using System.Collections;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using UnityEngine;
using UnityEngine.XR;
using UnityEngine.XR.Management;

public class StartupHeadsetCheck : MonoBehaviour
{
#if UNITY_STANDALONE_WIN && !UNITY_EDITOR
    [DllImport("user32.dll", CharSet = CharSet.Unicode)]
    private static extern int MessageBox(System.IntPtr hWnd, string text, string caption, uint type);
#endif

    private IEnumerator Start()
    {
        // Let OpenXR/XR Management initialize.
        yield return null;
        yield return null;
        yield return null;
        yield return null;

        if (!IsOpenXRRunning())
        {
            ShowWindowsErrorMessage();
            Application.Quit();
        }
    }

    private bool IsOpenXRRunning()
    {
        XRManagerSettings xrManager = XRGeneralSettings.Instance?.Manager;

        if (xrManager == null || xrManager.activeLoader == null)
        {
            return false;
        }

        var displays = new List<XRDisplaySubsystem>();
        SubsystemManager.GetSubsystems(displays);

        foreach (XRDisplaySubsystem display in displays)
        {
            if (display.running)
            {
                return true;
            }
        }

        return false;
    }

    private void ShowWindowsErrorMessage()
    {
#if UNITY_STANDALONE_WIN && !UNITY_EDITOR
        MessageBox(
            System.IntPtr.Zero,
            "No VR headset detected.\n\n" +
            "Please connect your headset and make sure your OpenXR runtime is active.\n\n" +
            "SteamVR headset: start SteamVR.\n" +
            "Meta Quest Link/Air Link: start Meta Quest Link.\n" +
            "WMR headset: start Mixed Reality Portal.\n\n" +
            "Then restart the game.",
            "VR Headset Not Detected",
            0x10 // MB_ICONERROR
        );
#else
        Debug.LogError("No VR headset detected.");
#endif
    }
}