/*******************************************************************************************
*
*   raylib [shaders] example - basic pbr
*
*   Example complexity rating: [★★★★] 4/4
*
*   Example originally created with raylib 5.0, last time updated with raylib 5.5
*
*   Example contributed by Afan OLOVCIC (@_DevDad) and reviewed by Ramon Santamaria (@raysan5)
*
*   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) 2023-2025 Afan OLOVCIC (@_DevDad)
*
*   Model: "Old Rusty Car" (https://skfb.ly/LxRy) by Renafox,
*   licensed under Creative Commons Attribution-NonCommercial
*   (http://creativecommons.org/licenses/by-nc/4.0/)
*
********************************************************************************************/

using System.Numerics;
using Examples.Shared;
using static Raylib_cs.Raylib;

namespace Examples.Shaders;

public class BasicPbr : IExample
{
#if BROWSER
    const int GlslVersion = 100;    // WebGL1 needs GLSL ES 100
#else
    private const int GlslVersion = 330;
#endif

    private const int screenWidth = 800;
    private const int screenHeight = 450;

    public string Name => "Shaders / Basic PBR";

    public string Title => "raylib [shaders] example - basic pbr";

    public ConfigFlags ConfigFlags => ConfigFlags.Msaa4xHint;

    private Camera3D camera;
    private Shader shader;
    private Model car;
    private Model floor;
    private PbrLight[] lights;

    private int metallicValueLoc;
    private int roughnessValueLoc;
    private int emissiveIntensityLoc;
    private int emissiveColorLoc;
    private int textureTilingLoc;

    private Vector2 carTextureTiling;
    private Vector2 floorTextureTiling;

    public unsafe void Init()
    {
        // Define the camera to look into our 3d world
        camera = new();
        camera.Position = new Vector3(2.0f, 2.0f, 6.0f);
        camera.Target = new Vector3(0.0f, 0.5f, 0.0f);
        camera.Up = new Vector3(0.0f, 1.0f, 0.0f);
        camera.FovY = 45.0f;
        camera.Projection = CameraProjection.Perspective;

        // Load PBR shader and setup all required locations
        shader = LoadShader($"resources/shaders/glsl{GlslVersion}/pbr.vs", $"resources/shaders/glsl{GlslVersion}/pbr.fs");

        shader.Locs[(int)ShaderLocationIndex.MapAlbedo] = GetShaderLocation(shader, "albedoMap");
        // WARNING: Metalness, roughness, and ambient occlusion are all packed into a MRA texture
        // They are passed as to the SHADER_LOC_MAP_METALNESS location for convenience,
        // shader already takes care of it accordingly
        shader.Locs[(int)ShaderLocationIndex.MapMetalness] = GetShaderLocation(shader, "mraMap");
        shader.Locs[(int)ShaderLocationIndex.MapNormal] = GetShaderLocation(shader, "normalMap");
        // WARNING: Similar to the MRA map, the emissive map packs different information
        // into a single texture: it stores height and emission data
        // It is binded to SHADER_LOC_MAP_EMISSION location an properly processed on shader
        shader.Locs[(int)ShaderLocationIndex.MapEmission] = GetShaderLocation(shader, "emissiveMap");
        shader.Locs[(int)ShaderLocationIndex.ColorDiffuse] = GetShaderLocation(shader, "albedoColor");

        // Setup additional required shader locations, including lights data
        shader.Locs[(int)ShaderLocationIndex.VectorView] = GetShaderLocation(shader, "viewPos");
        var lightCountLoc = GetShaderLocation(shader, "numOfLights");
        var maxLightCount = 4;
        SetShaderValue(shader, lightCountLoc, &maxLightCount, ShaderUniformDataType.Int);

        // Setup ambient color and intensity parameters
        var ambientIntensity = 0.02f;
        var ambientColor = new Color(26, 32, 135, 255);
        var ambientColorNormalized = new Vector3(ambientColor.R / 255.0F, ambientColor.G / 255.0F, ambientColor.B / 255.0F);
        SetShaderValue(shader, GetShaderLocation(shader, "ambientColor"), &ambientColorNormalized, ShaderUniformDataType.Vec3);
        SetShaderValue(shader, GetShaderLocation(shader, "ambient"), &ambientIntensity, ShaderUniformDataType.Float);

