/**
 * 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.
 **/

#ifndef QUICKSTEP_EXPRESSIONS_AGGREGATION_AGGREGATE_FUNCTION_COUNT_HPP_
#define QUICKSTEP_EXPRESSIONS_AGGREGATION_AGGREGATE_FUNCTION_COUNT_HPP_

#include <string>
#include <vector>

#include "expressions/aggregation/AggregateFunction.hpp"
#include "expressions/aggregation/AggregationID.hpp"
#include "utility/Macros.hpp"

namespace quickstep {

class AggregationHandle;
class Type;

/** \addtogroup Expressions
 *  @{
 */

/**
 * @brief AggregateFunction representing SQL COUNT.
 **/
class AggregateFunctionCount : public AggregateFunction {
 public:
  static const AggregateFunctionCount& Instance() {
    static AggregateFunctionCount instance;
    return instance;
  }

  std::string getName() const override {
    return "COUNT";
  }

  bool canApplyToTypes(
      const std::vector<const Type*> &argument_types) const override;

  const Type* resultTypeForArgumentTypes(
      const std::vector<const Type*> &argument_types) const override;

  AggregationHandle* createHandle(
      const std::vector<const Type*> &argument_types) const override;

 private:
  AggregateFunctionCount()
      : AggregateFunction(AggregationID::kCount) {
  }

  DISALLOW_COPY_AND_ASSIGN(AggregateFunctionCount);
};

/** @} */

}  // namespace quickstep

#endif  // QUICKSTEP_EXPRESSIONS_AGGREGATION_AGGREGATE_FUNCTION_COUNT_HPP_