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

namespace BaseGames.World
{
    /// <summary>
    /// 挂在 Player 上，检测附近可交互物，驱动 UI 提示显示/隐藏。
    /// 通过 InputReaderSO.InteractEvent 绑定交互输入。
    /// </summary>
    public class InteractableDetector : MonoBehaviour
    {
        [SerializeField] private float                        _detectRadius = 1.5f;
        [SerializeField] private LayerMask                    _interactableLayer;
        [SerializeField] private InputReaderSO                _inputReader;
        [SerializeField] private InteractPromptEventChannelSO _onShowInteractPrompt;
        [SerializeField] private VoidEventChannelSO           _onHideInteractPrompt;

        private IInteractable _nearest;
        private IInteractable _previousNearest;

        // 预分配检测缓冲区，避免 OverlapCircleAll 每帧 GC 分配
        private readonly Collider2D[] _overlapBuffer = new Collider2D[16];

        // Collider → IInteractable 缓存，避免 FindNearest 每帧重复 GetComponentInParent
        private readonly Dictionary<Collider2D, IInteractable> _componentCache = new();

        private void OnEnable()
        {
            _inputReader.InteractEvent += TryInteract;
        }

        private void OnDisable()
        {
            _inputReader.InteractEvent -= TryInteract;
            _componentCache.Clear(); // 清理缓存，防止跨场景持有旧引用
        }

        private void Update()
        {
            int count = Physics2D.OverlapCircleNonAlloc(
                transform.position, _detectRadius, _overlapBuffer, _interactableLayer);
            _nearest = FindNearest(_overlapBuffer, count);

            if (_nearest != _previousNearest)
            {
                if (_previousNearest != null)
                {
                    _previousNearest.OnPlayerExitRange();
                    _onHideInteractPrompt?.Raise();
                }

                if (_nearest != null)
                {
                    _nearest.OnPlayerEnterRange(transform);
                    _onShowInteractPrompt?.Raise(new InteractPromptEvent("Interact", _nearest.InteractPrompt));
                }

                _previousNearest = _nearest;
            }
        }

        private void TryInteract()
        {
            if (_nearest != null && _nearest.CanInteract)
                _nearest.Interact(transform);
        }

        private IInteractable FindNearest(Collider2D[] hits, int count)
        {
            IInteractable best        = null;
            float         bestSqrDist = float.MaxValue;

            for (int i = 0; i < count; i++)
            {
                var col = hits[i];
                if (col == null) continue;

                // 查缓存，未命中时才调用 GetComponentInParent（避免每帧反射开销）
                if (!_componentCache.TryGetValue(col, out var interactable))
                {
                    interactable = col.GetComponentInParent<IInteractable>();
                    _componentCache[col] = interactable;
                }

                if (interactable == null || !interactable.CanInteract) continue;

                // 用 sqrMagnitude 比较距离，省去 Distance 的 sqrt 开销
                float sqrDist = ((Vector2)transform.position - (Vector2)col.transform.position).sqrMagnitude;
                if (sqrDist < bestSqrDist)
                {
                    bestSqrDist = sqrDist;
                    best        = interactable;
                }
            }

            return best;
        }

        private void OnDrawGizmosSelected()
        {
            Gizmos.color = Color.cyan;
            Gizmos.DrawWireSphere(transform.position, _detectRadius);
        }
    }
}