileLock.tryReadLock();
  }

  public boolean tryWriteLock() {
    return tsFileLock.tryWriteLock();
  }

  void doUpgrade() {
    if (UpgradeUtils.isNeedUpgrade(this)) {
      UpgradeSevice.getINSTANCE().submitUpgradeTask(new UpgradeTask(this));
    }
  }

  public void removeModFile() throws IOException {
    getModFile().remove();
    modFile = null;
  }

  /**
   * Remove the data file, its resource file, and its modification file physically.
   */
  public void remove() {
    file.delete();
    fsFactory.getFile(file.getPath() + RESOURCE_SUFFIX).delete();
    fsFactory.getFile(file.getPath() + ModificationFile.FILE_SUFFIX).delete();
  }

  public void removeResourceFile() {
    fsFactory.getFile(file.getPath() + RESOURCE_SUFFIX).delete();
  }

  void moveTo(File targetDir) {
    fsFactory.moveFile(file, fsFactory.getFile(targetDir, file.getName()));
    fsFactory.moveFile(fsFactory.getFile(file.getPath() + RESOURCE_SUFFIX),
        fsFactory.getFile(targetDir, file.getName() + RESOURCE_SUFFIX));
    fsFactory.getFile(file.getPath() + ModificationFile.FILE_SUFFIX).delete();
  }

  @Override
  public String toString() {
    return file.toString();
  }

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

  @Override
  public int hashCode() {
    return Objects.hash(file);
  }

  public void setClosed(boolean closed) {
    this.closed = closed;
  }

  public boolean isDeleted() {
    return deleted;
  }

  public void setDeleted(boolean deleted) {
    this.deleted = deleted;
  }

  boolean isMerging() {
    return isMerging;
  }

  public void setMerging(boolean merging) {
    isMerging = merging;
  }

  /**
   * check if any of the device lives over the given time bound
   */
  public boolean stillLives(long timeLowerBound) {
    if (timeLowerBound == Long.MAX_VALUE) {
      return true;
    }
    for (long endTime : endTimes) {
      // the file cannot be deleted if any device still lives
      if (endTime >= timeLowerBound) {
        return true;
      }
    }
    return false;
  }

  protected void setStartTimes(long[] startTimes) {
    this.startTimes = startTimes;
  }

  protected void setEndTimes(long[] endTimes) {
    this.endTimes = endTimes;
  }

  /**
   * set a file flag indicating that the file is being closed, so during recovery we could know we
   * should close the file.
   */
  void setCloseFlag() {
    try {
      if (!fsFactory.getFile(file.getAbsoluteFile() + CLOSING_SUFFIX).createNewFile()) {
        logger.error("Cannot create close flag for {}", file);
      }
    } catch (IOException e) {
      logger.error("Cannot create close flag for {}", file, e);
    }
  }

  /**
   * clean the close flag (if existed) when the file is successfully closed.
   */
  public void cleanCloseFlag() {
    if (!fsFactory.getFile(file.getAbsoluteFile() + CLOSING_SUFFIX).delete()) {
      logger.error("Cannot clean close flag for {}", file);
    }
  }

  public boolean isCloseFlagSet() {
    return fsFactory.getFile(file.getAbsoluteFile() + CLOSING_SUFFIX).exists();
  }

  public Set<Long> getHistoricalVersions() {
    return historicalVersions;
  }

  public void setHistoricalVersions(Set<Long> historicalVersions) {
    this.historicalVersions = historicalVersions;
  }

  public void setProcessor(TsFileProcessor processor) {
    this.processor = processor;
  }

  public TimeseriesMetadata getTimeSeriesMetadata() {
    return timeSeriesMetadata;
  }

  public void setUpgradedResources(List<TsFileResource> upgradedResources) {
    this.upgradedResources = upgradedResources;
  }

  public List<TsFileResource> getUpgradedResources() {
    return upgradedResources;
  }

  public void setSeq(boolean isSeq) {
    this.isSeq = isSeq;
  }

  public boolean isSeq() {
    return isSeq;
  }

  public void setUpgradeTsFileResourceCallBack(
      UpgradeTsFileResourceCallBack upgradeTsFileResourceCallBack) {
    this.upgradeTsFileResourceCallBack = upgradeTsFileResourceCallBack;
  }

  public UpgradeTsFileResourceCallBack getUpgradeTsFileResourceCallBack() {
    return upgradeTsFileResourceCallBack;
  }

  /**
   * make sure Either the deviceToIndex is not empty Or the path contains a partition folder
   */
  public long getTimePartition() {
    if (deviceToIndex != null && !deviceToIndex.isEmpty()) {
      return StorageEngine.getTimePartition(startTimes[deviceToIndex.values().iterator().next()]);
    }
    String[] splits = FilePathUtils.splitTsFilePath(this);
    return Long.parseLong(splits[splits.length - 2]);
  }

