using Raylib_cs;
using Sand.Core;
using System.Numerics;
using System.Diagnostics;

namespace Sand.App;

internal static partial class SandApp
{
    private const int ScreenWidth = 1280;
    private const int ScreenHeight = 800;
    private const int SidebarWidth = 220;
    private const int SettingsWidth = 320;
    private const int ParticleSize = 4;

    public static void Run()
    {
        var state = CreateState();

        Raylib.SetConfigFlags(ConfigFlags.ResizableWindow);
        Raylib.InitWindow(ScreenWidth, ScreenHeight, $"Sand - C# Port ({state.BackendName})");
        Raylib.SetTargetFPS(120);

        var frameImage = Raylib.GenImageColor(state.SimWidth, state.SimHeight, Color.Black);
        state.FrameTexture = Raylib.LoadTextureFromImage(frameImage);
        Raylib.UnloadImage(frameImage);

        while (!Raylib.WindowShouldClose())
        {
            var frameStart = Stopwatch.GetTimestamp();
            Update(state);
            Draw(state);
            var frameEnd = Stopwatch.GetTimestamp();
            state.LastAppFrameTimeMicroseconds = ToMicroseconds(frameStart, frameEnd);
            state.LastAppOtherTimeMicroseconds = Math.Max(
                0,
                state.LastAppFrameTimeMicroseconds -
                state.LastUpdateTimeMicroseconds -
                state.LastFrameBuildCallTimeMicroseconds -
                state.LastTextureUploadTimeMicroseconds -
                state.LastDrawTimeMicroseconds);
        }

        Raylib.UnloadTexture(state.FrameTexture);
        Raylib.CloseWindow();
    }

    private static AppState CreateState()
    {
        var contentRoot = Path.Combine(AppContext.BaseDirectory, "Content", "part");
        var library = ParticleLibraryLoader.LoadFromDirectory(contentRoot);
        var settings = new SimulationSettings
        {
            StorageMode = SimulationStorageMode.Dense,
            PauseSim = false,
            EnableDebug = true,
            EnableFps = true,
            EnableCursor = true,
            EnableGasEffect = true,
        };

        var simWidth = (ScreenWidth - SidebarWidth) / ParticleSize;
        var simHeight = ScreenHeight / ParticleSize;
        var simulation = CreateSimulationBackend(simWidth, simHeight, library, settings);
        var categories = BuildCategories(library, simulation.BackendName);
        var currentCategory = "Solids";

        return new AppState
        {
            Library = library,
            Settings = settings,
            Simulation = simulation,
            Categories = categories,
            CurrentCategory = currentCategory,
            CurrentParticle = categories[currentCategory][0].Id,
            BackendName = simulation.BackendName,
            BrushRadius = 3,
            SimWidth = simWidth,
            SimHeight = simHeight,
            UploadBuffer = new byte[simWidth * simHeight * 4],
            LastWindDirection = new Vector2(1f, 0f),
            SettingItems =
            [
                new SettingItem("Cursor", () => settings.EnableCursor, () => settings.EnableCursor = !settings.EnableCursor),
                new SettingItem("Glow", () => settings.EnableGlow, () => settings.EnableGlow = !settings.EnableGlow),
                new SettingItem("Gas FX", () => settings.EnableGasEffect, () => settings.EnableGasEffect = !settings.EnableGasEffect),
                new SettingItem("Wind FX", () => settings.EnableWindVisuals, () => settings.EnableWindVisuals = !settings.EnableWindVisuals),
                new SettingItem("Pressure FX", () => settings.EnablePressureVisuals, () => settings.EnablePressureVisuals = !settings.EnablePressureVisuals),
                new SettingItem("Debug", () => settings.EnableDebug, () => settings.EnableDebug = !settings.EnableDebug),
                new SettingItem("FPS", () => settings.EnableFps, () => settings.EnableFps = !settings.EnableFps),
                new SettingItem("Temp FX", () => settings.EnableTempVisuals, () => settings.EnableTempVisuals = !settings.EnableTempVisuals),
                new SettingItem("Wrap", () => settings.WrapParticles, () => settings.WrapParticles = !settings.WrapParticles),
                new SettingItem("Outer Wall", () => settings.OuterWall, () => settings.OuterWall = !settings.OuterWall),
            ],
        };
    }

