// 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.

#pragma once

#include <fmt/format.h>

#include <glog/logging.h>

#include <stddef.h>

#include <memory>

#include <ostream>

#include <string>

#include <utility>

#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/data_type/data_type.h"

#include "core/data_type/data_type_array.h"

#include "core/pod_array_fwd.h"

#include "core/types.h"

#include "exprs/function/function.h"

namespace doris {

class FunctionContext;

} // namespace doris

namespace doris {

class FunctionArrayCompact : public IFunction {

public:

    static constexpr auto name = "array_compact";

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

    using NullMapType = PaddedPODArray<UInt8>;

    /// Get function name.

    String get_name() const override { return name; }

    bool is_variadic() const override { return false; }

    size_t get_number_of_arguments() const override { return 1; }

    DataTypePtr get_return_type_impl(const DataTypes& arguments) const override {

        DCHECK(arguments[0]->get_primitive_type() == TYPE_ARRAY)

                << "first argument for function: " << name << " should be DataTypeArray"

                << " and arguments[0] is " << arguments[0]->get_name();

        return arguments[0];

    }

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

                        uint32_t result, size_t input_rows_count) const override {

        ColumnPtr src_column =

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

        const auto& src_column_array = check_and_get_column<ColumnArray>(*src_column);

        if (!src_column_array) {

            return Status::RuntimeError(

                    fmt::format("unsupported types for function {}({})", get_name(),

                                block.get_by_position(arguments[0]).type->get_name()));

        }

        const auto& src_offsets = src_column_array->get_offsets();

        const auto* src_nested_column = &src_column_array->get_data();

        DCHECK(src_nested_column != nullptr);

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

        auto nested_type = assert_cast<const DataTypeArray&>(*src_column_type).get_nested_type();

        auto dest_column_ptr = ColumnArray::create(nested_type->create_column(),

                                                   ColumnArray::ColumnOffsets::create());

        IColumn* dest_nested_column = &dest_column_ptr->get_data();

        auto& dest_offsets = dest_column_ptr->get_offsets();

        DCHECK(dest_nested_column != nullptr);

        auto res_val = _execute(*src_nested_column, src_offsets, *dest_nested_column, dest_offsets);

        if (!res_val) {

            return Status::RuntimeError(

                    fmt::format("execute failed or unsupported types for function {}({})",

                                get_name(), block.get_by_position(arguments[0]).type->get_name()));

        }

        block.replace_by_position(result, std::move(dest_column_ptr));

        return Status::OK();

    }

private:

    bool _execute(const IColumn& src_column, const ColumnArray::Offsets64& src_offsets,

                  IColumn& dest_column, ColumnArray::Offsets64& dest_offsets) const {

        ColumnArray::Offset64 src_offsets_size = src_offsets.size();

        ColumnArray::Offset64 src_pos = 0;

        ColumnArray::Offset64 dest_pos = 0;

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

            auto src_offset = src_offsets[i];

            if (src_pos < src_offset) {

                // Insert first element

                dest_column.insert_from(src_column, src_pos);

                ++src_pos;

                ++dest_pos;

                // For the rest of elements, insert if the element is different from the previous.

                for (; src_pos < src_offset; ++src_pos) {

                    if (0 != (src_column.compare_at(src_pos - 1, src_pos, src_column, 1))) {

                        dest_column.insert_from(src_column, src_pos);

                        ++dest_pos;

                    }

                }

            }

            dest_offsets.push_back(dest_pos);

        }

        return true;

    }

};

} // namespace doris