using System.Collections;
using UnityEngine;
using UnityEngine.SceneManagement;
using BaseGames.Core.Events;

namespace BaseGames.Core
{
    /// <summary>
    /// 场景管理服务接口。
    /// </summary>
    public interface ISceneService
    {
        /// <summary>异步加载指定场景（Additive）。</summary>
        IEnumerator LoadSceneCoroutine(SceneLoadRequest request);
        /// <summary>卸载当前房间场景（保留 Persistent）。</summary>
        IEnumerator UnloadCurrentRoomCoroutine();
        /// <summary>加载主菜单。</summary>
        IEnumerator LoadMainMenuCoroutine();
    }

    /// <summary>
    /// 场景管理服务。
    /// </summary>
    [DefaultExecutionOrder(-900)]
    public class SceneService : MonoBehaviour, ISceneService
    {
        [Header("Event Channels - Listen")]
        [SerializeField] private SceneLoadRequestEventChannelSO _onSceneLoadRequest;

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

        [SerializeField] private float _fadeDuration = 0.3f;

        private string _currentRoomScene;
        private readonly CompositeDisposable _subscriptions = new();

        private void OnEnable()
        {
            _onSceneLoadRequest?.Subscribe(HandleSceneLoadRequest).AddTo(_subscriptions);
        }

        private void OnDisable() => _subscriptions.Clear();

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

        public IEnumerator LoadSceneCoroutine(SceneLoadRequest request)
        {
            _onFadeOutRequest?.Raise();
            yield return new WaitForSeconds(_fadeDuration);

            if (!string.IsNullOrEmpty(_currentRoomScene))
            {
                var unload = SceneManager.UnloadSceneAsync(_currentRoomScene);
                yield return new WaitUntil(() => unload.isDone);
            }

            var load = SceneManager.LoadSceneAsync(request.SceneName, LoadSceneMode.Additive);
            yield return new WaitUntil(() => load.isDone);

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

        public IEnumerator UnloadCurrentRoomCoroutine()
        {
            if (string.IsNullOrEmpty(_currentRoomScene)) yield break;
            var op = SceneManager.UnloadSceneAsync(_currentRoomScene);
            yield return new WaitUntil(() => op.isDone);
            _currentRoomScene = null;
        }

        public IEnumerator LoadMainMenuCoroutine()
        {
            yield return LoadSceneCoroutine(new SceneLoadRequest
            {
                SceneName         = "MainMenu",
                EntryTransitionId = null,
                ShowLoadingScreen = false,
                IsRespawn         = false
            });
        }
    }
}