/*******************************************************************************************
*
*   raylib [core] example - vr simulator
*
*   Example complexity rating: [★★★☆] 3/4
*
*   Example originally created with raylib 2.5, last time updated with raylib 4.0
*
*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
*   BSD-like license that allows static linking with closed source software
*
*   Copyright (c) 2017-2025 Ramon Santamaria (@raysan5)
*
********************************************************************************************/

namespace Examples.Core;

public partial class VrSimulator : IExample
{
    private const int screenWidth = 800;
    private const int screenHeight = 450;

#if BROWSER
    const int GlslVersion = 100;    // WebGL1 needs GLSL ES 100
#else
    private const int GlslVersion = 330;
#endif

    public string Name => "Core / VR Simulator";

    public string Title => "raylib [core] example - vr simulator";

    public bool CursorDisabled => true;

    private VrStereoConfig config;
    private Shader distortion;
    private RenderTexture2D target;
    private Rectangle sourceRec;
    private Rectangle destRec;
    private Camera3D camera;
    private Vector3 cubePosition;

    public unsafe void Init()
    {
        // VR device parameters definition
        var device = new VrDeviceInfo
        {
            // Oculus Rift CV1 parameters for simulator
            HResolution = 2160,                 // Horizontal resolution in pixels
            VResolution = 1200,                 // Vertical resolution in pixels
            HScreenSize = 0.133793f,            // Horizontal size in meters
            VScreenSize = 0.0669f,              // Vertical size in meters
            EyeToScreenDistance = 0.041f,       // Distance between eye and display in meters
            LensSeparationDistance = 0.07f,     // Lens separation distance in meters
            InterpupillaryDistance = 0.07f,     // IPD (distance between pupils) in meters
        };

        // NOTE: CV1 uses fresnel-hybrid-asymmetric lenses with specific compute shaders
        // Following parameters are just an approximation to CV1 distortion stereo rendering
        device.LensDistortionValues[0] = 1.0f;      // Lens distortion constant parameter 0
        device.LensDistortionValues[1] = 0.22f;     // Lens distortion constant parameter 1
        device.LensDistortionValues[2] = 0.24f;     // Lens distortion constant parameter 2
        device.LensDistortionValues[3] = 0.0f;      // Lens distortion constant parameter 3
        device.ChromaAbCorrection[0] = 0.996f;      // Chromatic aberration correction parameter 0
        device.ChromaAbCorrection[1] = -0.004f;     // Chromatic aberration correction parameter 1
        device.ChromaAbCorrection[2] = 1.014f;      // Chromatic aberration correction parameter 2
        device.ChromaAbCorrection[3] = 0.0f;        // Chromatic aberration correction parameter 3

        // Load VR stereo config for VR device parameteres (Oculus Rift CV1 parameters)
        config = LoadVrStereoConfig(device);

        // Distortion shader (uses device lens distortion and chroma)
        distortion = LoadShader(null, $"resources/shaders/glsl{GlslVersion}/distortion.fs");

        // Update distortion shader with lens and distortion-scale parameters
        Raylib.SetShaderValue(
            distortion,
            GetShaderLocation(distortion, "leftLensCenter"),
            config.LeftLensCenter,
            ShaderUniformDataType.Vec2
        );
        Raylib.SetShaderValue(
            distortion,
            GetShaderLocation(distortion, "rightLensCenter"),
            config.RightLensCenter,
            ShaderUniformDataType.Vec2
        );
        Raylib.SetShaderValue(
            distortion,
            GetShaderLocation(distortion, "leftScreenCenter"),
            config.LeftScreenCenter,
            ShaderUniformDataType.Vec2
        );
        Raylib.SetShaderValue(
            distortion,
            GetShaderLocation(distortion, "rightScreenCenter"),
            config.RightScreenCenter,
            ShaderUniformDataType.Vec2
        );

