using Godot;

public partial class Main : Node3D
{
    [Signal]
    public delegate void FocusLostEventHandler();

    [Signal]
    public delegate void FocusGainedEventHandler();

    [Signal]
    public delegate void PoseRecenteredEventHandler();

    [Export]
    public int MaximumRefreshRate { get; set; } = 90;

    private OpenXRInterface _xrInterface;
    private bool _xrIsFocused;

    public override void _Ready()
    {
        _xrInterface = (OpenXRInterface)XRServer.FindInterface("OpenXR");
        if (_xrInterface != null && _xrInterface.IsInitialized())
        {
            GD.Print("OpenXR instantiated successfully.");
            Viewport vp = GetViewport();
            vp.UseXR = true;
            DisplayServer.WindowSetVsyncMode(DisplayServer.VSyncMode.Disabled);
            if (RenderingServer.GetRenderingDevice() != null)
                vp.VrsMode = Viewport.VrsModeEnum.XR;

            _xrInterface.SessionBegun += OnSessionBegun;
            _xrInterface.SessionVisible += OnSessionVisible;
            _xrInterface.SessionFocussed += OnSessionFocussed;
            _xrInterface.SessionStopping += OnSessionStopping;
            _xrInterface.PoseRecentered += OnPoseRecentered;
        }
        else
        {
            GD.PushWarning("OpenXR not instantiated, running in flat preview mode. Check headset and XR runtime.");
        }
    }

    private void OnSessionBegun()
    {
        float currentRefreshRate = _xrInterface.DisplayRefreshRate;
        GD.Print(currentRefreshRate > 0.0f
            ? $"OpenXR: refresh rate reported as {currentRefreshRate}"
            : "OpenXR: no refresh rate given by XR runtime");

        float newRate = currentRefreshRate;
        var availableRates = _xrInterface.GetAvailableDisplayRefreshRates();
        if (availableRates.Count == 0)
            GD.Print("OpenXR: target does not support refresh rate extension");
        else if (availableRates.Count == 1)
            newRate = (float)availableRates[0];
        else
        {
            foreach (float rate in availableRates)
            {
                if (rate > newRate && rate <= MaximumRefreshRate)
                    newRate = rate;
            }
        }

        if (currentRefreshRate != newRate)
        {
            GD.Print($"OpenXR: setting refresh rate to {newRate}");
            _xrInterface.DisplayRefreshRate = newRate;
            currentRefreshRate = newRate;
        }

        Engine.PhysicsTicksPerSecond = (int)currentRefreshRate;
    }

    private void OnSessionVisible()
    {
        if (_xrIsFocused)
        {
            GD.Print("OpenXR lost focus");
            _xrIsFocused = false;
            GetTree().Paused = true;
            EmitSignal(SignalName.FocusLost);
        }
    }

    private void OnSessionFocussed()
    {
        GD.Print("OpenXR gained focus");
        _xrIsFocused = true;
        GetTree().Paused = false;
        EmitSignal(SignalName.FocusGained);
    }

    private void OnSessionStopping()
    {
        GD.Print("OpenXR is stopping");
    }

    private void OnPoseRecentered()
    {
        EmitSignal(SignalName.PoseRecentered);
    }
}