variardic.cpp

#include <iostream>
#include <string>
#include <vector>

struct ResultT
{
    //dummy data
    std::string someData;
    ResultT()
    {
        someData += "None|";
    }
};

class RtpRFC
{
public:

    bool valid() const { return  false;}

    RtpRFC& operator()(ResultT& rt) {
        rt.someData += "RtpRFC|";
        return *this;
    }
};



struct StunRFC
{

    StunRFC& operator()(ResultT& rt) {
        rt.someData += "StunRFC|";
        return *this;
    }

    bool valid() const {return true;}

};



template<typename T>
T packetHandlerT(ResultT& res, T protocol)
{
    return protocol(res);
}

template <typename RFC, typename  RES>
struct PairedWrapper
{
    RFC first;
    RES second;
    PairedWrapper(RFC rfc, RES res) :
        first{rfc},
        second{res}
    {}
};

/*terminator*/
ResultT VParse() {
    return  {};
}

template <typename T, typename...ARgs>
auto VParse(T type, ARgs...FArgs)
{
    auto resultready = packetHandlerT(type.second, type.first);
    if (resultready.valid())
        return type.second;
    // how to not pass the result ready here?
    else {
        return VParse(FArgs...);
    }
}



int main(void)
{

    ResultT someNetworkData[10];
    // some loop with results
    for(int i=0; i < 10; i++) {
        auto res = someNetworkData[i];
        auto outputstun = packetHandlerT<StunRFC>(res, StunRFC{});
        auto outputrtp = packetHandlerT<RtpRFC>(res, RtpRFC{});
        if (outputrtp.valid()); // do one
        else if(outputstun.valid()); // do other
        else; // if more ad more ifs
    }
    // parse specific w/Variardic

    for(int i=0; i < 10; i++) {
        auto res = someNetworkData[i];
        //in the case we expect to see a sequence ot 1 or 2 rtp then STUN
        auto result = VParse(PairedWrapper{RtpRFC{}, res} ,
                             PairedWrapper{RtpRFC{}, res},
                             PairedWrapper{RtpRFC{}, res},
                             PairedWrapper{StunRFC{}, res});

                      //get either StunRFC or RtpRfc or some other future protocol without
                                                                    // going to the before example

        //variardic template never shrinks, compile time reqursion
        std::cout << result.someData << "\r\n";
    }

    return 0;
}