using System.Text;
using VFXReviewWorker;
using Xunit;

namespace VFXReviewWorker.Tests;

/// <summary>
/// Reference vectors from the xxHash specification. The delivery builder
/// verifies packaged files against digests recorded here at validation time, so
/// a wrong implementation would not be caught by round-tripping our own code —
/// only by pinning the published values.
/// </summary>
public class XxHash64Tests
{
    [Theory]
    [InlineData("", 0xEF46DB3751D8E999UL)]
    [InlineData("a", 0xD24EC4F1A98C6E5BUL)]
    [InlineData("abc", 0x44BC2CF5AD770999UL)]
    public void MatchesReferenceVectors(string input, ulong expected)
    {
        Assert.Equal(expected, XxHash64.Hash(Encoding.ASCII.GetBytes(input)));
    }

    [Fact]
    public void StreamingInChunksMatchesSingleShot()
    {
        var data = new byte[1000];
        new Random(42).NextBytes(data);
        var oneShot = XxHash64.Hash(data);

        // Chunk sizes deliberately straddle the 32-byte stripe boundary.
        foreach (var chunk in new[] { 1, 7, 31, 32, 33, 64, 999 })
        {
            var state = new XxHash64.State(0);
            for (var i = 0; i < data.Length; i += chunk)
            {
                state.Update(new ReadOnlySpan<byte>(data, i, Math.Min(chunk, data.Length - i)));
            }
            Assert.Equal(oneShot, state.Digest());
        }
    }

    [Fact]
    public void HashFileIsStableAndContentSensitive()
    {
        var path = Path.GetTempFileName();
        try
        {
            File.WriteAllText(path, "frame data");
            var first = XxHash64.HashFile(path);
            Assert.Equal(first, XxHash64.HashFile(path));

            File.WriteAllText(path, "frame datb");
            Assert.NotEqual(first, XxHash64.HashFile(path));
        }
        finally
        {
            File.Delete(path);
        }
    }
}