class_name DefenseResolver
extends RefCounted


static func resolve_effective_defense(context: Dictionary, attack_tags: Array[StringName] = []) -> Dictionary:
	var defense_state := StringName(str(context.get("defense_state", &"Vulnerable")))
	# 背刺破格挡只作用于姿态本身的 Parrying，先降级再合并 effect 修饰符：
	# 否则霸体（SuperArmor，优先级低于 Parrying）会先被格挡态吞掉、
	# 再随背刺降级一起丢失，违反霸体「无击退、不打断」的承诺。
	if defense_state == &"Parrying" and not bool(context.get("attack_from_front", true)):
		defense_state = &"Vulnerable"
	var modifiers := _defense_modifiers(context, attack_tags)
	for modifier: Resource in modifiers:
		var modified_state := StringName(str(modifier.get("defense_state")))
		if not modified_state.is_empty():
			defense_state = _stronger_defense_state(defense_state, modified_state)
	var damage_mult := _damage_mult_for_state(defense_state, context)
	var interrupts := defense_state != &"Invincible" and defense_state != &"SuperArmor" and defense_state != &"Parrying"
	for modifier: Resource in modifiers:
		damage_mult *= float(modifier.get("damage_mult"))
		interrupts = interrupts and bool(modifier.get("interrupts"))
	return {
		"defense_state": defense_state,
		"damage_mult": damage_mult,
		"interrupts": interrupts,
	}


static func _damage_mult_for_state(defense_state: StringName, context: Dictionary = {}) -> float:
	match defense_state:
		&"Invincible":
			return 0.0
		&"Parrying":
			return _parry_damage_mult(context)
		&"SuperArmor":
			return 1.0
		_:
			return 1.0


static func _parry_damage_mult(context: Dictionary) -> float:
	match StringName(str(context.get("block_judgement", &"perfect"))):
		&"good":
			return 0.2
		&"bad":
			return 0.4
		&"miss":
			return 1.0
	return 0.0


static func _defense_modifiers(context: Dictionary, attack_tags: Array[StringName]) -> Array[Resource]:
	var modifiers: Array[Resource] = []
	if context.has("defense_modifiers"):
		modifiers = _resource_array(context["defense_modifiers"])
	else:
		var container = context.get("effect_container", null)
		if container != null and container.has_method("defense_modifiers"):
			modifiers = _resource_array(container.call("defense_modifiers"))
	var matched: Array[Resource] = []
	for modifier: Resource in modifiers:
		if _modifier_matches_attack_tags(modifier, attack_tags):
			matched.append(modifier)
	return matched


static func _resource_array(value: Variant) -> Array[Resource]:
	var result: Array[Resource] = []
	if value is Array:
		for item: Variant in value:
			if item is Resource:
				result.append(item)
	return result


static func _modifier_matches_attack_tags(modifier: Resource, attack_tags: Array[StringName]) -> bool:
	var required_tags := _string_name_array(modifier.get("required_attack_tags"))
	return required_tags.is_empty() or _has_any(attack_tags, required_tags)


static func _string_name_array(value: Variant) -> Array[StringName]:
	var result: Array[StringName] = []
	if value is Array:
		for item: Variant in value:
			result.append(StringName(str(item)))
	return result


static func _has_any(values: Array[StringName], candidates: Array[StringName]) -> bool:
	for value: StringName in values:
		if candidates.has(value):
			return true
	return false


static func _stronger_defense_state(current_state: StringName, candidate_state: StringName) -> StringName:
	return candidate_state if _defense_priority(candidate_state) > _defense_priority(current_state) else current_state


static func _defense_priority(defense_state: StringName) -> int:
	match defense_state:
		&"Invincible":
			return 4
		&"Parrying":
			return 3
		&"SuperArmor":
			return 2
		&"Vulnerable":
			return 1
		_:
			return 0