/*
 * 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.compactions;

import static org.apache.hadoop.hbase.regionserver.StripeStoreFileManager.OPEN_KEY;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.CellComparator;
import org.apache.hadoop.hbase.regionserver.HStoreFile;
import org.apache.hadoop.hbase.regionserver.StoreConfigInformation;
import org.apache.hadoop.hbase.regionserver.StoreUtils;
import org.apache.hadoop.hbase.regionserver.StripeStoreConfig;
import org.apache.hadoop.hbase.regionserver.StripeStoreFlusher;
import org.apache.hadoop.hbase.regionserver.throttle.ThroughputController;
import org.apache.hadoop.hbase.security.User;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.ConcatenatedLists;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.hadoop.hbase.util.Pair;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

/**
 * Stripe store implementation of compaction policy.
 */
@InterfaceAudience.Private
public class StripeCompactionPolicy extends CompactionPolicy {
  private final static Logger LOG = LoggerFactory.getLogger(StripeCompactionPolicy.class);
  // Policy used to compact individual stripes.
  private ExploringCompactionPolicy stripePolicy = null;

  private StripeStoreConfig config;

  public StripeCompactionPolicy(Configuration conf, StoreConfigInformation storeConfigInfo,
    StripeStoreConfig config) {
    super(conf, storeConfigInfo);
    this.config = config;
    stripePolicy = new ExploringCompactionPolicy(conf, storeConfigInfo);
  }

  public List<HStoreFile> preSelectFilesForCoprocessor(StripeInformationProvider si,
    List<HStoreFile> filesCompacting) {
    // We sincerely hope nobody is messing with us with their coprocessors.
    // If they do, they are very likely to shoot themselves in the foot.
    // We'll just exclude all the filesCompacting from the list.
    ArrayList<HStoreFile> candidateFiles = new ArrayList<>(si.getStoreFiles());
    candidateFiles.removeAll(filesCompacting);
    return candidateFiles;
  }

  public StripeCompactionRequest createEmptyRequest(StripeInformationProvider si,
    CompactionRequestImpl request) {
    // Treat as L0-ish compaction with fixed set of files, and hope for the best.
    if (si.getStripeCount() > 0) {
      return new BoundaryStripeCompactionRequest(request, si.getStripeBoundaries());
    }
    Pair<Long, Integer> targetKvsAndCount =
      estimateTargetKvs(request.getFiles(), this.config.getInitialCount());
    return new SplitStripeCompactionRequest(request, OPEN_KEY, OPEN_KEY,
      targetKvsAndCount.getSecond(), targetKvsAndCount.getFirst());
  }

  public StripeStoreFlusher.StripeFlushRequest selectFlush(CellComparator comparator,
    StripeInformationProvider si, int kvCount) {
    if (this.config.isUsingL0Flush()) {
      // L0 is used, return dumb request.
      return new StripeStoreFlusher.StripeFlushRequest(comparator);
    }
    if (si.getStripeCount() == 0) {
      // No stripes - start with the requisite count, derive KVs per stripe.
      int initialCount = this.config.getInitialCount();
      return new StripeStoreFlusher.SizeStripeFlushRequest(comparator, initialCount,
        kvCount / initialCount);
    }
    // There are stripes - do according to the boundaries.
    return new StripeStoreFlusher.BoundaryStripeFlushRequest(comparator, si.getStripeBoundaries());
  }

  public StripeCompactionRequest selectCompaction(StripeInformationProvider si,
    List<HStoreFile> filesCompacting, boolean isOffpeak) throws IOException {
    // TODO: first cut - no parallel compactions. To have more fine grained control we
    // probably need structure more sophisticated than a list.
    if (!filesCompacting.isEmpty()) {
      LOG.debug("Not selecting compaction: " + filesCompacting.size() + " files compacting");
      return null;
    }

    // We are going to do variations of compaction in strict order of preference.
    // A better/more advanced approach is to use a heuristic to see which one is "more
    // necessary" at current time.

