UE4_EscapeGame_GrabBug

// Joao Costa 2017

#include "Unreal4_Escape.h"
#include "Grabber.h"


// Sets default values for this component's properties
UGrabber::UGrabber()
{
    // Set this component to be initialized when the game starts, and to be ticked every frame.  You can turn these features
    // off to improve performance if you don't need them.
    PrimaryComponentTick.bCanEverTick = true;

    // ...
}


// Called when the game starts
void UGrabber::BeginPlay()
{
    Super::BeginPlay();

    /// Get the owner
    this->Owner = GetOwner();

    /// Find necessary handles
    this->FindPhysicsHandleComponent();
    this->FindInputComponent();
}

// Called every frame
void UGrabber::TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction* ThisTickFunction)
{
    Super::TickComponent(DeltaTime, TickType, ThisTickFunction);

    /// Keep the player position updated
    this->UpdatePlayerViewpoint();

    /// Draw and aux debug line
    DrawDebugLine(
        GetWorld(),
        this->GetRayCastLineStart(),
        this->GetRayCastLineEnd(),
        FColor(255, 0, 0),
        false,
        0.0f,
        0,
        2.0f
    );

    /// Move grabbed object if there is one
    if (this->PhysicsHandle->GrabbedComponent)
    {
        /// Mode the handle
        this->PhysicsHandle->SetTargetLocation(this->GetRayCastLineEnd());
    }
}

// Find physics handle
void UGrabber::FindPhysicsHandleComponent() {
    /// Attach Physics handle
    this->PhysicsHandle = this->Owner->FindComponentByClass<UPhysicsHandleComponent>();

    /// Verify correct attachment
    if (!this->PhysicsHandle) {
        UE_LOG(LogTemp, Error, TEXT("%s mising physics handle component"), *this->Owner->GetName());
    }
}

// Find input component
void UGrabber::FindInputComponent() {
    /// Attach Input handler
    this->InputComponent = this->Owner->FindComponentByClass<UInputComponent>();

    /// Verify correct attachment
    if (!this->InputComponent) {
        UE_LOG(LogTemp, Error, TEXT("%s mising input handle"), *this->Owner->GetName());
    }
    else {
        this->InputComponent->BindAction("Grab", IE_Pressed, this, &UGrabber::Grab);
        this->InputComponent->BindAction("Grab", IE_Released, this, &UGrabber::Release);
    }
}

void UGrabber::Grab() {
    UE_LOG(LogTemp, Warning, TEXT("Grab key pressed"));

    /// Ray-cast and check objects within reach
    FHitResult HitResult = this->GetFirstPhysicsBodyInReach();
    auto ComponentToGrab = HitResult.GetComponent();
    auto ActorHit = HitResult.GetActor();

    /// Attach physics handle if there's and object within reach
    if (ActorHit) {
        /// DEBUG AUX
        UE_LOG(LogTemp, Warning, TEXT("Player hit actor %s"), *(ActorHit->GetName()));

        /// Update the viewpoint
        this->UpdatePlayerViewpoint();
        /// Attach the physic handle
        this->PhysicsHandle->GrabComponentAtLocationWithRotation(
            ComponentToGrab,
            NAME_None,
            this->PlayerViewPoint.Location,
            FRotator(0.0f, 0.0f, 0.0f)
        );
    }
}

void UGrabber::Release() {
    UE_LOG(LogTemp, Warning, TEXT("Grab key released"));

    /// Release the handle
    this->PhysicsHandle->ReleaseComponent();
}

// Store Player Viewpoint
void UGrabber::UpdatePlayerViewpoint()
{
    /// Get current player viewpoint and update attributes
    GetWorld()->GetFirstPlayerController()->GetPlayerViewPoint(
        this->PlayerViewPoint.Location,
        this->PlayerViewPoint.Rotation
    );
}

// Get reach line start
const FVector UGrabber::GetRayCastLineStart()
{
    /// Update the viewpoint
    this->UpdatePlayerViewpoint();
    return this->PlayerViewPoint.Location;
}

// Get reach line end
const FVector UGrabber::GetRayCastLineEnd()
{
    /// Update the viewpoint
    this->UpdatePlayerViewpoint();
    return this->PlayerViewPoint.Location + this->PlayerViewPoint.Rotation.Vector() * this->GrabReach;
}

// Setup trace parameters
const FCollisionQueryParams UGrabber::GetRayCastParameters()
{
    return FCollisionQueryParams(FName(TEXT("")), false, this->Owner);
}

// Get physics body in witthin reach
const FHitResult UGrabber::GetFirstPhysicsBodyInReach()
{
    FHitResult HitResult;
    GetWorld()->LineTraceSingleByObjectType(
        HitResult,
        this->GetRayCastLineStart(),
        this->GetRayCastLineEnd(),
        FCollisionObjectQueryParams(ECollisionChannel::ECC_PhysicsBody),
        this->GetRayCastParameters()
    );

    return HitResult;
}