using UnityEngine;
using PathBerserker2d;
using BaseGames.Enemies;
using System;
using System.Collections.Generic;

namespace BaseGames.Enemies.Navigation
{
    /// <summary>
    /// PathBerserker2d 导航代理包装器（架构 07_EnemyModule §5 能力驱动版）。
    ///
    /// 设计原则：
    /// <list type="bullet">
    ///   <item>连接段穿越（跳跃/攀爬/传送等）委托给 <see cref="INavLinkHandler"/> 能力组件执行</item>
    ///   <item>能力自行驱动动画 + 物理，本组件只做"调度 → 等回调 → 通知 PB2d 继续"</item>
    ///   <item>无对应能力时自动回退到 TransformBasedMovement（兜底行为）</item>
    ///   <item>Awake 自动发现 GameObject 上的全部 INavLinkHandler，并禁用 TBM 对应 FeatureFlag</item>
    /// </list>
    /// </summary>
    [RequireComponent(typeof(NavAgent))]
    [RequireComponent(typeof(TransformBasedMovement))]
    public class EnemyNavAgent : MonoBehaviour, IPathAgent
    {
        // ── 序列化 ──────────────────────────────────────────────────────
        [Tooltip("边缘检测前向距离（m）")]
        [SerializeField] private float _edgeCheckFwdOffset = 0.3f;
        [Tooltip("边缘检测向下射线长度（m）")]
        [SerializeField] private float _edgeCheckDownLen   = 0.6f;
        [Tooltip("边缘检测 LayerMask（留空 = 所有层）")]
        [SerializeField] private LayerMask _groundMask     = ~0;

        [Header("重寻路防抖（PathBerserker2d 不可每帧 UpdatePath，否则路径永远算不完）")]
        [Tooltip("目标位移阈值(m)：目标移动超过此值才重算路径")]
        [SerializeField] private float _repathTargetThreshold = 0.5f;
        [Tooltip("两次重算最小间隔(s)：留出跨帧路径计算完成的时间")]
        [SerializeField] private float _repathMinInterval     = 0.25f;

        [Header("目标点吸附")]
        [Tooltip("把巡逻/移动目标吸附到最近可行走段时，允许目标离最近段的最大真实距离(m)。语义同 PB2d 的 " +
                 "closestToSegmentMaxDistance——想多大就多大；只要目标在此距离内一定吸附得到。仅当目标离所有" +
                 "烘焙段都超过此值(真正脱离导航面)才判失败。")]
        [SerializeField] private float _maxSnapDistance        = 10f;

        [Header("受阻检测（寻路移动无进展即判被挡）")]
        [Tooltip("卡死检测窗口时长(s)：段上移动时，此时长内朝子目标推进小于阈值即判受阻")]
        [SerializeField] private float _stuckWindowSeconds = 0.5f;
        [Tooltip("卡死推进阈值(m)：窗口内朝子目标的距离缩小不足此值即判卡死")]
        [SerializeField] private float _stuckMinProgress   = 0.05f;

        // 重寻路防抖状态
        private Vector2 _lastPathGoal;
        private bool    _hasPathGoal;
        private float   _lastPathTime;

        // ── IPathAgent 公开状态 ────────────────────────────────────────
        public bool        IsMoving        => _navAgent != null && _navAgent.IsFollowingAPath;
        public bool        IsOnLink        => _navAgent != null && _navAgent.IsOnLink;
        public NavLinkType CurrentLinkType => _currentLinkType;
        public Vector2     CurrentLinkStart => _currentLinkStart;
        public Vector2     CurrentLinkEnd   => _currentLinkEnd;

        /// <summary>上次寻路移动是否因不可达/被挡而受阻（走到最近点或原地停，而非到达原目标）。新目标 RequestMoveTo 后复位。</summary>
        public bool LastMoveObstructed => _lastMoveObstructed;

        /// <summary>取上次寻路失败时算出的最近可达世界点。无则返回 false。</summary>
        public bool TryGetClosestReachable(out Vector2 worldPos)
        {
            if (_navAgent != null) return _navAgent.TryGetClosestReachablePosition(out worldPos);
            worldPos = Vector2.zero;
            return false;
        }

        // ── IPathAgent 事件 ────────────────────────────────────────────
        public event Action<NavLinkType> OnLinkStarted;
        public event Action<NavLinkType> OnLinkCompleted;
        public event Action              OnNavPathFailed;
        public event Action              OnGoalReached;

        // ── 私有 ────────────────────────────────────────────────────────
        private NavAgent               _navAgent;
        private TransformBasedMovement _movement;
        private EnemyMovement          _enemyMovement;

        // 能力 handler 注册表（NavLinkType → INavLinkHandler）
        private readonly Dictionary<NavLinkType, INavLinkHandler> _handlers
            = new Dictionary<NavLinkType, INavLinkHandler>();
        private INavLinkHandler _activeHandler;

