/*
    * 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;
  
  import java.io.Serializable;
  import java.util.Comparator;
  
  import org.apache.hadoop.hbase.KeyValue.Type;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.util.Bytes;
  
  import com.google.common.primitives.Longs;
  
  /**
   * Compare two HBase cells.  Do not use this method comparing <code>-ROOT-</code> or
   * <code>hbase:meta</code> cells.  Cells from these tables need a specialized comparator, one that
   * takes account of the special formatting of the row where we have commas to delimit table from
   * regionname, from row.  See KeyValue for how it has a special comparator to do hbase:meta cells
   * and yet another for -ROOT-.
   */
  @edu.umd.cs.findbugs.annotations.SuppressWarnings(
      value="UNKNOWN",
      justification="Findbugs doesn't like the way we are negating the result of a compare in below")
  @InterfaceAudience.Private
  @InterfaceStability.Evolving
  public class CellComparator implements Comparator<Cell>, Serializable {
    private static final long serialVersionUID = -8760041766259623329L;
  
    @Override
    public int compare(Cell a, Cell b) {
      return compare(a, b, false);
    }
  
    /**
     * Compare cells.
     * TODO: Replace with dynamic rather than static comparator so can change comparator
     * implementation.
     * @param a
     * @param b
     * @param ignoreSequenceid True if we are to compare the key portion only and ignore
     * the sequenceid. Set to false to compare key and consider sequenceid.
     * @return 0 if equal, -1 if a < b, and +1 if a > b.
     */
    public static int compare(final Cell a, final Cell b, boolean ignoreSequenceid) {
      // row
      int c = compareRows(a, b);
      if (c != 0) return c;
  
      c = compareWithoutRow(a, b);
      if(c != 0) return c;
  
      if (!ignoreSequenceid) {
        // Negate following comparisons so later edits show up first
        // mvccVersion: later sorts first
        return Longs.compare(b.getMvccVersion(), a.getMvccVersion());
      } else {
        return c;
      }
    }
  
    public static int findCommonPrefixInRowPart(Cell left, Cell right, int rowCommonPrefix) {
      return findCommonPrefix(left.getRowArray(), right.getRowArray(), left.getRowLength()
          - rowCommonPrefix, right.getRowLength() - rowCommonPrefix, left.getRowOffset()
          + rowCommonPrefix, right.getRowOffset() + rowCommonPrefix);
    }
  
    private static int findCommonPrefix(byte[] left, byte[] right, int leftLength, int rightLength,
        int leftOffset, int rightOffset) {
      int length = Math.min(leftLength, rightLength);
      int result = 0;
  
      while (result < length && left[leftOffset + result] == right[rightOffset + result]) {
        result++;
      }
      return result;
    }
  
    public static int findCommonPrefixInFamilyPart(Cell left, Cell right, int familyCommonPrefix) {
      return findCommonPrefix(left.getFamilyArray(), right.getFamilyArray(), left.getFamilyLength()
          - familyCommonPrefix, right.getFamilyLength() - familyCommonPrefix, left.getFamilyOffset()
          + familyCommonPrefix, right.getFamilyOffset() + familyCommonPrefix);
    }
 
   public static int findCommonPrefixInQualifierPart(Cell left, Cell right,
       int qualifierCommonPrefix) {
     return findCommonPrefix(left.getQualifierArray(), right.getQualifierArray(),
         left.getQualifierLength() - qualifierCommonPrefix, right.getQualifierLength()
             - qualifierCommonPrefix, left.getQualifierOffset() + qualifierCommonPrefix,
         right.getQualifierOffset() + qualifierCommonPrefix);
   }
 
