box.gd

extends RigidBody2D

const EVENT_START_DRAG = 0
const EVENT_END_DRAG = 1
const EVENT_DRAGGING = 2

const ALPHA = 0.1
const EPSILON = 0.0005
const SCALE_FACTOR = 25
const STATE_EXPIRATION_TIME = 1.0 / 20.0

var dragging = false
var host = true;
var packet_peer = null

var state = null
var state_timer = 0

func _ready():
	set_process_input(true)
	set_can_sleep(false)

func _integrate_forces(s):
	if (not host and state != null and state_timer < STATE_EXPIRATION_TIME):
		state_timer += s.get_step()

		# Lerp
		var rot = slerp_rot(transform.get_rotation(), state[1], ALPHA)
		var pos = lerp_pos(transform.get_origin(), state[0], 1.0 - ALPHA)

		# Transforms
		var transform = s.get_transform().rotated(rot - get_rotation())
		transform.origin = pos
		s.set_transform(transform)

		# Forces
		s.set_linear_velocity(state[2])
		s.set_angular_velocity(state[3])

func _input_event(_viewport, event, _shape_idx):
	if (event is InputEventMouseButton and event.pressed):
		dragging = true
		start_drag()
		broadcast(["event", "start_drag", get_name()])

func _input(event):
	if (event is InputEventMouseMotion and dragging):
		var rect = get_tree().get_root().get_visible_rect()
		var pos = event.position

		if (pos.x <= 0 or pos.y <= 0 or pos.x >= (rect.size.x - 1) or pos.y >= (rect.size.y - 1)):
			dragging = false
			stop_drag()
			broadcast(["event", "stop_drag", get_name()])
		else:
			drag(pos)
			broadcast(["event", "drag", get_name(), pos])

	elif (event is InputEventMouseButton and not event.pressed and dragging):
		dragging = false
		stop_drag()
		broadcast(["event", "stop_drag", get_name()])

func start_drag():
	set_gravity_scale(0)
	set_linear_velocity(Vector2(0,0))

func stop_drag():
	set_gravity_scale(1)
	set_applied_force(Vector2(0,0))

func drag(pos):
	set_applied_force((pos - get_position()) * SCALE_FACTOR)

func broadcast(packet):
	if (host):
		get_node("/root/demo").broadcast(packet)
	else:
		packet_peer.put_var(packet)

func set_state(p_state):
	self.state = p_state
	self.state_timer = 0

# Lerp vector
func lerp_pos(v1, v2, alpha):
	return v1 * alpha + v2 * (1.0 - alpha)

# Spherically linear interpolation of rotation
func slerp_rot(r1, r2, alpha):
	var v1 = Vector2(cos(r1), sin(r1))
	var v2 = Vector2(cos(r2), sin(r2))
	var v = slerp(v1, v2, alpha)
	return atan2(v.y, v.x)

# Spherical linear interpolation of two 2D vectors
func slerp(v1, v2, alpha):
	var cos_angle = clamp(v1.dot(v2), -1.0, 1.0)

	if (cos_angle > 1.0 - EPSILON):
		return lerp_pos(v1, v2, alpha).normalized()

	var angle = acos(cos_angle)
	var angle_alpha = angle * alpha
	var v3 = (v2 - (cos_angle * v1)).normalized()
	return v1 * cos(angle_alpha) + v3 * sin(angle_alpha)