        Raylib.SetShaderValue(
            distortion,
            GetShaderLocation(distortion, "scale"),
            config.Scale,
            ShaderUniformDataType.Vec2
        );
        Raylib.SetShaderValue(
            distortion,
            GetShaderLocation(distortion, "scaleIn"),
            config.ScaleIn,
            ShaderUniformDataType.Vec2
        );

        SetShaderValue(
            distortion,
            GetShaderLocation(distortion, "deviceWarpParam"),
            device.LensDistortionValues,
            ShaderUniformDataType.Vec4
        );
        SetShaderValue(
            distortion,
            GetShaderLocation(distortion, "chromaAbParam"),
            device.ChromaAbCorrection,
            ShaderUniformDataType.Vec4
        );

        // Initialize framebuffer for stereo rendering
        // NOTE: Screen size should match HMD aspect ratio
        target = LoadRenderTexture(device.HResolution, device.VResolution);

        // The target's height is flipped (in the source Rectangle), due to OpenGL reasons
        sourceRec = new(0.0f, 0.0f, (float)target.Texture.Width, -(float)target.Texture.Height);
        destRec = new(0.0f, 0.0f, (float)GetScreenWidth(), (float)GetScreenHeight());

        // Define the camera to look into our 3d world
        camera = new();
        camera.Position = new Vector3(5.0f, 2.0f, 5.0f);    // Camera position
        camera.Target = new Vector3(0.0f, 2.0f, 0.0f);      // Camera looking at point
        camera.Up = new Vector3(0.0f, 1.0f, 0.0f);          // Camera up vector
        camera.FovY = 60.0f;                                // Camera field-of-view Y
        camera.Projection = CameraProjection.Perspective;   // Camera projection type

        cubePosition = new(0.0f, 0.0f, 0.0f);
    }

    public void Update()
    {
        // Update
        //----------------------------------------------------------------------------------
        UpdateCamera(ref camera, CameraMode.FirstPerson);
        //----------------------------------------------------------------------------------

        // Draw
        //----------------------------------------------------------------------------------
        BeginTextureMode(target);
        ClearBackground(Color.RayWhite);
        BeginVrStereoMode(config);
        BeginMode3D(camera);

        DrawCube(cubePosition, 2.0f, 2.0f, 2.0f, Color.Red);
        DrawCubeWires(cubePosition, 2.0f, 2.0f, 2.0f, Color.Maroon);
        DrawGrid(40, 1.0f);

        EndMode3D();
        EndVrStereoMode();
        EndTextureMode();

        BeginDrawing();
        ClearBackground(Color.RayWhite);
        BeginShaderMode(distortion);
        DrawTexturePro(target.Texture, sourceRec, destRec, new Vector2(0.0f, 0.0f), 0.0f, Color.White);
        EndShaderMode();
        DrawFPS(10, 10);
        EndDrawing();
        //----------------------------------------------------------------------------------
    }

    public void Unload()
    {
        UnloadVrStereoConfig(config);   // Unload stereo config

        UnloadRenderTexture(target);    // Unload stereo render fbo
        UnloadShader(distortion);       // Unload distortion shader
    }

    public static int Main()
    {
        // Initialization
        //--------------------------------------------------------------------------------------
        // NOTE: screenWidth/screenHeight should match VR device aspect ratio
        InitWindow(screenWidth, screenHeight, "raylib [core] example - vr simulator");

        DisableCursor();                    // Limit cursor to relative movement inside the window

        SetTargetFPS(60);                   // Set our game to run at 60 frames-per-second
        //--------------------------------------------------------------------------------------

        var game = new VrSimulator();
        game.Init();

        // Main game loop
        while (!WindowShouldClose())        // Detect window close button or ESC key
        {
            game.Update();
        }

        game.Unload();

        // De-Initialization
        //--------------------------------------------------------------------------------------
        CloseWindow();                  // Close window and OpenGL context
        //--------------------------------------------------------------------------------------

        return 0;
    }
}