meeting-assistant/MeetingAssistant.Tests/WindowsScreenshotImageCropperTests.cs

#if WINDOWS
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using MeetingAssistant.Screenshots;
using Microsoft.Extensions.DependencyInjection;
using Xunit.Abstractions;

namespace MeetingAssistant.Tests;

public sealed class WindowsScreenshotImageCropperTests(ITestOutputHelper output)
{
    [WindowsFact("System.Drawing screenshot cropping")]
    public Task WindowsCropUsesOcrPixelCoordinates() =>
        AssertCropAsync(new ScreenshotCropCoordinates(0, 0, 2, 2));

    [WindowsFact("System.Drawing screenshot cropping")]
    public Task WindowsCropPreservesExpectedPixelsAtNonzeroOrigin() =>
        AssertCropAsync(new ScreenshotCropCoordinates(1, 1, 3, 2));

    [WindowsFact("System.Drawing screenshot cropping")]
    public async Task WindowsCropRejectsInvalidBounds()
    {
        using var fixture = new ImageFixture();
        await using var factory = new IsolatedApplicationFactory();
        using var client = factory.CreateClient();
        var cropper = GetWindowsCropper(factory);
        ScreenshotCropCoordinates[] invalidBounds =
        [
            new(-1, 0, 1, 1), new(0, -1, 1, 1),
            new(0, 0, 0, 1), new(0, 0, 1, 0),
            new(0, 0, -1, 1), new(0, 0, 1, -1),
            new(4, 0, 1, 1), new(0, 3, 1, 1),
            new(3, 0, 2, 1), new(0, 2, 1, 2)
        ];

        foreach (var bounds in invalidBounds)
        {
            var failure = await Assert.ThrowsAsync<InvalidDataException>(() =>
                cropper.SaveCroppedScreenshotAsync(fixture.InputPath, bounds, CancellationToken.None));
            Assert.Contains("outside image bounds 4x3", failure.Message);
            Assert.False(File.Exists(fixture.CroppedPath));
            output.WriteLine($"Rejected {bounds.X},{bounds.Y},{bounds.Width},{bounds.Height}; no output created.");
        }
    }

    private async Task AssertCropAsync(ScreenshotCropCoordinates bounds)
    {
        using var fixture = new ImageFixture();
        await using var factory = new IsolatedApplicationFactory();
        using var client = factory.CreateClient();
        var cropper = GetWindowsCropper(factory);

        var path = await cropper.SaveCroppedScreenshotAsync(
            fixture.InputPath, bounds, CancellationToken.None);

        Assert.Equal(fixture.CroppedPath, path);
        using var cropped = new Bitmap(path!);
        Assert.Equal(bounds.Width, cropped.Width);
        Assert.Equal(bounds.Height, cropped.Height);
        for (var y = 0; y < cropped.Height; y++)
        {
            for (var x = 0; x < cropped.Width; x++)
            {
                Assert.Equal(ImageFixture.PixelAt(bounds.X + x, bounds.Y + y).ToArgb(),
                    cropped.GetPixel(x, y).ToArgb());
            }
        }
        output.WriteLine($"Verified every pixel of {bounds.Width}x{bounds.Height} at original origin {bounds.X},{bounds.Y}.");
    }

    private IScreenshotImageCropper GetWindowsCropper(IsolatedApplicationFactory factory)
    {
        var cropper = factory.Services.GetRequiredService<IScreenshotImageCropper>();
        Assert.IsType<WindowsScreenshotImageCropper>(cropper);
        output.WriteLine($"Registered cropper: {cropper.GetType().Name}; host: {RuntimeInformation.OSDescription}; " +
            $"architecture: {RuntimeInformation.ProcessArchitecture}; runtime: {RuntimeInformation.FrameworkDescription}; " +
            "target: net10.0-windows10.0.19041.0.");
        return cropper;
    }

    private sealed class ImageFixture : IDisposable
    {
        private readonly string root = Path.Combine(Path.GetTempPath(), $"meeting-assistant-windows-crop-{Guid.NewGuid():N}");

        public ImageFixture()
        {
            Directory.CreateDirectory(root);
            using var image = new Bitmap(4, 3, PixelFormat.Format32bppArgb);
            for (var y = 0; y < image.Height; y++)
            {
                for (var x = 0; x < image.Width; x++)
                {
                    image.SetPixel(x, y, PixelAt(x, y));
                }
            }
            image.Save(InputPath, ImageFormat.Png);
        }

        public string InputPath => Path.Combine(root, "input.png");
        public string CroppedPath => Path.Combine(root, "input-cropped.png");

        // Each original coordinate has a distinct opaque color; no resampling tolerance hides a shifted origin.
        public static Color PixelAt(int x, int y) => Color.FromArgb(255, 30 + x * 50, 20 + y * 70, 10 + x * 15 + y * 5);

        public void Dispose() => Directory.Delete(root, recursive: true);
    }
}
#endif