using System;
using UnityEditor;
using UnityEngine.Assertions;
#if UNITY_2017_2_OR_NEWER
using UnityEngine.XR;
using XRSettings = UnityEngine.XR.XRSettings;
#elif UNITY_5_6_OR_NEWER
using UnityEngine.VR;
using XRSettings = UnityEngine.VR.VRSettings;
#endif

namespace UnityEngine.Experimental.Rendering
{
    [Serializable]
    public class XRGraphicsConfig
    { // XRGConfig stores the desired XR settings for a given SRP asset.

        public float renderScale;
        public float viewportScale;
        public bool useOcclusionMesh;
        public float occlusionMaskScale;
        public bool showDeviceView;
        public GameViewRenderMode gameViewRenderMode;
        
        public void SetConfig()
        { // If XR is enabled, sets XRSettings from our saved config
            if (!enabled)
                Assert.IsFalse(enabled);
            XRSettings.eyeTextureResolutionScale = renderScale;
            XRSettings.renderViewportScale = viewportScale;
            XRSettings.useOcclusionMesh = useOcclusionMesh;
            XRSettings.occlusionMaskScale = occlusionMaskScale;
            XRSettings.showDeviceView = showDeviceView;
            XRSettings.gameViewRenderMode = gameViewRenderMode;
        }
        public void SetViewportScale(float viewportScale)
        { // Only sets viewport- since this is probably the only thing getting updated every frame
            if (!enabled)
                Assert.IsFalse(enabled);
            XRSettings.renderViewportScale = viewportScale;
        }

        public static readonly XRGraphicsConfig s_DefaultXRConfig = new XRGraphicsConfig
        {
            renderScale = 1.0f,
            viewportScale = 1.0f,
            useOcclusionMesh = true,
            occlusionMaskScale = 1.0f,
            showDeviceView = true,
            gameViewRenderMode = GameViewRenderMode.BothEyes
        };

        public static XRGraphicsConfig GetActualXRSettings()
        {
            XRGraphicsConfig getXRSettings = new XRGraphicsConfig();
            
            if (!enabled)
                Assert.IsFalse(enabled);
            
            getXRSettings.renderScale = XRSettings.eyeTextureResolutionScale;
            getXRSettings.viewportScale = XRSettings.renderViewportScale;
            getXRSettings.useOcclusionMesh = XRSettings.useOcclusionMesh;
            getXRSettings.occlusionMaskScale = XRSettings.occlusionMaskScale;
            getXRSettings.showDeviceView = XRSettings.showDeviceView;
            getXRSettings.gameViewRenderMode = XRSettings.gameViewRenderMode;            
            return getXRSettings;
        }

#if UNITY_EDITOR
        public static bool tryEnable
        { // TryEnable gets updated before "play" is pressed- we use this for updating GUI only. 
            get { return PlayerSettings.virtualRealitySupported; }
        }
#endif

        public static bool enabled
        { // SRP should use this to safely determine whether XR is enabled at runtime.
            get
            {
#if ENABLE_VR
                return XRSettings.enabled;
#else
                return false;
#endif
            }
        }

#if UNITY_EDITOR
        // FIXME: We should probably have StereoREnderingPath defined in UnityEngine.XR, not UnityEditor...
        public static StereoRenderingPath stereoRenderingMode
        {
            get
            {
                if (!enabled)
                    Assert.IsFalse(enabled);
#if UNITY_2018_3_OR_NEWER
                return (StereoRenderingPath)XRSettings.stereoRenderingMode;
#else
                if (eyeTextureDesc.vrUsage == VRTextureUsage.TwoEyes)
                    return StereoRenderingPath.SinglePass;
                else if (eyeTextureDesc.dimension == UnityEngine.Rendering.TextureDimension.Tex2DArray)
                    return StereoRenderingPath.Instancing;
                else
                    return StereoRenderingPath.MultiPass;
#endif
            }
        }
#endif
        public static RenderTextureDescriptor eyeTextureDesc
        {
            get
            {
                if (!enabled)
                    Assert.IsFalse(enabled);
                return XRSettings.eyeTextureDesc;
            }
        }

        public static int eyeTextureWidth
        {
            get
            {
                if (!enabled)
                    Assert.IsFalse(enabled);
                return XRSettings.eyeTextureWidth;
            }
        }
        public static int eyeTextureHeight
        {
            get
            {
                if (!enabled)
                    Assert.IsFalse(enabled);
                return XRSettings.eyeTextureHeight;
            }
        }
    }
}