#include <Columns/ColumnDecimal.h>
#include <Columns/ColumnFixedString.h>
#include <Columns/ColumnString.h>
#include <Columns/ColumnVector.h>
#include <Common/BitHelpers.h>
#include <Common/hex.h>
#include <DataTypes/DataTypeString.h>
#include <DataTypes/DataTypeFixedString.h>
#include <Functions/FunctionFactory.h>
#include <Functions/IFunction.h>
#include <Functions/FunctionHelpers.h>
#include <IO/WriteHelpers.h>
#include <Interpreters/Context_fwd.h>
#include <Interpreters/castColumn.h>

#include <span>

namespace DB::ErrorCodes
{
extern const int ARGUMENT_OUT_OF_BOUND;
extern const int ILLEGAL_COLUMN;
extern const int ILLEGAL_TYPE_OF_ARGUMENT;
extern const int LOGICAL_ERROR;
extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
}

namespace
{
enum class Representation
{
    BigEndian,
    LittleEndian
};

std::pair<int, int> determineBinaryStartIndexWithIncrement(const ptrdiff_t num_bytes, const Representation representation)
{
    if (representation == Representation::BigEndian)
        return {0, 1};
    else if (representation == Representation::LittleEndian)
        return {num_bytes - 1, -1};

    throw DB::Exception(DB::ErrorCodes::LOGICAL_ERROR, "{} is not handled yet", magic_enum::enum_name(representation));
}

void formatHex(const std::span<const UInt8> src, UInt8 * dst, const Representation representation)
{
    const auto src_size = std::ssize(src);
    const auto [src_start_index, src_increment] = determineBinaryStartIndexWithIncrement(src_size, representation);
    for (int src_pos = src_start_index, dst_pos = 0; src_pos >= 0 && src_pos < src_size; src_pos += src_increment, dst_pos += 2)
        writeHexByteLowercase(src[src_pos], dst + dst_pos);
}

void parseHex(const UInt8 * __restrict src, const std::span<UInt8> dst, const Representation representation)
{
    const auto dst_size = std::ssize(dst);
    const auto [dst_start_index, dst_increment] = determineBinaryStartIndexWithIncrement(dst_size, representation);
    const auto * src_as_char = reinterpret_cast<const char *>(src);
    for (auto dst_pos = dst_start_index, src_pos = 0; dst_pos >= 0 && dst_pos < dst_size; dst_pos += dst_increment, src_pos += 2)
        dst[dst_pos] = unhex2(src_as_char + src_pos);
}

class UUIDSerializer
{
public:
    enum class Variant
    {
        Default = 1,
        Microsoft = 2
    };

    explicit UUIDSerializer(const Variant variant)
        : first_half_binary_representation(variant == Variant::Microsoft ? Representation::LittleEndian : Representation::BigEndian)
    {
        if (variant != Variant::Default && variant != Variant::Microsoft)
            throw DB::Exception(DB::ErrorCodes::LOGICAL_ERROR, "{} is not handled yet", magic_enum::enum_name(variant));
    }

    void deserialize(const UInt8 * src16, UInt8 * dst36) const
    {
        formatHex({src16, 4}, &dst36[0], first_half_binary_representation);
        dst36[8] = '-';
        formatHex({src16 + 4, 2}, &dst36[9], first_half_binary_representation);
        dst36[13] = '-';
        formatHex({src16 + 6, 2}, &dst36[14], first_half_binary_representation);
        dst36[18] = '-';
        formatHex({src16 + 8, 2}, &dst36[19], Representation::BigEndian);
        dst36[23] = '-';
        formatHex({src16 + 10, 6}, &dst36[24], Representation::BigEndian);
    }

    void serialize(const UInt8 * src36, UInt8 * dst16) const
    {
        /// If string is not like UUID - implementation specific behaviour.
        parseHex(&src36[0], {dst16 + 0, 4}, first_half_binary_representation);
        parseHex(&src36[9], {dst16 + 4, 2}, first_half_binary_representation);
        parseHex(&src36[14], {dst16 + 6, 2}, first_half_binary_representation);
        parseHex(&src36[19], {dst16 + 8, 2}, Representation::BigEndian);
        parseHex(&src36[24], {dst16 + 10, 6}, Representation::BigEndian);
    }

