using UnityEngine;
using BaseGames.AI;

namespace BaseGames.Enemies
{
    /// <summary>
    /// 敌人移动执行器：唯一的移动/朝向入口。AI 状态与能力经 IEnemyLocomotion
    /// 声明意图，本组件每帧把当前模式翻译为对 EnemyBase/IPathAgent 的调用。
    /// 取代散落的 MoveTo/StopMovement/FacePlayer/FaceTarget 直调与三个协程能力。
    /// </summary>
    [DisallowMultipleComponent]
    public sealed class EnemyLocomotion : MonoBehaviour, IEnemyLocomotion
    {
        [Header("巡逻策略（Wander/Pace/Waypoints）")]
        [SerializeField] private PatrolStrategy _patrolStrategy = PatrolStrategy.Wander;

        [Header("Wander 策略参数")]
        [Tooltip("到达一个随机游走点后的停顿时长下限（秒）。停顿期间原地待机（播 Idle），再挑下一个点。")]
        [SerializeField] [Min(0f)] private float _wanderPauseMin = 0.5f;
        [Tooltip("到达一个随机游走点后的停顿时长上限（秒）。与下限相同=固定时长；两者都为 0=不停顿、立即挑下一个点。")]
        [SerializeField] [Min(0f)] private float _wanderPauseMax = 1.5f;

        [Header("Waypoints 策略参数")]
        [SerializeField] private Transform[] _waypoints;
        [SerializeField] private bool _pingPong;
        [SerializeField] private float _waypointArriveRadius = 0.4f;

        private EnemyBase _enemy;
        private LocomotionMode _mode = LocomotionMode.Idle;
        private Transform _approachTarget;
        private Vector2 _facePoint;
        private LocomotionMode _gaitMode;
        private bool _gaitInit;
        private float _paceDir = 1f;
        private bool _paceBlockedPrev;
        private float _paceWindowStartX;
        private int _paceWindowFrames;
        private int _wpIndex = -1;
        private int _wpDir = 1;
        private bool _warnedNoWaypoints;
        // 当前路点吸附后的"站得住"目标（宽度由 Nav 层解析，本层不感知身体尺寸）
        private Vector2 _wpResolvedGoal;
        // Wander 到点停顿状态
        private bool _wanderPausing;
        private float _wanderPauseTimer;

        public LocomotionMode CurrentMode => _mode;
        public bool IsMoving => _enemy != null && _enemy.Nav != null && _enemy.Nav.IsMoving;

        private void Awake()
        {
            _enemy = GetComponentInParent<EnemyBase>();
            if (_enemy == null)
                Debug.LogError("[EnemyLocomotion] 找不到 EnemyBase。", this);
        }

        // ── IEnemyLocomotion（声明意图，不立即 actuate 之外的副作用）──
        public void SetMode(LocomotionMode mode)
        {
            if (_mode == mode) return;
            _mode = mode;
            _wanderPausing = false; // 切换模式清 Wander 停顿态
            if (mode == LocomotionMode.Idle) _enemy?.StopMovement();
            if (mode == LocomotionMode.Patrol && _enemy?.Stats != null)
                _enemy.Nav?.SetSpeed(_enemy.Stats.WalkSpeed);
        }

        public void Approach(Transform target)
        {
            _mode = LocomotionMode.Approach;
            _approachTarget = target;
            if (_enemy?.Stats != null) _enemy.Nav?.SetSpeed(_enemy.Stats.RunSpeed);
        }

        public void MoveTo(Vector2 point)
        {
            _mode = LocomotionMode.Approach;
            _approachTarget = null;
            _enemy?.MoveTo(point);
        }

        public void Face(Vector2 lookAt)
        {
            _mode = LocomotionMode.Face;
            _facePoint = lookAt;
        }

        public void Stop()
        {
            _mode = LocomotionMode.Idle;
            _enemy?.StopMovement();
        }

        // ── 每帧把模式翻译成执行 ──
        private void Update()
        {
            if (_enemy == null) return;
            // Wander 到点停顿期间用 Idle 步态（原地待机，否则站着播 Walk=原地踏步）。
            LocomotionMode gait = (_mode == LocomotionMode.Patrol
                                   && _patrolStrategy == PatrolStrategy.Wander
                                   && _wanderPausing)
                ? LocomotionMode.Idle : _mode;
            if (!_gaitInit || _gaitMode != gait)
            {
                _enemy.PlayLocomotionClip(gait);
                // 招式动画锁定期内不算"已应用"，解锁后重新同步步态（否则 Skill_End 后卡在收招动画）
                if (!_enemy.IsAnimLocked) { _gaitMode = gait; _gaitInit = true; }
            }
            switch (_mode)
            {
                case LocomotionMode.Idle:
                    break; // SetMode(Idle) 已停；保持
                case LocomotionMode.Patrol:
                    TickPatrol();
                    break;
                case LocomotionMode.Face:
                    _enemy.StopMovement();
                    _enemy.FaceTarget(_facePoint);
                    break;
                case LocomotionMode.Approach:
                    if (_approachTarget != null) _enemy.MoveTo(_approachTarget.position);
                    break;
            }
        }

