grunk/src/player/hold_component.gd

extends Node3D
## Component for managing physics object holding

## Held object position lerp acceleration.
@export var hold_accel := 20.0

## The maximum distance the object may be from the hold point before breaking the hold.
@export var max_distance := 3.0

## Temporary linear damping for held objects
@export var hold_damping := 8.0

## Temporary collision layer.
@export_flags_3d_physics var hold_collision_layer := 0

## Temporary collision mask.
@export_flags_3d_physics var hold_collision_physics := 1

## The object currently being held.
var _held_object: RigidBody3D

var _original_damping: float
var _original_collision_layer: int
var _original_collision_mask: int

var _linear_velocity := Vector3.ZERO

@onready var interact_ray: RayCast3D = %InteractRay
@onready var hold_point: Marker3D = %HoldPoint


func attach(prop: RigidBody3D, hold_distance: float) -> void:
	hold_point.position = Vector3(0, 0, -hold_distance)
	_held_object = prop

	_original_damping = prop.linear_damp
	prop.linear_damp = hold_damping

	_original_collision_layer = prop.collision_layer
	prop.collision_layer = hold_collision_layer

	_original_collision_mask = prop.collision_mask
	prop.collision_mask = hold_collision_physics


func drop() -> void:
	_held_object.linear_damp = _original_damping
	_held_object.collision_layer = _original_collision_layer
	_held_object.collision_mask = _original_collision_mask
	_held_object.linear_velocity = _linear_velocity
	_held_object = null
	_linear_velocity = Vector3.ZERO


func holding_object() -> bool:
	return !!_held_object


func _physics_process(delta: float) -> void:
	# Object hold action logic
	if Input.is_action_just_pressed("interact"):
		if _held_object:
			drop()
		elif interact_ray.is_colliding():
			var body := interact_ray.get_collider() as RigidBody3D
			var hold_component := Holdable.get_component(body)
			if hold_component:
				attach(body, hold_component.hold_distance)

	# Held object logic
	if not _held_object:
		return

	var diff := hold_point.global_position - (_held_object.global_position)
	if diff.length() > max_distance:
		drop()
		return

	var held_object_last_position := _held_object.global_position

	var weight := 1 - exp(-hold_accel * delta)
	_held_object.global_position = _held_object.global_position.lerp(
		hold_point.global_position, weight
	)
	_held_object.global_basis = _held_object.global_basis.slerp(global_basis, weight)

	_linear_velocity = (_held_object.global_position - held_object_last_position) / delta