    // This can happen due to region split. We can skip it later; for now preserve
    // compact-all-things behavior.
    Collection<HStoreFile> allFiles = si.getStoreFiles();
    if (StoreUtils.hasReferences(allFiles)) {
      LOG.debug("There are references in the store; compacting all files");
      long targetKvs = estimateTargetKvs(allFiles, config.getInitialCount()).getFirst();
      SplitStripeCompactionRequest request =
        new SplitStripeCompactionRequest(allFiles, OPEN_KEY, OPEN_KEY, targetKvs);
      request.setMajorRangeFull();
      request.getRequest().setAfterSplit(true);
      return request;
    }

    int stripeCount = si.getStripeCount();
    List<HStoreFile> l0Files = si.getLevel0Files();

    // See if we need to make new stripes.
    boolean shouldCompactL0 =
      this.config.getLevel0MinFiles() <= l0Files.size() || allL0FilesExpired(si);
    if (stripeCount == 0) {
      if (!shouldCompactL0) {
        return null; // nothing to do.
      }
      return selectL0OnlyCompaction(si);
    }

    boolean canDropDeletesNoL0 = l0Files.isEmpty();
    if (shouldCompactL0) {
      if (!canDropDeletesNoL0) {
        // If we need to compact L0, see if we can add something to it, and drop deletes.
        StripeCompactionRequest result =
          selectSingleStripeCompaction(si, !shouldSelectL0Files(si), canDropDeletesNoL0, isOffpeak);
        if (result != null) {
          return result;
        }
      }
      LOG.debug("Selecting L0 compaction with " + l0Files.size() + " files");
      return selectL0OnlyCompaction(si);
    }

    // Try to delete fully expired stripes
    StripeCompactionRequest result = selectExpiredMergeCompaction(si, canDropDeletesNoL0);
    if (result != null) {
      return result;
    }

    // Ok, nothing special here, let's see if we need to do a common compaction.
    // This will also split the stripes that are too big if needed.
    return selectSingleStripeCompaction(si, false, canDropDeletesNoL0, isOffpeak);
  }

  public boolean needsCompactions(StripeInformationProvider si, List<HStoreFile> filesCompacting) {
    // Approximation on whether we need compaction.
    return filesCompacting.isEmpty() && (StoreUtils.hasReferences(si.getStoreFiles())
      || (si.getLevel0Files().size() >= this.config.getLevel0MinFiles())
      || needsSingleStripeCompaction(si) || hasExpiredStripes(si) || allL0FilesExpired(si));
  }

  @Override
  public boolean shouldPerformMajorCompaction(Collection<HStoreFile> filesToCompact)
    throws IOException {
    return false; // there's never a major compaction!
  }

  @Override
  public boolean throttleCompaction(long compactionSize) {
    return compactionSize > comConf.getThrottlePoint();
  }

  /**
   * @param si StoreFileManager.
   * @return Whether any stripe potentially needs compaction.
   */
  protected boolean needsSingleStripeCompaction(StripeInformationProvider si) {
    int minFiles = this.config.getStripeCompactMinFiles();
    for (List<HStoreFile> stripe : si.getStripes()) {
      if (stripe.size() >= minFiles) return true;
    }
    return false;
  }

  protected StripeCompactionRequest selectSingleStripeCompaction(StripeInformationProvider si,
    boolean includeL0, boolean canDropDeletesWithoutL0, boolean isOffpeak) throws IOException {
    ArrayList<ImmutableList<HStoreFile>> stripes = si.getStripes();

