namespace Sand.Core;

public sealed partial class SandSimulation
{
    public void Step(float dt)
    {
        if (_settings.PauseSim)
        {
            return;
        }

        if (_settings.EnableAcceleration && Accelerator is not null)
        {
            Accelerator.Step(this, dt);
            return;
        }

        int preStepStartX;
        int preStepStartY;
        int preStepEndX;
        int preStepEndY;
        var hadPreStepBounds = AreFieldVisualsEnabled()
            ? TryGetSimulationBounds(out preStepStartX, out preStepStartY, out preStepEndX, out preStepEndY)
            : TryGetOccupiedBoundsOnly(out preStepStartX, out preStepStartY, out preStepEndX, out preStepEndY);
        _deferVisualDirtyTracking = true;
        DecayFields(dt);

        if (ParticleCount == 0)
        {
            _deferVisualDirtyTracking = false;
            MarkBoundsUnionDirty(hadPreStepBounds, preStepStartX, preStepStartY, preStepEndX, preStepEndY);
            Frame++;
            FrameStats.Frame = Frame;
            FrameStats.ProcessedCells = 0;
            FrameStats.ParticleCount = 0;
            FrameStats.MinActiveX = 0;
            FrameStats.MinActiveY = 0;
            FrameStats.MaxActiveX = 0;
            FrameStats.MaxActiveY = 0;
            FrameStats.LoadedChunkCount = 0;
            FrameStats.ActiveChunkCount = 0;
            FrameStats.DirtyChunkCount = 0;
            FrameStats.SteppedChunkCount = 0;
            FrameStats.SleepingChunkCount = 0;
            FrameStats.FieldPageCount = 0;
            FrameStats.MoveAttemptCount = 0;
            FrameStats.VerticalMoveAttemptCount = 0;
            FrameStats.DiagonalMoveAttemptCount = 0;
            FrameStats.LateralMoveAttemptCount = 0;
            FrameStats.SuccessfulMoveCount = 0;
            FrameStats.SwapAttemptCount = 0;
            FrameStats.StalledMovableCount = 0;
            FrameStats.MovementOnlyFastPathCount = 0;
            FrameStats.FullRuntimeStepCount = 0;
            FrameStats.FullRuntimeSolidCount = 0;
            FrameStats.FullRuntimeLiquidCount = 0;
            FrameStats.FullRuntimeGasCount = 0;
            FrameStats.MovedParticleCount = 0;
            FrameStats.SwappedParticleCount = 0;
            FrameStats.VisualDirtyPageCount = 0;
            FrameStats.FrameBuildBytesTouched = 0;
            FrameStats.ActivationTimeMicroseconds = 0;
            FrameStats.MovementTimeMicroseconds = 0;
            FrameStats.RuntimeTimeMicroseconds = 0;
            FrameStats.FieldDecayTimeMicroseconds = 0;
            FrameStats.RenderTimeMicroseconds = 0;
            return;
        }

        EnsureOccupiedBounds();
        var margin = _settings.WrapParticles ? 0 : 1;
        var startX = _settings.WrapParticles ? 0 : Math.Max(0, _minOccupiedX - margin);
        var endX = _settings.WrapParticles ? Width - 1 : Math.Min(Width - 1, _maxOccupiedX + margin);
        var startY = _settings.WrapParticles ? 0 : Math.Max(0, _minOccupiedY - margin);
        var endY = _settings.WrapParticles ? Height - 1 : Math.Min(Height - 1, _maxOccupiedY + margin);

