vfxreview/RenderWorker/VFXReviewWorker.Tests/ExrHeaderTests.cs

using VFXReviewWorker;
using Xunit;

namespace VFXReviewWorker.Tests;

/// <summary>
/// The timecode check is the reason the validation engine exists (§8.1a), so
/// the header parse and the timecode arithmetic are pinned here against a
/// synthetic EXR built byte by byte.
/// </summary>
public class ExrHeaderTests
{
    [Fact]
    public void ReadsTimecodeResolutionChannelsAndFps()
    {
        var path = ExrFixture.Write(timecode: "18:58:57:12", width: 1920, height: 1080,
            channels: new[] { ("A", 1), ("B", 1), ("G", 1), ("R", 1) }, fpsNum: 24, compression: 4);
        try
        {
            var header = ExrHeader.Read(path);

            Assert.Equal(new Timecode(18, 58, 57, 12, false), header.Timecode);
            Assert.Equal(1920, header.DataWidth);
            Assert.Equal(1080, header.DataHeight);
            Assert.Equal(24, header.FramesPerSecond);
            Assert.Equal("half", header.BitDepth);
            Assert.True(header.HasAlpha);
            Assert.Equal("PIZ", header.CompressionName);
        }
        finally { File.Delete(path); }
    }

    [Fact]
    public void MissingTimecodeIsReportedAsAbsentNotAsZero()
    {
        var path = ExrFixture.Write(timecode: null, width: 1920, height: 1080,
            channels: new[] { ("B", 1), ("G", 1), ("R", 1) }, fpsNum: 24, compression: 3);
        try
        {
            var header = ExrHeader.Read(path);
            Assert.Null(header.Timecode);
            Assert.False(header.HasAlpha);
        }
        finally { File.Delete(path); }
    }

    [Fact]
    public void NonExrFileThrows()
    {
        var path = Path.GetTempFileName();
        try
        {
            File.WriteAllText(path, "this is not an exr at all, not even close");
            Assert.Throws<InvalidDataException>(() => ExrHeader.Read(path));
            Assert.Null(ExrHeader.TryRead(path));
        }
        finally { File.Delete(path); }
    }

    [Theory]
    // The BCD packing means the raw value reads back as its own hex digits.
    [InlineData(0x18585712u, 18, 58, 57, 12)]
    [InlineData(0x00004117u, 0, 0, 41, 17)]
    [InlineData(0x00000000u, 0, 0, 0, 0)]
    public void DecodesPackedSmpteTimecode(uint packed, int hh, int mm, int ss, int ff)
    {
        Assert.Equal(new Timecode(hh, mm, ss, ff, false), Timecode.FromPacked(packed));
    }

    [Fact]
    public void FrameArithmeticRoundTrips()
    {
        var tc = new Timecode(18, 58, 57, 12, false);
        Assert.Equal(tc, Timecode.FromFrames(tc.ToFrames(24), 24));

        // 133 frames on from 18:58:57:12 at 24 fps is 18:59:03:01 — the real
        // first/last frame pair measured on UNG_102_019_010 v005.
        Assert.Equal(new Timecode(18, 59, 3, 1, false), Timecode.FromFrames(tc.ToFrames(24) + 133, 24));
    }

    [Fact]
    public void ApiTimecodeIsOneHandleAheadOfThePlate()
    {
        // The defect class from §8.1a: the API stores the editorial in-point and
        // the plate starts 8 frames earlier, so a comp anchored to the API value
        // renders 8 frames late.
        var plate = Timecode.Parse("13:44:06:02")!.Value;
        var api = Timecode.Parse("13:44:06:10")!.Value;
        Assert.Equal(8, api.ToFrames(24) - plate.ToFrames(24));
    }

    [Fact]
    public void FrameDerivedTimecodeIsFrameNumberOverFps()
    {
        // 00:00:41:17 is frame 1001 at 24 fps — the signature of a comp built
        // with no source timecode at all.
        Assert.Equal(1001, Timecode.Parse("00:00:41:17")!.Value.ToFrames(24));
    }

