shoc-backend/SeaHavenIndustries.Tests/VideoDurationProbeTests.cs

using System.Buffers.Binary;
using System.Text;
using SeaHaven.Services.Helpers;

namespace SeaHavenIndustries.Tests;

public class VideoDurationProbeTests
{
    internal static byte[] Box(string type, params byte[][] children)
    {
        var body = children.SelectMany(child => child).ToArray();
        var box = new byte[8 + body.Length];
        BinaryPrimitives.WriteUInt32BigEndian(box, (uint)box.Length);
        Encoding.ASCII.GetBytes(type).CopyTo(box, 4);
        body.CopyTo(box, 8);
        return box;
    }

    internal static byte[] MovieHeader(uint timescale, ulong duration, bool version1 = false)
    {
        var body = new byte[version1 ? 32 : 20];
        body[0] = version1 ? (byte)1 : (byte)0;
        if (version1)
        {
            BinaryPrimitives.WriteUInt32BigEndian(body.AsSpan(20), timescale);
            BinaryPrimitives.WriteUInt64BigEndian(body.AsSpan(24), duration);
        }
        else
        {
            BinaryPrimitives.WriteUInt32BigEndian(body.AsSpan(12), timescale);
            BinaryPrimitives.WriteUInt32BigEndian(body.AsSpan(16), (uint)duration);
        }
        return Box("mvhd", body);
    }

    /// <summary>A phone-style file: ftyp, a large mdat, then moov at the end (not fast-start).</summary>
    internal static byte[] Mp4(uint timescale, ulong duration, bool version1 = false, int mediaBytes = 4096)
    {
        var ftyp = Box("ftyp", Encoding.ASCII.GetBytes("isom"), new byte[4]);
        var mdat = Box("mdat", new byte[mediaBytes]);
        var moov = Box("moov", MovieHeader(timescale, duration, version1));
        return ftyp.Concat(mdat).Concat(moov).ToArray();
    }

    [Fact]
    public void ReadsDurationFromMoovAfterMediaData()
    {
        Assert.Equal(95.0, VideoDurationProbe.TryReadDurationSeconds(new MemoryStream(Mp4(600, 57_000))));
    }

    [Fact]
    public void ReadsVersionOneMovieHeader()
    {
        Assert.Equal(30.5, VideoDurationProbe.TryReadDurationSeconds(
            new MemoryStream(Mp4(1000, 30_500, version1: true))));
    }

    [Fact]
    public void FollowsSixtyFourBitBoxSizes()
    {
        var ftyp = Box("ftyp", Encoding.ASCII.GetBytes("qt  "), new byte[4]);
        var mdatBody = new byte[512];
        var mdat = new byte[16 + mdatBody.Length];
        BinaryPrimitives.WriteUInt32BigEndian(mdat, 1);
        Encoding.ASCII.GetBytes("mdat").CopyTo(mdat, 4);
        BinaryPrimitives.WriteUInt64BigEndian(mdat.AsSpan(8), (ulong)mdat.Length);
        var moov = Box("moov", MovieHeader(90_000, 90_000UL * 120));
        var file = ftyp.Concat(mdat).Concat(moov).ToArray();

        Assert.Equal(120.0, VideoDurationProbe.TryReadDurationSeconds(new MemoryStream(file)));
    }

    [Theory]
    [InlineData("no-moov")]
    [InlineData("truncated")]
    [InlineData("zero-timescale")]
    [InlineData("oversized-box")]
    public void UnreadableStructureReturnsNull(string shape)
    {
        var bytes = shape switch
        {
            "no-moov" => Box("ftyp", Encoding.ASCII.GetBytes("isom"), new byte[4]).Concat(Box("mdat", new byte[64])).ToArray(),
            "truncated" => Mp4(600, 57_000)[..^10],
            "zero-timescale" => Mp4(0, 57_000),
            _ => Box("ftyp", new byte[8]).Concat(new byte[] { 0x7F, 0xFF, 0xFF, 0xFF, (byte)'m', (byte)'o', (byte)'o', (byte)'v' }).ToArray(),
        };

        Assert.Null(VideoDurationProbe.TryReadDurationSeconds(new MemoryStream(bytes)));
    }

    [Fact]
    public void NonSeekableStreamReturnsNull()
    {
        Assert.Null(VideoDurationProbe.TryReadDurationSeconds(new NonSeekableStream(Mp4(600, 57_000))));
    }

    [Theory]
    [InlineData(90.0, true)]
    [InlineData(90.5, false)]
    public void ContractAllowsUpToNinetySeconds(double seconds, bool allowed)
    {
        var message = WorkOrderMediaContract.ValidateVideoDuration(
            new MemoryStream(Mp4(1000, (ulong)(seconds * 1000))));

        Assert.Equal(allowed ? null : "Videos must be 90 seconds or shorter.", message);
    }

    private sealed class NonSeekableStream(byte[] bytes) : MemoryStream(bytes)
    {
        public override bool CanSeek => false;
    }
}