/**
    *
    * 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 java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  import java.util.SortedSet;
  import java.util.concurrent.atomic.AtomicLong;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.KeyValueUtil;
  import org.apache.hadoop.hbase.client.Scan;
  import org.apache.hadoop.hbase.io.hfile.HFileScanner;
  import org.apache.hadoop.hbase.regionserver.StoreFile.Reader;
  
  /**
   * KeyValueScanner adaptor over the Reader.  It also provides hooks into
   * bloom filter things.
   */
  @InterfaceAudience.LimitedPrivate("Coprocessor")
  public class StoreFileScanner implements KeyValueScanner {
    static final Log LOG = LogFactory.getLog(HStore.class);
  
    // the reader it comes from:
    private final StoreFile.Reader reader;
    private final HFileScanner hfs;
    private Cell cur = null;
  
    private boolean realSeekDone;
    private boolean delayedReseek;
    private Cell delayedSeekKV;
  
    private boolean enforceMVCC = false;
    private boolean hasMVCCInfo = false;
    // A flag represents whether could stop skipping KeyValues for MVCC
    // if have encountered the next row. Only used for reversed scan
    private boolean stopSkippingKVsIfNextRow = false;
  
    private static AtomicLong seekCount;
  
    private ScanQueryMatcher matcher;
    
    private long readPt;
  
    /**
     * Implements a {@link KeyValueScanner} on top of the specified {@link HFileScanner}
     * @param hfs HFile scanner
     */
    public StoreFileScanner(StoreFile.Reader reader, HFileScanner hfs, boolean useMVCC,
        boolean hasMVCC, long readPt) {
      this.readPt = readPt;
      this.reader = reader;
      this.hfs = hfs;
      this.enforceMVCC = useMVCC;
      this.hasMVCCInfo = hasMVCC;
    }
  
    /**
     * Return an array of scanners corresponding to the given
     * set of store files.
     */
    public static List<StoreFileScanner> getScannersForStoreFiles(
        Collection<StoreFile> files,
        boolean cacheBlocks,
        boolean usePread, long readPt) throws IOException {
      return getScannersForStoreFiles(files, cacheBlocks,
                                     usePread, false, readPt);
    }
  
    /**
     * Return an array of scanners corresponding to the given set of store files.
     */
    public static List<StoreFileScanner> getScannersForStoreFiles(
        Collection<StoreFile> files, boolean cacheBlocks, boolean usePread,
       boolean isCompaction, long readPt) throws IOException {
     return getScannersForStoreFiles(files, cacheBlocks, usePread, isCompaction,
         null, readPt);
   }
 
   /**
    * Return an array of scanners corresponding to the given set of store files,
    * And set the ScanQueryMatcher for each store file scanner for further
    * optimization
    */
   public static List<StoreFileScanner> getScannersForStoreFiles(
       Collection<StoreFile> files, boolean cacheBlocks, boolean usePread,
       boolean isCompaction, ScanQueryMatcher matcher, long readPt) throws IOException {
     List<StoreFileScanner> scanners = new ArrayList<StoreFileScanner>(
         files.size());
     for (StoreFile file : files) {
       StoreFile.Reader r = file.createReader();
       StoreFileScanner scanner = r.getStoreFileScanner(cacheBlocks, usePread,
           isCompaction, readPt);
       scanner.setScanQueryMatcher(matcher);
       scanners.add(scanner);
     }
     return scanners;
   }
 
   public String toString() {
     return "StoreFileScanner[" + hfs.toString() + ", cur=" + cur + "]";
   }
 
   public Cell peek() {
     return cur;
   }
 
   public Cell next() throws IOException {
     Cell retKey = cur;
 
     try {
       // only seek if we aren't at the end. cur == null implies 'end'.
       if (cur != null) {
         hfs.next();
         setCurrentCell(hfs.getKeyValue());
         if (hasMVCCInfo || this.reader.isBulkLoaded()) {
           skipKVsNewerThanReadpoint();
         }
       }
     } catch(IOException e) {
       throw new IOException("Could not iterate " + this, e);
     }
     return retKey;
   }
 
   public boolean seek(Cell key) throws IOException {
     if (seekCount != null) seekCount.incrementAndGet();
 
     try {
       try {
         if(!seekAtOrAfter(hfs, key)) {
           close();
           return false;
         }
 
         setCurrentCell(hfs.getKeyValue());
 
         if (!hasMVCCInfo && this.reader.isBulkLoaded()) {
           return skipKVsNewerThanReadpoint();
         } else {
           return !hasMVCCInfo ? true : skipKVsNewerThanReadpoint();
         }
       } finally {
         realSeekDone = true;
       }
     } catch (IOException ioe) {
       throw new IOException("Could not seek " + this + " to key " + key, ioe);
     }
   }
 
   public boolean reseek(Cell key) throws IOException {
     if (seekCount != null) seekCount.incrementAndGet();
 
     try {
       try {
         if (!reseekAtOrAfter(hfs, key)) {
           close();
           return false;
         }
         setCurrentCell(hfs.getKeyValue());
 
