TaskManager.h
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TaskManager.h
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	#ifndef _ECHO_TASKMANAGER_H_
	#define _ECHO_TASKMANAGER_H_
	#include <list>
	#include <queue>
	#include <echo/Types.h>
	#include <echo/Chrono/Chrono.h>
	#include <echo/Kernel/Task.h>
	#include <echo/cpp/functional>

	namespace Echo
	{
	class Task;

	/**
	* TaskManagers manages a list of tasks.
	* Tasks are added to task managers in order to be updated, receive pause and resume
	* notifications and are started and stopped as needed.
	*
	*/
	class TaskManager : public InheritableEnableSharedFromThis<TaskManager>
	{
	public:
	typedef function< void(void) > Action;

	TaskManager(std::string name = "");
	virtual ~TaskManager();

	/**
	* Check if the manager has a task.
	*/
	bool HasTask(Task* task) const;

	/**
	* Check if the manager has a task.
	*/
	bool HasTask(Task& task) const
	{
	return HasTask(&task);
	}

	/**
	* Check if the manager has at least one task.
	*/
	inline bool HasAtLeastOneTask() const
	{
	return !mTaskList.empty();
	}

	/**
	* Set the TaskManager name.
	*/
	virtual void SetTaskManagerName(const std::string& name)
	{
	mManagerName = name;
	}

	/**
	* Get the TaskManager name.
	*/
	const std::string& GetTaskManagerName() const
	{
	return mManagerName;
	}

	/**
	* Get whether the TaskManager is executing.
	*/
	bool GetExecuting() const
	{
	return mExecuting;
	}

	/**
	* Get whether the TaskManager is paused.
	* The paused state of a manager changes when PauseAllActiveTasks(),
	* ResumeAllPreviouslyActiveTasks() or ResumeAllTasks() is called.
	*/
	bool GetPaused() const
	{
	return mPaused;
	}

	/**
	* Calling this method will cause the Task's OnStart() method to be called.
	* If any task fails to start (OnStart() returns false) then all tasks are stopped and
	* this method will return false. This method returns true if all tasks successfully start.
	*
	* Normally this method is called by another TaskManager or TaskGroup when a Kernel starts,
	* however if you are managing the Updates of a TaskManager yourself call this method to
	* before you begin calling UpdateTasks(). This essentially changes the state of
	* TaskManager to "executing" to ensure newly added tasks are started and updated. Call
	* this method on your manually updated TaskManager before updates even if you haven't
	* added any tasks.
	*
	* The main purpose of StartTasks() is to provide tasks an opportunity to do something at
	* the beginning of their execution, which is different to Puase() and Resume(), which might
	* happen many times during execution. This provides tasks an OnStart() notification.
	*
	* All tasks in the list, whether active or not, will have their Start(), and subsequently
	* OnStart() methods called.
	*/
	bool StartTasks();

	/**
	* Stop all tasks.
	* This modifies the internal state of the manager to not executing.
	*
	* The method does not modify the task lists. i.e. the active task list will remain active.
	* It is expected that after StopTasks() you will no longer call UpdateTasks(), however if
	* you do the active tasks will still be updated. This is not a bug and by design to allow
	* task manages top be stopped, moved then started again without changing the task lists.
	*
	* Similar to StartTasks() the main purpose of StopTasks() is to provide tasks an opportunity
	* to do something at end of their execution, which is different to Puase() and Resume(),
	* which might happen many times during execution. This provides tasks an OnStart()
	* notification.
	*
	* All tasks in the list, whether active or not, will have their Stop(), and subsequently
	* OnStop() called.
	*/
	void StopTasks();

	/**
	* Add a task to the manager.
	*
	* After a Tasks is added it will be resumed if it was previously paused. This is due to the
	* assumption that a Task that is added to the manager is ready to be updated. If you want
	* a task to be paused, add it then pause it.
	*
	* If the TaskManager is executing the Task's Start() method will be called.
	*
	* Tasks will notify any managers they are members of when they are deleted so this is
	* effectively as safe as using a shared pointer.
	* @returns false if the task has already been added to this manager or if the Task's Start()
	* method returns false.
	*/
	bool AddTask(Task* task)
	{
	return AddTask(task, shared_ptr<Task>());
	}

	/**
	* Overload of AddTask() that takes a reference.
	* Tasks will notify any managers they are members of when they are deleted so this is
	* effectively as safe as using a shared pointer.
	* @see AddTask(Task* task)
	*/
	bool AddTask(Task& task)
	{
	return AddTask(&task,shared_ptr<Task>());
	}

	/**
	* Overload of AddTask() that takes a shared pointer.
	* @see AddTask(Task* task)
	*/
	bool AddTask(shared_ptr<Task> task)
	{
	return AddTask(task.get(),task);
	}

	/**
	* Remove a task from the manager.
	*/
	void RemoveTask(Task* tTask);

	/**
	* Remove a task from the manager.
	*/
	void RemoveTask(Task& task)
	{
	RemoveTask(&task);
	}

