// 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.

// This file is copied from

// https://github.com/ClickHouse/ClickHouse/blob/master/src/Functions/Nullif.cpp

// and modified by Doris

#include <glog/logging.h>

#include <stddef.h>

#include <algorithm>

#include <boost/iterator/iterator_facade.hpp>

#include <memory>

#include <vector>

#include "common/status.h"

#include "vec/aggregate_functions/aggregate_function.h"

#include "vec/columns/column.h"

#include "vec/columns/column_const.h"

#include "vec/common/assert_cast.h"

#include "vec/core/block.h"

#include "vec/core/column_numbers.h"

#include "vec/core/column_with_type_and_name.h"

#include "vec/core/columns_with_type_and_name.h"

#include "vec/core/types.h"

#include "vec/data_types/data_type.h"

#include "vec/data_types/data_type_nothing.h"

#include "vec/data_types/data_type_nullable.h"

#include "vec/data_types/data_type_number.h"

#include "vec/functions/function.h"

#include "vec/functions/simple_function_factory.h"

namespace doris {

class FunctionContext;

} // namespace doris

namespace doris::vectorized {

class FunctionNullIf : public IFunction {

public:

    struct NullPresence {

        bool has_nullable = false;

        bool has_null_constant = false;

    };

    static constexpr auto name = "nullif";

    static FunctionPtr create() { return std::make_shared<FunctionNullIf>(); }

    String get_name() const override { return name; }

    size_t get_number_of_arguments() const override { return 2; }

    bool use_default_implementation_for_nulls() const override { return false; }

    DataTypePtr get_return_type_impl(const DataTypes& arguments) const override {

        return make_nullable(arguments[0]);

    }

    NullPresence get_null_resense(const ColumnsWithTypeAndName& args) const {

        NullPresence res;

        for (const auto& elem : args) {

            if (!res.has_nullable) res.has_nullable = elem.type->is_nullable();

            if (!res.has_null_constant) res.has_null_constant = elem.type->only_null();

        }

        return res;

    }

    DataTypePtr get_return_type_for_equal(const ColumnsWithTypeAndName& arguments) const {

        ColumnsWithTypeAndName args_without_low_cardinality(arguments);

        for (ColumnWithTypeAndName& arg : args_without_low_cardinality) {

            bool is_const = arg.column && is_column_const(*arg.column);

            if (is_const)

                arg.column = assert_cast<const ColumnConst&>(*arg.column).remove_low_cardinality();

        }

        if (!arguments.empty()) {

            NullPresence null_presence = get_null_resense(arguments);

            if (null_presence.has_null_constant) {

                return make_nullable(std::make_shared<DataTypeNothing>());

            }

            if (null_presence.has_nullable) {

                return make_nullable(std::make_shared<doris::vectorized::DataTypeUInt8>());

            }

        }

        return std::make_shared<doris::vectorized::DataTypeUInt8>();

    }

    // nullIf(col1, col2) == if(col1 = col2, NULL, col1)

    Status execute_impl(FunctionContext* context, Block& block, const ColumnNumbers& arguments,

                        size_t result, size_t input_rows_count) override {

        const ColumnsWithTypeAndName eq_columns {

                block.get_by_position(arguments[0]),

                block.get_by_position(arguments[1]),

        };

        auto result_type = get_return_type_for_equal(eq_columns);

        Block eq_temporary_block({block.get_by_position(arguments[0]),

                                  block.get_by_position(arguments[1]),

                                  {nullptr, result_type, ""}});

        auto equals_func =

                SimpleFunctionFactory::instance().get_function("eq", eq_columns, result_type);

        DCHECK(equals_func);

        RETURN_IF_ERROR(

                equals_func->execute(context, eq_temporary_block, {0, 1}, 2, input_rows_count));

        const ColumnWithTypeAndName new_result_column {

                block.get_by_position(result),

        };

        const ColumnWithTypeAndName if_column {

                eq_temporary_block.get_by_position(2),

        };

        const ColumnsWithTypeAndName if_columns {

                if_column,

                {block.get_by_position(result).type->create_column_const_with_default_value(

                         input_rows_count),

                 block.get_by_position(result).type, "NULL"},

                block.get_by_position(arguments[0]),

        };

        Block temporary_block(

                {if_column,

                 {block.get_by_position(result).type->create_column_const_with_default_value(

                          input_rows_count),

                  block.get_by_position(result).type, "NULL"},

                 block.get_by_position(arguments[0]),

                 new_result_column});

        auto func_if = SimpleFunctionFactory::instance().get_function("if", if_columns,

                                                                      new_result_column.type);

        DCHECK(func_if);

        RETURN_IF_ERROR(func_if->execute(context, temporary_block, {0, 1, 2}, 3, input_rows_count));

        block.get_by_position(result).column = temporary_block.get_by_position(3).column;

        return Status::OK();

    }

};

void register_function_nullif(SimpleFunctionFactory& factory) {

    factory.register_function<FunctionNullIf>();

}

} // namespace doris::vectorized