pgLab/pglablib/ASyncDBConnection.h

#ifndef ASYNCDBCONNECTION_H
#define ASYNCDBCONNECTION_H

#include <QObject>

#include "Pgsql_Connection.h"
#include "Pgsql_Params.h"
#include "Pgsql_Result.h"
#include "Expected.h"
#include "ConnectionConfig.h"
#include <QElapsedTimer>
#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 on that routine is called.
 */
class ASyncDBConnection: public QObject {
    Q_OBJECT
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();

	/** Sends command to the server.

	When the result is in on_result will be	called directly within the thread.

	If the command gives multiple results on_result will be called for each result.
	*/
	bool send(const std::string &command, on_result_callback on_result);
	bool send(const std::string &command, Pgsql::Params params, on_result_callback on_result);

	bool cancel();
    
signals:
    void onStateChanged(ASyncDBConnection::State state);
    void onNotice(Pgsql::ErrorDetails notice);

private:
	Pgsql::Connection m_connection;
    boost::asio::ip::tcp::socket m_asioSock;
	ConnectionConfig m_config;
	State m_state = State::NotConnected;
    Pgsql::Canceller m_canceller;
    
    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);
};

Q_DECLARE_METATYPE(ASyncDBConnection::State);
Q_DECLARE_METATYPE(Pgsql::ErrorDetails);


#endif // ASYNCDBCONNECTION_H