        /// <summary>
        /// 段内随机游走：随机点限制在当前所站的导航段上（不跨 NavLink，避免崖边夹停/卡 link），
        /// 到达一个点后原地停顿 [_wanderPauseMin, _wanderPauseMax] 秒（期间播 Idle），再挑下一个点。
        /// </summary>
        private void TickWander()
        {
            if (_enemy.Nav == null) return;

            // 移动中：清停顿态，等到达
            if (_enemy.Nav.IsMoving) { _wanderPausing = false; return; }

            // 已到达（或尚未出发）：先停顿计时，再挑下一个点
            if (!_wanderPausing)
            {
                _wanderPausing    = true;
                _wanderPauseTimer = Random.Range(_wanderPauseMin, Mathf.Max(_wanderPauseMin, _wanderPauseMax));
            }

            _wanderPauseTimer -= Time.deltaTime;
            if (_wanderPauseTimer <= 0f)
            {
                _wanderPausing = false;
                _enemy.Nav.WalkToRandomOnSegment();
            }
        }

        private void TickPatrol()
        {
            switch (_patrolStrategy)
            {
                case PatrolStrategy.Wander:
                    TickWander();
                    break;

                case PatrolStrategy.Pace: // 撞墙/悬崖翻向的来回踱步（速度驱动，不依赖 nav）
                    var mv = _enemy.Movement;
                    // 用与移动层夹紧同一判定(WouldBlockAhead，即时按请求方向+碰撞体前缘)，
                    // 保证"夹停在地形边缘"与"掉头"一致，不会夹停却不翻向。
                    bool blocked = mv != null && mv.WouldBlockAhead(_paceDir);
                    // 兜底卡死检测(窗口净位移)：命令前进但一段时间净位移过小(撞上未挂检测层的墙/
                    // 卡角，含贴墙微抖)也视为受阻，使巡逻对场景配置鲁棒。用净位移而非逐帧差，
                    // 避免"贴墙推进-被弹回"的微抖每帧重置计数。
                    float px = _enemy.transform.position.x;
                    if (++_paceWindowFrames >= 12)
                    {
                        if (Mathf.Abs(px - _paceWindowStartX) < 0.05f) blocked = true;
                        _paceWindowStartX = px;
                        _paceWindowFrames = 0;
                    }
                    // 边沿触发：仅"障碍首次出现"翻一次；翻后按新方向即时判定，天然消抖，
                    // 且两侧都堵(窄台)时翻一次即停住、不来回抖。
                    if (blocked && !_paceBlockedPrev)
                    {
                        _paceDir = -_paceDir;
                        _paceWindowStartX = px; _paceWindowFrames = 0; // 翻向后重开窗口
                    }
                    _paceBlockedPrev = blocked;
                    _enemy.MoveInDirection(_paceDir);
                    break;

                case PatrolStrategy.Waypoints:
                    if (_waypoints == null || _waypoints.Length == 0)
                    {
                        if (!_warnedNoWaypoints)
                        {
                            Debug.LogWarning("[EnemyLocomotion] PatrolStrategy=Waypoints 但未配置 _waypoints，无法巡逻。", this);
                            _warnedNoWaypoints = true;
                        }
                        break;
                    }
                    // 仅首次或"已到达当前路点"时推进并寻路——不依赖 IsMoving
                    // （PathBerserker2d 寻路跨帧异步，IsMoving 在寻路计算期间为 false，会误触发每帧推进）。
                    // 到达判定对"吸附后的可达点"做，而非原始路点：原始路点可能摆在空中/崖外，
                    // 与之的距离永远进不了到达半径 → 卡死；吸附点是身体站得住的可达点。
                    if (_wpIndex < 0 ||
                        Vector2.Distance(_enemy.transform.position, _wpResolvedGoal) <= _waypointArriveRadius)
                    {
                        AdvanceWaypoint();
                        SetWaypointGoal();
                    }
                    break;
            }
        }

        /// <summary>
        /// 解析当前路点为"身体站得住的可达点"并出发。宽度处理下沉给 Nav 层（<see cref="IPathAgent.ResolveStandablePoint"/>），
        /// 本层只递原始路点坐标、不感知身体尺寸。吸附失败＝路点摆得离导航面太远，显式报错暴露根因，不静默兜底。
        /// </summary>
        private void SetWaypointGoal()
        {
            Vector2 raw = _waypoints[_wpIndex].position;
            if (_enemy.Nav == null || !_enemy.Nav.ResolveStandablePoint(raw, out _wpResolvedGoal))
            {
                _wpResolvedGoal = raw;
                Debug.LogWarning($"[EnemyLocomotion] 路点 '{_waypoints[_wpIndex].name}'(index {_wpIndex}) 无法吸附到任何可行走导航段" +
                                 "（超出搜索半径）。请检查该路点是否摆放在贴近地面/平台的可行走处。", this);
            }
            _enemy.MoveTo(_wpResolvedGoal);
        }

        private void AdvanceWaypoint()
        {
            if (_pingPong)
            {
                int next = _wpIndex + _wpDir;
                if (next < 0 || next >= _waypoints.Length) { _wpDir = -_wpDir; next = _wpIndex + _wpDir; }
                _wpIndex = Mathf.Clamp(next, 0, _waypoints.Length - 1);
            }
            else
            {
                _wpIndex = (_wpIndex + 1) % _waypoints.Length;
            }
        }
    }
}