pgLab/core/QueuedBackgroundTask.h

#pragma once 

#include <functional>
#include <QRunnable>
//#include <QVector>
#include <QMutex>
#include <QWaitCondition>

/** Base class for an object that can be queued for execution in the background.
 * 
 * It is meaned for long running processes the end user might want to abort,
 * pause and check progress on.
 */
class QueuedBackgroundTask: public QRunnable {
public:
	using CompletionFunction = std::function<void(QRunnable *)>;

	explicit QueuedBackgroundTask(CompletionFunction on_completion);
	virtual ~QueuedBackgroundTask();

	void cancel();
	void wait();
	bool hasException() const;
	void rethrow();

protected:

	bool m_canceled = false;
	bool m_started = false;
	bool m_finished = false;
	std::exception_ptr doRunException = nullptr;
	CompletionFunction m_completionFunction = nullptr;

	QMutex stateMutex;
	QWaitCondition finished;

	virtual void run() override;

	virtual void doRun() = 0;

//    /** Task should exit it's run method but remember it's state, it might be resumed later.
//     */
//    void requestPause();
    
//    /** Request to stop running and forget progress
//     */
//    void requestAbort();
    
//    QString getProgressInfo();
};

//class BackgroundTaskInfo {
//public:
//};

///** Manages objects of type QueuedBackgroundTask
// *
// * The basic operation of this queue is hand everything directly of to the default
// * threadpool and that will decide when to run each task. But extra functions are
// * provided to control tasks to allow the program to have a UI for controlling the tasks
// */
//class BackgroundTaskQueue {
    
//public:
    
//    /** Returns a list of tasks in the queue and their progress.
//     *
//     * When building a UI to show realtime activity then make sure to first register the update events
//     * then get the snapshot. After that you can use the events to update the contents of the UI.
//     */
//    QVector<BackgroundTaskInfo> getTaskInfoSnapshort();
    
//    void pauseTask( );
    
//    /** Resume a paused task
//     */
//    void resumeTask( );
    
//    void abortTask( );
    
//};