    int bqIndex = -1;
    List<HStoreFile> bqSelection = null;
    int stripeCount = stripes.size();
    long bqTotalSize = -1;
    for (int i = 0; i < stripeCount; ++i) {
      // If we want to compact L0 to drop deletes, we only want whole-stripe compactions.
      // So, pass includeL0 as 2nd parameter to indicate that.
      List<HStoreFile> selection = selectSimpleCompaction(stripes.get(i),
        !canDropDeletesWithoutL0 && includeL0, isOffpeak, false);
      if (selection.isEmpty()) continue;
      long size = 0;
      for (HStoreFile sf : selection) {
        size += sf.getReader().length();
      }
      if (
        bqSelection == null || selection.size() > bqSelection.size()
          || (selection.size() == bqSelection.size() && size < bqTotalSize)
      ) {
        bqSelection = selection;
        bqIndex = i;
        bqTotalSize = size;
      }
    }
    if (bqSelection == null) {
      LOG.debug("No good compaction is possible in any stripe");
      return null;
    }
    List<HStoreFile> filesToCompact = new ArrayList<>(bqSelection);
    // See if we can, and need to, split this stripe.
    int targetCount = 1;
    long targetKvs = Long.MAX_VALUE;
    boolean hasAllFiles = filesToCompact.size() == stripes.get(bqIndex).size();
    String splitString = "";
    if (hasAllFiles && bqTotalSize >= config.getSplitSize()) {
      if (includeL0) {
        // We want to avoid the scenario where we compact a stripe w/L0 and then split it.
        // So, if we might split, don't compact the stripe with L0.
        return null;
      }
      Pair<Long, Integer> kvsAndCount = estimateTargetKvs(filesToCompact, config.getSplitCount());
      targetKvs = kvsAndCount.getFirst();
      targetCount = kvsAndCount.getSecond();
      splitString = "; the stripe will be split into at most " + targetCount + " stripes with "
        + targetKvs + " target KVs";
    }

    LOG.debug("Found compaction in a stripe with end key [" + Bytes.toString(si.getEndRow(bqIndex))
      + "], with " + filesToCompact.size() + " files of total size " + bqTotalSize + splitString);

    // See if we can drop deletes.
    StripeCompactionRequest req;
    if (includeL0) {
      assert hasAllFiles;
      List<HStoreFile> l0Files = si.getLevel0Files();
      LOG.debug("Adding " + l0Files.size() + " files to compaction to be able to drop deletes");
      ConcatenatedLists<HStoreFile> sfs = new ConcatenatedLists<>();
      sfs.addSublist(filesToCompact);
      sfs.addSublist(l0Files);
      req = new BoundaryStripeCompactionRequest(sfs, si.getStripeBoundaries());
    } else {
      req = new SplitStripeCompactionRequest(filesToCompact, si.getStartRow(bqIndex),
        si.getEndRow(bqIndex), targetCount, targetKvs);
    }
    if (hasAllFiles && (canDropDeletesWithoutL0 || includeL0)) {
      req.setMajorRange(si.getStartRow(bqIndex), si.getEndRow(bqIndex));
    }
    req.getRequest().setOffPeak(isOffpeak);
    return req;
  }

  /**
   * Selects the compaction of a single stripe using default policy.
   * @param sfs          Files.
   * @param allFilesOnly Whether a compaction of all-or-none files is needed.
   * @return The resulting selection.
   */
  private List<HStoreFile> selectSimpleCompaction(List<HStoreFile> sfs, boolean allFilesOnly,
    boolean isOffpeak, boolean forceCompact) {
    int minFilesLocal =
      Math.max(allFilesOnly ? sfs.size() : 0, this.config.getStripeCompactMinFiles());
    int maxFilesLocal = Math.max(this.config.getStripeCompactMaxFiles(), minFilesLocal);
    List<HStoreFile> selected =
      stripePolicy.applyCompactionPolicy(sfs, false, isOffpeak, minFilesLocal, maxFilesLocal);
    if (forceCompact && (selected == null || selected.isEmpty()) && !sfs.isEmpty()) {
      return stripePolicy.selectCompactFiles(sfs, maxFilesLocal, isOffpeak);
    }
    return selected;
  }

  private boolean shouldSelectL0Files(StripeInformationProvider si) {
    return si.getLevel0Files().size() > this.config.getStripeCompactMaxFiles()
      || getTotalFileSize(si.getLevel0Files()) > comConf.getMaxCompactSize();
  }