        // Get location for shader parameters that can be modified in real time
        metallicValueLoc = GetShaderLocation(shader, "metallicValue");
        roughnessValueLoc = GetShaderLocation(shader, "roughnessValue");
        emissiveIntensityLoc = GetShaderLocation(shader, "emissivePower");
        emissiveColorLoc = GetShaderLocation(shader, "emissiveColor");
        textureTilingLoc = GetShaderLocation(shader, "tiling");

        // Load old car model using PBR maps and shader
        // WARNING: We know this model consists of a single model.meshes[0] and
        // that model.materials[0] is by default assigned to that mesh
        // There could be more complex models consisting of multiple meshes and
        // multiple materials defined for those meshes... but always 1 mesh = 1 material
        car = LoadModel("resources/models/gltf/old_car_new.glb");

        // Assign already setup PBR shader to model.materials[0], used by models.meshes[0]
        car.Materials[0].Shader = shader;

        // Setup materials[0].maps default parameters
        car.Materials[0].Maps[(int)MaterialMapIndex.Albedo].Color = Color.White;
        car.Materials[0].Maps[(int)MaterialMapIndex.Metalness].Value = 1.0f;
        car.Materials[0].Maps[(int)MaterialMapIndex.Roughness].Value = 0.0f;
        car.Materials[0].Maps[(int)MaterialMapIndex.Occlusion].Value = 1.0f;
        car.Materials[0].Maps[(int)MaterialMapIndex.Emission].Color = new Color(255, 162, 0, 255);

        // Setup materials[0].maps default textures
        car.Materials[0].Maps[(int)MaterialMapIndex.Albedo].Texture = LoadTexture("resources/old_car_d.png");
        car.Materials[0].Maps[(int)MaterialMapIndex.Metalness].Texture = LoadTexture("resources/old_car_mra.png");
        car.Materials[0].Maps[(int)MaterialMapIndex.Normal].Texture = LoadTexture("resources/old_car_n.png");
        car.Materials[0].Maps[(int)MaterialMapIndex.Emission].Texture = LoadTexture("resources/old_car_e.png");

        // Load floor model mesh and assign material parameters
        // NOTE: A basic plane shape can be generated instead of being loaded from a model file
        floor = LoadModel("resources/models/gltf/plane.glb");
        //Mesh floorMesh = GenMeshPlane(10, 10, 10, 10);
        //GenMeshTangents(&floorMesh);      // TODO: Review tangents generation
        //Model floor = LoadModelFromMesh(floorMesh);

        // Assign material shader for our floor model, same PBR shader
        floor.Materials[0].Shader = shader;

        floor.Materials[0].Maps[(int)MaterialMapIndex.Albedo].Color = Color.White;
        floor.Materials[0].Maps[(int)MaterialMapIndex.Metalness].Value = 0.8f;
        floor.Materials[0].Maps[(int)MaterialMapIndex.Roughness].Value = 0.1f;
        floor.Materials[0].Maps[(int)MaterialMapIndex.Occlusion].Value = 1.0f;
        floor.Materials[0].Maps[(int)MaterialMapIndex.Emission].Color = Color.Black;

        floor.Materials[0].Maps[(int)MaterialMapIndex.Albedo].Texture = LoadTexture("resources/road_a.png");
        floor.Materials[0].Maps[(int)MaterialMapIndex.Metalness].Texture = LoadTexture("resources/road_mra.png");
        floor.Materials[0].Maps[(int)MaterialMapIndex.Normal].Texture = LoadTexture("resources/road_n.png");

        // Models texture tiling parameter can be stored in the Material struct if required (CURRENTLY NOT USED)
        // NOTE: Material.params[4] are available for generic parameters storage (float)
        carTextureTiling = new Vector2(0.5f, 0.5f);
        floorTextureTiling = new Vector2(0.5f, 0.5f);

