pgLab/pglab/ASyncDBConnection.h

#ifndef ASYNCDBCONNECTION_H
#define ASYNCDBCONNECTION_H

#include "Pgsql_Connection.h"
#include "Pgsql_Params.h"
#include "Pgsql_Result.h"
#include "Expected.h"
#include "ConnectionConfig.h"
#include <QElapsedTimer>
#include <functional>
#include <mutex>
#include <boost/asio/ip/tcp.hpp>
#include <boost/asio/io_service.hpp>

/** \brief Class that handles asynchronous execution of queries.
 *
 * Queries are passed to this class with a routine to call on completion
 * when the result is received that routine is called. The asynchronous
 * processing is done using boost::asio.
 *
 * You can cancel a running query but even then you have to wait for the result.
 */
class ASyncDBConnection {
public:
	enum class State {
		NotConnected,
		Connecting,
		Connected, ///< connected and idle
		QuerySend, ///< connected query send expecting result
		CancelSend, ///< cancel send expecting result
		Terminating ///< shutting down
	};

	using on_result_callback = std::function<void(Expected<std::shared_ptr<Pgsql::Result>>, qint64)>;

	explicit ASyncDBConnection(boost::asio::io_service &ios);
    ~ASyncDBConnection();

	State state() const;
	void setupConnection(const ConnectionConfig &config);
	void closeConnection();

	/** \defgroup send These function send queries to the server.
	 *
	 * The query string can actually contain multiple queries.
	 * These functions report their results through a callback function.
	 * If the command gives multiple results on_result will be called for each result.
	 *
	 * \note when the io_service that was passed to the constructor is running
	 * on a different thread the callback also will be done on that thread. Forward
	 * the call to your own thread if needed.
	 *
	 * \note while you can pass multiple queries to a single send call it is not allowed to
	 *   send new queries while not all results have been received.
	 */

	/** \ingroup send
	 * \brief Function to send a command without parameters to the server.
	 */
	bool send(const std::string &command, on_result_callback on_result);
	/** \ingroup send
	 * \brief Function to send a a command with parameters to the server.
	 */
	bool send(const std::string &command, Pgsql::Params params, on_result_callback on_result);

	bool cancel();
    
	using StateChangeReceiver = std::function<void(ASyncDBConnection::State)>;
	void setStateChangeReceiver(StateChangeReceiver state_change_receiver);

	using NoticeReceiver = std::function<void(Pgsql::ErrorDetails)>;
	void setNoticeReceiver(NoticeReceiver notice_receiver);

private:
	Pgsql::Connection m_connection;
    boost::asio::ip::tcp::socket m_asioSock;
	ConnectionConfig m_config;
	State m_state = State::NotConnected;
    Pgsql::Canceller m_canceller;
	StateChangeReceiver m_stateChangeReceiver;
	NoticeReceiver m_noticeReceiver;

    QElapsedTimer m_timer;
    
    void async_connect_handler(boost::system::error_code ec, std::size_t s);
    void async_query_handler(boost::system::error_code ec, std::size_t s, on_result_callback on_result);
    void doStateCallback(State state);
    void processNotice(const PGresult *result);
};

#endif // ASYNCDBCONNECTION_H