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 * OPC Foundation MIT License 1.00
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using System;
using System.IO;
using System.Text.Json;
using Crdt;
using NUnit.Framework;

namespace Opc.Ua.Redundancy.Server.Tests
{
    /// <summary>
    /// Round-trip tests for the <see cref="ByteStringCrdtSerializer"/>, which
    /// must distinguish a null <see cref="ByteString"/> from an empty one.
    /// </summary>
    [TestFixture]
    [Category("Distributed")]
    public sealed class ByteStringCrdtSerializerTests
    {
        [Test]
        public void RoundTripsNullEmptyAndDataValues()
        {
            var clock = new HybridLogicalClock(ReplicaId.FromUInt64(1), TimeProvider.System);
            var map = new LWWMap<string, ByteString>();
            map.Set("data", new ByteString(new byte[] { 9, 8, 7 }), clock);
            map.Set("empty", new ByteString(Array.Empty<byte>()), clock);
            map.Set("null", default, clock);

            byte[] bytes = map.ToByteArray(CrdtValues.String, ByteStringCrdtSerializer.Instance);
            var restored = LWWMap<string, ByteString>.ReadFrom(
                bytes, CrdtValues.String, ByteStringCrdtSerializer.Instance, CrdtReaderOptions.Default);

            Assert.That(restored.TryGetValue("data", out ByteString data), Is.True);
            Assert.That(data.ToArray(), Is.EqualTo(new byte[] { 9, 8, 7 }));

            Assert.That(restored.TryGetValue("empty", out ByteString empty), Is.True);
            Assert.That(empty.IsNull, Is.False, "an empty ByteString must not decode as null");
            Assert.That(empty.ToArray(), Is.Empty);

            Assert.That(restored.TryGetValue("null", out ByteString nul), Is.True);
            Assert.That(nul.IsNull, Is.True, "a null ByteString must decode as null");
        }

        [Test]
        public void RoundTripsJsonNullAndDataValues()
        {
            ByteString data = JsonRoundTrip(new ByteString(new byte[] { 4, 5, 6 }));
            Assert.That(data.IsNull, Is.False);
            Assert.That(data.ToArray(), Is.EqualTo(new byte[] { 4, 5, 6 }));

            ByteString empty = JsonRoundTrip(new ByteString(Array.Empty<byte>()));
            Assert.That(empty.IsNull, Is.False, "an empty ByteString must not decode as null");
            Assert.That(empty.ToArray(), Is.Empty);

            ByteString nul = JsonRoundTrip(default);
            Assert.That(nul.IsNull, Is.True, "a null ByteString must decode as null");
        }

        private static ByteString JsonRoundTrip(ByteString value)
        {
            using var stream = new MemoryStream();
            using (var writer = new Utf8JsonWriter(stream))
            {
                ByteStringCrdtSerializer.Instance.WriteJson(writer, value);
                writer.Flush();
            }

            var reader = new Utf8JsonReader(stream.ToArray());
            reader.Read();
            return ByteStringCrdtSerializer.Instance.ReadJson(ref reader);
        }
    }
}