        // Create some lights
        lights = new PbrLight[4];
        lights[0] = PbrLights.CreateLight(
            0,
            PbrLightType.Point,
            new Vector3(-1.0f, 1.0f, -2.0f),
            new Vector3(0.0f, 0.0f, 0.0f),
            Color.Yellow,
            4.0f,
            shader);
        lights[1] = PbrLights.CreateLight(1,
            PbrLightType.Point,
            new Vector3(2.0f, 1.0f, 1.0f),
            new Vector3(0.0f, 0.0f, 0.0f),
            Color.Green,
            3.3f,
            shader);
        lights[2] = PbrLights.CreateLight(
            2, PbrLightType.Point,
            new Vector3(-2.0f, 1.0f, 1.0f),
            new Vector3(0.0f, 0.0f, 0.0f),
            Color.Red,
            8.3f,
            shader);
        lights[3] = PbrLights.CreateLight(
            3,
            PbrLightType.Point,
            new Vector3(1.0f, 1.0f, -2.0f),
            new Vector3(0.0f, 0.0f, 0.0f),
            Color.Blue,
            2.0f,
            shader);

        // Setup material texture maps usage in shader
        // NOTE: By default, the texture maps are always used
        var usage = 1;
        SetShaderValue(shader, GetShaderLocation(shader, "useTexAlbedo"), &usage, ShaderUniformDataType.Int);
        SetShaderValue(shader, GetShaderLocation(shader, "useTexNormal"), &usage, ShaderUniformDataType.Int);
        SetShaderValue(shader, GetShaderLocation(shader, "useTexMRA"), &usage, ShaderUniformDataType.Int);
        SetShaderValue(shader, GetShaderLocation(shader, "useTexEmissive"), &usage, ShaderUniformDataType.Int);
    }

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

        // Update the shader with the camera view vector (points towards { 0.0f, 0.0f, 0.0f })
        var cameraPos = camera.Position;
        SetShaderValue(shader, shader.Locs[(int)ShaderLocationIndex.VectorView], cameraPos, ShaderUniformDataType.Vec3);

        // Check key inputs to enable/disable lights
        if (IsKeyPressed(KeyboardKey.One))
        {
            lights[2].Enabled = !lights[2].Enabled;
        }

        if (IsKeyPressed(KeyboardKey.Two))
        {
            lights[1].Enabled = !lights[1].Enabled;
        }

        if (IsKeyPressed(KeyboardKey.Three))
        {
            lights[3].Enabled = !lights[3].Enabled;
        }

        if (IsKeyPressed(KeyboardKey.Four))
        {
            lights[0].Enabled = !lights[0].Enabled;
        }

        // Update light values on shader (actually, only enable/disable them)
        for (var i = 0; i < 4; i++)
        {
            UpdateLight(shader, lights[i]);
        }
        //----------------------------------------------------------------------------------

        // Draw
        //----------------------------------------------------------------------------------
        BeginDrawing();

        ClearBackground(Color.Black);

        BeginMode3D(camera);

        // Set floor model texture tiling and emissive color parameters on shader
        SetShaderValue(shader, textureTilingLoc, floorTextureTiling, ShaderUniformDataType.Vec2);
        var floorEmissiveColor = ColorNormalize(floor.Materials[0].Maps[(int)MaterialMapIndex.Emission].Color);
        SetShaderValue(shader, emissiveColorLoc, &floorEmissiveColor, ShaderUniformDataType.Vec4);

        // Set floor metallic and roughness values
        var floorMetallicValue = floor.Materials[0].Maps[(int)MaterialMapIndex.Metalness].Value;
        SetShaderValue(shader, metallicValueLoc, &floorMetallicValue, ShaderUniformDataType.Float);
        var floorRoughnessValue = floor.Materials[0].Maps[(int)MaterialMapIndex.Roughness].Value;
        SetShaderValue(shader, roughnessValueLoc, &floorRoughnessValue, ShaderUniformDataType.Float);

