/*
 * 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.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.phoenix.expression.Expression;
import org.apache.phoenix.expression.aggregator.Aggregator;
import org.apache.phoenix.expression.aggregator.MinAggregator;
import org.apache.phoenix.parse.FunctionParseNode.Argument;
import org.apache.phoenix.parse.FunctionParseNode.BuiltInFunction;
import org.apache.phoenix.parse.MinAggregateParseNode;
import org.apache.phoenix.schema.SortOrder;
import org.apache.phoenix.schema.tuple.Tuple;
import org.apache.phoenix.schema.types.PDataType;

/**
 * Built-in function for finding MIN.
 * @since 0.1
 */
@BuiltInFunction(name = MinAggregateFunction.NAME, nodeClass = MinAggregateParseNode.class,
    args = { @Argument() })
public class MinAggregateFunction extends DelegateConstantToCountAggregateFunction {
  public static final String NAME = "MIN";

  public MinAggregateFunction() {
  }

  public MinAggregateFunction(List<Expression> childExpressions) {
    super(childExpressions, null);
  }

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

  @Override
  public boolean evaluate(Tuple tuple, ImmutableBytesWritable ptr) {
    boolean wasEvaluated = super.evaluate(tuple, ptr);
    if (!wasEvaluated) {
      return false;
    }
    if (isConstantExpression()) {
      getAggregatorExpression().evaluate(tuple, ptr);
    }
    return true;
  }

  @Override
  public Aggregator newServerAggregator(Configuration conf) {
    Expression child = getAggregatorExpression();
    final PDataType type = child.getDataType();
    final Integer maxLength = child.getMaxLength();
    return new MinAggregator(child.getSortOrder()) {
      @Override
      public PDataType getDataType() {
        return type;
      }

      @Override
      public Integer getMaxLength() {
        return maxLength;
      }
    };
  }

  @Override
  public SortOrder getSortOrder() {
    return getAggregatorExpression().getSortOrder();
  }

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