class_name LaserBeam
extends Node2D
## 直线激光束：从所在位置垂直向上延伸，被第一个命中的敌人截断，
## 对其造成持续伤害（dps）。视觉为核心线 + 外发光双层 Line2D。

var dps := 10.0
var width := 5.0
var color := Color(0.55, 0.9, 1.0)
var active := false

var _core: Line2D
var _glow: Line2D
var _acc := 0.0
var _t := 0.0


func _ready() -> void:
	z_index = 5
	_glow = Line2D.new()
	_glow.width = width * 2.8
	_glow.default_color = Color(color, 0.28)
	_glow.points = [Vector2.ZERO, Vector2(0.0, -10.0)]
	add_child(_glow)
	_core = Line2D.new()
	_core.width = width
	_core.default_color = color
	_core.points = [Vector2.ZERO, Vector2(0.0, -10.0)]
	add_child(_core)
	visible = false


## 从自身祖先中解析所属游戏的敌容器（避免多实例时全局组查找拿错容器）
func _get_enemies_container() -> Node2D:
	var node := get_parent()
	while node != null:
		var candidate := node.get_node_or_null("Enemies")
		if candidate != null:
			return candidate as Node2D
		node = node.get_parent()
	return null


func _process(delta: float) -> void:
	if not active:
		if visible:
			visible = false
		return
	visible = true
	_t += delta

	var muzzle := global_position
	var hit_y := -40.0
	var target: EnemyBase = null
	var container := _get_enemies_container()
	if container != null:
		for enemy in container.get_children():
			if enemy is EnemyBase and not (enemy as EnemyBase).dead:
				var e := enemy as EnemyBase
				if absf(e.global_position.x - muzzle.x) < e.hit_radius + width * 0.5:
					# 光束向上：命中敌人底缘；若炮口已进入敌人范围则从炮口起算
					var hy := minf(muzzle.y, e.global_position.y + e.hit_radius)
					if hy >= hit_y:
						hit_y = hy
						target = e

	var length := maxf(muzzle.y - hit_y, 0.0)
	var pulse := 1.0 + 0.1 * sin(_t * 42.0)
	_core.width = width * pulse
	_glow.width = width * 2.8 * pulse
	_core.points = [Vector2.ZERO, Vector2(0.0, -length)]
	_glow.points = [Vector2.ZERO, Vector2(0.0, -length)]

	if target != null and is_instance_valid(target):
		_acc += dps * delta
		if _acc >= 1.0:
			var whole := int(_acc)
			_acc -= float(whole)
			target.apply_damage(whole)