qgstaskmanager.h

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/***************************************************************************
                          qgstaskmanager.h
                          ----------------
    begin                : April 2016
    copyright            : (C) 2016 by Nyall Dawson
    email                : nyall dot dawson at gmail dot com
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

#ifndef QGSTASKMANAGER_H
#define QGSTASKMANAGER_H

#include <QObject>
#include "qgis_sip.h"
#include <QMap>
#include <QFuture>
#include <QReadWriteLock>

#include "qgis_core.h"
#include "qgsmaplayer.h"

class QgsTask;
class QgsTaskRunnableWrapper;

typedef QList< QgsTask * > QgsTaskList;

class CORE_EXPORT QgsTask : public QObject
{
    Q_OBJECT

  public:

    enum TaskStatus
    {
      Queued, 
      OnHold, 
      Running, 
      Complete, 
      Terminated, 
    };
    Q_ENUM( TaskStatus )

    
    enum Flag
    {
      CanCancel = 1 << 1, 
      AllFlags = CanCancel, 
    };
    Q_DECLARE_FLAGS( Flags, Flag )

    
    QgsTask( const QString &description = QString(), QgsTask::Flags flags = AllFlags );

    ~QgsTask() override;

    Flags flags() const { return mFlags; }

    void setDescription( const QString &description );

    bool canCancel() const { return mFlags & CanCancel; }

    bool isActive() const { return mOverallStatus == Running; }

    TaskStatus status() const { return mOverallStatus; }

    QString description() const { return mDescription; }

    double progress() const { return mTotalProgress; }

    qint64 elapsedTime() const;

    virtual void cancel();

    void hold();

    void unhold();

    enum SubTaskDependency
    {
      SubTaskIndependent = 0, 
      ParentDependsOnSubTask, 
    };

    void addSubTask( QgsTask *subTask SIP_TRANSFER, const QgsTaskList &dependencies = QgsTaskList(),
                     SubTaskDependency subTaskDependency = SubTaskIndependent );

    void setDependentLayers( const QList<QgsMapLayer *> &dependentLayers );

    QList< QgsMapLayer * > dependentLayers() const;

    bool waitForFinished( int timeout = 30000 );

  signals:

    void progressChanged( double progress );

    void statusChanged( int status );

    void begun();

    void taskCompleted();

    void taskTerminated();

  protected:

    virtual bool run() = 0;

    virtual void finished( bool result ) { Q_UNUSED( result ) }

    bool isCanceled() const { return mShouldTerminate; }

  protected slots:

    void setProgress( double progress );

  private slots:
    void subTaskStatusChanged( int status );

  private:

    Flags mFlags;
    QString mDescription;
    TaskStatus mStatus = Queued;
    TaskStatus mOverallStatus = Queued;

    QMutex mNotFinishedMutex;

    QSemaphore mNotStartedMutex;

    double mProgress = 0.0;
    double mTotalProgress = 0.0;
    bool mShouldTerminate = false;
    int mStartCount = 0;

    struct SubTask
    {
      SubTask( QgsTask *task, const QgsTaskList &dependencies, SubTaskDependency dependency )
        : task( task )
        , dependencies( dependencies )
        , dependency( dependency )
      {}
      QgsTask *task = nullptr;
      QgsTaskList dependencies;
      SubTaskDependency dependency;
    };
    QList< SubTask > mSubTasks;

    QgsWeakMapLayerPointerList mDependentLayers;

    QElapsedTimer mElapsedTime;


    void start();

    void completed();

    void terminated();

    void processSubTasksForCompletion();

    void processSubTasksForTermination();

    void processSubTasksForHold();

    friend class QgsTaskManager;
    friend class QgsTaskRunnableWrapper;
    friend class TestQgsTaskManager;

};


Q_DECLARE_OPERATORS_FOR_FLAGS( QgsTask::Flags )


class CORE_EXPORT QgsTaskManager : public QObject
{
    Q_OBJECT

  public:

    QgsTaskManager( QObject *parent SIP_TRANSFERTHIS = nullptr );

    ~QgsTaskManager() override;

    struct TaskDefinition
    {

      explicit TaskDefinition( QgsTask *task, const QgsTaskList &dependentTasks = QgsTaskList() )
        : task( task )
        , dependentTasks( dependentTasks )
      {}

      QgsTask *task = nullptr;

      QgsTaskList dependentTasks;

    };

    long addTask( QgsTask *task SIP_TRANSFER, int priority = 0 );

    long addTask( const TaskDefinition &task SIP_TRANSFER, int priority = 0 );

    QgsTask *task( long id ) const;

    QList<QgsTask *> tasks() const;

    int count() const;

    long taskId( QgsTask *task ) const;

    void cancelAll();

    bool dependenciesSatisfied( long taskId ) const;

    QSet< long > dependencies( long taskId ) const SIP_SKIP;

    QList< QgsMapLayer * > dependentLayers( long taskId ) const;

    QList< QgsTask * > tasksDependentOnLayer( QgsMapLayer *layer ) const;

    QList< QgsTask * > activeTasks() const;

    int countActiveTasks() const;

  public slots:

    void triggerTask( QgsTask *task );

  signals:

    void progressChanged( long taskId, double progress );

    void finalTaskProgressChanged( double progress );

    void statusChanged( long taskId, int status );

    void taskAdded( long taskId );

    void taskAboutToBeDeleted( long taskId );

    void allTasksFinished();

    void countActiveTasksChanged( int count );

    void taskTriggered( QgsTask *task );

  private slots:

    void taskProgressChanged( double progress );
    void taskStatusChanged( int status );
    void layersWillBeRemoved( const QList<QgsMapLayer *> &layers );

  private:

    struct TaskInfo
    {
      TaskInfo( QgsTask *task = nullptr, int priority = 0 );
      void createRunnable();
      QgsTask *task = nullptr;
      QAtomicInt added;
      int priority;
      QgsTaskRunnableWrapper *runnable = nullptr;
    };

    mutable QMutex *mTaskMutex;

    QMap< long, TaskInfo > mTasks;
    QMap< long, QgsTaskList > mTaskDependencies;
    QMap< long, QgsWeakMapLayerPointerList > mLayerDependencies;

    long mNextTaskId = 1;

    QSet< QgsTask * > mActiveTasks;
    QSet< QgsTask * > mParentTasks;
    QSet< QgsTask * > mSubTasks;

    QSet< QgsTask * > mPendingDeletion;

    long addTaskPrivate( QgsTask *task,
                         QgsTaskList dependencies,
                         bool isSubTask,
                         int priority );

    bool cleanupAndDeleteTask( QgsTask *task );

    void processQueue();

    void cancelDependentTasks( long taskId );

    bool resolveDependencies( long firstTaskId, long currentTaskId, QSet< long > &results ) const;

    bool hasCircularDependencies( long taskId ) const;

    friend class TestQgsTaskManager;
};

#endif //QGSTASKMANAGER_H