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 position = new Vector3(0, 0, 2);
        var rotation = Quaternion.Euler(0, 0, 0);
        SetOverlayTransformRelative(overlayHandle, OpenVR.k_unTrackedDeviceIndex_Hmd, position, rotation);

        var filePath = Application.streamingAssetsPath + "/EYEna.png";
        SetOverlayFromFile(overlayHandle, filePath);

        SetOverlaySize(overlayHandle, 0.5f);

        ShowOverlay(overlayHandle);
    }

    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(handle);
            if (error != EVROverlayError.None) {
                throw new Exception("Failed to dispose overlay: " + error);
            }
        }
    }

    private void SetOverlayFromFile(ulong handle, string path) {
        var error = OpenVR.Overlay.SetOverlayFromFile(handle, path);
        if (error != EVROverlayError.None) {
            throw new Exception("Failed to draw image file: " + error);
        }
    }

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

    private void SetOverlaySize(ulong handle, float size) {
        var error = OpenVR.Overlay.SetOverlayWidthInMeters(handle, size);
        if (error != EVROverlayError.None) {
            throw new Exception("Failed to set overlay size: " + error);
        }
    }

    private void SetOverlayTransformAbsolute(ulong handle, Vector3 position, Quaternion rotation) {
        var rigidTransform = new SteamVR_Utils.RigidTransform(position, rotation);
        var matrix = rigidTransform.ToHmdMatrix34();
        var error = OpenVR.Overlay.SetOverlayTransformAbsolute(handle, ETrackingUniverseOrigin.TrackingUniverseStanding, ref matrix);
        if (error != EVROverlayError.None) {
            throw new Exception("Failed to set overlay position: " + error);
        }
    }

    private void SetOverlayTransformRelative(ulong handle, uint deviceIndex, Vector3 position, Quaternion rotation) {
        var rigidTransform = new SteamVR_Utils.RigidTransform(position, rotation);
        var matrix = rigidTransform.ToHmdMatrix34();
        var error = OpenVR.Overlay.SetOverlayTransformTrackedDeviceRelative(handle, deviceIndex, ref matrix);
        if (error != EVROverlayError.None) {
            throw new Exception("Failed to set overlay position: " + error);
        }
    }
}