/**
    * 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.client;
  
  import static org.apache.hadoop.hbase.client.ConnectionUtils.filterCells;
  
  import java.io.IOException;
  import java.util.List;
  
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  
  /**
   * A ScanResultCache that may return partial result.
   * <p>
   * As we can only scan from the starting of a row when error, so here we also implement the logic
   * that skips the cells that have already been returned.
   */
  @InterfaceAudience.Private
  class AllowPartialScanResultCache extends ScanResultCache {
  
    // used to filter out the cells that already returned to user as we always start from the
    // beginning of a row when retry.
    private Cell lastCell;
  
    private boolean lastResultPartial;
  
    public AllowPartialScanResultCache(List<Result> cache) {
      super(cache);
    }
  
    private void recordLastResult(Result result) {
      lastCell = result.rawCells()[result.rawCells().length - 1];
      lastResultPartial = result.mayHaveMoreCellsInRow();
    }
  
    @Override
    public void loadResultsToCache(Result[] results, boolean isHeartbeatMessage) throws IOException {
      if (results.length == 0) {
        if (!isHeartbeatMessage && lastResultPartial) {
          // An empty non heartbeat result indicate that there must be a row change. So if the
          // lastResultPartial is true then we need to increase numberOfCompleteRows.
          numberOfCompleteRows++;
        }
        return;
      }
      int i;
      for (i = 0; i < results.length; i++) {
        Result r = filterCells(results[i], lastCell);
        if (r != null) {
          results[i] = r;
          break;
        }
      }
      if (i == results.length) {
        return;
      }
      if (lastResultPartial && !CellUtil.matchingRow(lastCell, results[0].getRow())) {
        // there is a row change, so increase numberOfCompleteRows
        numberOfCompleteRows++;
      }
      recordLastResult(results[results.length - 1]);
      addResultArrayToCache(results, i, results.length);
    }
  
    @Override
    protected void checkUpdateNumberOfCompleteRowsAndCache(Result rs) {
      if (!rs.mayHaveMoreCellsInRow()) {
        numberOfCompleteRows++;
      }
      addResultToCache(rs);
    }
  
    @Override
    public void clear() {
      // we do not cache anything
      super.clear();
    }
  }