         if (!hasMVCCInfo && this.reader.isBulkLoaded()) {
           return skipKVsNewerThanReadpoint();
         } else {
           return !hasMVCCInfo ? true : skipKVsNewerThanReadpoint();
         }
       } finally {
         realSeekDone = true;
       }
     } catch (IOException ioe) {
       throw new IOException("Could not reseek " + this + " to key " + key,
           ioe);
     }
   }
 
   protected void setCurrentCell(Cell newVal) throws IOException {
     this.cur = newVal;
     if (this.cur != null && this.reader.isBulkLoaded()) {
       CellUtil.setSequenceId(cur, this.reader.getSequenceID());
     }
   }
 
   protected boolean skipKVsNewerThanReadpoint() throws IOException {
     // We want to ignore all key-values that are newer than our current
     // readPoint
     Cell startKV = cur;
     while(enforceMVCC
         && cur != null
         && (cur.getMvccVersion() > readPt)) {
       hfs.next();
       setCurrentCell(hfs.getKeyValue());
       if (this.stopSkippingKVsIfNextRow
           && getComparator().compareRows(cur.getRowArray(), cur.getRowOffset(),
               cur.getRowLength(), startKV.getRowArray(), startKV.getRowOffset(),
               startKV.getRowLength()) > 0) {
         return false;
       }
     }
 
     if (cur == null) {
       close();
       return false;
     }
 
     return true;
   }
 
   public void close() {
     // Nothing to close on HFileScanner?
     cur = null;
   }
 
   /**
    *
    * @param s
    * @param k
    * @return false if not found or if k is after the end.
    * @throws IOException
    */
   public static boolean seekAtOrAfter(HFileScanner s, Cell k)
   throws IOException {
     int result = s.seekTo(k);
     if(result < 0) {
       if (result == HConstants.INDEX_KEY_MAGIC) {
         // using faked key
         return true;
       }
       // Passed KV is smaller than first KV in file, work from start of file
       return s.seekTo();
     } else if(result > 0) {
       // Passed KV is larger than current KV in file, if there is a next
       // it is the "after", if not then this scanner is done.
       return s.next();
     }
     // Seeked to the exact key
     return true;
   }
 
   static boolean reseekAtOrAfter(HFileScanner s, Cell k)
   throws IOException {
     //This function is similar to seekAtOrAfter function
     int result = s.reseekTo(k);
     if (result <= 0) {
       if (result == HConstants.INDEX_KEY_MAGIC) {
         // using faked key
         return true;
       }
       // If up to now scanner is not seeked yet, this means passed KV is smaller
       // than first KV in file, and it is the first time we seek on this file.
       // So we also need to work from the start of file.
       if (!s.isSeeked()) {
         return  s.seekTo();
       }
       return true;
     }
     // passed KV is larger than current KV in file, if there is a next
     // it is after, if not then this scanner is done.
     return s.next();
   }
 
   @Override
   public long getSequenceID() {
     return reader.getSequenceID();
   }
 
   /**
    * Pretend we have done a seek but don't do it yet, if possible. The hope is
    * that we find requested columns in more recent files and won't have to seek
    * in older files. Creates a fake key/value with the given row/column and the
    * highest (most recent) possible timestamp we might get from this file. When
    * users of such "lazy scanner" need to know the next KV precisely (e.g. when
    * this scanner is at the top of the heap), they run {@link #enforceSeek()}.
    * <p>
    * Note that this function does guarantee that the current KV of this scanner
    * will be advanced to at least the given KV. Because of this, it does have
    * to do a real seek in cases when the seek timestamp is older than the
    * highest timestamp of the file, e.g. when we are trying to seek to the next
    * row/column and use OLDEST_TIMESTAMP in the seek key.
    */
   @Override
   public boolean requestSeek(Cell kv, boolean forward, boolean useBloom)
       throws IOException {
     if (kv.getFamilyLength() == 0) {
       useBloom = false;
     }
 
     boolean haveToSeek = true;
     if (useBloom) {
       // check ROWCOL Bloom filter first.
       if (reader.getBloomFilterType() == BloomType.ROWCOL) {
         haveToSeek = reader.passesGeneralBloomFilter(kv.getRowArray(),
             kv.getRowOffset(), kv.getRowLength(), kv.getQualifierArray(),
             kv.getQualifierOffset(), kv.getQualifierLength());
       } else if (this.matcher != null && !matcher.hasNullColumnInQuery() &&
           ((CellUtil.isDeleteFamily(kv) || CellUtil.isDeleteFamilyVersion(kv)))) {
         // if there is no such delete family kv in the store file,
         // then no need to seek.
         haveToSeek = reader.passesDeleteFamilyBloomFilter(kv.getRowArray(),
             kv.getRowOffset(), kv.getRowLength());
       }
     }
 
     delayedReseek = forward;
     delayedSeekKV = kv;
 
