Checker.h

#pragma once
 
#include <xrpl/beast/net/IPAddressConversion.h>
 
#include <boost/asio/io_context.hpp>
#include <boost/asio/ip/tcp.hpp>
#include <boost/intrusive/list.hpp>
 
#include <condition_variable>
#include <memory>
#include <mutex>
 
namespace xrpl::PeerFinder {

template <class Protocol = boost::asio::ip::tcp>
class Checker
{
private:
    using error_code = boost::system::error_code;
 
    struct BasicAsyncOp : boost::intrusive::list_base_hook<
                              boost::intrusive::link_mode<boost::intrusive::normal_link>>
    {
        virtual ~BasicAsyncOp() = default;
 
        virtual void
        stop() = 0;
 
        virtual void
        operator()(error_code const& ec) = 0;
    };
 
    template <class Handler>
    struct AsyncOp : BasicAsyncOp
    {
        using socket_type = Protocol::socket;
        using endpoint_type = Protocol::endpoint;
 
        Checker& checker;
        socket_type socket;
        Handler handler;
 
        AsyncOp(Checker& owner, boost::asio::io_context& ioContext, Handler&& handler);
 
        ~AsyncOp() override
        {
            checker.remove(*this);
        }
 
        void
        stop() override;
 
        void
        operator()(error_code const& ec) override;  // NOLINT(readability-identifier-naming)
    };
 
    //--------------------------------------------------------------------------
 
    using list_type =
        boost::intrusive::make_list<BasicAsyncOp, boost::intrusive::constant_time_size<true>>::type;
 
    std::mutex mutex_;
    std::condition_variable cond_;
    boost::asio::io_context& ioContext_;
    list_type list_;
    bool stop_ = false;
 
public:
    explicit Checker(boost::asio::io_context& ioContext);

    ~Checker();

    void
    stop();

    void
    wait();

    template <class Handler>
    void
    asyncConnect(beast::IP::Endpoint const& endpoint, Handler&& handler);
 
private:
    void
    remove(BasicAsyncOp& op);
};
 
//------------------------------------------------------------------------------
 
template <class Protocol>
template <class Handler>
Checker<Protocol>::AsyncOp<Handler>::AsyncOp(
    Checker& owner,
    boost::asio::io_context& ioContext,
    Handler&&
        handler)  // NOLINT(cppcoreguidelines-rvalue-reference-param-not-moved) -- forwarded in init
    : checker(owner), socket(ioContext), handler(std::forward<Handler>(handler))
{
}
 
template <class Protocol>
template <class Handler>
void
Checker<Protocol>::AsyncOp<Handler>::stop()
{
    error_code ec;
    socket.cancel(ec);
}
 
template <class Protocol>
template <class Handler>
void
Checker<Protocol>::AsyncOp<Handler>::operator()(error_code const& ec)
{
    handler(ec);
}
 
//------------------------------------------------------------------------------
 
template <class Protocol>
Checker<Protocol>::Checker(boost::asio::io_context& ioContext) : ioContext_(ioContext)
{
}
 
template <class Protocol>
Checker<Protocol>::~Checker()
{
    wait();
}
 
template <class Protocol>
void
Checker<Protocol>::stop()
{
    std::scoped_lock const lock(mutex_);
    if (!stop_)
    {
        stop_ = true;
        for (auto& c : list_)
            c.stop();
    }
}
 
template <class Protocol>
void
Checker<Protocol>::wait()
{
    std::unique_lock<std::mutex> lock(mutex_);
    while (!list_.empty())
        cond_.wait(lock);
}
 
template <class Protocol>
template <class Handler>
void
Checker<Protocol>::asyncConnect(beast::IP::Endpoint const& endpoint, Handler&& handler)
{
    auto const op =
        std::make_shared<AsyncOp<Handler>>(*this, ioContext_, std::forward<Handler>(handler));
    {
        std::scoped_lock const lock(mutex_);
        list_.push_back(*op);
    }
    op->socket.async_connect(
        beast::IPAddressConversion::toAsioEndpoint(endpoint),
        std::bind(&BasicAsyncOp::operator(), op, std::placeholders::_1));
}
 
template <class Protocol>
void
Checker<Protocol>::remove(BasicAsyncOp& op)
{
    std::scoped_lock const lock(mutex_);
    list_.erase(list_.iterator_to(op));
    if (list_.size() == 0)
        cond_.notify_all();
}
 
}  // namespace xrpl::PeerFinder