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// 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 <algorithm>

#include <cstring>

#include <vector>

#include "common/status.h"

#include "core/column/column_nullable.h"

#include "core/column/column_string.h"

#include "core/data_type/data_type_number.h"

#include "core/string_ref.h"

#include "exprs/function/simple_function_factory.h"

#include "util/simd/vstring_function.h"

namespace doris {

#include "common/compile_check_begin.h"

class FunctionHammingDistance : public IFunction {

public:

    using ResultDataType = DataTypeInt64;

    using ResultPaddedPODArray = PaddedPODArray<Int64>;

    using ResultColumnType = ColumnVector<ResultDataType::PType>;

    static constexpr auto name = "hamming_distance";

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

    String get_name() const override { return name; }

    size_t get_number_of_arguments() const override { return 2; }

    DataTypePtr get_return_type_impl(const DataTypes& arguments) const override {

        const bool has_nullable = std::ranges::any_of(

                arguments, [](const DataTypePtr& type) { return type->is_nullable(); });

        if (has_nullable) {

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

        }

        return std::make_shared<ResultDataType>();

    }

    bool use_default_implementation_for_nulls() const override { return false; }

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

                        uint32_t result, size_t input_rows_count) const override {

        const auto& [left_col, left_const] =

                unpack_if_const(block.get_by_position(arguments[0]).column);

        const auto& [right_col, right_const] =

                unpack_if_const(block.get_by_position(arguments[1]).column);

        const auto* left_nullable = check_and_get_column<ColumnNullable>(left_col.get());

        const auto* right_nullable = check_and_get_column<ColumnNullable>(right_col.get());

        const IColumn* left_nested =

                left_nullable ? &left_nullable->get_nested_column() : left_col.get();

        const IColumn* right_nested =

                right_nullable ? &right_nullable->get_nested_column() : right_col.get();

        const auto* left_str_col = check_and_get_column<ColumnString>(left_nested);

        const auto* right_str_col = check_and_get_column<ColumnString>(right_nested);

        if (!left_str_col || !right_str_col) {

            return Status::NotSupported("Illegal columns {}, {} of argument of function {}",

                                        left_col->get_name(), right_col->get_name(), get_name());

        }

        auto res_col = ResultColumnType::create(input_rows_count);

        auto& res_data = res_col->get_data();

        const NullMap* left_null_map =

                left_nullable ? &left_nullable->get_null_map_data() : nullptr;

        const NullMap* right_null_map =

                right_nullable ? &right_nullable->get_null_map_data() : nullptr;

        const bool has_nullable = left_null_map != nullptr || right_null_map != nullptr;

        if (!has_nullable) {

            if (left_const) {

                RETURN_IF_ERROR(scalar_vector(left_str_col->get_data_at(0).trim_tail_padding_zero(),

                                              *right_str_col, res_data));

            } else if (right_const) {

                RETURN_IF_ERROR(vector_scalar(

                        *left_str_col, right_str_col->get_data_at(0).trim_tail_padding_zero(),

                        res_data));

            } else {

                RETURN_IF_ERROR(vector_vector(*left_str_col, *right_str_col, res_data));

            }

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

            return Status::OK();

        }

        auto null_col = ColumnUInt8::create(input_rows_count, 0);

        auto& null_map = null_col->get_data();

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

            const size_t left_idx = left_const ? 0 : i;

            const size_t right_idx = right_const ? 0 : i;

            const bool left_is_null = left_null_map && (*left_null_map)[left_idx];

            const bool right_is_null = right_null_map && (*right_null_map)[right_idx];

            if (left_is_null || right_is_null) {

                null_map[i] = 1;

                res_data[i] = 0;

                continue;

            }

            RETURN_IF_ERROR(

                    hamming_distance(left_str_col->get_data_at(left_idx).trim_tail_padding_zero(),

                                     right_str_col->get_data_at(right_idx).trim_tail_padding_zero(),

                                     res_data[i], i));

        }

        block.replace_by_position(result,

                                  ColumnNullable::create(std::move(res_col), std::move(null_col)));

        return Status::OK();

    }

private:

    static Status vector_vector(const ColumnString& lcol, const ColumnString& rcol,

                                ResultPaddedPODArray& res) {

        DCHECK_EQ(lcol.size(), rcol.size());

        const size_t size = lcol.size();

        res.resize(size);

        std::vector<size_t> left_offsets;

        std::vector<size_t> right_offsets;

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

            RETURN_IF_ERROR(hamming_distance(lcol.get_data_at(i).trim_tail_padding_zero(),

                                             rcol.get_data_at(i).trim_tail_padding_zero(),

                                             left_offsets, right_offsets, res[i], i));

        }

        return Status::OK();

    }

    static Status vector_scalar(const ColumnString& lcol, const StringRef& rdata,

                                ResultPaddedPODArray& res) {

        const size_t size = lcol.size();

        res.resize(size);

        const bool right_ascii = simd::VStringFunctions::is_ascii(rdata);

        std::vector<size_t> right_offsets;

        utf8_char_offsets(rdata, right_offsets);

        std::vector<size_t> left_offsets;

