using UnityEngine;
using BaseGames.Enemies;

namespace BaseGames.Enemies.Navigation
{
    /// <summary>
    /// 飞行单位直线导航代理，实现 <see cref="IEnemyNavigator"/>。
    /// 不依赖寻路网格，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>飞行单位直飞，无地形阻挡概念，<see cref="IsBlocked"/> 恒为 false。</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;IEnemyNavigator&gt;() 自动发现此组件。
    /// </summary>
    [RequireComponent(typeof(Rigidbody2D))]
    public sealed class FlyingNavigator : MonoBehaviour, IEnemyNavigator
    {
        [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（TryPickWanderPoint）")]
        [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;

        // ── 状态 ───────────────────────────────────────────────────────
        private Rigidbody2D    _rb;
        private EnemyMovement  _movement;
        private Vector2        _target;
        private bool           _hasTarget;
        private bool           _arrived;

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

        // ── IEnemyNavigator 属性 ────────────────────────────────────────
        public bool IsMoving   => _hasTarget && !_arrived;
        public bool HasArrived => _arrived;

        // 飞行单位直飞，无地形阻挡概念。
        public bool IsBlocked => false;

        // ── 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 (_hasTarget && !_arrived)
                UpdateChase();
            else
                UpdateHover();
        }

        // ── IEnemyNavigator 方法 ────────────────────────────────────────
        public void MoveTowards(Vector2 target)
        {
            // 幂等：同目标重复调用不重置状态（避免每帧重发目标导致已到达状态被反复清空）。
            if (_hasTarget && (target - _target).sqrMagnitude <= 1e-6f)
                return;

            _target    = target;
            _hasTarget = true;
            _arrived   = false;
        }

        public void Stop()
        {
            _hasTarget   = false;
            _arrived     = false;
            _rb.velocity = Vector2.zero;
        }

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

        public bool TryPickWanderPoint(out Vector2 point)
        {
            // 在当前位置随机偏移一个 2D 方向，供上层游荡状态调用；不主动发起移动。
            Vector2 offset = Random.insideUnitCircle.normalized * _randomWalkRadius;
            point = (Vector2)transform.position + offset;
            return true;
        }

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

            if (sqrDist <= _stoppingDist * _stoppingDist)
            {
                _rb.velocity = Vector2.zero;
                _arrived     = true;
                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);
        }
    }
}