  private StripeCompactionRequest selectL0OnlyCompaction(StripeInformationProvider si) {
    List<HStoreFile> l0Files = si.getLevel0Files();
    List<HStoreFile> selectedFiles = l0Files;
    if (shouldSelectL0Files(si)) {
      selectedFiles = selectSimpleCompaction(l0Files, false, false, true);
      assert !selectedFiles.isEmpty() : "Selected L0 files should not be empty";
    }
    StripeCompactionRequest request;
    if (si.getStripeCount() == 0) {
      Pair<Long, Integer> estimate = estimateTargetKvs(selectedFiles, config.getInitialCount());
      long targetKvs = estimate.getFirst();
      int targetCount = estimate.getSecond();
      request =
        new SplitStripeCompactionRequest(selectedFiles, OPEN_KEY, OPEN_KEY, targetCount, targetKvs);
      if (selectedFiles.size() == l0Files.size()) {
        ((SplitStripeCompactionRequest) request).setMajorRangeFull(); // L0 only, can drop deletes.
      }
      LOG.debug("Creating {} initial stripes with {} kvs each via L0 compaction of {}/{} files",
        targetCount, targetKvs, selectedFiles.size(), l0Files.size());
    } else {
      request = new BoundaryStripeCompactionRequest(selectedFiles, si.getStripeBoundaries());
      LOG.debug("Boundary L0 compaction of {}/{} files", selectedFiles.size(), l0Files.size());
    }
    return request;
  }

  private StripeCompactionRequest selectExpiredMergeCompaction(StripeInformationProvider si,
    boolean canDropDeletesNoL0) {
    long cfTtl = this.storeConfigInfo.getStoreFileTtl();
    if (cfTtl == Long.MAX_VALUE) {
      return null; // minversion might be set, cannot delete old files
    }
    long timestampCutoff = EnvironmentEdgeManager.currentTime() - cfTtl;
    // Merge the longest sequence of stripes where all files have expired, if any.
    int start = -1, bestStart = -1, length = 0, bestLength = 0;
    ArrayList<ImmutableList<HStoreFile>> stripes = si.getStripes();
    OUTER: for (int i = 0; i < stripes.size(); ++i) {
      for (HStoreFile storeFile : stripes.get(i)) {
        if (storeFile.getReader().getMaxTimestamp() < timestampCutoff) continue;
        // Found non-expired file, this stripe has to stay.
        if (length > bestLength) {
          bestStart = start;
          bestLength = length;
        }
        start = -1;
        length = 0;
        continue OUTER;
      }
      if (start == -1) {
        start = i;
      }
      ++length;
    }
    if (length > bestLength) {
      bestStart = start;
      bestLength = length;
    }
    if (bestLength == 0) return null;
    if (bestLength == 1) {
      // This is currently inefficient. If only one stripe expired, we will rewrite some
      // entire stripe just to delete some expired files because we rely on metadata and it
      // cannot simply be updated in an old file. When we either determine stripe dynamically
      // or move metadata to manifest, we can just drop the "expired stripes".
      if (bestStart == (stripes.size() - 1)) return null;
      ++bestLength;
    }
    LOG.debug("Merging " + bestLength + " stripes to delete expired store files");
    int endIndex = bestStart + bestLength - 1;
    ConcatenatedLists<HStoreFile> sfs = new ConcatenatedLists<>();
    sfs.addAllSublists(stripes.subList(bestStart, endIndex + 1));
    SplitStripeCompactionRequest result = new SplitStripeCompactionRequest(sfs,
      si.getStartRow(bestStart), si.getEndRow(endIndex), 1, Long.MAX_VALUE);
    if (canDropDeletesNoL0) {
      result.setMajorRangeFull();
    }
    return result;
  }

  protected boolean hasExpiredStripes(StripeInformationProvider si) {
    // Find if exists a stripe where all files have expired, if any.
    ArrayList<ImmutableList<HStoreFile>> stripes = si.getStripes();
    for (ImmutableList<HStoreFile> stripe : stripes) {
      if (allFilesExpired(stripe)) {
        return true;
      }
    }
    return false;
  }

  protected boolean allL0FilesExpired(StripeInformationProvider si) {
    return allFilesExpired(si.getLevel0Files());
  }

