using UnityEngine;

namespace BaseGames.Enemies
{
    /// <summary>
    /// 角色身体碰撞体的唯一权威查询口。
    /// 几何实时取自碰撞体 bounds（随位置/动画变化，不缓存数值），仅缓存碰撞体引用。
    /// 唯一数据源见 <see cref="EnemyBase.Body"/>——其它组件不得自行解析身体碰撞体。
    /// </summary>
    public interface IEnemyBody
    {
        Collider2D Collider   { get; }
        /// <summary>世界空间包围盒；实时查询。</summary>
        Bounds     Bounds     { get; }
        float      Width      { get; }
        float      Height     { get; }
        float      HalfWidth  { get; }
        float      HalfHeight { get; }
        Vector2    Center     { get; }
        /// <summary>脚底中点 (center.x, min.y)。</summary>
        Vector2    FootPoint  { get; }

        /// <summary>朝 <paramref name="dir"/> 的前缘 X（dir≥0 取 max.x，否则 min.x）。</summary>
        float FrontEdgeX(float dir);
        /// <summary>朝 <paramref name="dir"/> 的后缘 X（前缘的相反侧）。</summary>
        float RearEdgeX(float dir);
        /// <summary>
        /// 身体是否已**整体**越过世界 X 坐标：
        /// dir≥0 时后缘(min.x) ≥ worldX；dir&lt;0 时后缘(max.x) ≤ worldX。
        /// </summary>
        bool HasPassed(float worldX, float dir);
    }

    /// <summary>
    /// <see cref="IEnemyBody"/> 的实现（纯 C# 类，非 MonoBehaviour）。
    /// 懒解析碰撞体 → 编辑器模式（Gizmo / OnValidate，Awake 未执行）同样可用。
    /// </summary>
    public sealed class EnemyBody : IEnemyBody
    {
        private readonly GameObject _owner;
        private readonly Collider2D _explicitCollider;
        private Collider2D _resolved;

        /// <param name="owner">宿主 GameObject（未显式指定碰撞体时从其上取 Collider2D）。</param>
        /// <param name="explicitCollider">显式指定的身体碰撞体；可为 null。</param>
        public EnemyBody(GameObject owner, Collider2D explicitCollider)
        {
            _owner            = owner;
            _explicitCollider = explicitCollider;
        }

        public Collider2D Collider
        {
            get
            {
                if (_explicitCollider != null) return _explicitCollider;
                if (_resolved == null && _owner != null) _resolved = _owner.GetComponent<Collider2D>();
                return _resolved;
            }
        }

        /// <summary>
        /// 碰撞体缺失时返回以宿主位置为中心的零尺寸包围盒。
        /// 该错误已由 <see cref="EnemyBase"/> 在 Awake/OnValidate 显式报出，此处不重复每帧刷屏。
        /// </summary>
        public Bounds Bounds
        {
            get
            {
                var col = Collider;
                if (col != null) return col.bounds;
                return new Bounds(_owner != null ? _owner.transform.position : Vector3.zero, Vector3.zero);
            }
        }

        public float   Width      => Bounds.size.x;
        public float   Height     => Bounds.size.y;
        public float   HalfWidth  => Bounds.extents.x;
        public float   HalfHeight => Bounds.extents.y;
        public Vector2 Center     => Bounds.center;
        public Vector2 FootPoint  { get { var b = Bounds; return new Vector2(b.center.x, b.min.y); } }

        public float FrontEdgeX(float dir) { var b = Bounds; return FrontEdge(b.min.x, b.max.x, dir); }
        public float RearEdgeX (float dir) { var b = Bounds; return RearEdge (b.min.x, b.max.x, dir); }
        public bool  HasPassed(float worldX, float dir)
        {
            var b = Bounds;
            return BodyPassed(b.min.x, b.max.x, worldX, dir);
        }

        // ── 方向纯函数（static，便于无场景依赖单测；符号最易写反，集中于此）──────
        public static float FrontEdge(float minX, float maxX, float dir) => dir >= 0f ? maxX : minX;
        public static float RearEdge (float minX, float maxX, float dir) => dir >= 0f ? minX : maxX;
        public static bool  BodyPassed(float minX, float maxX, float worldX, float dir)
            => dir >= 0f ? minX >= worldX : maxX <= worldX;
    }
}