        _activeStepToken = Frame + 1;
        var processedCells = 0;

        for (var y = endY; y >= startY; y--)
        {
            for (var x = startX; x <= endX; x++)
            {
                if (_processedFrame[x, y] == _activeStepToken)
                {
                    continue;
                }

                var typeId = TypeId[x, y];
                if (typeId == 0)
                {
                    continue;
                }

                var seed = Hash(x, y, Frame);
                var leftFirst = (seed & 1u) == 0;
                MarkProcessed(x, y);
                processedCells++;

                if (TickLifetime(x, y, dt))
                {
                    continue;
                }

                typeId = TypeId[x, y];
                if (TickSpark(x, y, typeId, ref seed))
                {
                    continue;
                }

                typeId = TypeId[x, y];
                AutoIgnite(x, y, typeId);
                ApplyRuntimeEmissionAndProduction(x, y, typeId, ref seed);
                if (TickBurning(x, y, typeId, ref seed))
                {
                    continue;
                }

                typeId = TypeId[x, y];
                if (TickSpecialBehavior(x, y, typeId, ref seed))
                {
                    continue;
                }

                typeId = TypeId[x, y];
                ApplyPhaseTransitions(x, y, ref typeId);
                if (typeId == 0)
                {
                    continue;
                }

                if (ApplyLocalReactions(x, y, ref typeId, ref seed))
                {
                    continue;
                }

                typeId = TypeId[x, y];
                if (TickPressure(x, y, typeId, ref seed))
                {
                    continue;
                }

                ApplyTemperatureDiffusion(x, y, typeId);
                ApplyMovement(x, y, typeId, leftFirst, ref seed);
            }
        }

        if (_settings.OuterWall && _idWall != 0)
        {
            ApplyBoundaryWallsFast();
        }

        _deferVisualDirtyTracking = false;
        MarkBoundsUnionDirty(hadPreStepBounds, preStepStartX, preStepStartY, preStepEndX, preStepEndY);
        Frame++;
        _activeStepToken = 0;
        _staleOccupiedBoundsFrames = _boundsDirty ? _staleOccupiedBoundsFrames + 1 : 0;
        FrameStats.Frame = Frame;
        FrameStats.ProcessedCells = processedCells;
        FrameStats.ParticleCount = ParticleCount;
        FrameStats.MinActiveX = _hasOccupiedBounds ? _minOccupiedX : 0;
        FrameStats.MinActiveY = _hasOccupiedBounds ? _minOccupiedY : 0;
        FrameStats.MaxActiveX = _hasOccupiedBounds ? _maxOccupiedX : 0;
        FrameStats.MaxActiveY = _hasOccupiedBounds ? _maxOccupiedY : 0;
        FrameStats.LoadedChunkCount = 0;
        FrameStats.ActiveChunkCount = 0;
        FrameStats.DirtyChunkCount = 0;
        FrameStats.SteppedChunkCount = 0;
        FrameStats.SleepingChunkCount = 0;
        FrameStats.FieldPageCount = 0;
        FrameStats.MoveAttemptCount = 0;
        FrameStats.VerticalMoveAttemptCount = 0;
        FrameStats.DiagonalMoveAttemptCount = 0;
        FrameStats.LateralMoveAttemptCount = 0;
        FrameStats.SuccessfulMoveCount = 0;
        FrameStats.SwapAttemptCount = 0;
        FrameStats.StalledMovableCount = 0;
        FrameStats.MovementOnlyFastPathCount = 0;
        FrameStats.FullRuntimeStepCount = 0;
        FrameStats.FullRuntimeSolidCount = 0;
        FrameStats.FullRuntimeLiquidCount = 0;
        FrameStats.FullRuntimeGasCount = 0;
        FrameStats.MovedParticleCount = 0;
        FrameStats.SwappedParticleCount = 0;
        FrameStats.VisualDirtyPageCount = 0;
        FrameStats.FrameBuildBytesTouched = 0;
        FrameStats.ActivationTimeMicroseconds = 0;
        FrameStats.MovementTimeMicroseconds = 0;
        FrameStats.RuntimeTimeMicroseconds = 0;
        FrameStats.FieldDecayTimeMicroseconds = 0;
        FrameStats.RenderTimeMicroseconds = 0;
    }

    public ReadOnlySpan<byte> BuildRgbFrame()
    {
        UpdateCachedVisualBuffers();
        return _rgbBuffer;
    }