        DrawModel(floor, Vector3.Zero, 5.0f, Color.White); // Draw floor model

        // Set old car model texture tiling, emissive color and emissive intensity parameters on shader
        SetShaderValue(shader, textureTilingLoc, carTextureTiling, ShaderUniformDataType.Vec2);
        var carEmissiveColor = ColorNormalize(car.Materials[0].Maps[(int)MaterialMapIndex.Emission].Color);
        SetShaderValue(shader, emissiveColorLoc, &carEmissiveColor, ShaderUniformDataType.Vec4);
        var emissiveIntensity = 0.01f;
        SetShaderValue(shader, emissiveIntensityLoc, &emissiveIntensity, ShaderUniformDataType.Float);

        // Set old car metallic and roughness values
        var carMetallicValue = car.Materials[0].Maps[(int)MaterialMapIndex.Metalness].Value;
        SetShaderValue(shader, metallicValueLoc, &carMetallicValue, ShaderUniformDataType.Float);
        var carRoughnessValue = car.Materials[0].Maps[(int)MaterialMapIndex.Roughness].Value;
        SetShaderValue(shader, roughnessValueLoc, &carRoughnessValue, ShaderUniformDataType.Float);

        DrawModel(car, Vector3.Zero, 0.25f, Color.White); // Draw car model

        // Draw spheres to show the lights positions
        for (var i = 0; i < 4; i++)
        {
            var color = lights[i].Color;
            var lightColor = new Color((byte)(color.X * 255), (byte)(color.Y * 255), (byte)(color.Z * 255),
                (byte)(color.W * 255));

            if (lights[i].Enabled)
            {
                DrawSphereEx(lights[i].Position, 0.2f, 8, 8, lightColor);
            }
            else
            {
                DrawSphereWires(lights[i].Position, 0.2f, 8, 8, ColorAlpha(lightColor, 0.3f));
            }
        }

        EndMode3D();

        DrawText("Toggle lights: [1][2][3][4]", 10, 40, 20, Color.LightGray);

        DrawText("(c) Old Rusty Car model by Renafox (https://skfb.ly/LxRy)", screenWidth - 320, screenHeight - 20, 10, Color.LightGray);

        DrawFPS(10, 10);

        EndDrawing();
        //----------------------------------------------------------------------------------
    }

    public unsafe void Unload()
    {
        // Unbind (disconnect) shader from car.material[0]
        // to avoid UnloadMaterial() trying to unload it automatically
        car.Materials[0].Shader = new();
        UnloadMaterial(car.Materials[0]);
        car.Materials[0].Maps = null;
        UnloadModel(car);

        floor.Materials[0].Shader = new();
        UnloadMaterial(floor.Materials[0]);
        floor.Materials[0].Maps = null;
        UnloadModel(floor);

        UnloadShader(shader);
    }

    public static int Main()
    {
        // Initialization
        //--------------------------------------------------------------------------------------
        // Enable Multi Sampling Anti Aliasing 4x (if available)
        SetConfigFlags(ConfigFlags.Msaa4xHint);
        InitWindow(screenWidth, screenHeight, "raylib [shaders] example - basic pbr");

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

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

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

        game.Unload();

        // De-Initialization
        //--------------------------------------------------------------------------------------
        CloseWindow();
        //--------------------------------------------------------------------------------------

        return 0;
    }

    private static void UpdateLight(Shader shader, PbrLight light)
    {
        SetShaderValue(shader, light.EnabledLoc, light.Enabled ? 1 : 0, ShaderUniformDataType.Int);
        SetShaderValue(shader, light.TypeLoc, (int)light.Type, ShaderUniformDataType.Int);

        // Send to shader light position values
        SetShaderValue(shader, light.PositionLoc, light.Position, ShaderUniformDataType.Vec3);

        // Send to shader light target position values
        SetShaderValue(shader, light.TargetLoc, light.Target, ShaderUniformDataType.Vec3);
        SetShaderValue(shader, light.ColorLoc, light.Color, ShaderUniformDataType.Vec4);
        SetShaderValue(shader, light.IntensityLoc, light.Intensity, ShaderUniformDataType.Float);
    }
}