	/**
	* Remove a task from the manager.
	* The task does not need to be added using a shared pointer for this to work since
	* TaskManagers use raw pointers for comparison.
	*/
	void RemoveTask(shared_ptr<Task> task)
	{
	RemoveTask(task.get());
	}

	/**
	* Remove a task by name from the manager.
	* The name of a task is not cached when added, so the comparison is against any current task names.
	*/
	void RemoveTask(const std::string& taskName);

	/**
	* Remove all tasks from the manager.
	* This clears all tasks from the task list.
	*/
	void RemoveAllTasks();

	/**
	* Pause a task by name.
	* This method performs a search and if a task is found it is paused.
	* @see FindTask()
	* @param taskName the name of the task to look for.
	* @param deepSearch whether or not to perform a deepSearch.
	* @return true if the task was found.
	*/
	bool PauseTask(const std::string& taskName, bool deepSearch);

	/**
	* Resume a task by name.
	* This method performs a search and if a task is found it is resumed.
	* @see FindTask()
	* @param taskName the name of the task to look for.
	* @param deepSearch whether or not to perform a deepSearch.
	* @return true if the task was found.
	*/
	bool ResumeTask(const std::string& taskName, bool deepSearch);

	/**
	* Search for a task.
	* Searching is performed in this object first then if deepSearch is true the search
	* will continue in each child TaskManager.
	* @param name the name of the task to search for.
	* @param deepSearch if a matching task isn't found in the TaskManager each task will be checked to see if
	* it is a TaskManager and continue the search from there.
	* @return A pointer to the task if found, otherwise a null pointer.
	*/
	Task* FindTask(const std::string& name, bool deepSearch);

	/**
	* Search for a task by name and attempt to get the shared pointer for it.
	* @note The task needs to have been added using AddTask(shared_ptr<Task>).
	* @see FindTask()
	* @return A pointer to the task if found, otherwise a null pointer.
	*/
	shared_ptr<Task> FindSharedTask(const std::string& name, bool deepSearch);

	/**
	* Search for a task by name and attempt to get the cast pointer for it.
	* @see FindTask()
	* @return A pointer to the task if found, otherwise null pointer.
	*/
	template< class T >
	T* FindTask(const std::string& name, bool deepSearch)
	{
	return dynamic_cast<T*>(FindTask(name, deepSearch));
	}

	/**
	* Search for a task by name and attempt to get the cast shared pointer for it.
	* @note The task needs to have been added using AddTask(shared_ptr<Task>).
	* @see FindSharedTask()
	* @return A pointer to the task if found, otherwise a null pointer.
	*/
	template< class T >
	shared_ptr<T> FindSharedTask(const std::string& name, bool deepSearch)
	{
	return dynamic_pointer_cast<T>(FindSharedTask(name, deepSearch));
	}

	/**
	* Pause all active tasks.
	* This results in the TaskManager state changing to paused.
	*/
	void PauseAllActiveTasks(bool applicationPause = false);

	/**
	* Resume all previously active tasks.
	* This results in the task manager's state to change to resumed.
	*/
	void ResumeAllPreviouslyActiveTasks(bool applicationResume = false);

	/**
	* Resume all tasks.
	* This method resumes all active tasks but does not change the task managers resumed state.
	*/
	void ResumeAllTasks(bool applicationResume = false);

	void TaskWasPaused(Task& task);
	void TaskWasResumed(Task& task);

	/**
	* Update all active tasks.
	* Calling this after StopTasks() may still result in tasks being updated. @see StopTasks() for more information.
	*/
	void UpdateTasks(Seconds lastFrameTime);

	//!\ brief Get the number of active tasks in this manager.
	//!\ param includeChildTaskManagerTasks if true include the number of tasks active in child state manages too.
	//!\ param outputTaskList Outputs task names to std cout.
	//!\ param indendDepth this method is recursive and this parameter is used to set the indent depth for the task lists.
	size_t GetNumberOfActiveTasks(bool includeChildTaskManagerTasks = true, bool outputTaskList = false,size_t indentDepth = 0) const;

	//!\ brief Get the number of tasks in this manager.
	//!\ param includeChildTaskManagerTasks if true include the number of tasks active in child state manages too.
	//!\ param outputTaskList Outputs task names to std cout.
	//!\ param indendDepth this method is recursive and this parameter is used to set the indent depth for the task lists.
	size_t GetNumberOfTasks(bool includeChildTaskManagerTasks = false, bool outputTaskList = false,size_t indentDepth = 0) const;

	/**
	* Queue some action to be executed following the completion of the current or next UpdateTasks() call.
	* Actions are executed after UpdateTasks() finishes updating tasks so if the action is queued during an update it will
	* be performed immediately after, otherwise it will be performed after the next UpdateTasks() call.
	* updated.
	* This can be used when you're in a situation that you want to clean up some task in a hierarchy but doing so would delete
	* object that are in use/part way through updating. TaskManager tasks care of these situations with tasks automatically
	* and never updates deleted, removed or paused tasks even part way through an update but it has no control over
	* specialised Tasks.
	* @note Actions cannot be cancelled so only queue actions that you know will be valid when the TaskManager gets around to
	* executing them.
	* @param action Generic action to be called. The action is executed once then discarded.
	*/
	void QueuePostUpdateAction(Action action);
	private:
	void UpdateLists();