    private static ISimulationBackend CreateSimulationBackend(int simWidth, int simHeight, IParticleLibrary library, SimulationSettings settings)
    {
        var backend = Environment.GetEnvironmentVariable("SAND_BACKEND");
        var storageMode = settings.StorageMode;
        if (string.Equals(backend, "chunk", StringComparison.OrdinalIgnoreCase))
        {
            storageMode = SimulationStorageMode.ChunkPrototype;
        }
        else if (string.Equals(backend, "dense", StringComparison.OrdinalIgnoreCase))
        {
            storageMode = SimulationStorageMode.Dense;
        }

        if (storageMode == SimulationStorageMode.ChunkPrototype)
        {
            return new ChunkPrototypeSimulationBackend(simWidth, simHeight, ParticleSize, library, settings);
        }

        return new CoreSimulationBackend(new SandSimulation(simWidth, simHeight, ParticleSize, library, settings));
    }

    private static Dictionary<string, List<ParticleDef>> BuildCategories(IParticleLibrary library, string backendName)
    {
        if (string.Equals(backendName, "chunk", StringComparison.OrdinalIgnoreCase))
        {
            return BuildChunkPrototypeCategories(library);
        }

        var special = library.Definitions.Where(static d => d.IsSpecial).OrderBy(static d => d.Name).ToList();
        if (!special.Any(static d => d.Id == "air"))
        {
            special.Add(new ParticleDef
            {
                Id = "air",
                Name = "Air",
                Kind = ParticleKind.Gas,
                IsSpecial = true,
                Color = new Rgb24(160, 210, 255),
            });
        }

        special = special.OrderBy(static d => d.Name).ToList();

        return new Dictionary<string, List<ParticleDef>>
        {
            ["Solids"] = library.Definitions.Where(static d => d.Kind == ParticleKind.Solid && !d.IsSpecial).OrderBy(static d => d.Name).ToList(),
            ["Liquids"] = library.Definitions.Where(static d => d.Kind == ParticleKind.Liquid).OrderBy(static d => d.Name).ToList(),
            ["Gases"] = library.Definitions.Where(static d => d.Kind == ParticleKind.Gas).OrderBy(static d => d.Name).ToList(),
            ["Special"] = special,
        };
    }

    private static Dictionary<string, List<ParticleDef>> BuildChunkPrototypeCategories(IParticleLibrary library)
    {
        var special = library.Definitions.Where(static d => d.IsSpecial).OrderBy(static d => d.Name).ToList();
        if (!special.Any(static d => d.Id == "air"))
        {
            special.Add(new ParticleDef
            {
                Id = "air",
                Name = "Air",
                Kind = ParticleKind.Gas,
                IsSpecial = true,
                Color = new Rgb24(160, 210, 255),
            });
        }

        special = special.OrderBy(static d => d.Name).ToList();
        return new Dictionary<string, List<ParticleDef>>
        {
            ["Solids"] = library.Definitions.Where(static d => d.Kind == ParticleKind.Solid && !d.IsSpecial).OrderBy(static d => d.Name).ToList(),
            ["Liquids"] = library.Definitions.Where(static d => d.Kind == ParticleKind.Liquid).OrderBy(static d => d.Name).ToList(),
            ["Gases"] = library.Definitions.Where(static d => d.Kind == ParticleKind.Gas).OrderBy(static d => d.Name).ToList(),
            ["Special"] = special,
        };
    }

    private static long ToMicroseconds(long startTimestamp, long endTimestamp)
    {
        return (long)((endTimestamp - startTimestamp) * 1_000_000.0 / Stopwatch.Frequency);
    }
}