  private boolean allFilesExpired(final List<HStoreFile> storeFiles) {
    if (storeFiles == null || storeFiles.isEmpty()) {
      return false;
    }
    long cfTtl = this.storeConfigInfo.getStoreFileTtl();
    if (cfTtl == Long.MAX_VALUE) {
      return false; // minversion might be set, cannot delete old files
    }
    long timestampCutoff = EnvironmentEdgeManager.currentTime() - cfTtl;
    for (HStoreFile storeFile : storeFiles) {
      // Check store file is not empty and has not expired
      if (
        storeFile.getReader().getMaxTimestamp() >= timestampCutoff
          && storeFile.getReader().getEntries() != 0
      ) {
        return false;
      }
    }
    return true;
  }

  private static long getTotalKvCount(final Collection<HStoreFile> candidates) {
    long totalSize = 0;
    for (HStoreFile storeFile : candidates) {
      totalSize += storeFile.getReader().getEntries();
    }
    return totalSize;
  }

  public static long getTotalFileSize(final Collection<HStoreFile> candidates) {
    long totalSize = 0;
    for (HStoreFile storeFile : candidates) {
      totalSize += storeFile.getReader().length();
    }
    return totalSize;
  }

  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "FL_FLOATS_AS_LOOP_COUNTERS",
      justification = "valid usage")
  private Pair<Long, Integer> estimateTargetKvs(Collection<HStoreFile> files, double splitCount) {
    // If the size is larger than what we target, we don't want to split into proportionally
    // larger parts and then have to split again very soon. So, we will increase the multiplier
    // by one until we get small enough parts. E.g. 5Gb stripe that should have been split into
    // 2 parts when it was 3Gb will be split into 3x1.67Gb parts, rather than 2x2.5Gb parts.
    long totalSize = getTotalFileSize(files);
    long targetPartSize = config.getSplitPartSize();
    assert targetPartSize > 0 && splitCount > 0;
    double ratio = totalSize / (splitCount * targetPartSize); // ratio of real to desired size
    while (ratio > 1.0) {
      // Ratio of real to desired size if we increase the multiplier.
      double newRatio = totalSize / ((splitCount + 1.0) * targetPartSize);
      if ((1.0 / newRatio) >= ratio) {
        // New ratio is < 1.0, but further than the last one.
        break;
      }
      ratio = newRatio;
      splitCount += 1.0;
    }
    long kvCount = (long) (getTotalKvCount(files) / splitCount);
    return new Pair<>(kvCount, (int) Math.ceil(splitCount));
  }

  /** Stripe compaction request wrapper. */
  public abstract static class StripeCompactionRequest {
    protected CompactionRequestImpl request;
    protected byte[] majorRangeFromRow = null, majorRangeToRow = null;

    public List<Path> execute(StripeCompactor compactor, ThroughputController throughputController)
      throws IOException {
      return execute(compactor, throughputController, null);
    }

    /**
     * Executes the request against compactor (essentially, just calls correct overload of compact
     * method), to simulate more dynamic dispatch.
     * @param compactor Compactor.
     * @return result of compact(...)
     */
    public abstract List<Path> execute(StripeCompactor compactor,
      ThroughputController throughputController, User user) throws IOException;

    public StripeCompactionRequest(CompactionRequestImpl request) {
      this.request = request;
    }

    /**
     * Sets compaction "major range". Major range is the key range for which all the files are
     * included, so they can be treated like major-compacted files.
     * @param startRow Left boundary, inclusive.
     * @param endRow   Right boundary, exclusive.
     */
    public void setMajorRange(byte[] startRow, byte[] endRow) {
      this.majorRangeFromRow = startRow;
      this.majorRangeToRow = endRow;
    }

    public CompactionRequestImpl getRequest() {
      return this.request;
    }

    public void setRequest(CompactionRequestImpl request) {
      assert request != null;
      this.request = request;
      this.majorRangeFromRow = this.majorRangeToRow = null;
    }
  }

