using System.Numerics;
using Raylib_cs;

namespace PhysicsEngine
{
    class Program
    {
        private static Font robotoFont;
        private static WorldModel world;

        static void Main(string[] args)
        {
            Raylib.SetConfigFlags(ConfigFlags.FullscreenMode | ConfigFlags.VSyncHint);
            Raylib.InitWindow(0, 0, "Physics Engine");

            robotoFont = Raylib.LoadFont("Roboto-Regular.ttf");
            Raylib.SetTextureFilter(robotoFont.Texture, TextureFilter.Bilinear);

            Camera camera = new Camera();
            world = new WorldModel();

            Scenario();

            const float physicsTimeStep = 1.0f / 60.0f;
            float accumulator = 0.0f;

            // main loop
            while (!Raylib.WindowShouldClose())
            {
                float frameTime = Raylib.GetFrameTime();
                if (frameTime > 0.25f)
                {
                    frameTime = 0.25f;
                }

                // update Camera
                camera.Update(frameTime);

                // update physics accumulator
                accumulator += frameTime;
                while (accumulator >= physicsTimeStep)
                {
                    UpdatePhysics(physicsTimeStep);
                    accumulator -= physicsTimeStep;
                }

                // render loop
                Raylib.BeginDrawing();
                Raylib.ClearBackground(MuiDarkColor.BackgroundDefault.ToColor());

                camera.DrawGrid();

                // draw bodies
                Raylib.BeginMode2D(camera.RaylibCamera);
                RenderScene();
                Raylib.EndMode2D();

                camera.DrawHUD();
                DrawText("Physics Engine", 20, 20, 30, MuiDarkColor.TextPrimary.ToColor());

                Raylib.EndDrawing();
            }

            Raylib.UnloadFont(robotoFont);
            Raylib.CloseWindow();
        }

        public static void DrawText(string text, int posX, int posY, float fontSize, Color color)
        {
            Raylib.DrawTextEx(robotoFont, text, new Vector2(posX, posY), fontSize, 1.0f, color);
        }

        private static void UpdatePhysics(float dt)
        {
            world.Step(dt);
        }

        private static void RenderScene()
        {
            foreach (var body in world.Bodies)
            {
                body.Draw();
            }
        }

        private static void Scenario()
        {
            float worldWidth = 12.8f;
            float worldHeight = 7.2f;
            float wallThickness = 1.0f;

            // 1. Static world borders
            Box floor = new Box(new Vector2(worldWidth * 0.5f, worldHeight + (wallThickness * 0.5f)), new Vector2(worldWidth + wallThickness * 2, wallThickness), 0f);
            floor.BaseColor = Color.DarkGray;
            floor.Friction = 0.9f;
            world.AddBody(floor);

            Box ceiling = new Box(new Vector2(worldWidth * 0.5f, -wallThickness * 0.5f), new Vector2(worldWidth + wallThickness * 2, wallThickness), 0f);
            ceiling.BaseColor = Color.DarkGray;
            world.AddBody(ceiling);

            Box leftWall = new Box(new Vector2(-wallThickness * 0.5f, worldHeight * 0.5f), new Vector2(wallThickness, worldHeight + wallThickness * 2), 0f);
            leftWall.BaseColor = Color.DarkGray;
            world.AddBody(leftWall);

            Box rightWall = new Box(new Vector2(worldWidth + wallThickness * 0.5f, worldHeight * 0.5f), new Vector2(wallThickness, worldHeight + wallThickness * 2), 0f);
            rightWall.BaseColor = Color.DarkGray;
            world.AddBody(rightWall);

            // 2. Static Ramps and Platforms
            Box platform = new Box(new Vector2(9.0f, 4.5f), new Vector2(3.5f, 0.3f), 0f);
            platform.BaseColor = Color.Gray;
            platform.Friction = 0.8f;
            world.AddBody(platform);

            Box ramp = new Box(new Vector2(2.0f, 3.5f), new Vector2(3.5f, 0.3f), 0f);
            ramp.Rotation = 0.35f; // Slopes down toward center stack
            ramp.BaseColor = Color.Gray;
            ramp.Friction = 0.6f;
            world.AddBody(ramp);

            // 3. Main Ground Box Tower (5 boxes high)
            float stackX = 5.0f;
            float boxHeight = 0.6f;
            float boxWidth = 0.6f;
            float startY = worldHeight - (boxHeight * 0.5f); // Sits cleanly on the floor surface (Y = 7.2)

            Color[] stackColors = new Color[] 
            { 
                Color.DarkGreen, Color.Green, Color.Lime, Color.DarkPurple, Color.Yellow 
            };

            for (int i = 0; i < 5; i++)
            {
                float y = startY - (i * boxHeight);
                Box stackBox = new Box(new Vector2(stackX, y), new Vector2(boxWidth, boxHeight), 20f);
                stackBox.BaseColor = stackColors[i % stackColors.Length];
                stackBox.Friction = 0.8f;
                stackBox.Restitution = 0.0f;
                world.AddBody(stackBox);
            }

            // 4. Secondary Platform Stack (3 boxes high)
            float platformStackX = 9.0f;
            float platformTopY = 4.5f - 0.15f; // Top surface of platform
            float platformStartY = platformTopY - (boxHeight * 0.5f);

            for (int i = 0; i < 3; i++)
            {
                float y = platformStartY - (i * boxHeight);
                Box pBox = new Box(new Vector2(platformStackX, y), new Vector2(0.5f, boxHeight), 12f);
                pBox.BaseColor = Color.Blue;
                pBox.Friction = 0.8f;
                pBox.Restitution = 0.0f;
                world.AddBody(pBox);
            }

            // 5. Dynamic Circles for Stack Interaction
            // Circle balanced on top of the main ground stack
            float mainStackTopY = startY - (4 * boxHeight) - (boxHeight * 0.5f);
            Circle stackCap = new Circle(new Vector2(stackX, mainStackTopY - 0.3f), 0.3f, 8f);
            stackCap.BaseColor = Color.Orange;
            stackCap.Friction = 0.8f;
            stackCap.Restitution = 0.0f;
            world.AddBody(stackCap);

            // Heavy ball spawned on the ramp to roll down and strike the main stack
            Circle rollingBall = new Circle(new Vector2(1.0f, 1.5f), 0.45f, 350f);
            rollingBall.BaseColor = Color.Red;
            rollingBall.Friction = 0.5f;
            rollingBall.Restitution = 0.1f;
            world.AddBody(rollingBall);

            // Bouncy ball dropped over the platform stack to test stability under impact
            Circle droppingBall = new Circle(new Vector2(9.0f, 0.8f), 0.35f, 10f);
            droppingBall.BaseColor = Color.Gold;
            droppingBall.Friction = 0.4f;
            droppingBall.Restitution = 0.4f;
            droppingBall.Velocity = new Vector2(0.0f, 2.0f);
            world.AddBody(droppingBall);
        }
    }
}