   /**************** equals ****************************/
 
   public static boolean equals(Cell a, Cell b){
     return equalsRow(a, b)
         && equalsFamily(a, b)
         && equalsQualifier(a, b)
         && equalsTimestamp(a, b)
         && equalsType(a, b);
   }
 
   public static boolean equalsRow(Cell a, Cell b){
     return Bytes.equals(
       a.getRowArray(), a.getRowOffset(), a.getRowLength(),
       b.getRowArray(), b.getRowOffset(), b.getRowLength());
   }
 
   public static boolean equalsFamily(Cell a, Cell b){
     return Bytes.equals(
       a.getFamilyArray(), a.getFamilyOffset(), a.getFamilyLength(),
       b.getFamilyArray(), b.getFamilyOffset(), b.getFamilyLength());
   }
 
   public static boolean equalsQualifier(Cell a, Cell b){
     return Bytes.equals(
       a.getQualifierArray(), a.getQualifierOffset(), a.getQualifierLength(),
       b.getQualifierArray(), b.getQualifierOffset(), b.getQualifierLength());
   }
 
   public static boolean equalsTimestamp(Cell a, Cell b){
     return a.getTimestamp() == b.getTimestamp();
   }
 
   public static boolean equalsType(Cell a, Cell b){
     return a.getTypeByte() == b.getTypeByte();
   }
 
   public static int compareColumns(final Cell left, final Cell right) {
     int lfoffset = left.getFamilyOffset();
     int rfoffset = right.getFamilyOffset();
     int lclength = left.getQualifierLength();
     int rclength = right.getQualifierLength();
     int lfamilylength = left.getFamilyLength();
     int rfamilylength = right.getFamilyLength();
     int diff = compare(left.getFamilyArray(), lfoffset, lfamilylength, right.getFamilyArray(),
         rfoffset, rfamilylength);
     if (diff != 0) {
       return diff;
     } else {
       return compare(left.getQualifierArray(), left.getQualifierOffset(), lclength,
           right.getQualifierArray(), right.getQualifierOffset(), rclength);
     }
   }
 
   public static int compareFamilies(Cell left, Cell right) {
     return Bytes.compareTo(left.getFamilyArray(), left.getFamilyOffset(), left.getFamilyLength(),
         right.getFamilyArray(), right.getFamilyOffset(), right.getFamilyLength());
   }
 
   public static int compareQualifiers(Cell left, Cell right) {
     return Bytes.compareTo(left.getQualifierArray(), left.getQualifierOffset(),
         left.getQualifierLength(), right.getQualifierArray(), right.getQualifierOffset(),
         right.getQualifierLength());
   }
 
   public int compareFlatKey(Cell left, Cell right) {
     int compare = compareRows(left, right);
     if (compare != 0) {
       return compare;
     }
     return compareWithoutRow(left, right);
   }
 
   /**
    * Do not use comparing rows from hbase:meta. Meta table Cells have schema (table,startrow,hash)
    * so can't be treated as plain byte arrays as this method does.
    */
   public static int compareRows(final Cell left, final Cell right) {
     return Bytes.compareTo(left.getRowArray(), left.getRowOffset(), left.getRowLength(),
         right.getRowArray(), right.getRowOffset(), right.getRowLength());
   }
 
   /**
    * Do not use comparing rows from hbase:meta. Meta table Cells have schema (table,startrow,hash)
    * so can't be treated as plain byte arrays as this method does.
    */
   public static int compareRows(byte[] left, int loffset, int llength, byte[] right, int roffset,
       int rlength) {
     return Bytes.compareTo(left, loffset, llength, right, roffset, rlength);
   }
 
   public static int compareWithoutRow(final Cell leftCell, final Cell rightCell) {
     // If the column is not specified, the "minimum" key type appears the
     // latest in the sorted order, regardless of the timestamp. This is used
     // for specifying the last key/value in a given row, because there is no
     // "lexicographically last column" (it would be infinitely long). The
     // "maximum" key type does not need this behavior.
     // Copied from KeyValue. This is bad in that we can't do memcmp w/ special rules like this.
     // TODO
     if (leftCell.getFamilyLength() + leftCell.getQualifierLength() == 0
           && leftCell.getTypeByte() == Type.Minimum.getCode()) {
       // left is "bigger", i.e. it appears later in the sorted order
       return 1;
     }
     if (rightCell.getFamilyLength() + rightCell.getQualifierLength() == 0
         && rightCell.getTypeByte() == Type.Minimum.getCode()) {
       return -1;
     }
     boolean sameFamilySize = (leftCell.getFamilyLength() == rightCell.getFamilyLength());
     if (!sameFamilySize) {
       // comparing column family is enough.
 