     if (haveToSeek) {
       // This row/column might be in this store file (or we did not use the
       // Bloom filter), so we still need to seek.
       realSeekDone = false;
       long maxTimestampInFile = reader.getMaxTimestamp();
       long seekTimestamp = kv.getTimestamp();
       if (seekTimestamp > maxTimestampInFile) {
         // Create a fake key that is not greater than the real next key.
         // (Lower timestamps correspond to higher KVs.)
         // To understand this better, consider that we are asked to seek to
         // a higher timestamp than the max timestamp in this file. We know that
         // the next point when we have to consider this file again is when we
         // pass the max timestamp of this file (with the same row/column).
         setCurrentCell(KeyValueUtil.createFirstOnRowColTS(kv, maxTimestampInFile));
       } else {
         // This will be the case e.g. when we need to seek to the next
         // row/column, and we don't know exactly what they are, so we set the
         // seek key's timestamp to OLDEST_TIMESTAMP to skip the rest of this
         // row/column.
         enforceSeek();
       }
       return cur != null;
     }
 
     // Multi-column Bloom filter optimization.
     // Create a fake key/value, so that this scanner only bubbles up to the top
     // of the KeyValueHeap in StoreScanner after we scanned this row/column in
     // all other store files. The query matcher will then just skip this fake
     // key/value and the store scanner will progress to the next column. This
     // is obviously not a "real real" seek, but unlike the fake KV earlier in
     // this method, we want this to be propagated to ScanQueryMatcher.
     setCurrentCell(KeyValueUtil.createLastOnRowCol(kv));
 
     realSeekDone = true;
     return true;
   }
 
   Reader getReader() {
     return reader;
   }
 
   KeyValue.KVComparator getComparator() {
     return reader.getComparator();
   }
 
   @Override
   public boolean realSeekDone() {
     return realSeekDone;
   }
 
   @Override
   public void enforceSeek() throws IOException {
     if (realSeekDone)
       return;
 
     if (delayedReseek) {
       reseek(delayedSeekKV);
     } else {
       seek(delayedSeekKV);
     }
   }
 
   public void setScanQueryMatcher(ScanQueryMatcher matcher) {
     this.matcher = matcher;
   }
 
   @Override
   public boolean isFileScanner() {
     return true;
   }
 
   // Test methods
 
   static final long getSeekCount() {
     return seekCount.get();
   }
   static final void instrument() {
     seekCount = new AtomicLong();
   }
 
   @Override
   public boolean shouldUseScanner(Scan scan, SortedSet<byte[]> columns, long oldestUnexpiredTS) {
     return reader.passesTimerangeFilter(scan, oldestUnexpiredTS)
         && reader.passesKeyRangeFilter(scan) && reader.passesBloomFilter(scan, columns);
   }
 
   @Override
   @SuppressWarnings("deprecation")
   public boolean seekToPreviousRow(Cell key) throws IOException {
     try {
       try {
         KeyValue seekKey = KeyValueUtil.createFirstOnRow(key.getRowArray(), key.getRowOffset(),
             key.getRowLength());
         if (seekCount != null) seekCount.incrementAndGet();
         if (!hfs.seekBefore(seekKey.getBuffer(), seekKey.getKeyOffset(),
             seekKey.getKeyLength())) {
           close();
           return false;
         }
         KeyValue firstKeyOfPreviousRow = KeyValueUtil.createFirstOnRow(hfs.getKeyValue()
             .getRowArray(), hfs.getKeyValue().getRowOffset(), hfs.getKeyValue().getRowLength());
 
         if (seekCount != null) seekCount.incrementAndGet();
         if (!seekAtOrAfter(hfs, firstKeyOfPreviousRow)) {
           close();
           return false;
         }
 
         setCurrentCell(hfs.getKeyValue());
         this.stopSkippingKVsIfNextRow = true;
         boolean resultOfSkipKVs;
         try {
           resultOfSkipKVs = skipKVsNewerThanReadpoint();
         } finally {
           this.stopSkippingKVsIfNextRow = false;
         }
         if (!resultOfSkipKVs
             || getComparator().compareRows(cur, firstKeyOfPreviousRow) > 0) {
           return seekToPreviousRow(firstKeyOfPreviousRow);
         }
 
         return true;
       } finally {
         realSeekDone = true;
       }
     } catch (IOException ioe) {
       throw new IOException("Could not seekToPreviousRow " + this + " to key "
           + key, ioe);
     }
   }
 
   @Override
   public boolean seekToLastRow() throws IOException {
     byte[] lastRow = reader.getLastRowKey();
     if (lastRow == null) {
       return false;
     }
     KeyValue seekKey = KeyValueUtil.createFirstOnRow(lastRow);
     if (seek(seekKey)) {
       return true;
     } else {
       return seekToPreviousRow(seekKey);
     }
   }
 
   @Override
   public boolean backwardSeek(Cell key) throws IOException {
     seek(key);
     if (cur == null
         || getComparator().compareRows(cur.getRowArray(), cur.getRowOffset(),
             cur.getRowLength(), key.getRowArray(), key.getRowOffset(),
             key.getRowLength()) > 0) {
       return seekToPreviousRow(key);
     }
     return true;
   }
 
   @Override
   public Cell getNextIndexedKey() {
     return hfs.getNextIndexedKey();
   }
 }