class_name Boss
extends EnemyBase
## 关底 Boss：四发重型轰炸机。
## 进场悬停后左右巡逻；弹幕双模式交替（瞄准连发 / 扇形散布），
## 半血进入狂暴阶段（弹速、频率、弹幕密度提升）。
## 死亡时爆炸链 + 震屏 + 清除全场敌弹。

const TEX := preload("res://assets/svg/boss_plane.svg")
const CENTER_X := 270.0
const ENTER_Y := 150.0
const ENTER_SPEED := 100.0
const PATROL_AMP := 145.0
const MUZZLE := Vector2(0.0, 55.0)

var difficulty := 1.0
var max_hp := 120

var _t := 0.0
var _entered := false
var _pattern_index := 0
var _pattern_timer := 1.4
var _burst_left := 0
var _burst_tick := 0.0


func setup(p_difficulty: float) -> void:
	difficulty = p_difficulty
	hp = int(60.0 + 60.0 * difficulty)
	max_hp = hp
	score_value = 5000
	drops_powerup = true
	hit_radius = 62.0
	position = Vector2(CENTER_X, -120.0)


func _ready() -> void:
	collision_layer = 4
	collision_mask = 0
	var sprite := Sprite2D.new()
	sprite.texture = TEX
	add_child(sprite)
	var shape := CollisionShape2D.new()
	var rect := RectangleShape2D.new()
	rect.size = Vector2(190.0, 84.0)
	shape.shape = rect
	add_child(shape)


func _process(delta: float) -> void:
	if dead:
		return
	if not _entered:
		position.y += ENTER_SPEED * delta
		if position.y >= ENTER_Y:
			position.y = ENTER_Y
			_entered = true
		return

	_t += delta * (1.25 if _in_phase2() else 1.0)
	position.x = CENTER_X + sin(_t * 0.55) * PATROL_AMP
	position.y = ENTER_Y + sin(_t * 1.6) * 16.0

	if _burst_left > 0:
		_burst_tick -= delta
		if _burst_tick <= 0.0:
			_burst_tick = 0.14
			_burst_left -= 1
			_fire_bullet(_aim_direction() * _bullet_speed(), MUZZLE)
	else:
		_pattern_timer -= delta
		if _pattern_timer <= 0.0:
			_fire_pattern()


func _in_phase2() -> bool:
	return hp <= max_hp / 2.0


func _bullet_speed() -> float:
	return (235.0 + 40.0 * difficulty) * (1.12 if _in_phase2() else 1.0)


func _fire_pattern() -> void:
	var phase2 := _in_phase2()
	if _pattern_index % 2 == 0:
		# 瞄准连发
		_burst_left = 5 if phase2 else 3
		_burst_tick = 0.0
		_pattern_timer = 1.5 if phase2 else 2.0
	else:
		# 扇形散布
		var count := 8 if phase2 else 5
		var spread := 50.0 if phase2 else 36.0
		var speed := _bullet_speed()
		for i in count:
			var angle := deg_to_rad(-spread + spread * 2.0 * float(i) / float(count - 1))
			_fire_bullet(Vector2.DOWN.rotated(angle) * speed, MUZZLE)
		_pattern_timer = 1.7 if phase2 else 2.2
	_pattern_index += 1


func _die() -> void:
	_spawn_drop(Powerup.Kind.POWER)
	var game := get_tree().get_first_node_in_group("game") as Game
	if game != null and is_instance_valid(game):
		game.add_score(score_value)
		game.add_bomb()
		game.clear_enemy_bullets()
		game.shake(9.0)
	for i in 8:
		var offset := Vector2(randf_range(-92.0, 92.0), randf_range(-56.0, 56.0))
		if game != null and is_instance_valid(game):
			game.spawn_explosion(global_position + offset, randf_range(1.3, 2.0))
		await get_tree().create_timer(0.12).timeout
	if game != null and is_instance_valid(game):
		game.spawn_explosion(global_position, 3.0)
	await get_tree().create_timer(0.3).timeout
	queue_free()