extends Node2D

# Forgejo #87: a brief spray of sparks off the hull that just fired.
#
# Firing was silent at the ship's end - a bolt simply appeared in front of it.
# With a whole fleet shooting there was nothing tying a shot to the vessel it
# came from, which mattered more once the player started aiming: you could not
# see which of your ships were actually in the fight.
#
# Deliberately tiny and short. This fires several times a second per vessel,
# so it has to be legible at a glance and gone before the next one - anything
# with weight would turn a firing fleet into a smear.
#
# No class_name, and it loads itself by path: a global class-name identifier
# is not reliably resolvable from a script reached through a preload chain,
# which is what happens here. Same reason as ResourcePickupVFX.

const SELF_PATH: String = "res://vfx/MuzzleSparkVFX.gd"
const SPARK_COUNT: int = 4
const DURATION: float = 0.13
const SPREAD: float = 0.5
const LENGTH: float = 9.0
const COLOR: Color = Color(1.0, 0.88, 0.42)

var age: float = 0.0
var color: Color = COLOR
var sparks: Array = []


# The colour is optional and defaults to the gun's own: #90 wanted the laser
# to do something at the hull too, and a cyan weapon throwing gold sparks
# would read as a different weapon firing from the same ship.
static func spawn(parent: Node, world_position: Vector2, direction: Vector2,
		spark_color: Color = COLOR) -> void:
	if direction.length() < 0.001:
		return
	var vfx: Node2D = (load(SELF_PATH) as GDScript).new()
	vfx.position = world_position
	vfx.rotation = direction.angle()
	vfx.color = spark_color
	parent.add_child(vfx)


func _ready() -> void:
	# Built once here rather than per frame: the streaks never change shape,
	# only how far along their own line they have travelled, so _draw reads
	# fixed values. Same discipline as the explosion particles.
	for i in range(SPARK_COUNT):
		sparks.append({
			"angle": randf_range(-SPREAD, SPREAD),
			"speed": randf_range(190.0, 340.0),
			"length": randf_range(LENGTH * 0.6, LENGTH),
		})
	queue_redraw()


func _process(delta: float) -> void:
	age += delta
	if age >= DURATION:
		queue_free()
		return
	queue_redraw()


func _draw() -> void:
	var t: float = clampf(age / DURATION, 0.0, 1.0)
	var fade: float = 1.0 - t
	for spark in sparks:
		var heading: Vector2 = Vector2.RIGHT.rotated(float(spark.angle))
		var start: Vector2 = heading * float(spark.speed) * age
		var end: Vector2 = start + heading * float(spark.length)
		NeonDraw.draw_glowing_line(self, start, end, color, fade, 0.35,
			color.darkened(0.7))