# mob_combat_reaction_system.gd —— 怪物主动仇恨视野、追击脱战与连击击退硬直（40250 官方 1:1 对齐）
# 对齐源码：
#   - 40250 server/game/src/char_state.cpp:250-380 (StateBattle, StateIdle, 追击与脱战)
#   - 40250 server/game/src/battle.cpp:110-180 (battle_hit, 攻击判定与受击推力)
#   - 40250 ClientVS22/source/UserInterface/ActorInstanceBattle.cpp (__HitGood, __HitGreate)
class_name MobCombatReactionSystem
extends RefCounted

const DEFAULT_AGGRO_RADIUS := 18.0    # 主动怪索敌视野半径 (18 米)
const MAX_LEASH_DISTANCE := 40.0      # 最大追击拉脱距离 (40 米)
const KNOCKBACK_FORCE_M := 1.5        # 四连击击退推力距离 (1.5 米)

enum MobAIState {
	IDLE,       # 巡逻/游荡
	CHASE,      # 仇恨追击玩家
	RETREAT,    # 超过拉脱距离，放弃仇恨返回出生点
}

## 检查是否进入主动怪仇恨视野
static func check_aggro(mob_pos: Vector3, player_pos: Vector3, is_aggressive := true, aggro_radius := DEFAULT_AGGRO_RADIUS) -> bool:
	if not is_aggressive:
		return false
	var dist := mob_pos.distance_to(player_pos)
	return dist <= aggro_radius

## 检查是否超出追击拉脱最大距离
static func check_leash_exceeded(mob_pos: Vector3, spawn_pos: Vector3, max_leash := MAX_LEASH_DISTANCE) -> bool:
	var dist := mob_pos.distance_to(spawn_pos)
	return dist > max_leash

## 执行拉脱脱战重置 (40250 char_state.cpp 怪物脱战回位并回满生命值)
static func perform_leash_reset(mob_data: Dictionary, spawn_pos: Vector3) -> Dictionary:
	var max_hp := int(mob_data.get("max_hp", 1000))
	mob_data["hp"] = max_hp
	mob_data["target_vid"] = 0
	mob_data["state"] = MobAIState.RETREAT
	return {
		"leashed": true,
		"reset_hp": max_hp,
		"return_pos": spawn_pos,
		"msg": "怪物超出追击范围，脱离战斗并回满生命值返回出生点！"
	}

## 计算普通连击与受击反应 (40250 battle.cpp: 第1-2击普通受击，第3-4击击退击倒)
## combo_step: 1..4 当前连击段数
## attack_heading_rad: 攻击朝向弧度 (用于计算受力击退向量)
static func calculate_combo_reaction(combo_step: int, mob_pos: Vector3, attack_heading_rad: float) -> Dictionary:
	var normalized_step := ((combo_step - 1) % 4) + 1
	if normalized_step in [1, 2]:
		# 前两击：普通受击硬直 (HitReaction.good)
		return {
			"reaction_type": "DAMAGE_STUN",
			"is_knockback": false,
			"push_offset": Vector3.ZERO,
			"anim": "damage",
			"stun_duration": 0.2, # 0.2 秒受击硬直
		}
	else:
		# 第三、四击：强力击退并击倒 (HitReaction.greate)
		# 顺着攻击朝向将怪物向后击退 1.5 米
		var push_dir := Vector3(sin(attack_heading_rad), 0, cos(attack_heading_rad)).normalized()
		var push_vec := push_dir * KNOCKBACK_FORCE_M
		var new_pos := mob_pos + push_vec
		return {
			"reaction_type": "KNOCKBACK_FLYING",
			"is_knockback": true,
			"push_offset": push_vec,
			"target_pos": new_pos,
			"anim": "knockdown",
			"standup_anim": "standup",
			"knockdown_duration": 0.8, # 倒地至起身耗时
		}