        // 受阻状态（供意图层结算）
        private bool  _lastMoveObstructed;
        private bool  _redirectedToClosest;  // 本轮已改道到最近点，避免每帧重复下发
        private bool  _obstructionSignal;    // 受阻信号(寻路失败/卡死)，延后到 FixedUpdate 统一处理
        // 卡死检测窗口
        private float _stuckWinTimer;
        private float _stuckWinStartDist;
        private bool  _stuckWinInit;

        // 连接段状态缓存
        private NavLinkType _currentLinkType  = NavLinkType.None;
        private bool        _wasNavOnSegment;
        private Vector2     _currentLinkStart;
        private Vector2     _currentLinkEnd;

        // ── 初始化 ─────────────────────────────────────────────────────
        private void Awake()
        {
            _navAgent = GetComponent<NavAgent>();
            _movement  = GetComponent<TransformBasedMovement>();
            _enemyMovement = GetComponent<EnemyMovement>();

            // 物理原生移动：禁用 TBM 段移动——不让它直接写 transform.position（会与 Dynamic 刚体物理冲突）。
            // 段上的水平移动改由 EnemyMovement 用 velocity 执行、刚体重力保持贴地（见 FixedUpdate）。
            if (_movement != null)
                _movement.enabledFeatures &= ~TransformBasedMovement.FeatureFlags.SegmentMovement;

            // 自动发现 INavLinkHandler 组件并注册（包含子对象）
            foreach (var handler in GetComponentsInChildren<INavLinkHandler>(true))
                RegisterLinkHandler(handler);

            _navAgent.OnStartLinkTraversal += HandleLinkStart;
            _navAgent.OnSegmentTraversal   += HandleSegmentTraversal;
            _navAgent.OnFailedToFindPath   += HandlePathFailed;
            _navAgent.OnReachedGoal        += HandleGoalReached;
        }

        private void OnDestroy()
        {
            if (_navAgent == null) return;
            _navAgent.OnStartLinkTraversal -= HandleLinkStart;
            _navAgent.OnSegmentTraversal   -= HandleSegmentTraversal;
            _navAgent.OnFailedToFindPath   -= HandlePathFailed;
            _navAgent.OnReachedGoal        -= HandleGoalReached;
        }

        // ── Handler 注册 ───────────────────────────────────────────────
        /// <summary>
        /// 注册能力为某连接段类型的处理器。
        /// 注册后 TransformBasedMovement 中对应 FeatureFlag 将被禁用，由能力全权负责该类型穿越。
        /// </summary>
        public void RegisterLinkHandler(INavLinkHandler handler)
        {
            if (handler == null) return;
            foreach (var type in handler.HandledLinkTypes)
            {
                _handlers[type] = handler;
                // 禁用 TBM 对该类型的处理，完全交给能力
                var flag = TypeToFeatureFlag(type);
                if (flag != 0 && _movement != null)
                    _movement.enabledFeatures &= ~flag;
            }
        }

        /// <summary>移除某处理器（例如能力被永久禁用时）。TBM FeatureFlag 自动恢复。</summary>
        public void UnregisterLinkHandler(INavLinkHandler handler)
        {
            if (handler == null) return;
            foreach (var type in handler.HandledLinkTypes)
            {
                if (_handlers.TryGetValue(type, out var registered) && ReferenceEquals(registered, handler))
                {
                    _handlers.Remove(type);
                    // 恢复 TBM 对该类型的处理
                    var flag = TypeToFeatureFlag(type);
                    if (flag != 0 && _movement != null)
                        _movement.enabledFeatures |= flag;
                }
            }
        }

        // ── IPathAgent ─────────────────────────────────────────────────
        public void RequestMoveTo(Vector2 target)
        {
            if (_navAgent == null) return;
            // PathBerserker2d 明确警告不可每帧 UpdatePath（路径计算跨帧，每帧重启则永不完成、agent 永不移动）。
            // 防抖：目标未明显移动 且 距上次重算不足间隔 → 跳过，让当前路径算完并跟随。
            if (_hasPathGoal
                && Vector2.Distance(target, _lastPathGoal) < _repathTargetThreshold
                && Time.time - _lastPathTime < _repathMinInterval)
                return;

            _lastPathGoal = target;
            _hasPathGoal  = true;
            _lastPathTime = Time.time;
            _lastMoveObstructed  = false;   // 新目标 → 复位受阻态
            _redirectedToClosest = false;
            ResetStuckWindow();
            _navAgent.UpdatePath(target);
        }

        public void StopNavigation()
        {
            _activeHandler?.AbortLinkTraversal();
            _activeHandler = null;
            _hasPathGoal   = false; // 复位防抖，下次请求立即重新寻路
            _navAgent?.Stop();
        }

        public bool IsAtDestination() => _navAgent == null || _navAgent.IsIdle;

        public void SetSpeed(float speed)
        {
            if (_movement != null) _movement.movementSpeed = speed;
        }

        public bool CanReach(Vector2 target) => _navAgent?.CanReach(target) ?? false;

        public bool WalkToRandom() => _navAgent?.SetRandomDestination() ?? false;

