MessageBus.hpp

#pragma once
#include <score/serialization/DataStreamVisitor.hpp>
 
#include <boost/pfr.hpp>
 
#include <avnd/common/tag.hpp>
#include <avnd/concepts/message_bus.hpp>
 
namespace oscr
{
 
struct Serializer
{
  DataStreamReader& r;
 
  template <typename F>
  void operator()(const F& f)
  {
    if constexpr(std::is_arithmetic_v<F>)
      r.stream().stream << f;
    else if constexpr(std::is_aggregate_v<F>)
      boost::pfr::for_each_field(f, *this);
    else if constexpr(avnd::list_ish<F>)
    {
      r.stream().stream << (int64_t)std::ssize(f);
      for(const auto& val : f)
      {
        (*this)(val);
      }
    }
    else
      r.stream() << f;
  }
 
  template <typename... Args>
  void operator()(const std::variant<Args...>& f)
  {
    r.stream().stream << (int)f.index();
    std::visit(*this, f);
  }
};
 
struct MessageBusSender
{
  std::function<void(QByteArray)>& bus;
 
  // Case for zero-argument message bus (e.g. just a ping)
  void operator()() { this->bus(QByteArray{}); }
 
  template <typename T>
    requires std::is_trivial_v<T>
  void operator()(const T& msg)
  {
    // Here we can just do a memcpy
    this->bus(QByteArray((const char*)&msg, sizeof(msg)));
  }
 
  template <typename T>
    requires(
        !std::is_trivial_v<T> && avnd::relocatable<T>
        && alignof(T) <= alignof(max_align_t))
  void operator()(const T& msg)
  {
    QByteArray b(msg.size(), Qt::Uninitialized);
    auto dst = reinterpret_cast<T*>(b.data());
    new(dst) T(msg);
 
    this->bus(std::move(b));
  }
 
  template <typename T>
    requires(
        !std::is_trivial_v<T> && avnd::relocatable<T>
        && alignof(T) <= alignof(max_align_t))
  void operator()(T&& msg)
  {
    QByteArray b(sizeof(msg), Qt::Uninitialized);
    auto dst = reinterpret_cast<T*>(b.data());
    std::construct_at(dst, std::move(msg));
 
    this->bus(std::move(b));
  }
 
  template <typename T>
    requires(
        !std::is_trivial_v<T>
        && (!avnd::relocatable<T> || (alignof(T) > alignof(max_align_t))))
  void operator()(const T& msg)
  {
    // Here we gotta serialize... :D
    QByteArray buf;
 
    DataStreamReader str{&buf};
    Serializer{str}(msg);
 
    this->bus(std::move(buf));
  }
 
  template <typename T>
  void operator()(const std::shared_ptr<T>& msg)
  {
    SCORE_ASSERT(msg);
    return (*this)(std::move(*msg));
  }
  template <typename T>
  void operator()(std::unique_ptr<T> msg)
  {
    SCORE_ASSERT(msg);
    return (*this)(std::move(*msg));
  }
};
 
struct Deserializer
{
  DataStreamWriter& r;
 
  template <typename F>
  requires std::is_aggregate_v<F>
  void operator()(F& f) { boost::pfr::for_each_field(f, *this); }
 
  template <typename F>
    requires(std::is_arithmetic_v<F>)
  void operator()(F& f)
  {
    r.stream().stream >> f;
  }
 
  template <typename F>
    requires avnd::list_ish<F>
  void operator()(F& f)
  {
    int64_t sz;
    r.stream().stream >> sz;
    SCORE_ASSERT(sz >= 0);
    for(int64_t i = 0; i < sz; i++)
    {
      using type = typename F::value_type;
      type val;
      (*this)(val);
      f.push_back(std::move(val));
    }
  }
 
  template <std::size_t I, typename... Args>
  bool write_variant(std::variant<Args...>& f)
  {
    auto& elt = f.template emplace<I>();
    (*this)(elt);
    return true;
  }
 
  template <typename... Args>
  void operator()(std::variant<Args...>& f)
  {
    int index{};
    r.stream().stream >> index;
 
    SCORE_ASSERT(index >= 0);
    SCORE_ASSERT(index < sizeof...(Args));
    [&]<std::size_t... I>(std::index_sequence<I...>)
    {
      (((index == I) && write_variant<I>(f)) || ...);
    }
    (std::make_index_sequence<sizeof...(Args)>{});
  }
 
  void operator()(auto& f) { r.stream() >> f; }
};
 
struct MessageBusReader
{
  QByteArray& mess;
 
  // Case for zero-argument message bus (e.g. just a ping)
  void operator()() { }
 
  template <typename T>
  requires std::is_trivial_v<T>
  void operator()(T& msg)
  {
    // Here we can just do a memcpy
    memcpy(&msg, mess.data(), mess.size());
  }
  template <typename T>
    requires(
        !std::is_trivial_v<T> && avnd::relocatable<T>
        && alignof(T) <= alignof(max_align_t))
  void operator()(T& msg)
  {
    auto src = reinterpret_cast<T*>(mess.data());
    msg = std::move(*src);
    std::destroy_at(src);
  }
 
  template <typename T>
    requires(
        !std::is_trivial_v<T>
        && (!avnd::relocatable<T> || (alignof(T) > alignof(max_align_t))))
  void operator()(T& msg)
  {
    // Deserialize... :D
 
    DataStreamWriter str{mess};
    Deserializer{str}(msg);
  }
};
 
}