draconisplusplus/include/rfl/msgpack/Writer.hpp

#ifndef RFL_MSGPACK_WRITER_HPP_
#define RFL_MSGPACK_WRITER_HPP_

#include <exception>
#include <map>
#include <msgpack.h>
#include <sstream>
#include <stdexcept>
#include <string>
#include <string_view>
#include <type_traits>
#include <variant>
#include <vector>

#include "../Box.hpp"
#include "../Ref.hpp"
#include "../Result.hpp"
#include "../always_false.hpp"

namespace rfl::msgpack {

  class Writer {
   public:
    struct MsgpackOutputArray {};

    struct MsgpackOutputObject {};

    struct MsgpackOutputVar {};

    using OutputArrayType  = MsgpackOutputArray;
    using OutputObjectType = MsgpackOutputObject;
    using OutputVarType    = MsgpackOutputVar;

    Writer(msgpack_packer* _pk) : pk_(_pk) {}

    ~Writer() = default;

    OutputArrayType array_as_root(const size_t _size) const noexcept { return new_array(_size); }

    OutputObjectType object_as_root(const size_t _size) const noexcept { return new_object(_size); }

    OutputVarType null_as_root() const noexcept {
      msgpack_pack_nil(pk_);
      return OutputVarType {};
    }

    template <class T>
    OutputVarType value_as_root(const T& _var) const noexcept {
      return new_value(_var);
    }

    OutputArrayType add_array_to_array(const size_t _size, OutputArrayType* _parent)
      const noexcept {
      return new_array(_size);
    }

    OutputArrayType add_array_to_object(
      const std::string_view& _name,
      const size_t            _size,
      OutputObjectType*       _parent
    ) const noexcept {
      msgpack_pack_str(pk_, _name.size());
      msgpack_pack_str_body(pk_, _name.data(), _name.size());
      return new_array(_size);
    }

    OutputObjectType add_object_to_array(const size_t _size, OutputArrayType* _parent)
      const noexcept {
      return new_object(_size);
    }

    OutputObjectType add_object_to_object(
      const std::string_view& _name,
      const size_t            _size,
      OutputObjectType*       _parent
    ) const noexcept {
      msgpack_pack_str(pk_, _name.size());
      msgpack_pack_str_body(pk_, _name.data(), _name.size());
      return new_object(_size);
    }

    template <class T>
    OutputVarType add_value_to_array(const T& _var, OutputArrayType* _parent) const noexcept {
      return new_value(_var);
    }

    template <class T>
    OutputVarType add_value_to_object(
      const std::string_view& _name,
      const T&                _var,
      OutputObjectType*       _parent
    ) const noexcept {
      msgpack_pack_str(pk_, _name.size());
      msgpack_pack_str_body(pk_, _name.data(), _name.size());
      return new_value(_var);
    }

    OutputVarType add_null_to_array(OutputArrayType* _parent) const noexcept {
      msgpack_pack_nil(pk_);
      return OutputVarType {};
    }

    OutputVarType add_null_to_object(const std::string_view& _name, OutputObjectType* _parent)
      const noexcept {
      msgpack_pack_str(pk_, _name.size());
      msgpack_pack_str_body(pk_, _name.data(), _name.size());
      msgpack_pack_nil(pk_);
      return OutputVarType {};
    }

    void end_array(OutputArrayType* _arr) const noexcept {}

    void end_object(OutputObjectType* _obj) const noexcept {}

   private:
    OutputArrayType new_array(const size_t _size) const noexcept {
      msgpack_pack_array(pk_, _size);
      return OutputArrayType {};
    }

    OutputObjectType new_object(const size_t _size) const noexcept {
      msgpack_pack_map(pk_, _size);
      return OutputObjectType {};
    }

    template <class T>
    OutputVarType new_value(const T& _var) const noexcept {
      if constexpr (std::is_same<std::remove_cvref_t<T>, std::string>()) {
        msgpack_pack_str(pk_, _var.size());
        msgpack_pack_str_body(pk_, _var.c_str(), _var.size());
      } else if constexpr (std::is_same<std::remove_cvref_t<T>, bool>()) {
        if (_var) {
          msgpack_pack_true(pk_);
        } else {
          msgpack_pack_false(pk_);
        }
      } else if constexpr (std::is_floating_point<std::remove_cvref_t<T>>()) {
        msgpack_pack_double(pk_, static_cast<double>(_var));
      } else if constexpr (std::is_integral<std::remove_cvref_t<T>>()) {
        msgpack_pack_int64(pk_, static_cast<std::int64_t>(_var));
      } else {
        static_assert(rfl::always_false_v<T>, "Unsupported type.");
      }
      return OutputVarType {};
    }

   private:
    /// The underlying packer.
    msgpack_packer* pk_;
  };

} // namespace rfl::msgpack

#endif // MSGPACK_PARSER_HPP_