mqtt5/include/async_mqtt5/impl/autoconnect_stream.hpp

#ifndef ASYNC_MQTT5_AUTOCONNECT_STREAM_HPP
#define ASYNC_MQTT5_AUTOCONNECT_STREAM_HPP

#include <utility>

#include <boost/asio/ip/tcp.hpp>

#include <async_mqtt5/detail/async_mutex.hpp>
#include <async_mqtt5/detail/async_traits.hpp>

#include <async_mqtt5/impl/endpoints.hpp>
#include <async_mqtt5/impl/read_op.hpp>
#include <async_mqtt5/impl/reconnect_op.hpp>
#include <async_mqtt5/impl/write_op.hpp>

namespace async_mqtt5::detail {

namespace asio = boost::asio;
using error_code = boost::system::error_code;

template <
	typename StreamType,
	typename StreamContext = std::monostate
>
class autoconnect_stream {
public:
	using self_type = autoconnect_stream<StreamType, StreamContext>;
	using stream_type = StreamType;
	using stream_context_type = StreamContext;
	using executor_type = typename stream_type::executor_type;
private:
	using stream_ptr = std::shared_ptr<stream_type>;

	executor_type _stream_executor;
	async_mutex _conn_mtx;
	asio::steady_timer _read_timer, _connect_timer;
	endpoints _endpoints;

	stream_ptr _stream_ptr;
	stream_context_type& _stream_context;

	template <typename Owner, typename Handler>
	friend class read_op;

	template <typename Owner, typename Handler>
	friend class write_op;

	template <typename Stream>
	friend class reconnect_op;

	template <typename Owner, typename DisconnectContext>
	friend class disconnect_op;

public:
	autoconnect_stream(
		const executor_type& ex, stream_context_type& context
	) :
		_stream_executor(ex),
		_conn_mtx(_stream_executor),
		_read_timer(_stream_executor), _connect_timer(_stream_executor),
		_endpoints(_stream_executor, _connect_timer),
		_stream_context(context)
	{
		replace_next_layer(construct_next_layer());
	}

	using next_layer_type = stream_type;
	next_layer_type& next_layer() {
		return *_stream_ptr;
	}

	const next_layer_type& next_layer() const {
		return *_stream_ptr;
	}

	executor_type get_executor() const noexcept {
		return _stream_executor;
	}

	void brokers(std::string hosts, uint16_t default_port) {
		_endpoints.brokers(std::move(hosts), default_port);
	}

	bool is_open() const noexcept {
		return lowest_layer(*_stream_ptr).is_open();
	}

	void open() {
		error_code ec;
		lowest_layer(*_stream_ptr).open(asio::ip::tcp::v4(), ec);
		lowest_layer(*_stream_ptr).set_option(asio::ip::tcp::no_delay(true), ec);
	}

	void cancel() {
		error_code ec;
		lowest_layer(*_stream_ptr).cancel(ec);
	}

	void close() {
		error_code ec;
		shutdown(asio::ip::tcp::socket::shutdown_both);
		lowest_layer(*_stream_ptr).close(ec);
		_connect_timer.cancel();
	}

	void shutdown(asio::ip::tcp::socket::shutdown_type what) {
		error_code ec;
		lowest_layer(*_stream_ptr).shutdown(what, ec);
	}

	bool was_connected() const {
		error_code ec;
		lowest_layer(*_stream_ptr).remote_endpoint(ec);
		return ec == boost::system::errc::success;
	}

	template <typename BufferType, typename CompletionToken>
	decltype(auto) async_read_some(
		const BufferType& buffer, duration wait_for, CompletionToken&& token
	) {
		using Signature = void (error_code, size_t);

		auto initiation = [](
			auto handler, self_type& self,
			const BufferType& buffer, duration wait_for
		) {
			read_op { self, std::move(handler) }.perform(buffer, wait_for);
		};

		return asio::async_initiate<CompletionToken, Signature>(
			initiation, token, std::ref(*this), buffer, wait_for
		);
	}

	template <typename BufferType, typename CompletionToken>
	decltype(auto) async_write(
		const BufferType& buffer, CompletionToken&& token
	) {
		using Signature = void (error_code, size_t);

		auto initiation = [](
			auto handler, self_type& self, const BufferType& buffer
		) {
			write_op { self, std::move(handler) }.perform(buffer);
		};

		return asio::async_initiate<CompletionToken, Signature>(
			initiation, token, std::ref(*this), buffer
		);
	}

private:
	stream_ptr construct_next_layer() const {
		stream_ptr sptr;
		if constexpr (has_tls_context<StreamContext>)
			sptr = std::make_shared<stream_type>(
				_stream_executor, _stream_context.tls_context()
			);
		else
			sptr = std::make_shared<stream_type>(_stream_executor);

		error_code ec;
		lowest_layer(*sptr).set_option(
			asio::socket_base::reuse_address(true), ec
		);

		return sptr;
	}

	void replace_next_layer(stream_ptr sptr) {
		// close() will cancel all outstanding async operations on
		// _stream_ptr; cancelling posts operation_aborted to handlers
		// but handlers will be executed after std::exchange below;
		// handlers should therefore treat (operation_aborted && is_open())
		// equivalent to try_again.

		if (_stream_ptr)
			close();
		std::exchange(_stream_ptr, std::move(sptr));
	}

	template <typename CompletionToken>
	decltype(auto) async_reconnect(stream_ptr s, CompletionToken&& token) {
		using Signature = void (error_code);

		auto initiation = [](auto handler, self_type& self, stream_ptr s) {
			reconnect_op { self, std::move(handler) }.perform(s);
		};

		return asio::async_initiate<CompletionToken, Signature>(
			initiation, token, std::ref(*this), s
		);
	}
};


} // end namespace async_mqtt5::detail

#endif // !ASYNC_MQTT5_AUTOCONNECT_STREAM_HPP