presidents-brigade/Source/PresidentsBrigade/BasePawn.cpp

// Fill out your copyright notice in the Description page of Project Settings.


#include "BasePawn.h"
#include "Components/StaticMeshComponent.h"
#include "GameFramework/FloatingPawnMovement.h"
#include "DrawDebugHelpers.h"
#include "Kismet/KismetSystemLibrary.h"
#include "Util.h"

#define LogError(Msg) Util::log_error(TEXT("ABasePawn"), Msg)

// Sets default values
ABasePawn::ABasePawn(const FObjectInitializer &object_initializer): 
	APawn(object_initializer)
{
	// Create default components.
	root_component = object_initializer.CreateDefaultSubobject<USceneComponent>(this, FName("Root"));
	RootComponent = root_component;

	collision = object_initializer.CreateDefaultSubobject<UBoxComponent>(this, FName("Collision"));
	collision->SetupAttachment(RootComponent);
	collision->SetCollisionProfileName(FName("Pawn"));
	collision->SetCanEverAffectNavigation(false);

	player_mesh = object_initializer.CreateDefaultSubobject<USkeletalMeshComponent>(this, FName("PlayerMesh"));
	player_mesh->SetupAttachment(collision);
	player_mesh->SetCollisionEnabled(ECollisionEnabled::NoCollision);
	player_mesh->SetCanEverAffectNavigation(false);

	movement_component = object_initializer.CreateDefaultSubobject<UFloatingPawnMovement>(this, FName("MovementComponent"));
	movement_component->UpdatedComponent = collision;


	PrimaryActorTick.bCanEverTick = true;

	// Set defaults.
	max_health = 100;
	max_ammo = 25;
}

// Called when the game starts or when spawned
void ABasePawn::BeginPlay()
{
	Super::BeginPlay();

	/*
	 * Setup collision handler.
	 */
	collision->OnComponentHit.AddDynamic(this, &ABasePawn::handle_hit);


	/*
	 * Set base state.
	 */
	current_health = max_health;
	current_ammo = max_ammo;
}

void ABasePawn::handle_hit(
	UPrimitiveComponent* hit_component,
	AActor* other_actor,
	UPrimitiveComponent* other_component,
	FVector normal_impulse,
	const FHitResult& hit
)
{
	UClass* other_class = other_actor->GetClass();
	if (damage_class_map.Contains(other_class))
	{
		// Update current health.
		current_health -= damage_class_map[other_class];
	}

	handle_hit_internal(other_actor);
}

void ABasePawn::handle_hit_internal(AActor* other_actor)
{
	// do nothing by default;
}

UPawnMovementComponent* ABasePawn::GetMovementComponent() const
{
	return movement_component;
}

FVector ABasePawn::get_location() const
{
	return collision->GetComponentLocation();
}

// Called every frame
void ABasePawn::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);

	/*
	 * Auto-fire.
	 */
	shoot_time_elapsed += DeltaTime;
	if (shooting_enabled && shoot_time_elapsed > fire_rate_s)
	{
		shoot();
	}

	/*
	 * Handle death.
	 */
	if (current_health <= 0 && !death_handled)
	{
		handle_death();
		death_handled = true;
	}
}

void ABasePawn::handle_move_forward(float axis)
{
	if (axis != 0)
	{
		AddMovementInput(FVector(1,0,0), axis);
	}
}

void ABasePawn::handle_move_right(float axis)
{
	if (axis != 0)
	{
		AddMovementInput(FVector(0, 1, 0), axis);
	}
}

void ABasePawn::update_yaw_x(float x_component)
{
	yaw.x_component = x_component;
}

void ABasePawn::update_yaw_y(float y_component)
{
	yaw.y_component = y_component;
}

void ABasePawn::start_shooting()
{
	shooting_enabled = true;
	shoot();
}

void ABasePawn::stop_shooting()
{
	shooting_enabled = false;
}

void ABasePawn::shoot()
{
	if (current_ammo > 0)
	{
		const FVector player_location = get_location();
		FRotator rotator(0, yaw.calculate_yaw(), 0);
		if (use_aim_assist)
		{
			float assist_yaw;
			const bool success = aim_assist(player_location, rotator, assist_yaw);
			if (success)
			{
				rotator.Yaw = assist_yaw;
			}
		}

		FVector forward = FRotationMatrix(rotator).GetUnitAxis(EAxis::X);
		FVector spawn_location = player_location + (forward * 100);
		FActorSpawnParameters spawnParameters;
		spawnParameters.SpawnCollisionHandlingOverride = ESpawnActorCollisionHandlingMethod::AlwaysSpawn;
		spawnParameters.Owner = this;
		spawnParameters.Instigator = this;
		AActor* bullet = GetWorld()->SpawnActor<AActor>(
			bullet_actor_class,
			spawn_location,
			rotator,
			spawnParameters
		);

		shoot_time_elapsed = 0;
		current_ammo -= 1;
	}
}

/**
 * Calculate the yaw angle needed to hit the nearest enemy target.
 * 
 * @return Yaw angle offset.
 */
bool ABasePawn::aim_assist(const FVector start, const FRotator rotator, float &yaw_output)
{
	/*
	 * Create trace end based on start location and given rotator.
	 */
	FVector trace = start + FVector(10000, 0, 0);
	trace = rotator.RotateVector(trace);

	/*
	 * Run box trace for enemy targets.
	 */
	FHitResult out_hit;
	const bool succeeded = UKismetSystemLibrary::SphereTraceSingle(
		GetWorld(),
		start,
		trace,
		aim_assist_distance,
		ETraceTypeQuery::TraceTypeQuery3, // "Enemy" trace channel
		false,
		TArray<AActor*>(),
		EDrawDebugTrace::Type::None,
		out_hit,
		true,
		FLinearColor::Green,
		FLinearColor::Green,
		0
	);

	/*
	 * No enemies were within range.
	 */
	if (!succeeded)
	{
		return false;
	}

	ABasePawn* enemy_pawn = Cast<ABasePawn>(out_hit.Actor);
	/*
	 * Bad setup. We should only be hitting pawns.
	 */
	if (!enemy_pawn)
	{
		LogError("Aim assist trace hit non-pawn");
		return false;
	}

	const FVector enemy_vector = enemy_pawn->get_location() - start;
	yaw_output = enemy_vector.Rotation().Yaw;
	return true;
}

void ABasePawn::handle_death()
{
	/*
	 * Disable collision.
	 */
	collision->SetCollisionEnabled(ECollisionEnabled::NoCollision);

	if (death_effect)
	{
		death_effect->Destroy();
		death_effect = nullptr;
	}

	/*
	 * Spawn particle effect.
	 */
	FVector player_location = player_mesh->GetComponentLocation();
	FActorSpawnParameters spawnParameters;
	spawnParameters.SpawnCollisionHandlingOverride = ESpawnActorCollisionHandlingMethod::AlwaysSpawn;
    death_effect = GetWorld()->SpawnActor<AActor>(
		death_class,
		player_location,
		FRotator(0,0,0),
		spawnParameters
	);

	destroy_self();
}

void ABasePawn::destroy_self()
{
	/*
	 * Remove thyself from this world.
	 */
	Destroy();
}