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/**
 * 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 com.datatorrent.lib.streamquery.index;

import java.util.Map;

import javax.validation.constraints.Null;


/**
 * An implementation of Unary Expression that implements filter method using negate metric sql semantic on column value.
 * 
 * @displayName Negate Expression
 * @category Stream Manipulators
 * @tags expression, alias
 * @since 0.3.4
 */
public class NegateExpression extends UnaryExpression
{

  /**
   * @param column   Name of column value to be negated.
   */
  public NegateExpression(@Null String column, String alias)
  {
    super(column, alias);
    if (this.alias == null) {
      this.alias = "NEGATE(" + column + ")";
    }
  }

  /* (non-Javadoc)
   * @see com.datatorrent.lib.streamquery.index.Index#filter(java.util.Map, java.util.Map)
   */
  @Override
  public void filter(Map row, Map collect)
  {
    if (!row.containsKey(column)) {
      return;
    }
    collect.put(alias, -((Number)row.get(column)).doubleValue());
  }
}