ADC/net/adc_netproto.h

#pragma once

#include "../common/adc_traits.h"

namespace adc
{

namespace traits
{

template <typename T, typename R>
concept adc_netproto_c = adc_range_of_view_char_range<R> && requires(T t, const R& r) {
    { t.toLowLevel(r) } -> std::same_as<R>;
    { t.fromLowLevel(r) } -> std::same_as<R>;
};

}  // namespace traits


namespace constants
{

static constexpr char ADC_DEFAULT_NETPROTO_STOPSEQ[] = "\n";

static constexpr char ADC_DEFAULT_NETPROTO_STARTMARK[] = "\n\t\r\v\r\t\n";

}  // namespace constants


template <typename InetT, const char* STOPSEQ = constants::ADC_DEFAULT_NETPROTO_STOPSEQ>
struct AdcNetProtoStopSeq : InetT {
    static constexpr std::string_view stopSeq{STOPSEQ};
    static constexpr size_t stopSeqSize = stopSeq.size();

    static_assert(stopSeqSize, "STOP BYTE SEQUENCE MUST NOT BE AN EMPTY ONE!!!");

    using socket_t = typename InetT::socket;

    template <std::input_iterator IT>
    std::pair<IT, bool> matchCondition(IT begin, IT end)
    {
        auto res = std::make_pair(begin, false);

        if (begin == end) {
            return res;
        }

        res.first = std::search(begin, end, stopSeq.begin(), stopSeq.end());
        if (res.first != end) {
            std::advance(res.first, stopSeqSize);  // move iterator to the one-past-the-end position
            res.second = true;
        } else {
            // may be only a part of valid byte sequence was received,
            // so start next matching from previous begin-iterator
            res.first = begin;
        }

        return res;
    }

    /*  range of char range's views  */

    template <traits::adc_range_of_view_char_range R>
    R toLowLevel(const R& r)
    {
        R res = r;

        // just add to the back of the range "stop sequence" element
        std::back_inserter(res) = {stopSeq.begin(), stopSeq.end()};

        return res;
    }


    template <traits::adc_range_of_view_char_range R>
    R fromLowLevel(const R& r)
    {
        R res;

        auto N = std::distance(r.begin(), r.end());

        if (!N) {
            return res;
        }

        // just remove the last element (it is assumed the last element is the stop sequence)
        std::ranges::copy(r | std::views::take(N - 1), std::back_inserter(res));

        return res;
    }


    /*  range of char  */

    template <traits::adc_output_char_range R>
    R toLowLevel(const R& r)
    {
        R res = r;

        // just add to the back of the "stop sequence"
        std::ranges::copy(stopSeq, std::back_inserter(res));

        return res;
    }


    template <traits::adc_output_char_range R>
    R fromLowLevel(const R& r)
    {
        R res;

        auto N = std::distance(r.begin(), r.end());

        if (N <= stopSeq) {  // !!!!!!!!!!!
            return res;
        }

        // remove stopSeqSize bytes from the back of the input range
        std::ranges::copy(r | std::views::take(N - stopSeqSize), std::back_inserter(res));

        return res;
    }


    /*  from iterators to the input range  */

    template <std::input_iterator IT>
    std::pair<IT, IT> fromLowLevel(IT begin, IT end)
    {
        auto N = std::distance(begin, end);
        if (N <= stopSeqSize) {  // !!!!!!!!
            return std::make_pair(end, end);
        }

        std::advance(end, -stopSeqSize);

        return std::make_pair(begin, end);
    }
};


template <typename InetT, const char* START_MARK = constants::ADC_DEFAULT_NETPROTO_STARTMARK, size_t SIZE_FIELD_LEN = 8>
struct AdcNetProtoSizedBlob {
    static constexpr std::string_view startMark{START_MARK};
    static constexpr size_t sizeFieldLen = SIZE_FIELD_LEN;

    template <std::input_iterator IT>
    std::pair<IT, bool> matchCondition(IT begin, IT end)
    {
        auto res = std::make_pair(begin, false);

        if (std::distance(begin, end) <= (startMark.size() + sizeFieldLen)) {  // still unusefull part
            return res;
        }

        res.first = std::search(begin, end, startMark.begin(), startMark.end());
        if (res.first != end) {
            std::advance(res.first, startMark);
            auto it = res.first;
            std::advance(it, sizeFieldLen);

            std::string sz_str{res.first, it};
            size_t blob_size = 0;

            auto end_ptr = sz_str.data() + sizeFieldLen;
            auto [ptr, ec] = std::from_chars(sz_str.data(), end_ptr, blob_size, 16);  // heximal!!!
            if ((ec != std::errc()) || (ptr != end_ptr)) {
                return {begin, false};
            }

            std::advance(res.first, sizeFieldLen);
            if (std::distance(res.first, end) >= blob_size) {  // still partially received message?!
                std::advance(res.first, blob_size);            // move output iterator to the one-past-the-end position
                res.second = true;
            } else {  // still partially received message?!
                res.first = begin;
            }
        } else {
            // may be only a part of message was received,
            // so start next matching from previous begin-iterator
            res.first = begin;
        }

        return res;
    }
};

}  // namespace adc