       return Bytes.compareTo(leftCell.getFamilyArray(), leftCell.getFamilyOffset(),
           leftCell.getFamilyLength(), rightCell.getFamilyArray(), rightCell.getFamilyOffset(),
           rightCell.getFamilyLength());
     }
     int diff = compareColumns(leftCell, rightCell);
     if (diff != 0) return diff;
 
     diff = compareTimestamps(leftCell, rightCell);
     if (diff != 0) return diff;
 
     // Compare types. Let the delete types sort ahead of puts; i.e. types
     // of higher numbers sort before those of lesser numbers. Maximum (255)
     // appears ahead of everything, and minimum (0) appears after
     // everything.
     return (0xff & rightCell.getTypeByte()) - (0xff & leftCell.getTypeByte());
   }
 
   public static int compareTimestamps(final Cell left, final Cell right) {
     long ltimestamp = left.getTimestamp();
     long rtimestamp = right.getTimestamp();
     return compareTimestamps(ltimestamp, rtimestamp);
   }
 
   /********************* hashCode ************************/
 
   /**
    * Returns a hash code that is always the same for two Cells having a matching equals(..) result.
    */
   public static int hashCode(Cell cell){
     if (cell == null) {// return 0 for empty Cell
       return 0;
     }
 
     int hash = calculateHashForKeyValue(cell);
     hash = 31 * hash + (int)cell.getMvccVersion();
     return hash;
   }
 
   /**
    * Returns a hash code that is always the same for two Cells having a matching
    * equals(..) result. Note : Ignore mvcc while calculating the hashcode
    * 
    * @param cell
    * @return hashCode
    */
   public static int hashCodeIgnoreMvcc(Cell cell) {
     if (cell == null) {// return 0 for empty Cell
       return 0;
     }
 
     int hash = calculateHashForKeyValue(cell);
     return hash;
   }
 
   private static int calculateHashForKeyValue(Cell cell) {
     //pre-calculate the 3 hashes made of byte ranges
     int rowHash = Bytes.hashCode(cell.getRowArray(), cell.getRowOffset(), cell.getRowLength());
     int familyHash =
       Bytes.hashCode(cell.getFamilyArray(), cell.getFamilyOffset(), cell.getFamilyLength());
     int qualifierHash = Bytes.hashCode(cell.getQualifierArray(), cell.getQualifierOffset(),
       cell.getQualifierLength());
 
     //combine the 6 sub-hashes
     int hash = 31 * rowHash + familyHash;
     hash = 31 * hash + qualifierHash;
     hash = 31 * hash + (int)cell.getTimestamp();
     hash = 31 * hash + cell.getTypeByte();
     return hash;
   }
 
 
   /******************** lengths *************************/
 
   public static boolean areKeyLengthsEqual(Cell a, Cell b) {
     return a.getRowLength() == b.getRowLength()
         && a.getFamilyLength() == b.getFamilyLength()
         && a.getQualifierLength() == b.getQualifierLength();
   }
 
   public static boolean areRowLengthsEqual(Cell a, Cell b) {
     return a.getRowLength() == b.getRowLength();
   }
 