    [Theory]
    [InlineData("UNG_102_019_010_cmp_TT_v005.01001.exr", 1001)]
    [InlineData("UNG_108_030_010_cmp_TT_v003.01204.exr", 1204)]
    // AE-written renders separate the frame with an underscore, and turn up as
    // layers in a shot comp alongside dot-separated delivered plates.
    [InlineData("UNG_110_030_010_PRERENDER_01001.exr", 1001)]
    [InlineData("UNG_110_030_010_render_1001.exr", 1001)]
    [InlineData("no_frame_number.exr", null)]
    // A version suffix is not a frame number.
    [InlineData("UNG_110_030_010_BG01_TT_v001.exr", null)]
    public void ParsesFrameNumbersFromFilenames(string name, int? expected)
    {
        Assert.Equal(expected, SequencePattern.FrameFromName(name));
    }

    [Fact]
    public void ParsesOutputPattern()
    {
        var p = SequencePattern.FromOutputPattern("UNG_102_019_010_cmp_TT_v005.[#####].exr");
        Assert.Equal("UNG_102_019_010_cmp_TT_v005", p.Prefix);
        Assert.Equal(".exr", p.Extension);
        Assert.Equal(5, p.Padding);
    }
}

/// <summary>Builds a minimal but structurally real EXR header on disk.</summary>
internal static class ExrFixture
{
    public static string Write(string? timecode, int width, int height,
        (string Name, int PixelType)[] channels, int fpsNum, byte compression)
    {
        var path = Path.Combine(Path.GetTempPath(), $"vfxr_test_{Guid.NewGuid():N}.exr");
        using var fs = new FileStream(path, FileMode.Create, FileAccess.Write);
        using var w = new BinaryWriter(fs);

        w.Write(ExrHeader.Magic);
        w.Write(2); // version 2, no flags

        // channels (chlist)
        using (var chData = new MemoryStream())
        using (var cw = new BinaryWriter(chData))
        {
            foreach (var (name, pixelType) in channels)
            {
                WriteCString(cw, name);
                cw.Write(pixelType);
                cw.Write((byte)0);          // pLinear
                cw.Write(new byte[3]);      // reserved
                cw.Write(1);                // xSampling
                cw.Write(1);                // ySampling
            }
            cw.Write((byte)0);              // list terminator
            WriteAttr(w, "channels", "chlist", chData.ToArray());
        }

        WriteAttr(w, "compression", "compression", new[] { compression });

        var window = new byte[16];
        BitConverter.GetBytes(0).CopyTo(window, 0);
        BitConverter.GetBytes(0).CopyTo(window, 4);
        BitConverter.GetBytes(width - 1).CopyTo(window, 8);
        BitConverter.GetBytes(height - 1).CopyTo(window, 12);
        WriteAttr(w, "dataWindow", "box2i", window);
        WriteAttr(w, "displayWindow", "box2i", window);

        var rational = new byte[8];
        BitConverter.GetBytes(fpsNum).CopyTo(rational, 0);
        BitConverter.GetBytes(1u).CopyTo(rational, 4);
        WriteAttr(w, "framesPerSecond", "rational", rational);

        if (timecode is not null)
        {
            var parts = timecode.Split(':');
            uint Bcd(int v) => (uint)((v / 10) * 16 + v % 10);
            var packed = (Bcd(int.Parse(parts[0])) << 24) | (Bcd(int.Parse(parts[1])) << 16)
                       | (Bcd(int.Parse(parts[2])) << 8) | Bcd(int.Parse(parts[3]));
            var tcData = new byte[8];
            BitConverter.GetBytes(packed).CopyTo(tcData, 0);
            WriteAttr(w, "timeCode", "timecode", tcData);
            WriteAttr(w, "timeCodeString", "string", System.Text.Encoding.ASCII.GetBytes(timecode));
        }

        w.Write((byte)0); // end of header
        return path;
    }

    private static void WriteAttr(BinaryWriter w, string name, string type, byte[] data)
    {
        WriteCString(w, name);
        WriteCString(w, type);
        w.Write(data.Length);
        w.Write(data);
    }

    private static void WriteCString(BinaryWriter w, string s)
    {
        w.Write(System.Text.Encoding.ASCII.GetBytes(s));
        w.Write((byte)0);
    }
}