    public ReadOnlySpan<byte> BuildRgbaFrame()
    {
        UpdateCachedVisualBuffers();
        FrameStats.FrameBuildBytesTouched = (long)_rgbaBuffer.Length;
        FrameStats.RenderTimeMicroseconds = 0;
        return _rgbaBuffer;
    }

    public void BuildRgbaFrame(Span<byte> destination)
    {
        var expectedLength = Width * Height * 4;
        if (destination.Length < expectedLength)
        {
            throw new ArgumentException($"RGBA destination must be at least {expectedLength} bytes.", nameof(destination));
        }

        UpdateCachedVisualBuffers();
        _rgbaBuffer.AsSpan().CopyTo(destination);
        FrameStats.FrameBuildBytesTouched = (long)_rgbaBuffer.Length;
        FrameStats.RenderTimeMicroseconds = 0;
    }

    private Rgb24 ResolveVisualColor(int x, int y)
    {
        var typeId = TypeId[x, y];
        if (typeId == 0)
        {
            if (_settings.EnablePressureVisuals)
            {
                var pressure = MathF.Abs(_airPressure[x, y]);
                if (pressure > 0.08f)
                {
                    var tint = (byte)Math.Clamp((int)(pressure * 32f), 10, 140);
                    if (_airPressure[x, y] >= 0f)
                    {
                        return new Rgb24((byte)(26 + tint), (byte)(18 + tint / 3), 24);
                    }

                    return new Rgb24(18, (byte)(24 + tint / 4), (byte)(30 + tint));
                }
            }

            if (_settings.EnableWindVisuals)
            {
                var totalFieldX = _windFieldX[x, y] + _forceFieldX[x, y];
                var totalFieldY = _windFieldY[x, y] + _forceFieldY[x, y];
                var windStrength = MathF.Sqrt((totalFieldX * totalFieldX) + (totalFieldY * totalFieldY));
                if (windStrength > 0.08f)
                {
                    var tint = (byte)Math.Clamp((int)(windStrength * 40f), 10, 120);
                    return new Rgb24((byte)(16 + tint / 3), (byte)(24 + tint / 2), (byte)(32 + tint));
                }
            }

            return new Rgb24(0, 0, 0);
        }

        var color = SparkTime[x, y] > 0 ? new Rgb24(255, 255, 150) : _colorLut[typeId];
        if (_settings.EnableTempVisuals)
        {
            var delta = Temperature[x, y] - _settings.AmbientTemperature;
            if (delta > 5f)
            {
                var heat = (byte)Math.Clamp((int)(delta * 4f), 0, 120);
                color = new Rgb24(
                    (byte)Math.Min(255, color.R + heat),
                    (byte)Math.Max(0, color.G - heat / 3),
                    (byte)Math.Max(0, color.B - heat / 2));
            }
            else if (delta < -5f)
            {
                var cool = (byte)Math.Clamp((int)(Math.Abs(delta) * 4f), 0, 120);
                color = new Rgb24(
                    (byte)Math.Max(0, color.R - cool / 2),
                    (byte)Math.Max(0, color.G - cool / 3),
                    (byte)Math.Min(255, color.B + cool));
            }
        }

        if (_settings.EnableGasEffect && _kind[typeId] == (byte)ParticleKind.Gas)
        {
            var bias = (byte)(Hash(x, y, Frame) & 0x0F);
            color = new Rgb24(
                (byte)Math.Min(255, color.R + bias),
                (byte)Math.Min(255, color.G + bias),
                (byte)Math.Min(255, color.B + bias));
        }

        if (_settings.EnableGlow && (Burning[x, y] != 0 || typeId == _idFire || typeId == _idLava || SparkTime[x, y] > 0))
        {
            color = new Rgb24(
                (byte)Math.Min(255, color.R + 25),
                (byte)Math.Min(255, color.G + 18),
                (byte)Math.Min(255, color.B + 12));
        }

        return color;
    }

}