 
   /*********************common prefixes*************************/
 
   private static int compare(byte[] left, int leftOffset, int leftLength, byte[] right,
       int rightOffset, int rightLength) {
     return Bytes.compareTo(left, leftOffset, leftLength, right, rightOffset, rightLength);
   }
 
   public static int compareCommonRowPrefix(Cell left, Cell right, int rowCommonPrefix) {
     return compare(left.getRowArray(), left.getRowOffset() + rowCommonPrefix, left.getRowLength()
         - rowCommonPrefix, right.getRowArray(), right.getRowOffset() + rowCommonPrefix,
         right.getRowLength() - rowCommonPrefix);
   }
 
   public static int compareCommonFamilyPrefix(Cell left, Cell right,
       int familyCommonPrefix) {
     return compare(left.getFamilyArray(), left.getFamilyOffset() + familyCommonPrefix,
         left.getFamilyLength() - familyCommonPrefix, right.getFamilyArray(),
         right.getFamilyOffset() + familyCommonPrefix,
         right.getFamilyLength() - familyCommonPrefix);
   }
 
   public static int compareCommonQualifierPrefix(Cell left, Cell right,
       int qualCommonPrefix) {
     return compare(left.getQualifierArray(), left.getQualifierOffset() + qualCommonPrefix,
         left.getQualifierLength() - qualCommonPrefix, right.getQualifierArray(),
         right.getQualifierOffset() + qualCommonPrefix, right.getQualifierLength()
             - qualCommonPrefix);
   }
 
   /***************** special cases ****************************/
   /**
    * special case for KeyValue.equals
    */
   public static boolean equalsIgnoreMvccVersion(Cell a, Cell b){
     return 0 == compareStaticIgnoreMvccVersion(a, b);
   }
 
   private static int compareStaticIgnoreMvccVersion(Cell a, Cell b) {
     // row
     int c = compareRows(a, b);
     if (c != 0) return c;
 
     // family
     c = compareColumns(a, b);
     if (c != 0) return c;
 
     // timestamp: later sorts first
     c = compareTimestamps(a, b);
     if (c != 0) return c;
 
     //type
     c = (0xff & b.getTypeByte()) - (0xff & a.getTypeByte());
     return c;
   }
 
   private static int compareTimestamps(final long ltimestamp, final long rtimestamp) {
     // The below older timestamps sorting ahead of newer timestamps looks
     // wrong but it is intentional. This way, newer timestamps are first
     // found when we iterate over a memstore and newer versions are the
     // first we trip over when reading from a store file.
     if (ltimestamp < rtimestamp) {
       return 1;
     } else if (ltimestamp > rtimestamp) {
       return -1;
     }
     return 0;
   }
 
   /**
    * Counter part for the KeyValue.RowOnlyComparator
    */
   public static class RowComparator extends CellComparator {
     @Override
     public int compare(Cell a, Cell b) {
       return compareRows(a, b);
     }
   }
 
