#ifndef PACKER_HPP
#define PACKER_HPP

#include "luastack.hpp"
#include <cstdint>
#include <string>
#include <sstream>
#include <cassert>

class Packer {
private:
    std::ostringstream *oss_;

    // Packer is not copyable.
    Packer(const Packer &other) { assert(false); }
public:
    using fixhandle = size_t;
    Packer(std::ostringstream *s) : oss_(s) {}

    // Get the current file position.
    size_t tellp() { return oss_->tellp(); }
    
    void write_int8(int8_t v);
    void write_int16(int16_t v);
    void write_int32(int32_t v);
    void write_int64(int64_t v);

    // Sometimes, you want to write a length followed by a block of data.
    // Sometimes, you don't know the length until after you've written the block
    // of data.  To help with this situation, we provide the overwrite_int
    // functions.  Here's what you do:
    //
    // 1. write a dummy length into the stream.
    // 2. use 'tellp' to fetch the stream position *after* the dummy length.
    // 3. write the block of data.
    // 4. use an overwrite function below to overwrite the dummy length.
    //
    void overwrite_int8(size_t tell_after, int8_t value);
    void overwrite_int16(size_t tell_after, int16_t value);
    void overwrite_int32(size_t tell_after, int32_t value);
    void overwrite_int64(size_t tell_after, int64_t value);

    // The packer can be used as a lua_Writer.
    static int lua_writer(lua_State *L, const void *p, size_t sz, void *ud);
    void *lua_writer_ud() { return this; }
};

class Unpacker {
private:
    const char *data_;
    size_t size_;

public:
    Unpacker(const char *d, size_t s);
    const char *data() { return data_; }
    size_t size() { return size_; }
    
    int8_t  read_int8();
    int16_t read_int16();
    int32_t read_int32();
    int64_t read_int64();
    void skip(size_t n);
    Unpacker read_section(size_t n);

    // The unpacker can be used as a lua_Reader
    static const char *lua_reader(lua_State *L, void *ud, size_t *size);
    void *lua_reader_ud() { return this; }
};



#endif // PACKER_HPP