  /**
   * Request for stripe compactor that will cause it to split the source files into several separate
   * files at the provided boundaries.
   */
  private static class BoundaryStripeCompactionRequest extends StripeCompactionRequest {
    private final List<byte[]> targetBoundaries;

    /**
     * @param request          Original request.
     * @param targetBoundaries New files should be written with these boundaries.
     */
    public BoundaryStripeCompactionRequest(CompactionRequestImpl request,
      List<byte[]> targetBoundaries) {
      super(request);
      this.targetBoundaries = targetBoundaries;
    }

    public BoundaryStripeCompactionRequest(Collection<HStoreFile> files,
      List<byte[]> targetBoundaries) {
      this(new CompactionRequestImpl(files), targetBoundaries);
    }

    @Override
    public List<Path> execute(StripeCompactor compactor, ThroughputController throughputController,
      User user) throws IOException {
      return compactor.compact(this.request, this.targetBoundaries, this.majorRangeFromRow,
        this.majorRangeToRow, throughputController, user);
    }
  }

  /**
   * Request for stripe compactor that will cause it to split the source files into several separate
   * files into based on key-value count, as well as file count limit. Most of the files will be
   * roughly the same size. The last file may be smaller or larger depending on the interplay of the
   * amount of data and maximum number of files allowed.
   */
  private static class SplitStripeCompactionRequest extends StripeCompactionRequest {
    private final byte[] startRow, endRow;
    private final int targetCount;
    private final long targetKvs;

    /**
     * @param request     Original request.
     * @param startRow    Left boundary of the range to compact, inclusive.
     * @param endRow      Right boundary of the range to compact, exclusive.
     * @param targetCount The maximum number of stripe to compact into.
     * @param targetKvs   The KV count of each segment. If targetKvs*targetCount is less than total
     *                    number of kvs, all the overflow data goes into the last stripe.
     */
    public SplitStripeCompactionRequest(CompactionRequestImpl request, byte[] startRow,
      byte[] endRow, int targetCount, long targetKvs) {
      super(request);
      this.startRow = startRow;
      this.endRow = endRow;
      this.targetCount = targetCount;
      this.targetKvs = targetKvs;
    }

    public SplitStripeCompactionRequest(Collection<HStoreFile> files, byte[] startRow,
      byte[] endRow, long targetKvs) {
      this(files, startRow, endRow, Integer.MAX_VALUE, targetKvs);
    }

    public SplitStripeCompactionRequest(Collection<HStoreFile> files, byte[] startRow,
      byte[] endRow, int targetCount, long targetKvs) {
      this(new CompactionRequestImpl(files), startRow, endRow, targetCount, targetKvs);
    }

    @Override
    public List<Path> execute(StripeCompactor compactor, ThroughputController throughputController,
      User user) throws IOException {
      return compactor.compact(this.request, this.targetCount, this.targetKvs, this.startRow,
        this.endRow, this.majorRangeFromRow, this.majorRangeToRow, throughputController, user);
    }

    /**
     * Set major range of the compaction to the entire compaction range. See
     * {@link #setMajorRange(byte[], byte[])}.
     */
    public void setMajorRangeFull() {
      setMajorRange(this.startRow, this.endRow);
    }
  }

  /** The information about stripes that the policy needs to do its stuff */
  public static interface StripeInformationProvider {
    public Collection<HStoreFile> getStoreFiles();

    /**
     * Gets the start row for a given stripe.
     * @param stripeIndex Stripe index.
     * @return Start row. May be an open key.
     */
    public byte[] getStartRow(int stripeIndex);

    /**
     * Gets the end row for a given stripe.
     * @param stripeIndex Stripe index.
     * @return End row. May be an open key.
     */
    public byte[] getEndRow(int stripeIndex);

    /** Returns Level 0 files. */
    public List<HStoreFile> getLevel0Files();

    /** Returns All stripe boundaries; including the open ones on both ends. */
    public List<byte[]> getStripeBoundaries();

    /** Returns The stripes. */
    public ArrayList<ImmutableList<HStoreFile>> getStripes();

    /** Returns Stripe count. */
    public int getStripeCount();
  }
}