/*
 * 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.phoenix.expression.function;

import java.util.List;
import org.apache.hadoop.conf.Configuration;
import org.apache.phoenix.expression.Expression;
import org.apache.phoenix.expression.LiteralExpression;
import org.apache.phoenix.expression.aggregator.Aggregator;
import org.apache.phoenix.expression.aggregator.FirstLastValueBaseClientAggregator;
import org.apache.phoenix.expression.aggregator.FirstLastValueServerAggregator;
import org.apache.phoenix.parse.FirstValueAggregateParseNode;
import org.apache.phoenix.parse.FunctionParseNode;
import org.apache.phoenix.schema.types.PBoolean;

/**
 * Built-in function for
 * {@code FIRST_VALUE(<expression>) WITHIN GROUP (ORDER BY <expression> ASC/DESC) aggregate }
 * function
 */
@FunctionParseNode.BuiltInFunction(name = FirstValueFunction.NAME,
    nodeClass = FirstValueAggregateParseNode.class,
    args = { @FunctionParseNode.Argument(),
      @FunctionParseNode.Argument(allowedTypes = { PBoolean.class }, isConstant = true),
      @FunctionParseNode.Argument() })
public class FirstValueFunction extends FirstLastValueBaseFunction {

  public static final String NAME = "FIRST_VALUE";

  public FirstValueFunction() {
  }

  public FirstValueFunction(List<Expression> childExpressions) {
    this(childExpressions, null);
  }

  public FirstValueFunction(List<Expression> childExpressions, CountAggregateFunction delegate) {
    super(childExpressions, delegate);
  }

  @Override
  public Aggregator newServerAggregator(Configuration conf) {
    FirstLastValueServerAggregator aggregator = new FirstLastValueServerAggregator();

    boolean order = (Boolean) ((LiteralExpression) children.get(1)).getValue();
    aggregator.init(children, order, 0);

    return aggregator;
  }

  @Override
  public Aggregator newClientAggregator() {
    FirstLastValueBaseClientAggregator aggregator = new FirstLastValueBaseClientAggregator();
    aggregator.init(0, false);

    return aggregator;
  }

  @Override
  public String getName() {
    return NAME;
  }
}
