/**
    * 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.security.visibility;
  
  import java.io.IOException;
  import java.util.Map;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.filter.FilterBase;
  import org.apache.hadoop.hbase.util.ByteRange;
  import org.apache.hadoop.hbase.util.SimpleMutableByteRange;
  
  /**
   * This Filter checks the visibility expression with each KV against visibility labels associated
   * with the scan. Based on the check the KV is included in the scan result or gets filtered out.
   */
  @InterfaceAudience.Private
  class VisibilityLabelFilter extends FilterBase {
  
    private final VisibilityExpEvaluator expEvaluator;
    private final Map<ByteRange, Integer> cfVsMaxVersions;
    private final ByteRange curFamily;
    private final ByteRange curQualifier;
    private int curFamilyMaxVersions;
    private int curQualMetVersions;
  
    public VisibilityLabelFilter(VisibilityExpEvaluator expEvaluator,
        Map<ByteRange, Integer> cfVsMaxVersions) {
      this.expEvaluator = expEvaluator;
      this.cfVsMaxVersions = cfVsMaxVersions;
      this.curFamily = new SimpleMutableByteRange();
      this.curQualifier = new SimpleMutableByteRange();
    }
  
    @Override
    public boolean filterRowKey(Cell cell) throws IOException {
      // Impl in FilterBase might do unnecessary copy for Off heap backed Cells.
      return false;
    }
  
    @Override
    public ReturnCode filterKeyValue(Cell cell) throws IOException {
      if (curFamily.getBytes() == null
          || !(CellUtil.matchingFamily(cell, curFamily.getBytes(), curFamily.getOffset(),
              curFamily.getLength()))) {
        curFamily.set(cell.getFamilyArray(), cell.getFamilyOffset(), cell.getFamilyLength());
        // For this family, all the columns can have max of curFamilyMaxVersions versions. No need to
        // consider the older versions for visibility label check.
        // Ideally this should have been done at a lower layer by HBase (?)
        curFamilyMaxVersions = cfVsMaxVersions.get(curFamily);
        // Family is changed. Just unset curQualifier.
        curQualifier.unset();
      }
      if (curQualifier.getBytes() == null
          || !(CellUtil.matchingQualifier(cell, curQualifier.getBytes(), curQualifier.getOffset(),
              curQualifier.getLength()))) {
        curQualifier.set(cell.getQualifierArray(), cell.getQualifierOffset(),
            cell.getQualifierLength());
        curQualMetVersions = 0;
      }
      curQualMetVersions++;
      if (curQualMetVersions > curFamilyMaxVersions) {
        return ReturnCode.SKIP;
      }
  
      return this.expEvaluator.evaluate(cell) ? ReturnCode.INCLUDE : ReturnCode.SKIP;
    }
  
    @Override
    public void reset() throws IOException {
      this.curFamily.unset();
      this.curQualifier.unset();
      this.curFamilyMaxVersions = 0;
      this.curQualMetVersions = 0;
    }
  }