using SkiaSharp;
using Xunit;

namespace Jellyfin.Drawing.Skia.Tests;

public class SkiaEncoderSharpenTests
{
    private static SKBitmap CreateBitmap(int width, int height, SKColor fill)
    {
        var bitmap = new SKBitmap(new SKImageInfo(width, height, SKColorType.Rgba8888, SKAlphaType.Premul));
        using var canvas = new SKCanvas(bitmap);
        canvas.Clear(fill);
        return bitmap;
    }

    [Fact]
    public void SharpenInPlace_UniformImage_IsUnchanged()
    {
        // 1.4 * v - 4 * 0.1 * v = v for any uniform value.
        using var bitmap = CreateBitmap(8, 8, new SKColor(100, 150, 200));

        SkiaEncoder.SharpenInPlace(bitmap);

        for (var y = 0; y < bitmap.Height; y++)
        {
            for (var x = 0; x < bitmap.Width; x++)
            {
                Assert.Equal(new SKColor(100, 150, 200), bitmap.GetPixel(x, y));
            }
        }
    }

    [Fact]
    public void SharpenInPlace_BrightPixelOnDarkBackground_SharpensEdge()
    {
        using var bitmap = CreateBitmap(5, 5, new SKColor(50, 50, 50));
        bitmap.SetPixel(2, 2, new SKColor(250, 250, 250, 255));

        SkiaEncoder.SharpenInPlace(bitmap);

        // Center: 1.4 * 250 - 0.1 * 4 * 50 = 330 -> clamped to 255.
        Assert.Equal(new SKColor(255, 255, 255), bitmap.GetPixel(2, 2));
        // Direct neighbor: 1.4 * 50 - 0.1 * (250 + 3 * 50) = 30.
        Assert.Equal(new SKColor(30, 30, 30), bitmap.GetPixel(1, 2));
        // Far corner is only surrounded by background: unchanged.
        Assert.Equal(new SKColor(50, 50, 50), bitmap.GetPixel(0, 0));
    }

    [Fact]
    public void SharpenInPlace_EdgePixels_ClampOutOfBoundsTaps()
    {
        // A corner pixel reuses itself for the two out-of-bounds taps:
        // 1.4 * v - 0.1 * (2 * v + right + down).
        using var bitmap = CreateBitmap(3, 3, new SKColor(100, 100, 100));
        bitmap.SetPixel(0, 0, new SKColor(200, 200, 200, 255));

        SkiaEncoder.SharpenInPlace(bitmap);

        // 1.4 * 200 - 0.1 * (200 + 200 + 100 + 100) = 220.
        Assert.Equal(new SKColor(220, 220, 220), bitmap.GetPixel(0, 0));
    }

    [Fact]
    public void SharpenInPlace_UnsupportedColorType_IsLeftUntouched()
    {
        using var bitmap = new SKBitmap(new SKImageInfo(4, 4, SKColorType.Gray8, SKAlphaType.Opaque));
        bitmap.Erase(new SKColor(80, 80, 80));

        SkiaEncoder.SharpenInPlace(bitmap);

        Assert.Equal(80, bitmap.GetPixel(1, 1).Red);
    }
}