CollisionHandlingMovement.h

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/FloatingPawnMovement.h"
#include "Components/CapsuleComponent.h"

#include "CollisionHandlingMovement.generated.h"

/*
 * This Movement component is needed since in VR not only the pawn itself (UpdatedComponent) is moved but also the
 * user herself can walk and thereby move the CameraComponent, which can also lead to collisions or e.g. going up steps
 *
 * The four modes are:
 * - None: No controller movement is applied and no corrections regarding steps or collisions with walls are done
 * - Ghost: The same as above but now the Inputs can be used for unconstrained flying (also through objects)
 * - Fly: The user can fly but not through walls etc. When the user walks against a wall the scene is moved with her to
 *     avoid walking through The user can also walk up stairs with a maximum step height of MaxStepHeight
 * - Walk: Additionally to Fly, now gravity keeps the user on the floor
 */

UENUM(BlueprintType)
enum class EVRNavigationModes : uint8
{
	NAV_NONE UMETA(DisplayName = "None (no controller movement)"),
	NAV_GHOST UMETA(DisplayName = "Ghost (flying, also through walls)"),
	NAV_FLY UMETA(DisplayName = "Fly (prohibiting collisions)"),
	NAV_WALK UMETA(DisplayName = "Walk (gravity and prohibiting collisions)")
};

UCLASS()
class RWTHVRTOOLKIT_API UCollisionHandlingMovement : public UFloatingPawnMovement
{
	GENERATED_UCLASS_BODY()

public:
	virtual void BeginPlay() override;
	void CheckAndRevertCollisionSinceLastTick();

	void MoveOutOfNewDynamicCollisions();
	virtual void TickComponent(float DeltaTime, enum ELevelTick TickType,
							   FActorComponentTickFunction* ThisTickFunction) override;

	void SetHeadComponent(USceneComponent* NewHeadComponent);

	UFUNCTION(BlueprintCallable)
	bool AddActorToIgnore(AActor* ActorToIgnore);

	UFUNCTION(BlueprintCallable)
	bool RemoveActorFromIgnore(AActor* ActorToIgnore);

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "VR Movement")
	EVRNavigationModes NavigationMode = EVRNavigationModes::NAV_WALK;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "VR Movement", meta = (ClampMin = "0.0"))
	float MaxStepHeight = 40.0f;

	// if the height that the pawn would fall (in walking mode) is higher
	// it is not falling, set to <0.0f if you want to fall infinitely
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "VR Movement")
	float MaxFallingDepth = 1000.0f;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "VR Movement", meta = (ClampMax = "0.0"))
	float GravityAcceleration = -981.0f;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "VR Movement", meta = (ClampMin = "0.0"))
	float UpSteppingAcceleration = 981.0f;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "VR Movement", meta = (ClampMin = "0.0"))
	float CapsuleRadius = 40.0f;

private:
	// check for
	FHitResult CreateCapsuleTrace(const FVector& Start, const FVector& End, bool DrawDebug = false) const;
	TOptional<FVector> GetOverlapResolveDirection() const;
	void SetCapsuleColliderToUserSize() const;
	void CheckForPhysWalkingCollision();
	FVector GetCollisionSafeVirtualSteeringVec(FVector InputVector, float DeltaTime);
	void MoveByGravityOrStepUp(float DeltaSeconds);
	void ShiftVertically(float Distance, float VerticalAcceleration, float DeltaSeconds);

	UPROPERTY(VisibleAnywhere)
	UCapsuleComponent* CapsuleColliderComponent = nullptr;

	UPROPERTY(VisibleAnywhere, Transient, DuplicateTransient)
	USceneComponent* HeadComponent = nullptr;

	float VerticalSpeed = 0.0f;
	TOptional<FVector> LastCollisionFreeCapsulePosition;
	FVector LastSteeringCollisionVector;

	// just stored for performance gains;
	UPROPERTY(VisibleAnywhere, Transient, DuplicateTransient)
	TArray<AActor*> ActorsToIgnore;

	// if a collision happens and cannot be resolved (e.g. the user crouched, walked under something and stood up)
	// we remporarily deactivate all checks until the user is in a collision free situation again
	bool bCollisionChecksTemporarilyDeactivated = false;
};