        // 段内随机游走：按身体前缘安全余量内缩段两端，避免随机点落在角色宽度站不住的崖沿(WouldFallAhead 夹停)。
        public bool WalkToRandomOnSegment()
            => _navAgent?.SetRandomDestinationOnCurrentSegment(
                   _enemyMovement != null ? _enemyMovement.EdgeSafeMargin : 0f) ?? false;

        // 目标点吸附：把任意世界目标映射到最近可行走段、并按身体宽度(EdgeSafeMargin)从段两端内缩，
        // 得到"身体真正站得住"的点。身体宽度是本执行层独占的知识——意图层(AI/Locomotion)只递原始目标。
        // 用 PB2d 映射任意点到导航面的机制(_maxSnapDistance 内一定命中最近段)；返回 false 仅表示目标真正脱离导航面。
        public bool ResolveStandablePoint(Vector2 target, out Vector2 standable)
        {
            if (_navAgent == null) { standable = target; return false; }
            float margin = _enemyMovement != null ? _enemyMovement.EdgeSafeMargin : 0f;
            return _navAgent.TryGetStandablePointNear(target, _maxSnapDistance, margin, out standable);
        }

        public bool IsNearEdge()
        {
            var origin = (Vector2)transform.position;
            var facing = transform.localScale.x >= 0f ? Vector2.right : Vector2.left;
            return !Physics2D.Raycast(origin + facing * _edgeCheckFwdOffset,
                                      Vector2.down, _edgeCheckDownLen, _groundMask);
        }

        // ── 底层 NavAgent 直接访问 ──────────────────────────────────────
        /// <summary>原始 PB2d NavAgent，供需要 PB2d 高级功能的能力直接使用。</summary>
        public NavAgent RawNavAgent => _navAgent;

        // ── 连接段调度核心 ─────────────────────────────────────────────
        private void HandleLinkStart(NavAgent agent)
        {
            var seg = agent.CurrentPathSegment;
            _currentLinkType  = ParseLinkType(seg?.link?.LinkTypeName);
            _currentLinkStart = seg?.LinkStart ?? Vector2.zero;
            _currentLinkEnd   = seg?.LinkEnd   ?? Vector2.zero;

            OnLinkStarted?.Invoke(_currentLinkType);

            if (_handlers.TryGetValue(_currentLinkType, out var handler))
            {
                if (handler.CanHandleLink(_currentLinkType, _currentLinkStart, _currentLinkEnd))
                {
                    _activeHandler = handler;
                    handler.BeginLinkTraversal(_currentLinkType, _currentLinkStart, _currentLinkEnd,
                        onComplete: () =>
                        {
                            _activeHandler = null;
                            _navAgent?.CompleteLinkTraversal();
                        });
                    return;
                }

                // CanHandleLink 返回 false 且 TBM 已禁用 → NavAgent 会卡住，警告设计者
                Debug.LogWarning($"[EnemyNavAgent] '{handler.GetType().Name}' reported CanHandleLink=false " +
                                 $"for {_currentLinkType} (TBM disabled). NavAgent may stall. " +
                                 $"Check link distance/height vs. ability parameters.", this);
            }
            // 无 handler → TBM 兜底（其 FeatureFlag 仍开启）
        }

        private void HandleSegmentTraversal(NavAgent agent)
        {
            if (_currentLinkType != NavLinkType.None && !agent.IsOnLink)
            {
                var finished      = _currentLinkType;
                _currentLinkType  = NavLinkType.None;
                _currentLinkStart = Vector2.zero;
                _currentLinkEnd   = Vector2.zero;
                OnLinkCompleted?.Invoke(finished);
            }
        }

        private void HandlePathFailed(NavAgent _)
        {
            _obstructionSignal = true;   // 延后到 FixedUpdate 统一处理，避免在 NavAgent 失败回调内重入 UpdatePath
            OnNavPathFailed?.Invoke();
        }

        private void HandleGoalReached(NavAgent _) => OnGoalReached?.Invoke();

        // ── 物理原生移动桥 ─────────────────────────────────────────────
        /// <summary>
        /// 跟随路径段时：向 <see cref="EnemyMovement"/> 写入朝当前子目标的水平方向+速度（由 velocity+重力执行），
        /// 并在到达子目标时推进导航到下一段（TBM 段移动已在 Awake 禁用，改由本组件推进）。
        /// 不直接写 transform.position → 与 Dynamic 刚体物理不冲突，保留击退/击飞/落地等物理反馈。
        /// </summary>
        private void FixedUpdate()
        {
            if (_enemyMovement == null || _navAgent == null) return;

            bool onSegment = _navAgent.IsMovingOnSegment;
            _enemyMovement.NavDriving = onSegment; // 状态标记（供调试/上层判断"是否导航中"）

