extends Area2D

## 弹幕子弹：直线飞行，碰到玩家扣血。
## 贴图是代码生成的实心圆，不需要额外美术素材。

@export var speed: float = 70.0
@export var damage: int = 1
@export var lifetime: float = 8.0
@export var radius: int = 3
@export var bullet_color: Color = Color(1.0, 0.35, 0.7)
## 撞到地形/绳子之类的障碍就消失。
## 关掉（默认）的话子弹会**穿过一切**，只靠存活时间和出界来回收
@export var stop_on_obstacle: bool = false
## 掉到这个世界 y 以下就自动回收（默认在关卡底部之外）
@export var despawn_y: float = 340.0

var direction: Vector2 = Vector2.LEFT

var _age: float = 0.0
var _probe: RayCast2D = null

static var _cache: Dictionary = {}


## 生成（并缓存）一个实心圆贴图
static func circle_texture(r: int, color: Color) -> ImageTexture:
	var key := "%d|%s" % [r, color.to_html()]
	if _cache.has(key):
		return _cache[key]
	var size: int = r * 2 + 1
	var img := Image.create_empty(size, size, false, Image.FORMAT_RGBA8)
	img.fill(Color(0.0, 0.0, 0.0, 0.0))
	var limit := float(r * r) + float(r) * 0.6
	for y in size:
		for x in size:
			var dx := float(x - r)
			var dy := float(y - r)
			if dx * dx + dy * dy <= limit:
				img.set_pixel(x, y, color)
	var tex := ImageTexture.create_from_image(img)
	_cache[key] = tex
	return tex


func _ready() -> void:
	add_to_group("bullet")
	var sprite := get_node_or_null("Sprite") as Sprite2D
	if sprite != null:
		sprite.texture = circle_texture(radius, bullet_color)
	var hit := get_node_or_null("HitBox") as CollisionShape2D
	if hit != null and hit.shape is CircleShape2D:
		var circle := (hit.shape as CircleShape2D).duplicate() as CircleShape2D
		circle.radius = float(radius)
		hit.shape = circle
	_probe = get_node_or_null("Probe") as RayCast2D
	if _probe != null:
		_probe.enabled = stop_on_obstacle
	body_entered.connect(_on_body_entered)


func launch(dir: Vector2, spd: float = -1.0) -> void:
	direction = dir.normalized()
	if spd > 0.0:
		speed = spd


func _physics_process(delta: float) -> void:
	_age += delta
	if _age >= lifetime or global_position.y > despawn_y:
		queue_free()
		return

	var step := direction * speed * delta
	if stop_on_obstacle and _probe != null:
		_probe.target_position = step * 1.5
		_probe.force_raycast_update()
		if _probe.is_colliding():
			queue_free()
			return
	position += step


func _on_body_entered(body: Node2D) -> void:
	if body.has_method("hurt"):
		body.hurt(damage)
	queue_free()