class_name Droplet extends RigidBody2D

# bounce mode seems to settle with a consistent surface, but is erratic
# stick mode seems to make sand castles, but is very calm
enum Mode { BOUNCE, STICK }
const mode: Mode = Mode.BOUNCE

func _ready():
	var mat = PhysicsMaterial.new()
	mat.bounce = .1 if mode == Mode.BOUNCE else 0
	mat.friction = 0.0
	physics_material_override = mat
	
	# setup body entered signal, seems to also matter for STICK mode
	contact_monitor = true
	max_contacts_reported = 10
	body_entered.connect(_on_body_entered)

func _physics_process(delta):
	pass
	
func _integrate_forces(state):
	if mode == Mode.STICK:
		var v = state.linear_velocity
		var contacts = state.get_contact_count()
		for i in range(contacts):
			var body = state.get_contact_collider_object(i)
			var normal = state.get_contact_local_normal(i)
			var self_damp = .9
			var other_damp = 1 - self_damp
			v = v.bounce(normal) * self_damp
			state.linear_velocity = v # self bounce
			if body is RigidBody2D: # other body
				body.apply_central_impulse(normal * v.length() * (other_damp/contacts))

func _on_body_entered(body):
	if mode == Mode.BOUNCE:
		# trying to elicit stronger response from rigidBody that was struck
		# ends up being kind of erratic
		# at damp_factor .75: settles laterally, but erratic past half-full
		# at damp_factor of .5, it's pretty calm, but then can't overfill (expected?)
		var vel = get_linear_velocity()
		const damp_factor = 0.7
		var normal = (body.global_position - global_position).normalized()
		# reflect velocity across collision direction
		var bounced = vel.bounce(normal) # reflection
		set_linear_velocity(bounced * damp_factor)
		if body is RigidBody2D:
			body.apply_central_impulse(-bounced * damp_factor)