  /**
   * Used when load new TsFiles not generated by the server Check and get the time partition
   * TODO:when the partition violation happens, split the file and load into different partitions
   *
   * @throws PartitionViolationException if the data of the file cross partitions or it is empty
   */
  public long getTimePartitionWithCheck() throws PartitionViolationException {
    long partitionId = -1;
    for (Long startTime : startTimes) {
      long p = StorageEngine.getTimePartition(startTime);
      if (partitionId == -1) {
        partitionId = p;
      } else {
        if (partitionId != p) {
          throw new PartitionViolationException(this);
        }
      }
    }
    for (Long endTime : endTimes) {
      long p = StorageEngine.getTimePartition(endTime);
      if (partitionId == -1) {
        partitionId = p;
      } else {
        if (partitionId != p) {
          throw new PartitionViolationException(this);
        }
      }
    }
    if (partitionId == -1) {
      throw new PartitionViolationException(this);
    }
    return partitionId;
  }

  /**
   * Create a hardlink for the TsFile and modification file (if exists) The hardlink will have a
   * suffix like ".{sysTime}_{randomLong}"
   *
   * @return a new TsFileResource with its file changed to the hardlink or null the hardlink cannot
   * be created.
   */
  public TsFileResource createHardlink() {
    if (!file.exists()) {
      return null;
    }

    TsFileResource newResource;
    try {
      newResource = new TsFileResource(this);
    } catch (IOException e) {
      logger.error("Cannot create hardlink for {}", file, e);
      return null;
    }

    while (true) {
      String hardlinkSuffix =
          TsFileConstant.PATH_SEPARATOR + System.currentTimeMillis() + "_" + random.nextLong();
      File hardlink = new File(file.getAbsolutePath() + hardlinkSuffix);

      try {
        Files.createLink(Paths.get(hardlink.getAbsolutePath()), Paths.get(file.getAbsolutePath()));
        newResource.setFile(hardlink);
        if (modFile != null && modFile.exists()) {
          newResource.setModFile(modFile.createHardlink());
        }
        break;
      } catch (FileAlreadyExistsException e) {
        // retry a different name if the file is already created
      } catch (IOException e) {
        logger.error("Cannot create hardlink for {}", file, e);
        return null;
      }
    }
    return newResource;
  }

  public synchronized void setModFile(ModificationFile modFile) {
    this.modFile = modFile;
  }

  public long getMaxVersion() {
    long maxVersion = 0;
    if (historicalVersions != null && !historicalVersions.isEmpty()) {
      maxVersion = Collections.max(historicalVersions);
    }
    return maxVersion;
  }

  /**
   * @return initial resource map size
   */
  public long calculateRamSize() {
    return RamUsageEstimator.sizeOf(deviceToIndex) + RamUsageEstimator.sizeOf(startTimes) + 
        RamUsageEstimator.sizeOf(endTimes);
  }

  /**
   * Calculate the resource ram increment when insert data in TsFileProcessor
   * 
   * @return ramIncrement
   */
  public long estimateRamIncrement(String deviceToBeChecked) {
    long ramIncrement = 0L;
    if (!containsDevice(deviceToBeChecked)) {
      // 80 is the Map.Entry header ram size
      if (deviceToIndex.isEmpty()) {
        ramIncrement += 80;
      }
      // Map.Entry ram size
      ramIncrement += RamUsageEstimator.sizeOf(deviceToBeChecked) + 16;
      // if needs to extend the startTimes and endTimes arrays
      if (deviceToIndex.size() >= startTimes.length) {
        ramIncrement += startTimes.length * Long.BYTES;
      }
    }
    return ramIncrement;
  }

  public void delete() throws IOException {
    if (file.exists()) {
      Files.delete(file.toPath());
      Files.delete(FSFactoryProducer.getFSFactory()
          .getFile(file.toPath() + TsFileResource.RESOURCE_SUFFIX).toPath());
    }
  }

  public long getMaxPlanIndex() {
    return maxPlanIndex;
  }

  public long getMinPlanIndex() {
    return minPlanIndex;
  }

  public void updatePlanIndexes(long planIndex) {
    maxPlanIndex = Math.max(maxPlanIndex, planIndex);
    minPlanIndex = Math.min(minPlanIndex, planIndex);
    if (closed) {
      try {
        serialize();
      } catch (IOException e) {
        logger.error("Cannot serialize TsFileResource {} when updating plan index {}-{}", this,
            maxPlanIndex, planIndex);
      }
    }
  }

  public boolean isPlanIndexOverlap(TsFileResource another) {
    return another.maxPlanIndex >= this.minPlanIndex &&
           another.minPlanIndex <= this.maxPlanIndex;
  }
}