private:
    Representation first_half_binary_representation;
};

void checkArgumentCount(const DB::DataTypes & arguments, const std::string_view function_name)
{
    if (const auto argument_count = std::ssize(arguments); argument_count < 1 || argument_count > 2)
        throw DB::Exception(
            DB::ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH,
            "Number of arguments for function {} doesn't match: passed {}, should be 1 or 2",
            function_name,
            argument_count);
}

void checkFormatArgument(const DB::DataTypes & arguments, const std::string_view function_name)
{
    if (const auto argument_count = std::ssize(arguments);
        argument_count > 1 && !DB::WhichDataType(arguments[1]).isInt8() && !DB::WhichDataType(arguments[1]).isUInt8())
        throw DB::Exception(
            DB::ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
            "Illegal type {} of second argument of function {}, expected Int8 or UInt8 type",
            arguments[1]->getName(),
            function_name);
}

UUIDSerializer::Variant parseVariant(const DB::ColumnsWithTypeAndName & arguments)
{
    if (arguments.size() < 2)
        return UUIDSerializer::Variant::Default;

    const auto representation = static_cast<magic_enum::underlying_type_t<UUIDSerializer::Variant>>(arguments[1].column->getInt(0));
    const auto as_enum = magic_enum::enum_cast<UUIDSerializer::Variant>(representation);
    if (!as_enum)
        throw DB::Exception(DB::ErrorCodes::ARGUMENT_OUT_OF_BOUND, "Expected UUID variant, got {}", representation);

    return *as_enum;
}
}

namespace DB
{
constexpr size_t uuid_bytes_length = 16;
constexpr size_t uuid_text_length = 36;

class FunctionUUIDNumToString : public IFunction
{
public:
    static constexpr auto name = "UUIDNumToString";
    static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionUUIDNumToString>(); }

    String getName() const override { return name; }
    size_t getNumberOfArguments() const override { return 0; }
    bool isInjective(const ColumnsWithTypeAndName &) const override { return true; }
    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }
    bool isVariadic() const override { return true; }

    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
    {
        checkArgumentCount(arguments, name);

        const auto * ptr = checkAndGetDataType<DataTypeFixedString>(arguments[0].get());
        if (!ptr || ptr->getN() != uuid_bytes_length)
            throw Exception("Illegal type " + arguments[0]->getName() +
                            " of argument of function " + getName() +
                            ", expected FixedString(" + toString(uuid_bytes_length) + ")",
                            ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);

        checkFormatArgument(arguments, name);

        return std::make_shared<DataTypeString>();
    }

    bool useDefaultImplementationForConstants() const override { return true; }

    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t /*input_rows_count*/) const override
    {
        const ColumnWithTypeAndName & col_type_name = arguments[0];
        const ColumnPtr & column = col_type_name.column;
        const auto variant = parseVariant(arguments);
        if (const auto * col_in = checkAndGetColumn<ColumnFixedString>(column.get()))
        {
            if (col_in->getN() != uuid_bytes_length)
                throw Exception("Illegal type " + col_type_name.type->getName() +
                                " of column " + col_in->getName() +
                                " argument of function " + getName() +
                                ", expected FixedString(" + toString(uuid_bytes_length) + ")",
                                ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);

            const auto size = col_in->size();
            const auto & vec_in = col_in->getChars();

            auto col_res = ColumnString::create();

            ColumnString::Chars & vec_res = col_res->getChars();
            ColumnString::Offsets & offsets_res = col_res->getOffsets();
            vec_res.resize(size * (uuid_text_length + 1));
            offsets_res.resize(size);

            size_t src_offset = 0;
            size_t dst_offset = 0;

            const UUIDSerializer uuid_serializer(variant);
            for (size_t i = 0; i < size; ++i)
            {
                uuid_serializer.deserialize(&vec_in[src_offset], &vec_res[dst_offset]);
                src_offset += uuid_bytes_length;
                dst_offset += uuid_text_length;
                vec_res[dst_offset] = 0;
                ++dst_offset;
                offsets_res[i] = dst_offset;
            }

            return col_res;
        }
        else
            throw Exception("Illegal column " + arguments[0].column->getName()
                            + " of argument of function " + getName(),
                            ErrorCodes::ILLEGAL_COLUMN);
    }
};


class FunctionUUIDStringToNum : public IFunction
{
public:
    static constexpr auto name = "UUIDStringToNum";
    static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionUUIDStringToNum>(); }

