// 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.

#include "common/status.h"

#include "core/assert_cast.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_array.h"

#include "core/column/column_nullable.h"

#include "core/data_type/data_type.h"

#include "core/data_type/data_type_array.h"

#include "core/types.h"

#include "exprs/aggregate/aggregate_function.h"

#include "exprs/function/function.h"

#include "exprs/function/simple_function_factory.h"

namespace doris {

class FunctionArrayFlatten : public IFunction {

public:

    static constexpr auto name = "array_flatten";

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

    /// Get function name.

    String get_name() const override { return name; }

    size_t get_number_of_arguments() const override { return 1; }

    DataTypePtr get_return_type_impl(const DataTypes& arguments) const override {

        DataTypePtr arg = arguments[0];

        while (arg->get_primitive_type() == TYPE_ARRAY) {

            arg = remove_nullable(assert_cast<const DataTypeArray*>(arg.get())->get_nested_type());

        }

        return std::make_shared<DataTypeArray>(make_nullable(arg));

    }

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

                        uint32_t result, size_t input_rows_count) const override {

        auto src_column =

                block.get_by_position(arguments[0]).column->convert_to_full_column_if_const();

        auto* src_column_array_ptr =

                assert_cast<ColumnArray*>(remove_nullable(src_column)->assume_mutable().get());

        ColumnArray* nested_src_column_array_ptr = src_column_array_ptr;

        DataTypePtr src_data_type = block.get_by_position(arguments[0]).type;

        auto* src_data_type_array =

                assert_cast<const DataTypeArray*>(remove_nullable(src_data_type).get());

        auto result_column_offsets =

                assert_cast<ColumnArray::ColumnOffsets&>(src_column_array_ptr->get_offsets_column())

                        .clone();

        auto* offsets = assert_cast<ColumnArray::ColumnOffsets*>(result_column_offsets.get())

                                ->get_data()

                                .data();

        while (src_data_type_array->get_nested_type()->get_primitive_type() == TYPE_ARRAY) {

            nested_src_column_array_ptr = assert_cast<ColumnArray*>(

                    remove_nullable(src_column_array_ptr->get_data_ptr())->assume_mutable().get());

            for (size_t i = 0; i < input_rows_count; ++i) {

                offsets[i] = nested_src_column_array_ptr->get_offsets()[offsets[i] - 1];

            }

            src_column_array_ptr = nested_src_column_array_ptr;

            src_data_type_array = assert_cast<const DataTypeArray*>(

                    remove_nullable(src_data_type_array->get_nested_type()).get());

        }

        block.replace_by_position(

                result, ColumnArray::create(assert_cast<const ColumnNullable&>(

                                                    nested_src_column_array_ptr->get_data())

                                                    .clone(),

                                            std::move(result_column_offsets)));

        return Status::OK();

    }

};

void register_function_array_flatten(SimpleFunctionFactory& factory) {

    factory.register_function<FunctionArrayFlatten>();

}

} // namespace doris