message_reinit.hpp

// Copyright 2024 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#pragma once
#include "message_intf.hpp"

#include <stdplus/print.hpp>

#include <functional>
#include <optional>
#include <tuple>
#include <type_traits>
#include <utility>

namespace google
{
namespace hoth
{

template <typename Intf, typename... Data>
class MessageReinit : public MessageIntf
{
  public:
    template <typename... Ts>
    explicit MessageReinit(Ts&&... args) : data(std::forward<Ts>(args)...)
    {
        static_assert(std::is_base_of_v<MessageIntf, Intf>);
        try
        {
            intf.emplace(std::make_from_tuple<Intf>(data));
        }
        catch (const std::exception& e)
        {
            stdplus::print(stderr,
                           "Failed to eager initialize message handler: {}\n",
                           e.what());
        }
    }

    void send(const uint8_t* buf, size_t size, size_t seek) override
    {
        return reinitExec(&Intf::send, buf, size, seek);
    }

    void recv(uint8_t* buf, size_t size, size_t seek) override
    {
        return reinitExec(&Intf::recv, buf, size, seek);
    }

  private:
    std::tuple<std::remove_cv_t<std::remove_reference_t<Data>>...> data;
    std::optional<Intf> intf;

    template <typename Func, typename... Args>
    auto reinitExec(Func&& func, Args&&... args)
    {
        if (!intf)
        {
            intf.emplace(std::make_from_tuple<Intf>(data));
        }
        try
        {
            return std::invoke(std::forward<Func>(func), *intf,
                               std::forward<Args>(args)...);
        }
        catch (...)
        {
            intf.reset();
            throw;
        }
    }
};

} // namespace hoth
} // namespace google