Add JetStream metadata to msg parsed from reply string

.editorconfig

@@ -13,6 +13,7 @@ generated_code = true
 
 [*.cs]
 indent_size = 4
+max_line_length = 300
 
 # changes from VS2019 defaults
 csharp_style_namespace_declarations = file_scoped

src/NATS.Client.JetStream/Internal/ReplyToDateTimeAndSeq.cs

@@ -0,0 +1,28 @@
+namespace NATS.Client.JetStream.Internal;
+
+internal static class ReplyToDateTimeAndSeq
+{
+    internal static (DateTimeOffset? DateTime, long? Seq) Parse(string? reply)
+    {
+        if (reply == null)
+        {
+            return (null, null);
+        }
+
+        var ackSeperated = reply.Split(".");
+
+        // It must be seperated by 9 dots as defined in
+        // https://docs.nats.io/reference/reference-protocols/nats_api_reference#acknowledging-messages
+        if (ackSeperated.Length != 9)
+        {
+            return (null, null);
+        }
+
+        var timestamp = long.Parse(ackSeperated[^2]);
+        var offset = DateTimeOffset.FromUnixTimeMilliseconds(timestamp / 1000000);
+        var dateTime = new DateTimeOffset(offset.Ticks, TimeSpan.Zero);
+        var seq = long.Parse(ackSeperated[5]);
+
+        return (dateTime, seq);
+    }
+}

src/NATS.Client.JetStream/NatsJSMsg.cs

@@ -12,11 +12,13 @@
 {
     private readonly NatsJSContext _context;
     private readonly NatsMsg<T> _msg;
+    private readonly Lazy<(DateTimeOffset? DateTime, long? Sequence)> _replyToDateTimeAndSeq;
 
     internal NatsJSMsg(NatsMsg<T> msg, NatsJSContext context)
     {
         _msg = msg;
         _context = context;
+        _replyToDateTimeAndSeq = new Lazy<(DateTimeOffset? DateTime, long? Sequnce)>(() => ReplyToDateTimeAndSeq.Parse(msg.ReplyTo));
     }
 
     /// <summary>
@@ -50,6 +52,16 @@
     /// </summary>
     public INatsConnection? Connection => _msg.Connection;
 
+    /// <summary>
+    /// The sequence number of the message.
+    /// </summary>
+    public long? Sequence => _replyToDateTimeAndSeq.Value.Sequence;
+
+    /// <summary>
+    /// The time of the message.
+    /// </summary>
+    public DateTimeOffset? DateTime => _replyToDateTimeAndSeq.Value.DateTime;
+
     /// <summary>
     /// Acknowledges the message was completely handled.
     /// </summary>
@@ -102,10 +114,7 @@
 
         return _msg.ReplyAsync(
             payload: payload,
-            opts: new NatsPubOpts
-            {
-                WaitUntilSent = opts.WaitUntilSent ?? _context.Opts.AckOpts.WaitUntilSent,
-            },
+            opts: new NatsPubOpts {WaitUntilSent = opts.WaitUntilSent ?? _context.Opts.AckOpts.WaitUntilSent,},
             cancellationToken: cancellationToken);
     }
 }

tests/NATS.Client.JetStream.Tests/Internal/ReplyToDateTimeAndSeqTest.cs

@@ -0,0 +1,33 @@
+using NATS.Client.JetStream.Internal;
+
+namespace NATS.Client.JetStream.Tests.Internal;
+
+public class ReplyToDateTimeAndSeqTest
+{
+    [Fact]
+    public void ShouldParseReplyToDateTimeAndSeq()
+    {
+        var (dateTime, seq) = ReplyToDateTimeAndSeq.Parse("$JS.ACK.UnitTest.GetEvents_0.1.100.1.1696023331771188000.0");
+
+        dateTime!.Value.ToString("O").Should().Be("2023-09-29T21:35:31.7710000+00:00");
+        seq.Should().Be(100);
+    }
+
+    [Fact]
+    public void ShouldSetNullForReturnWhenReplyToIsNull()
+    {
+        var (dateTime, seq) = ReplyToDateTimeAndSeq.Parse(null);
+
+        dateTime.Should().BeNull();
+        seq.Should().BeNull();
+    }
+
+    [Fact]
+    public void ShouldSetNullWhenReplyToIsASimpleReqResponse()
+    {
+        var (dateTime, seq) = ReplyToDateTimeAndSeq.Parse("_INBOX.1");
+
+        dateTime.Should().BeNull();
+        seq.Should().BeNull();
+    }
+}