UnrealEngineUWP/Engine/Plugins/Runtime/StateTree/Source/StateTreeModule/Public/StateTreeTaskBase.h

// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "StateTreeTypes.h"
#include "StateTreeNodeBase.h"
#include "StateTreeTaskBase.generated.h"

struct FStateTreeExecutionContext;

/**
 * Base struct for StateTree Tasks.
 * Tasks are logic executed in an active state.
 */
USTRUCT(meta = (Hidden))
struct STATETREEMODULE_API FStateTreeTaskBase : public FStateTreeNodeBase
{
	GENERATED_BODY()

	/**
	 * Called when a new state is entered and task is part of active states. The change type parameter describes if the task's state
	 * was previously part of the list of active states (Sustained), or if it just became active (Changed).
	 * @param Context Reference to current execution context.
	 * @param ChangeType Describes the change type (Changed/Sustained).
	 * @param Transition Describes the states involved in the transition
	 * @return Succeed/Failed will end the state immediately and trigger to select new state, Running will carry on to tick the state.
	 */
	virtual EStateTreeRunStatus EnterState(FStateTreeExecutionContext& Context, const EStateTreeStateChangeType ChangeType, const FStateTreeTransitionResult& Transition) const { return EStateTreeRunStatus::Running; }

	/**
	* Called when a current state is exited and task is part of active states. The change type parameter describes if the task's state
	* will be active after the transition (Sustained), or if it will became inactive (Changed).
	* @param Context Reference to current execution context.
	* @param ChangeType Describes the change type (Changed/Sustained).
	* @param Transition Describes the states involved in the transition
	*/
	virtual void ExitState(FStateTreeExecutionContext& Context, const EStateTreeStateChangeType ChangeType, const FStateTreeTransitionResult& Transition) const {}

	/**
	 * Called Right after a state has been completed. StateCompleted is called in reverse order to allow to propagate state to Evaluators and Tasks that
	 * are executed earlier in the tree. Note that StateCompleted is not called if conditional transition changes the state.
	 * @param Context Reference to current execution context.
	 * @param CompletionStatus Describes the running status of the completed state (Succeeded/Failed).
	 * @param CompletedActiveStates Active states at the time of completion.
	 */
	virtual void StateCompleted(FStateTreeExecutionContext& Context, const EStateTreeRunStatus CompletionStatus, const FStateTreeActiveStates& CompletedActiveStates) const {}

	/**
	 * Called during state tree tick when the task is on active state.
	 * @param Context Reference to current execution context.
	 * @param DeltaTime Time since last StateTree tick.
	 * @return Running status of the state: Running if still in progress, Succeeded if execution is done and succeeded, Failed if execution is done and failed.
	 */
	virtual EStateTreeRunStatus Tick(FStateTreeExecutionContext& Context, const float DeltaTime) const { return EStateTreeRunStatus::Running; };

#if WITH_GAMEPLAY_DEBUGGER
	virtual void AppendDebugInfoString(FString& DebugString, const FStateTreeExecutionContext& Context) const;
#endif
};

/**
 * Base class (namespace) for all common Tasks that are generally applicable.
 * This allows schemas to safely include all conditions child of this struct. 
 */
USTRUCT(meta = (Hidden))
struct STATETREEMODULE_API FStateTreeTaskCommonBase : public FStateTreeTaskBase
{
	GENERATED_BODY()
};