using UnityEngine;
using Valve.VR;
using System;

public class Beamy : MonoBehaviour {
    private ulong overlayHandle = OpenVR.k_ulOverlayHandleInvalid;

    private void Start() {
        InitOpenVR();

        overlayHandle = CreateOverlay("f3.beamy", "Beamy");

        var filePath = Application.streamingAssetsPath + "/EYEna.png";
        var error = OpenVR.Overlay.SetOverlayFromFile(overlayHandle, filePath);
        if (error != EVROverlayError.None) {
            throw new Exception("Failed to draw image file: " + error);
        }

        error = OpenVR.Overlay.ShowOverlay(overlayHandle);
        if (error != EVROverlayError.None) {
            throw new Exception("Failed to show overlay: " + error);
        }
    }

    private void OnApplicationQuit() {
        DestroyOverlay(overlayHandle);
    }

    private void OnDestroy() {
        ShutdownOpenVR();
    }

    private void InitOpenVR() {
        if (OpenVR.System != null) return;
    
        var error = EVRInitError.None;
        OpenVR.Init(ref error, EVRApplicationType.VRApplication_Overlay);
        if (error != EVRInitError.None) {
            throw new Exception("Failed to initialize OpenVR: " + error);
        }
    }

    private void ShutdownOpenVR() {
        if (OpenVR.System != null) {
            OpenVR.Shutdown();
        }
    }

    private ulong CreateOverlay(string key, string name) {
        var handle = OpenVR.k_ulOverlayHandleInvalid;
        var error = OpenVR.Overlay.CreateOverlay(key, name, ref handle);
        if (error != EVROverlayError.None) {
            throw new Exception("Failed to create overlay: " + error);
        }
        return handle;
    }

    private void DestroyOverlay(ulong handle) {
        if (handle != OpenVR.k_ulOverlayHandleInvalid) {
            var error = OpenVR.Overlay.DestroyOverlay(overlayHandle);
            if (error != EVROverlayError.None) {
                throw new Exception("Failed to dispose overlay: " + error);
            }
        }
    }
}