	/**
	* Internal structure used to manage the different ways a task might be added to a manager and
	* to provide a consistent way for the manager to use Tasks without checking how each task was
	* added to the manager.
	*/
	class TaskInfo
	{
	public:
	TaskInfo(Task* task, shared_ptr<Task> taskPtr = shared_ptr<Task>())
	{
	mHasBeenRemoved = make_shared<bool>(false);
	mHasBeenPaused = make_shared<bool>(false);
	mWaitingForResume = make_shared<bool>(false);
	mWaitingForPauseProcessing = make_shared<bool>(false);
	mCurrentPriority = task->GetPriority();
	mTask = task;
	mTaskPtr = taskPtr;
	}

	TaskInfo(const TaskInfo& otherTaskInfo)
	{
	mTask = otherTaskInfo.mTask;
	mTaskPtr = otherTaskInfo.mTaskPtr;
	mHasBeenRemoved = otherTaskInfo.mHasBeenRemoved;
	mHasBeenPaused = otherTaskInfo.mHasBeenPaused;
	mWaitingForResume = otherTaskInfo.mWaitingForResume;
	mWaitingForPauseProcessing = otherTaskInfo.mWaitingForPauseProcessing;
	mCurrentPriority = otherTaskInfo.mCurrentPriority;
	}

	TaskInfo& operator=(const TaskInfo& otherTaskInfo)
	{
	if (this == &otherTaskInfo)
	return *this;

	mTask = otherTaskInfo.mTask;
	mTaskPtr = otherTaskInfo.mTaskPtr;
	mHasBeenRemoved = otherTaskInfo.mHasBeenRemoved;
	mHasBeenPaused = otherTaskInfo.mHasBeenPaused;
	mWaitingForResume = otherTaskInfo.mWaitingForResume;
	mWaitingForPauseProcessing = otherTaskInfo.mWaitingForPauseProcessing;
	mCurrentPriority = otherTaskInfo.mCurrentPriority;
	return *this;
	}

	bool operator<(const TaskInfo& other) const
	{
	return (mCurrentPriority < other.mCurrentPriority);
	}

	bool operator==(const TaskInfo& otherTaskInfo) const
	{
	return (mTask == otherTaskInfo.GetTask());
	}

	bool operator==(const Task* otherTask) const
	{
	return (mTask == otherTask);
	}

	inline Task* GetTask() const
	{
	return mTask;
	}

	inline shared_ptr<Task> GetSharedTask()
	{
	return mTaskPtr;
	}

	inline bool GetHasBeenRemoved() const
	{
	return *mHasBeenRemoved;
	}

	void SetHasBeenRemoved(bool hasBeenRemoved)
	{
	*mHasBeenRemoved = hasBeenRemoved;
	}

	inline bool GetHasBeenPaused() const
	{
	return *mHasBeenPaused;
	}

	void SetHasBeenPaused(bool hasBeenPaused)
	{
	*mHasBeenPaused = hasBeenPaused;
	}

	inline bool GetWaitingForResume() const
	{
	return *mWaitingForResume;
	}
	inline bool GetWaitingForPauseProcessing() const
	{
	return *mWaitingForPauseProcessing;
	}

	void SetWaitingForResume(bool hasBeenResumed)
	{
	*mWaitingForResume = hasBeenResumed;
	}
	void SetWaitingForPauseProcessing(bool hasBeenPaused)
	{
	*mWaitingForPauseProcessing = hasBeenPaused;
	}
	void UpdatePriority()
	{
	if(mTask)
	{
	mCurrentPriority = mTask->GetPriority();
	}
	}
	private:
	Task* mTask;
	shared_ptr<Task> mTaskPtr; //!< If the task is added as a shared pointer this will be set.
	u32 mCurrentPriority;
	/*
	* These members are always going to be valid pointers. They are shared
	* pointers to reflect the state between lists.
	*/
	shared_ptr<bool> mHasBeenRemoved; //!< Task has been removed.
	shared_ptr<bool> mHasBeenPaused; //!< Task has been paused.
	shared_ptr<bool> mWaitingForResume; //!< Task is waiting for resume processing to get into the active list.
	shared_ptr<bool> mWaitingForPauseProcessing;//!< Task is waiting for pause processing to be removed from the active list.
	};
	typedef std::list< TaskInfo > TaskList;
	typedef TaskList::iterator TaskListIterator;
	typedef TaskList::const_iterator TaskListConstIterator;

	bool AddTask(Task* task, shared_ptr<Task> taskPtr);

	std::vector<Action> mPostUpdateActions;
	std::string mManagerName;
	TaskList mTaskList;
	TaskList mActiveTaskList;
	TaskList mPreviouslyActiveTaskList;
	bool mExecuting;
	bool mPaused;
	bool mUpdating;
	};
	}
	#endif

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