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#pragma once

#include "stream.h" 

#include <util/generic/deque.h>
#include <util/generic/hash.h> 

class TCompressionCodecFactory { 
public:
    using TDecoderConstructor = std::function<THolder<IInputStream>(IInputStream*)>; 
    using TEncoderConstructor = std::function<THolder<IOutputStream>(IOutputStream*)>; 

    TCompressionCodecFactory(); 

    static inline TCompressionCodecFactory& Instance() noexcept { 
        return *SingletonWithPriority<TCompressionCodecFactory, 0>(); 
    } 

    inline const TDecoderConstructor* FindDecoder(TStringBuf name) const { 
        if (auto codec = Codecs_.FindPtr(name)) { 
            return &codec->Decoder; 
        } 

        return nullptr; 
    } 

    inline const TEncoderConstructor* FindEncoder(TStringBuf name) const { 
        if (auto codec = Codecs_.FindPtr(name)) { 
            return &codec->Encoder; 
        } 

        return nullptr; 
    } 

    inline TArrayRef<const TStringBuf> GetBestCodecs() const { 
        return BestCodecs_; 
    } 

private:
    void Add(TStringBuf name, TDecoderConstructor d, TEncoderConstructor e); 

    struct TCodec { 
        TDecoderConstructor Decoder; 
        TEncoderConstructor Encoder; 
    }; 

    TDeque<TString> Strings_;
    THashMap<TStringBuf, TCodec> Codecs_; 
    TVector<TStringBuf> BestCodecs_; 
};

namespace NHttp {
    template <typename F>
    TString ChooseBestCompressionScheme(F accepted, TArrayRef<const TStringBuf> available) {
        if (available.empty()) {
            return "identity";
        }

        if (accepted("*")) {
            return TString(available[0]);
        }

        for (const auto& coding : available) {
            TString s(coding);
            if (accepted(s)) {
                return s;
            }
        }

        return "identity";
    }
}