using System.Collections;
using UnityEngine;
using UnityEngine.SceneManagement;

/// <summary>
/// Main 启动页。
/// 点击事件在 Button 的 On Click() 里接线（Inspector 配置），代码里不查找节点。
/// </summary>
public class MainMenu : MonoBehaviour
{
    [Tooltip("点「启动」后要加载的场景名，必须已经加进 Build Settings")]
    [SerializeField] private string startSceneName = "Start";

    private bool _loading;

    /// <summary>启动：加载目标场景，加载完成后卸载 Main 场景自己。</summary>
    public void OnStartClicked()
    {
        if (_loading) return;   // 防连点，避免同时加载出两份
        _loading = true;
        StartCoroutine(LoadThenUnloadSelf());
    }

    /// <summary>退出游戏。</summary>
    public void OnExitClicked()
    {
        Application.Quit();
#if UNITY_EDITOR
        // 编辑器里 Application.Quit 不生效，方便本地测试
        UnityEditor.EditorApplication.isPlaying = false;
#endif
    }

    private IEnumerator LoadThenUnloadSelf()
    {
        Scene mainScene = gameObject.scene;

        AsyncOperation load = SceneManager.LoadSceneAsync(startSceneName, LoadSceneMode.Additive);
        if (load == null)
        {
            Debug.LogError("[MainMenu] 场景 \"" + startSceneName + "\" 加载失败，确认它已加入 Build Settings。", this);
            _loading = false;
            yield break;
        }

        yield return load;   // 等目标场景加载完成

        Scene loaded = SceneManager.GetSceneByName(startSceneName);
        if (loaded.IsValid())
            SceneManager.SetActiveScene(loaded);

        SceneManager.UnloadSceneAsync(mainScene);   // 加载完成后卸载 Main
    }
}