using System;
using UnityEngine;
using BaseGames.Enemies;

namespace BaseGames.Enemies.Navigation
{
    /// <summary>
    /// 飞行单位直线导航代理。
    /// 不依赖 PathBerserker2d 寻路，直接通过 Rigidbody2D.MovePosition 向目标点直飞。
    ///
    /// 特性：
    /// <list type="bullet">
    ///   <item>空闲时施加正弦波形悬停偏移，产生飘浮感。</item>
    ///   <item>NavLink 相关成员均返回安全默认值（飞行单位不使用平台连接段）。</item>
    ///   <item>目标到达后触发 <see cref="OnGoalReached"/> 事件（替代轮询 IsAtDestination）。</item>
    /// </list>
    ///
    /// 使用方式：挂载到飞行怪 Prefab 根节点，替代 EnemyNavAgent；
    /// <see cref="EnemyBase.Awake"/> 的 GetComponent&lt;IPathAgent&gt;() 自动发现此组件。
    /// </summary>
    [RequireComponent(typeof(Rigidbody2D))]
    public sealed class FlyingDirectNavigator : MonoBehaviour, IPathAgent
    {
        [Header("移动参数")]
        [Tooltip("直飞速度（m/s）")]
        [SerializeField] private float _moveSpeed       = 3f;
        [Tooltip("到达目标的判定距离（m）")]
        [SerializeField] private float _stoppingDist    = 0.15f;

        [Header("游荡参数（WalkToRandom）")]
        [Tooltip("随机游荡目标点距当前位置的最大半径（m）。")]
        [Min(0.1f)]
        [SerializeField] private float _randomWalkRadius = 3f;

        [Header("悬停参数（空闲 / 无目标时）")]
        [Tooltip("悬停横向摆动速度（m/s）")]
        [SerializeField] private float _hoverLateralSpeed  = 0.5f;
        [Tooltip("悬停纵向正弦频率（Hz）")]
        [SerializeField] private float _hoverSineFrequency = 1.2f;
        [Tooltip("悬停纵向正弦振幅（m/s）")]
        [SerializeField] private float _hoverSineAmplitude = 0.25f;
        [Tooltip("横向方向翻转周期（s）")]
        [SerializeField] private float _hoverFlipInterval  = 1.5f;

        // ── IPathAgent 事件 ────────────────────────────────────────────
        public event Action<NavLinkType> OnLinkStarted   { add { } remove { } }
        public event Action<NavLinkType> OnLinkCompleted { add { } remove { } }
        public event Action OnNavPathFailed              { add { } remove { } }
        public event Action OnGoalReached;

        // ── 状态 ───────────────────────────────────────────────────────
        private Rigidbody2D    _rb;
        private EnemyMovement  _movement;
        private Vector2?       _destination;
        private bool           _isMoving;
        private bool           _goalFired;

        private float _hoverTimer;
        private float _hoverFlipTimer;
        private float _hoverDir = 1f;

        // ── IPathAgent 属性 ────────────────────────────────────────────
        public bool IsMoving        => _isMoving;
        public bool IsOnLink        => false;
        public NavLinkType CurrentLinkType  => NavLinkType.None;
        public Vector2 CurrentLinkStart     => Vector2.zero;
        public Vector2 CurrentLinkEnd       => Vector2.zero;

        // ── Unity 生命周期 ─────────────────────────────────────────────
        private void Awake()
        {
            _rb       = GetComponent<Rigidbody2D>();
            _movement = GetComponent<EnemyMovement>();
            _rb.gravityScale = 0f;
            _rb.constraints  = RigidbodyConstraints2D.FreezeRotation;
        }

        private void FixedUpdate()
        {
            if (_destination.HasValue)
                UpdateChase();
            else
                UpdateHover();
        }

        // ── IPathAgent 方法 ────────────────────────────────────────────
        public void RequestMoveTo(Vector2 target)
        {
            _destination = target;
            _isMoving    = true;
            _goalFired   = false;
        }

        public void StopNavigation()
        {
            _destination = null;
            _isMoving    = false;
            _rb.velocity = Vector2.zero;
        }

        public bool IsAtDestination()
        {
            if (!_destination.HasValue) return true;
            return ((Vector2)transform.position - _destination.Value).sqrMagnitude
                   <= _stoppingDist * _stoppingDist;
        }

        public void SetSpeed(float speed) => _moveSpeed = speed;

        public bool IsNearEdge() => false;  // 飞行单位不检测平台边缘

        public bool CanReach(Vector2 target) => true;  // 飞行单位直飞，始终可达

        public bool WalkToRandom()
        {
            // 在当前位置随机偏移一个 2D 方向（供 BD_WalkRandom 调用）
            Vector2 offset = UnityEngine.Random.insideUnitCircle.normalized * _randomWalkRadius;
            RequestMoveTo((Vector2)transform.position + offset);
            return true;
        }

        // ── 内部移动逻辑 ───────────────────────────────────────────────
        private void UpdateChase()
        {
            Vector2 myPos   = _rb.position;
            Vector2 target  = _destination.Value;
            float   sqrDist = (target - myPos).sqrMagnitude;

            if (sqrDist <= _stoppingDist * _stoppingDist)
            {
                _rb.velocity = Vector2.zero;
                _isMoving    = false;
                _destination = null;
                if (!_goalFired)
                {
                    _goalFired = true;
                    OnGoalReached?.Invoke();
                }
                return;
            }

            Vector2 newPos = Vector2.MoveTowards(myPos, target, _moveSpeed * Time.fixedDeltaTime);
            _rb.MovePosition(newPos);

            // 面向移动方向（通过 EnemyMovement 输入信号，保持 _facingDir 与动画系统同步）
            float dx = target.x - myPos.x;
            if (Mathf.Abs(dx) > 0.05f)
            {
                int dir = dx > 0f ? 1 : -1;
                if (_movement != null)
                {
                    _movement.PendingInput.WantFace = true;
                    _movement.PendingInput.FaceDir  = dir;
                }
                else
                {
                    // 降级：没有 EnemyMovement 时直接翻转（独立飞行单位）
                    var s = transform.localScale;
                    s.x = Mathf.Abs(s.x) * dir;
                    transform.localScale = s;
                }
            }
        }

        private void UpdateHover()
        {
            _hoverFlipTimer += Time.fixedDeltaTime;
            if (_hoverFlipTimer >= _hoverFlipInterval)
            {
                _hoverFlipTimer = 0f;
                _hoverDir       = -_hoverDir;
            }

            float sineY  = Mathf.Sin(Time.time * _hoverSineFrequency * Mathf.PI * 2f) * _hoverSineAmplitude;
            _rb.velocity  = new Vector2(_hoverDir * _hoverLateralSpeed, sineY);
        }
    }
}