using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using BaseGames.Core;

namespace BaseGames.Camera
{
    /// <summary>
    /// 相机区域切换触发器。
    /// 当触发区域重叠时，玩家必须先离开当前所在的触发区域，才会切换到下一个区域，
    /// 而不是进入重叠区域时立即切换。
    /// </summary>
    [ExecuteAlways]
    [RequireComponent(typeof(PolygonCollider2D))]
    public class CameraTriggerZone : MonoBehaviour
    {
        [SerializeField] private CameraArea _targetArea;

        [Tooltip("玩家离开此触发区域时回退到的区域（留空则退出时不做处理）。\n" +
                 "通常设为上级/相邻的包含区域，使玩家返回时相机自然过渡。")]
        [SerializeField] private CameraArea _exitFallbackArea;

        [Tooltip("触发区域优先级。同时在多个触发区域内时，高优先级区域胜出。\n" +
                 "相同优先级则后进入的胜出（推荐默认值 1）。")]
        [SerializeField] private int _priority = 1;

        [SerializeField] private string _playerTag = "Player";

        private PolygonCollider2D _collider;
        private bool _isPlayerInside;

        // ── 静态：跨实例共享触发状态 ──────────────────────────────────────────
        // 玩家当前物理上所在的所有触发区域（按进入顺序排列）
        private static readonly List<CameraTriggerZone> s_InsideZones = new();
        // 当前已向 ICameraService 发出 SwitchArea 请求的触发区域
        private static CameraTriggerZone s_ActiveZone;

        private void Awake()
        {
            _collider = GetComponent<PolygonCollider2D>();
            _collider.isTrigger = true;
        }

        private void OnDisable()
        {
            if (!Application.isPlaying) return;
            if (!_isPlayerInside) return;

            _isPlayerInside = false;
            s_InsideZones.Remove(this);
            if (s_ActiveZone == this)
                Deactivate(this);
        }

        /// <summary>
        /// 若玩家出生时已在触发区域内，OnTriggerEnter2D 不会触发。
        /// 延迟一帧（确保 RoomController.Start 先完成基准区域设置）后主动检测。
        /// </summary>
        private IEnumerator Start()
        {
            if (!Application.isPlaying) yield break;

            // 等一帧：让 RoomController.Start（priority=0）先建立基准区域，
            // 再以 _priority 叠加子区域，保证栈顺序正确。
            yield return null;

            if (_targetArea == null) yield break;

            GameObject player = GameObject.FindWithTag(_playerTag);
            if (player == null || !_collider.OverlapPoint(player.transform.position)) yield break;

            // OnTriggerEnter2D 可能已先一步处理，避免重复加入
            if (!_isPlayerInside)
            {
                _isPlayerInside = true;
                s_InsideZones.Add(this);
            }

            if (s_ActiveZone == null)
                Activate(this);
        }

        private void OnTriggerEnter2D(Collider2D other)
        {
            if (!Application.isPlaying) return;
            if (!other.CompareTag(_playerTag)) return;
            if (_targetArea == null || _isPlayerInside) return;

            _isPlayerInside = true;
            s_InsideZones.Add(this);

            // 没有激活的触发区域 → 立即切换
            // 已有激活的触发区域 → 等玩家离开后再接管（避免重叠区域间提前切换）
            if (s_ActiveZone == null)
                Activate(this);
        }

        private void OnTriggerExit2D(Collider2D other)
        {
            if (!Application.isPlaying) return;
            if (!other.CompareTag(_playerTag)) return;
            if (!_isPlayerInside) return;

            _isPlayerInside = false;
            s_InsideZones.Remove(this);

            if (s_ActiveZone == this)
                Deactivate(this);
        }

        // ── 静态辅助方法 ────────────────────────────────────────────────────────

        private static void Activate(CameraTriggerZone zone)
        {
            s_ActiveZone = zone;
            ServiceLocator.GetOrDefault<ICameraService>()?.SwitchArea(zone._targetArea, zone._priority);
        }

        /// <summary>
        /// 离开 <paramref name="leaving"/> 时的处理：
        /// 若还有其他触发区域，先激活最优者再释放 leaving（避免短暂回退到房间基线）；
        /// 否则直接释放并使用 <see cref="_exitFallbackArea"/>。
        /// </summary>
        private static void Deactivate(CameraTriggerZone leaving)
        {
            ICameraService svc = ServiceLocator.GetOrDefault<ICameraService>();
            if (s_InsideZones.Count > 0)
            {
                // 先激活下一个，再释放 leaving —— 此时 _currentArea 已更新为 next，
                // ReleaseArea(leaving) 中 wasActive=false，仅从 _activeZones 移除，不触发额外跳转
                CameraTriggerZone next = SelectBest();
                s_ActiveZone = next;
                svc?.SwitchArea(next._targetArea, next._priority);
                svc?.ReleaseArea(leaving._targetArea, null);
            }
            else
            {
                s_ActiveZone = null;
                svc?.ReleaseArea(leaving._targetArea, leaving._exitFallbackArea);
            }
        }

        /// <summary>从 <see cref="s_InsideZones"/> 中选出优先级最高的区域。</summary>
        private static CameraTriggerZone SelectBest()
        {
            CameraTriggerZone best = s_InsideZones[0];
            for (int i = 1; i < s_InsideZones.Count; i++)
                if (s_InsideZones[i]._priority > best._priority)
                    best = s_InsideZones[i];
            return best;
        }

        private void OnDrawGizmos()
        {
            if (_collider == null) _collider = GetComponent<PolygonCollider2D>();
            if (_collider == null || _collider.pathCount == 0) return;

            var pts = new System.Collections.Generic.List<Vector2>();
            _collider.GetPath(0, pts);
            if (pts.Count < 2) return;

            Gizmos.matrix = transform.localToWorldMatrix;
            Vector2 off = _collider.offset;
            Gizmos.color = new Color(0.2f, 0.8f, 1f, 0.8f);
            for (int i = 0; i < pts.Count; i++)
            {
                Vector2 a = pts[i] + off;
                Vector2 b = pts[(i + 1) % pts.Count] + off;
                Gizmos.DrawLine(new Vector3(a.x, a.y), new Vector3(b.x, b.y));
            }
        }
    }
}