content: /**
   * 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.apex.malhar.contrib.misc.streamquery.function;
  
  import java.util.ArrayList;
  import java.util.Map;
  
  import javax.validation.constraints.NotNull;
  
  import org.apache.commons.lang.StringUtils;
  
  /**
   * An implementation of function index that implements sql first,last function semantic. <br>
   * <p>
   *   e.g : sql => SELECT FIRST/LAST(column_name) FROM table_name. <br>
   *   <br>
   *   <b> Properties : </b> <br>
   *   <b> column : </b> column name for first/last value.   <br>
   *   <b> alias  : </b> Alias name for output. <br>
   *   <b> isFirst : </b> return first value if true.
   * @displayName First Last Function
   * @category Stream Manipulators
   * @tags sql first, sql last
   * @since 0.3.4
   * @deprecated
   */
  @Deprecated
  public class FirstLastFunction extends FunctionIndex
  {
    /**
     * return first value if true.
     */
    private boolean isFirst;
  
    /**
     * @param column  column name for first/last value.
     * @param  alias   Alias name for output.
     * @param  isFirst return first value if true.
     */
    public FirstLastFunction(@NotNull String column, String alias, boolean isLast)
    {
      super(column, alias);
      isFirst = !isLast;
    }
  
    /**
     * Get first/last non null value for column.
     */
    @Override
    public Object compute(@NotNull ArrayList<Map<String, Object>> rows) throws Exception
    {
      if (rows.size() == 0) {
        return null;
      }
      if (isFirst) {
        for (int i = 0; i < rows.size(); i++) {
          if (rows.get(i).get(column) != null) {
            return rows.get(i).get(column);
          }
        }
      } else {
        for (int i = (rows.size() - 1); i >= 0; i--) {
          if (rows.get(i).get(column) != null) {
            return rows.get(i).get(column);
          }
        }
      }
      return null;
    }
  
    /**
     * Aggregate output name.
     * @return name string.
     */
    @Override
    protected String aggregateName()
    {
      if (!StringUtils.isEmpty(alias)) {
        return alias;
      }
      if (isFirst) {
        return "FIRST(" + column + ")";
      }
      return "LAST(" + column + ")";
    }
  
    public boolean isFirst()
    {
      return isFirst;
    }
  
    public void setFirst(boolean isFirst)
    {
      this.isFirst = isFirst;
    }
  
  }
  