spaceship/vfx/GasBombEffect.gd

class_name GasBombEffect
extends Node2D

# The gas bomb itself: the flight, the blast and the picture of both, with
# nothing in it about who threw it.
#
# Lifted out of GasBombController for the same reason LaserBeamEffect was
# lifted out of LaserController - the shot was something only the FLEET could
# do, and a garrisoned bomber needs the same shot from a different trigger
# and a different magazine. Added to the tree root, self-animating,
# self-freeing, and it outlives the vessel that threw it.

signal struck(hit_count: int)

const BOMB_COLOR := Color(0.96, 0.22, 0.72)
const AOE_RADIUS := 180.0
const PROJECTILE_SPEED := 720.0
const EXPLOSION_DURATION := 0.8

var target: Vector2 = Vector2.ZERO
var damage: int = 3
var trail: PackedVector2Array = PackedVector2Array()
var exploded: bool = false
var explosion_time: float = 0.0
var hit_count: int = 0


static func launch(world: Node, origin: Vector2, at: Vector2,
		blast_damage: int = 3) -> GasBombEffect:
	var effect := GasBombEffect.new()
	effect.position = origin
	effect.target = at
	effect.damage = blast_damage
	effect.trail = PackedVector2Array([origin])
	world.add_child(effect)
	return effect


func in_flight() -> bool:
	return not exploded


func _process(delta: float) -> void:
	if not exploded:
		_advance_flight(delta)
		queue_redraw()
		return
	explosion_time = maxf(explosion_time - delta, 0.0)
	queue_redraw()
	if explosion_time <= 0.0:
		queue_free()


func _advance_flight(delta: float) -> void:
	var distance: float = position.distance_to(target)
	if distance <= PROJECTILE_SPEED * delta:
		position = target
		_explode()
		return
	position = position.move_toward(target, PROJECTILE_SPEED * delta)
	trail.append(position)
	while trail.size() > 12:
		trail.remove_at(0)


func _explode() -> void:
	exploded = true
	explosion_time = EXPLOSION_DURATION
	hit_count = 0
	# Asteroids too - a blast that clears everything around it but leaves the
	# rocks untouched would need explaining, and they take damage the same way.
	#
	# #165: and STRUCTURES. The blast used to stop politely at anything the
	# player owned, which made a bomb dropped on a besieged mothership a free
	# way to clear the attackers off it. Everything inside the radius is
	# inside the radius; where it lands is the decision the weapon asks for.
	for target_node in get_tree().get_nodes_in_group("enemies") \
			+ get_tree().get_nodes_in_group("asteroids") \
			+ get_tree().get_nodes_in_group("player_buildings"):
		if is_instance_valid(target_node) and target_node is Node2D \
				and target_node.global_position.distance_to(target) <= AOE_RADIUS:
			target_node.take_damage(damage)
			hit_count += 1
	struck.emit(hit_count)


func _draw() -> void:
	# Drawn in this node's own space while it flies (it moves), and around the
	# blast point once it lands (it does not).
	if not exploded:
		if trail.size() >= 2:
			for i in range(1, trail.size()):
				var alpha: float = float(i) / trail.size()
				draw_line(trail[i - 1] - position, trail[i] - position,
					Color(BOMB_COLOR, alpha * 0.65), 4.0 + alpha * 4.0, true)
		draw_circle(Vector2.ZERO, 12.0, Color(BOMB_COLOR, 0.35))
		NeonDraw.draw_glowing_circle(self, Vector2.ZERO, 7.0, BOMB_COLOR, 1.0)
		return
	var progress: float = 1.0 - explosion_time / EXPLOSION_DURATION
	var radius: float = lerpf(24.0, AOE_RADIUS, minf(progress * 1.5, 1.0))
	draw_circle(Vector2.ZERO, radius, Color(BOMB_COLOR, (1.0 - progress) * 0.16))
	draw_ring(Vector2.ZERO, radius, BOMB_COLOR, 1.0 - progress)
	for i in range(7):
		var angle: float = TAU * float(i) / 7.0 + progress
		var cloud_at: Vector2 = Vector2(cos(angle), sin(angle)) * radius * 0.55
		draw_circle(cloud_at, 18.0 + 14.0 * progress,
			Color(BOMB_COLOR, (1.0 - progress) * 0.22))


func draw_ring(center: Vector2, radius: float, color: Color, alpha: float) -> void:
	draw_arc(center, radius, 0.0, TAU, 64, Color(color, 0.16 * alpha), 16.0, true)
	draw_arc(center, radius, 0.0, TAU, 64, Color(color, 0.5 * alpha), 6.0, true)
	draw_arc(center, radius, 0.0, TAU, 64, Color(1.0, 0.86, 0.96, 0.9 * alpha), 2.0, true)