using System.Collections;
using UnityEngine;
using UnityEngine.AddressableAssets;
using UnityEngine.ResourceManagement.AsyncOperations;
using UnityEngine.ResourceManagement.ResourceProviders;
using UnityEngine.SceneManagement;
using BaseGames.Core.Events;

namespace BaseGames.Core
{
    /// <summary>
    /// Addressables 场景加载器。
    /// 监听 EVT_SceneLoadRequest，Additive 加载指定场景，完成后发布 EVT_SceneLoaded。
    /// 完整实现由 SceneService 包装调用。
    /// </summary>
    [DefaultExecutionOrder(-950)]
    public class SceneLoader : MonoBehaviour
    {
        [Header("Event Channels - Listen")]
        [SerializeField] private SceneLoadRequestEventChannelSO _onSceneLoadRequest;

        [Header("Event Channels - Raise")]
        [SerializeField] private StringEventChannelSO _onSceneLoaded;

        private string _currentRoomScene;
        private AsyncOperationHandle<SceneInstance> _currentHandle;
        private readonly CompositeDisposable _subs = new();

        private void OnEnable()
        {
            _onSceneLoadRequest?.Subscribe(HandleRequest).AddTo(_subs);
        }

        private void OnDisable()
        {
            _subs.Clear();
        }

        private void HandleRequest(SceneLoadRequest request)
            => StartCoroutine(LoadSceneCoroutine(request));

        private IEnumerator LoadSceneCoroutine(SceneLoadRequest request)
        {
            // 先加载新场景（Additive），成功后再卸载旧场景
            // 顺序保证：若加载失败，旧场景仍保持可用，不会出现无场景的空状态
            var loadOp = Addressables.LoadSceneAsync(request.SceneName, LoadSceneMode.Additive);
            yield return loadOp;

            if (loadOp.Status != AsyncOperationStatus.Succeeded)
            {
                Debug.LogError($"[SceneLoader] 加载场景失败：{request.SceneName}（旧场景保持不变）");
                yield break;
            }

            // 新场景加载成功，再卸载旧场景
            if (!string.IsNullOrEmpty(_currentRoomScene) && _currentHandle.IsValid())
            {
                var unloadOp = Addressables.UnloadSceneAsync(_currentHandle);
                yield return unloadOp;
            }

            _currentHandle    = loadOp;
            _currentRoomScene = request.SceneName;
            _onSceneLoaded?.Raise(request.SceneName);
        }

        /// <summary>手动卸载当前房间场景（供 SceneService 调用）。</summary>
        public IEnumerator UnloadCurrentCoroutine()
        {
            if (!_currentHandle.IsValid()) yield break;
            var unloadOp = Addressables.UnloadSceneAsync(_currentHandle);
            yield return unloadOp;
            _currentRoomScene = null;
        }
    }
}