    String getName() const override { return name; }
    size_t getNumberOfArguments() const override { return 0; }
    bool isInjective(const ColumnsWithTypeAndName &) const override { return true; }
    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }
    bool isVariadic() const override { return true; }

    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
    {
        checkArgumentCount(arguments, name);

        /// String or FixedString(36)
        if (!isString(arguments[0]))
        {
            const auto * ptr = checkAndGetDataType<DataTypeFixedString>(arguments[0].get());
            if (!ptr || ptr->getN() != uuid_text_length)
                throw Exception("Illegal type " + arguments[0]->getName() +
                                " of first argument of function " + getName() +
                                ", expected FixedString(" + toString(uuid_text_length) + ")",
                                ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
        }

        checkFormatArgument(arguments, name);

        return std::make_shared<DataTypeFixedString>(uuid_bytes_length);
    }

    bool useDefaultImplementationForConstants() const override { return true; }

    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t /*input_rows_count*/) const override
    {
        const ColumnWithTypeAndName & col_type_name = arguments[0];
        const ColumnPtr & column = col_type_name.column;

        const UUIDSerializer uuid_serializer(parseVariant(arguments));
        if (const auto * col_in = checkAndGetColumn<ColumnString>(column.get()))
        {
            const auto & vec_in = col_in->getChars();
            const auto & offsets_in = col_in->getOffsets();
            const size_t size = offsets_in.size();

            auto col_res = ColumnFixedString::create(uuid_bytes_length);

            ColumnString::Chars & vec_res = col_res->getChars();
            vec_res.resize(size * uuid_bytes_length);

            size_t src_offset = 0;
            size_t dst_offset = 0;

            for (size_t i = 0; i < size; ++i)
            {
                /// If string has incorrect length - then return zero UUID.
                /// If string has correct length but contains something not like UUID - implementation specific behaviour.

                size_t string_size = offsets_in[i] - src_offset;
                if (string_size == uuid_text_length + 1)
                    uuid_serializer.serialize(&vec_in[src_offset], &vec_res[dst_offset]);
                else
                    memset(&vec_res[dst_offset], 0, uuid_bytes_length);

                dst_offset += uuid_bytes_length;
                src_offset += string_size;
            }

            return col_res;
        }
        else if (const auto * col_in_fixed = checkAndGetColumn<ColumnFixedString>(column.get()))
        {
            if (col_in_fixed->getN() != uuid_text_length)
                throw Exception("Illegal type " + col_type_name.type->getName() +
                                " of column " + col_in_fixed->getName() +
                                " argument of function " + getName() +
                                ", expected FixedString(" + toString(uuid_text_length) + ")",
                                ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);

            const auto size = col_in_fixed->size();
            const auto & vec_in = col_in_fixed->getChars();

            auto col_res = ColumnFixedString::create(uuid_bytes_length);

            ColumnString::Chars & vec_res = col_res->getChars();
            vec_res.resize(size * uuid_bytes_length);

            size_t src_offset = 0;
            size_t dst_offset = 0;

            for (size_t i = 0; i < size; ++i)
            {
                uuid_serializer.serialize(&vec_in[src_offset], &vec_res[dst_offset]);
                src_offset += uuid_text_length;
                dst_offset += uuid_bytes_length;
            }

            return col_res;
        }
        else
            throw Exception("Illegal column " + arguments[0].column->getName()
                            + " of argument of function " + getName(), ErrorCodes::ILLEGAL_COLUMN);
    }
};

REGISTER_FUNCTION(CodingUUID)
{
    factory.registerFunction<FunctionUUIDNumToString>();
    factory.registerFunction<FunctionUUIDStringToNum>();
}

}