   /**
    * Try to return a Cell that falls between <code>left</code> and <code>right</code> but that is
    * shorter; i.e. takes up less space. This trick is used building HFile block index.
    * Its an optimization. It does not always work.  In this case we'll just return the
    * <code>right</code> cell.
    * @param comparator Comparator to use.
    * @param left
    * @param right
    * @return A cell that sorts between <code>left</code> and <code>right</code>.
    */
   public static Cell getMidpoint(final KeyValue.KVComparator comparator, final Cell left,
       final Cell right) {
     // TODO: Redo so only a single pass over the arrays rather than one to compare and then a
     // second composing midpoint.
     if (right == null) {
       throw new IllegalArgumentException("right cell can not be null");
     }
     if (left == null) {
       return right;
     }
     // If Cells from meta table, don't mess around. meta table Cells have schema
     // (table,startrow,hash) so can't be treated as plain byte arrays. Just skip out without
     // trying to do this optimization.
     if (comparator != null && comparator instanceof KeyValue.MetaComparator) {
       return right;
     }
     int diff = compareRows(left, right);
     if (diff > 0) {
       throw new IllegalArgumentException("Left row sorts after right row; left=" +
         CellUtil.getCellKeyAsString(left) + ", right=" + CellUtil.getCellKeyAsString(right));
     }
     if (diff < 0) {
       // Left row is < right row.
       byte [] midRow = getMinimumMidpointArray(left.getRowArray(), left.getRowOffset(),
           left.getRowLength(),
         right.getRowArray(), right.getRowOffset(), right.getRowLength());
       // If midRow is null, just return 'right'.  Can't do optimization.
       if (midRow == null) return right;
       return CellUtil.createCell(midRow);
     }
     // Rows are same. Compare on families.
     diff = compareFamilies(left, right);
     if (diff > 0) {
       throw new IllegalArgumentException("Left family sorts after right family; left=" +
           CellUtil.getCellKeyAsString(left) + ", right=" + CellUtil.getCellKeyAsString(right));
     }
     if (diff < 0) {
       byte [] midRow = getMinimumMidpointArray(left.getFamilyArray(), left.getFamilyOffset(),
           left.getFamilyLength(),
         right.getFamilyArray(), right.getFamilyOffset(), right.getFamilyLength());
       // If midRow is null, just return 'right'.  Can't do optimization.
       if (midRow == null) return right;
       // Return new Cell where we use right row and then a mid sort family.
       return CellUtil.createCell(right.getRowArray(), right.getRowOffset(), right.getRowLength(),
         midRow, 0, midRow.length, HConstants.EMPTY_BYTE_ARRAY, 0,
         HConstants.EMPTY_BYTE_ARRAY.length);
     }
     // Families are same. Compare on qualifiers.
     diff = compareQualifiers(left, right);
     if (diff > 0) {
       throw new IllegalArgumentException("Left qualifier sorts after right qualifier; left=" +
           CellUtil.getCellKeyAsString(left) + ", right=" + CellUtil.getCellKeyAsString(right));
     }
     if (diff < 0) {
       byte [] midRow = getMinimumMidpointArray(left.getQualifierArray(), left.getQualifierOffset(),
           left.getQualifierLength(),
         right.getQualifierArray(), right.getQualifierOffset(), right.getQualifierLength());
       // If midRow is null, just return 'right'.  Can't do optimization.
       if (midRow == null) return right;
       // Return new Cell where we use right row and family and then a mid sort qualifier.
       return CellUtil.createCell(right.getRowArray(), right.getRowOffset(), right.getRowLength(),
         right.getFamilyArray(), right.getFamilyOffset(), right.getFamilyLength(),
         midRow, 0, midRow.length);
     }
     // No opportunity for optimization. Just return right key.
     return right;
   }
 
   /**
    * @param leftArray
    * @param leftOffset
    * @param leftLength
    * @param rightArray
    * @param rightOffset
    * @param rightLength
    * @return Return a new array that is between left and right and minimally sized else just return
    * null as indicator that we could not create a mid point.
    */
   private static byte [] getMinimumMidpointArray(final byte [] leftArray, final int leftOffset,
         final int leftLength,
       final byte [] rightArray, final int rightOffset, final int rightLength) {
     // rows are different
     int minLength = leftLength < rightLength ? leftLength : rightLength;
     int diffIdx = 0;
     while (diffIdx < minLength &&
         leftArray[leftOffset + diffIdx] == rightArray[rightOffset + diffIdx]) {
       diffIdx++;
     }
     byte [] minimumMidpointArray = null;
     if (diffIdx >= minLength) {
       // leftKey's row is prefix of rightKey's.
       minimumMidpointArray = new byte[diffIdx + 1];
       System.arraycopy(rightArray, rightOffset, minimumMidpointArray, 0, diffIdx + 1);
     } else {
       int diffByte = leftArray[leftOffset + diffIdx];
       if ((0xff & diffByte) < 0xff && (diffByte + 1) < (rightArray[rightOffset + diffIdx] & 0xff)) {
         minimumMidpointArray = new byte[diffIdx + 1];
         System.arraycopy(leftArray, leftOffset, minimumMidpointArray, 0, diffIdx);
         minimumMidpointArray[diffIdx] = (byte) (diffByte + 1);
       } else {
         minimumMidpointArray = new byte[diffIdx + 1];
         System.arraycopy(rightArray, rightOffset, minimumMidpointArray, 0, diffIdx + 1);
       }
     }
     return minimumMidpointArray;
   }
 }