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

            const auto left = lcol.get_data_at(i).trim_tail_padding_zero();

            RETURN_IF_ERROR(hamming_distance_with_offsets(

                    left, left_offsets, false, simd::VStringFunctions::is_ascii(left), rdata,

                    right_offsets, true, right_ascii, res[i], i));

        }

        return Status::OK();

    }

    static Status scalar_vector(const StringRef& ldata, const ColumnString& rcol,

                                ResultPaddedPODArray& res) {

        const size_t size = rcol.size();

        res.resize(size);

        const bool left_ascii = simd::VStringFunctions::is_ascii(ldata);

        std::vector<size_t> left_offsets;

        utf8_char_offsets(ldata, left_offsets);

        std::vector<size_t> right_offsets;

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

            const auto right = rcol.get_data_at(i).trim_tail_padding_zero();

            RETURN_IF_ERROR(hamming_distance_with_offsets(

                    ldata, left_offsets, true, left_ascii, right, right_offsets, false,

                    simd::VStringFunctions::is_ascii(right), res[i], i));

        }

        return Status::OK();

    }

    static void utf8_char_offsets(const StringRef& ref, std::vector<size_t>& offsets) {

        offsets.clear();

        offsets.reserve(ref.size);

        simd::VStringFunctions::get_char_len(ref.data, ref.size, offsets);

    }

    static bool utf8_char_equal(const StringRef& left, size_t left_off, size_t left_next,

                                const StringRef& right, size_t right_off, size_t right_next) {

        const size_t left_len = left_next - left_off;

        const size_t right_len = right_next - right_off;

        return left_len == right_len &&

               std::memcmp(left.data + left_off, right.data + right_off, left_len) == 0;

    }

    static Status hamming_distance_ascii(const StringRef& left, const StringRef& right,

                                         Int64& result, size_t row) {

        if (left.size != right.size) {

            return Status::InvalidArgument(

                    "hamming_distance requires strings of the same length at row {}", row);

        }

        Int64 distance = 0;

        for (size_t i = 0; i < left.size; ++i) {

            distance += static_cast<Int64>(left.data[i] != right.data[i]);

        }

        result = distance;

        return Status::OK();

    }

    static Status hamming_distance_utf8(const StringRef& left,

                                        const std::vector<size_t>& left_offsets,

                                        const StringRef& right,

                                        const std::vector<size_t>& right_offsets, Int64& result,

                                        size_t row) {

        if (left_offsets.size() != right_offsets.size()) {

            return Status::InvalidArgument(

                    "hamming_distance requires strings of the same length at row {}", row);

        }

        Int64 distance = 0;

        const size_t len = left_offsets.size();

        for (size_t i = 0; i + 1 < len; ++i) {

            const size_t left_off = left_offsets[i];

            const size_t left_next = left_offsets[i + 1];

            const size_t right_off = right_offsets[i];

            const size_t right_next = right_offsets[i + 1];

            distance += static_cast<Int64>(

                    !utf8_char_equal(left, left_off, left_next, right, right_off, right_next));

        }

        if (len > 0) {

            const size_t left_off = left_offsets[len - 1];

            const size_t right_off = right_offsets[len - 1];

            distance += static_cast<Int64>(

                    !utf8_char_equal(left, left_off, left.size, right, right_off, right.size));

        }

        result = distance;

        return Status::OK();

    }

    static Status hamming_distance(const StringRef& left, const StringRef& right,

                                   std::vector<size_t>& left_offsets,

                                   std::vector<size_t>& right_offsets, Int64& result, size_t row) {

        const bool left_ascii = simd::VStringFunctions::is_ascii(left);

        const bool right_ascii = simd::VStringFunctions::is_ascii(right);

        return hamming_distance_with_offsets(left, left_offsets, false, left_ascii, right,

                                             right_offsets, false, right_ascii, result, row);

    }

    static Status hamming_distance_with_offsets(

            const StringRef& left, std::vector<size_t>& left_offsets, bool left_offsets_ready,

            bool left_ascii, const StringRef& right, std::vector<size_t>& right_offsets,

            bool right_offsets_ready, bool right_ascii, Int64& result, size_t row) {

        if (left_ascii && right_ascii) {

            return hamming_distance_ascii(left, right, result, row);

        }

        if (!left_offsets_ready) {

            utf8_char_offsets(left, left_offsets);

        }

        if (!right_offsets_ready) {

            utf8_char_offsets(right, right_offsets);

        }

        return hamming_distance_utf8(left, left_offsets, right, right_offsets, result, row);

    }

    static Status hamming_distance(const StringRef& left, const StringRef& right, Int64& result,

                                   size_t row) {

        std::vector<size_t> left_offsets;

        std::vector<size_t> right_offsets;

        return hamming_distance(left, right, left_offsets, right_offsets, result, row);

    }

};

void register_function_hamming_distance(SimpleFunctionFactory& factory) {

    factory.register_function<FunctionHammingDistance>();

}

#include "common/compile_check_end.h"

} // namespace doris