using VFXReviewWorker;
using Xunit;

namespace VFXReviewWorker.Tests;

/// <summary>
/// The preview MP4 opens on the Netflix slate. ffmpeg's <c>thumbnail</c> filter
/// only considers the first 100 frames, so every thumbnail the pipeline has ever
/// produced was a picture of the slate card rather than of the shot — invisible
/// while thumbnails were only decoration in the QC queue, and unacceptable now
/// they can become a shot's thumbnail.
///
/// The fix is to seek past the slate, so the seek arithmetic is worth pinning.
/// </summary>
public class ThumbnailSeekTests
{
    private static PreviewBuildResult Build(double? pictureStart, int? frameCount) =>
        new() { PictureStartSeconds = pictureStart, FrameCount = frameCount };

    [Fact]
    public void SeeksAQuarterIntoPictureNotIntoTheFile()
    {
        // 5s slate, then 96 frames (4s) of picture at 24fps → 5 + 1 = 6s.
        var seek = PreviewStage.ThumbnailSeekSeconds(Build(5.0, 96), 24);
        Assert.NotNull(seek);
        Assert.Equal(6.0, seek!.Value, 3);
    }

    [Fact]
    public void HandlesATemplateWithNoSlateAtAll()
    {
        var seek = PreviewStage.ThumbnailSeekSeconds(Build(0.0, 240), 24);
        Assert.Equal(2.5, seek!.Value, 3);
    }

    [Fact]
    public void FallsBackWhenTheBuildDidNotReportWherePictureStarts()
    {
        // Older worker, or a template with no SHOT layer: null means "keep the
        // old whole-file behaviour" rather than guessing an offset.
        Assert.Null(PreviewStage.ThumbnailSeekSeconds(Build(null, 96), 24));
        Assert.Null(PreviewStage.ThumbnailSeekSeconds(null, 24));
    }

    [Theory]
    [InlineData(-1.0, 96, 24)]   // negative slate length
    [InlineData(5.0, 0, 24)]     // no picture frames
    [InlineData(5.0, -5, 24)]    // nonsense frame count
    [InlineData(5.0, 96, 0)]     // no fps to divide by
    public void RefusesNumbersThatDoNotDescribeARealClip(double start, int frames, double fps)
    {
        Assert.Null(PreviewStage.ThumbnailSeekSeconds(Build(start, frames), fps));
    }
}