@tool

# A draggable item in the game that can be picked up and displayed with an outline effect.
class_name DraggableRigid extends RigidBody2D

# pass self
signal picked(node: DraggableRigid)
signal dropped(node: DraggableRigid)

# 如果设置 replaced_area_monitor, 则鼠标事件由 replaced_area_monitor 替代监听
@export var replaced_area_monitor: Area2D
# z +1 when picked (-1 when dropped)
# @export var z_up_on_picked := true
@export var sprite_offset := Vector2.ZERO:
	set(val):
		sprite_offset = val
		if is_node_ready():
			sprite.offset = sprite_offset
@export var freezing := false:
	set(val):
		freezing = val
		refresh_gravity_and_collision()
		if freezing:
			if holding:
				_drop()
			elif touching:
				_on_mouse_exited()
@export var texture: Texture2D:
	# The texture to display for the item
	set(val):
		texture = val
		if is_node_ready():
			sprite.texture = texture
@export var limit_rect := Rect2(Vector2.ZERO, Vector2(564, 316))

@onready var sprite: Sprite2D = $Sprite2D

# Whether the item is currently being held by the player
var holding := false:
	set(val):
		holding = val
		refresh_gravity_and_collision()
var touching := false

# 静态变量优化：避免频繁的字符串比较
static var current_focusing_node: DraggableRigid = null
static var pending_enter_callables: Array[Callable] = []

# 缓存常量
const OUTLINE_THICKNESS := 1.0
const OUTLINE_TWEEN_DURATION := 0.2
const SHAKE_FPS := 15.0
const SHAKE_DURATION := 0.8
const SHAKE_DELTA := 12.0
const HUD_FADE_DURATION := 0.3

# 缓存变量
var _mouse_event_source: Node
var _outline_tween: Tween
var _shake_tween: Tween
var default_gravity_scale: float
var default_collision_layer: int


func _ready() -> void:
	sprite.texture = texture
	sprite.offset = sprite_offset
	if Engine.is_editor_hint():
		return
	default_gravity_scale = gravity_scale
	default_collision_layer = collision_layer
	# 初始化隐藏白边
	sprite.material.set_shader_parameter("thickness", 0.0)

	# 缓存事件源
	if replaced_area_monitor:
		_mouse_event_source = replaced_area_monitor
	else:
		_mouse_event_source = self
	_mouse_event_source.mouse_entered.connect(_on_mouse_entered)
	_mouse_event_source.mouse_exited.connect(_on_mouse_exited)


func refresh_gravity_and_collision() -> void:
	if holding or freezing:
		gravity_scale = 0.0
		default_collision_layer = 0
	else:
		gravity_scale = default_gravity_scale
		collision_layer = default_collision_layer


func is_focused() -> bool:
	return current_focusing_node == self


func _on_mouse_entered() -> bool:
	touching = true
	if freezing or not is_visible_in_tree():
		return false
	if holding or is_focused():
		return true

	# 尝试获得 current_focusing_item
	if current_focusing_node:
		if not pending_enter_callables.has(_on_mouse_entered):
			pending_enter_callables.append(_on_mouse_entered)
		return false

	current_focusing_node = self
	_toggle_outline(true)
	return true


func _on_mouse_exited() -> void:
	touching = false
	pending_enter_callables.erase(_on_mouse_entered)
	# freezing 不影响 mouse exited
	if is_focused() and not holding:
		current_focusing_node = null
		# 优化：使用 while 替代 for 循环，找到第一个成功的就停止
		while pending_enter_callables.size() > 0:
			var c = pending_enter_callables.pop_front()
			if c.call():
				break
	_toggle_outline(false)


func _notification(what: int) -> void:
	match what:
		NOTIFICATION_PREDELETE:
			if holding:
				_drop()
			elif touching:
				_on_mouse_exited()


func _unhandled_input(event: InputEvent) -> void:
	if freezing or Engine.is_editor_hint() or not is_visible_in_tree():
		return
	if event is InputEventMouseButton and event.button_index == MOUSE_BUTTON_LEFT and event.pressed:
		if is_focused() and not holding:
			get_viewport().set_input_as_handled()
			_try_pick.call_deferred()
		elif holding:
			get_viewport().set_input_as_handled()
			_drop()
	elif holding and event is InputEventMouseMotion:
		_update_pos_to_mouse()


func _update_pos_to_mouse() -> void:
	var mouse_pos := get_global_mouse_position()
	mouse_pos = mouse_pos.clamp(limit_rect.position, limit_rect.end)
	update_position(mouse_pos)


func update_position(pos: Vector2) -> void:
	PhysicsServer2D.body_set_state(
		get_rid(), PhysicsServer2D.BODY_STATE_TRANSFORM, Transform2D.IDENTITY.translated(pos)
	)


func _try_pick() -> void:
	if not is_focused():
		return
	_toggle_outline(false)
	holding = true
	_update_pos_to_mouse()
	picked.emit(self)


func _drop() -> void:
	if touching:
		_toggle_outline(true)
	if holding:
		holding = false
		if not touching:
			current_focusing_node = null
			for c in pending_enter_callables:
				if c.call():
					break
		dropped.emit(self)


func _toggle_outline(display: bool) -> void:
	# 避免重复创建 tween
	if _outline_tween and _outline_tween.is_running():
		_outline_tween.kill()

	_outline_tween = create_tween()
	var target_thickness := OUTLINE_THICKNESS if display else 0.0
	_outline_tween.tween_property(
		sprite.material, "shader_parameter/thickness", target_thickness, OUTLINE_TWEEN_DURATION
	)


func _exit_tree() -> void:
	if touching:
		_on_mouse_exited()


func force_hold() -> void:
	if holding:
		return
	if not is_focused() and current_focusing_node:
		current_focusing_node._drop()
	_toggle_outline(false)
	current_focusing_node = self
	holding = true
	_update_pos_to_mouse()
	picked.emit(self)


func invalid_shake() -> void:
	if _shake_tween and _shake_tween.is_running():
		_shake_tween.kill()
	# 抖动效果
	_shake_tween = create_tween()
	var count := int(SHAKE_DURATION * SHAKE_FPS)
	var delta_t := 1.0 / SHAKE_FPS
	sprite.modulate = Color.INDIAN_RED
	# 预计算随机值，避免在循环中多次调用 randf_range
	for i in count:
		var decay := exp(-float(i))
		var offset := Vector2(
			randf_range(-SHAKE_DELTA, SHAKE_DELTA) * decay,
			randf_range(-SHAKE_DELTA, SHAKE_DELTA) * decay
		)
		_shake_tween.tween_property(sprite, "offset", sprite_offset + offset, delta_t).set_trans(
			Tween.TRANS_CUBIC
		)

	_shake_tween.tween_callback(_reset_after_shake)


func _reset_after_shake() -> void:
	sprite.modulate = Color.WHITE
	sprite.offset = sprite_offset