// Copyright 2023 PingCAP, Inc.
//
// Licensed 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.

#pragma once

#include <AggregateFunctions/IAggregateFunction.h>
#include <Columns/ColumnAggregateFunction.h>
#include <Common/typeid_cast.h>
#include <DataTypes/DataTypeAggregateFunction.h>


namespace DB
{
/** Not an aggregate function, but an adapter of aggregate functions,
  * Aggregate functions with the `Merge` suffix accept `DataTypeAggregateFunction` as an argument
  * (state of the aggregate function obtained earlier using the aggregate function with the `State` suffix)
  * and combine them with aggregation.
  */

class AggregateFunctionMerge final : public IAggregateFunctionHelper<AggregateFunctionMerge>
{
private:
    AggregateFunctionPtr nested_func;

public:
    AggregateFunctionMerge(const AggregateFunctionPtr & nested_, const IDataType & argument)
        : nested_func(nested_)
    {
        const DataTypeAggregateFunction * data_type = typeid_cast<const DataTypeAggregateFunction *>(&argument);

        if (!data_type || data_type->getFunctionName() != nested_func->getName())
            throw Exception(
                "Illegal type " + argument.getName() + " of argument for aggregate function " + getName(),
                ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
    }

    String getName() const override { return nested_func->getName() + "Merge"; }

    DataTypePtr getReturnType() const override { return nested_func->getReturnType(); }

    void create(AggregateDataPtr __restrict place) const override { nested_func->create(place); }

    void destroy(AggregateDataPtr __restrict place) const noexcept override { nested_func->destroy(place); }

    bool hasTrivialDestructor() const override { return nested_func->hasTrivialDestructor(); }

    size_t sizeOfData() const override { return nested_func->sizeOfData(); }

    size_t alignOfData() const override { return nested_func->alignOfData(); }

    void add(AggregateDataPtr __restrict place, const IColumn ** columns, size_t row_num, Arena * arena) const override
    {
        nested_func->merge(place, static_cast<const ColumnAggregateFunction &>(*columns[0]).getData()[row_num], arena);
    }

    void merge(AggregateDataPtr __restrict place, ConstAggregateDataPtr rhs, Arena * arena) const override
    {
        nested_func->merge(place, rhs, arena);
    }

    void serialize(ConstAggregateDataPtr __restrict place, WriteBuffer & buf) const override
    {
        nested_func->serialize(place, buf);
    }

    void deserialize(AggregateDataPtr __restrict place, ReadBuffer & buf, Arena * arena) const override
    {
        nested_func->deserialize(place, buf, arena);
    }

    void insertResultInto(ConstAggregateDataPtr __restrict place, IColumn & to, Arena * arena) const override
    {
        nested_func->insertResultInto(place, to, arena);
    }

    bool allocatesMemoryInArena() const override { return nested_func->allocatesMemoryInArena(); }

    const char * getHeaderFilePath() const override { return __FILE__; }
};

} // namespace DB