#ifndef INCLUDED_BOBCAT_SYMCRYPTSTREAMBUFBASE_
#define INCLUDED_BOBCAT_SYMCRYPTSTREAMBUFBASE_

#include <memory>
#include <iosfwd>
#include <string>

#include <openssl/evp.h>

#include <bobcat/ifilterbuf>

namespace FBB
{

namespace IUO   // the facilities defined here are not further documented:
{               // the SymCryptStreambufBase class defined below should be
                // used by ISymCryptStreambuf only.


class SymCryptStreambufBase: public FBB::IFilterBuf
{
    EVP_CIPHER_CTX *d_ctx;

    size_t d_inBufSize;
    size_t d_blockSize;
    size_t d_outBufSize = 0;
    bool d_allDone = false;

    std::istream &d_in;
    
    int (*d_evpUpdate)(EVP_CIPHER_CTX *ctx, 
                unsigned char *out, int *outl, 
                unsigned char const *in, int inl);

    int (*d_evpFinal_ex)(EVP_CIPHER_CTX *, unsigned char *out, int *outl);

    std::unique_ptr<char> d_outBuf;
    std::unique_ptr<char> d_inBuf;

    public:
        SymCryptStreambufBase(
            int (*evpInit)(EVP_CIPHER_CTX *, EVP_CIPHER const *,
                ENGINE *impl, 
                unsigned char const *key, unsigned char const *iv),


            int (*evpUpdate)(EVP_CIPHER_CTX *ctx, unsigned char *out,
                int *outl, unsigned char const *in, int inl),

            int (*evpFinal)(EVP_CIPHER_CTX *ctx, unsigned char *out,
                int *outl),

            std::istream &in,       char const *type,
            std::string const &key, std::string const &iv,
            size_t bufSize,         size_t filterBufSize, 
            ENGINE *engine
        );

        ~SymCryptStreambufBase() override;        

    private:
        bool filter(char const **srcBegin, char const **srcEnd) override;
        void checkOutBufSize(size_t inputSize);
};

}   // IUO
}   // FBB

#endif
