// 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/IsNull.cpp

// and modified by Doris

#include <stddef.h>

#include <algorithm>

#include <boost/iterator/iterator_facade.hpp>

#include <memory>

#include <string>

#include "common/status.h"

#include "core/block/block.h"

#include "core/block/column_numbers.h"

#include "core/block/column_with_type_and_name.h"

#include "core/column/column.h"

#include "core/column/column_nullable.h"

#include "core/data_type/data_type_number.h"

#include "core/field.h"

#include "exprs/aggregate/aggregate_function.h"

#include "exprs/function/function.h"

namespace doris {

class FunctionContext;

} // namespace doris

namespace doris {

/// Implements the function is_null which returns true if a value

/// is null, false otherwise.

class FunctionIsNull : public IFunction {

public:

    static constexpr auto name = "is_null_pred";

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

    std::string get_name() const override { return name; }

    size_t get_number_of_arguments() const override { return 1; }

    bool use_default_implementation_for_nulls() const override { return false; }

    DataTypePtr get_return_type_impl(const DataTypes&) const override {

        return std::make_shared<DataTypeUInt8>();

    }

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

                        uint32_t result, size_t input_rows_count) const override {

        const ColumnWithTypeAndName& elem = block.get_by_position(arguments[0]);

        if (auto* nullable = check_and_get_column<ColumnNullable>(*elem.column)) {

            /// Merely return the embedded null map.

            block.get_by_position(result).column = nullable->get_null_map_column_ptr();

        } else {

            /// Since no element is nullable, return a zero-constant column representing

            /// a zero-filled null map.

            block.get_by_position(result).column = DataTypeUInt8().create_column_const(

                    elem.column->size(), Field::create_field<TYPE_BOOLEAN>(0));

        }

        return Status::OK();

    }

    Status evaluate_inverted_index(

            const ColumnsWithTypeAndName& arguments,

            const std::vector<IndexFieldNameAndTypePair>& data_type_with_names,

            std::vector<segment_v2::IndexIterator*> iterators, uint32_t num_rows,

            const InvertedIndexAnalyzerCtx* /*analyzer_ctx*/,

            segment_v2::InvertedIndexResultBitmap& bitmap_result) const override {

        if (iterators.empty() || iterators[0] == nullptr) {

            return Status::OK();

        }

        auto* index_iter = iterators[0];

        if (!index_iter->has_null()) {

            return Status::OK();

        }

        segment_v2::InvertedIndexQueryCacheHandle null_bitmap_cache_handle;

        RETURN_IF_ERROR(index_iter->read_null_bitmap(&null_bitmap_cache_handle));

        std::shared_ptr<roaring::Roaring> null_bitmap = null_bitmap_cache_handle.get_bitmap();

        if (!null_bitmap) {

            return Status::OK();

        }

        auto data_bitmap = std::make_shared<roaring::Roaring>(*null_bitmap);

        auto empty_null_bitmap = std::make_shared<roaring::Roaring>();

        bitmap_result = segment_v2::InvertedIndexResultBitmap(std::move(data_bitmap),

                                                              std::move(empty_null_bitmap));

        return Status::OK();

    }

};

} // namespace doris