            TickStuckDetection(onSegment);

            if (onSegment)
            {
                // 物理原生：朝子目标水平移动，由 EnemyMovement 施加 velocity、刚体重力保持贴地
                float dx = _navAgent.PathSubGoal.x - transform.position.x;
                _enemyMovement.PendingInput.MoveDir   = Mathf.Abs(dx) > 0.05f ? Mathf.Sign(dx) : 0f;
                _enemyMovement.PendingInput.MoveSpeed = _movement != null ? _movement.movementSpeed : 0f;

                // 段推进：到达当前子目标 → 推进到下一段
                if (_navAgent.HasReachedCurrentSubGoal(0.25f))
                    _navAgent.CompleteSegmentTraversal();
            }
            else if (_wasNavOnSegment && !_navAgent.IsFollowingAPath)
            {
                // 导航刚结束（到达目标 / 路径失败）→ 停下水平移动
                _enemyMovement.PendingInput.WantStop = true;
            }

            // 受阻信号统一处理（寻路失败/卡死）：此处不在 NavAgent 回调内，UpdatePath 安全
            if (_obstructionSignal)
            {
                _obstructionSignal = false;
                ProcessObstruction();
            }

            _wasNavOnSegment = onSegment;
        }

        // 卡死检测：段上移动时，滑动窗口内朝子目标推进不足阈值 → 判受阻(覆盖"障碍未进图"的物理空推)。
        private void TickStuckDetection(bool onSegment)
        {
            if (!onSegment) { _stuckWinInit = false; return; }

            float dist = Mathf.Abs(_navAgent.PathSubGoal.x - transform.position.x);
            if (!_stuckWinInit)
            {
                _stuckWinInit      = true;
                _stuckWinTimer     = 0f;
                _stuckWinStartDist = dist;
                return;
            }
            _stuckWinTimer += Time.fixedDeltaTime;
            if (_stuckWinTimer >= _stuckWindowSeconds)
            {
                if (_stuckWinStartDist - dist < _stuckMinProgress)
                    _obstructionSignal = true; // 窗口内几乎没靠近子目标 → 卡死
                _stuckWinTimer     = 0f;
                _stuckWinStartDist = dist;
            }
        }

        private void ResetStuckWindow() => _stuckWinInit = false;

        // 统一受阻处理：尽力改道到最近可达点(走到障碍前)，拿不到更近点则停下，交由意图层结算。
        private void ProcessObstruction()
        {
            _lastMoveObstructed = true;

            if (!_redirectedToClosest
                && _navAgent.TryGetClosestReachablePosition(out var closest)
                && Vector2.Distance(transform.position, closest) > _repathTargetThreshold)
            {
                _redirectedToClosest = true;
                ResetStuckWindow();
                _navAgent.UpdatePath(closest);   // 走向最近可达点
                return;
            }

            // 无更近点 / 已在最近点附近（含"障碍未进图"无 closest 数据）→ 停下
            _navAgent.Stop();
            _enemyMovement.PendingInput.WantStop = true;
        }

        // ── 工具 ───────────────────────────────────────────────────────
        private static NavLinkType ParseLinkType(string name) => name switch
        {
            "corner"   => NavLinkType.Corner,
            "jump"     => NavLinkType.Jump,
            "fall"     => NavLinkType.Fall,
            "teleport" => NavLinkType.Teleport,
            "climb"    => NavLinkType.Climb,
            "elevator" => NavLinkType.Elevator,
            null or "" => NavLinkType.Segment,
            _          => NavLinkType.Custom
        };

        /// <summary>NavLinkType → TransformBasedMovement.FeatureFlags 映射。</summary>
        private static TransformBasedMovement.FeatureFlags TypeToFeatureFlag(NavLinkType type) => type switch
        {
            NavLinkType.Jump     => TransformBasedMovement.FeatureFlags.JumpLinks,
            NavLinkType.Fall     => TransformBasedMovement.FeatureFlags.FallLinks,
            NavLinkType.Corner   => TransformBasedMovement.FeatureFlags.CornerLinks,
            NavLinkType.Climb    => TransformBasedMovement.FeatureFlags.ClimbLinks,
            NavLinkType.Elevator => TransformBasedMovement.FeatureFlags.ElevatorLinks,
            NavLinkType.Teleport => TransformBasedMovement.FeatureFlags.TeleportLinks,
            _                    => (TransformBasedMovement.FeatureFlags)0
        };
    }
}