task6: implement batch38 group E state snapshot and wait queue

dotnet/src/ZB.MOM.NatsNet.Server/JetStream/NatsConsumer.State.cs

@@ -1,10 +1,12 @@
 using System.Text.Json;
+using System.Text;
 
 namespace ZB.MOM.NatsNet.Server;
 
 internal sealed partial class NatsConsumer
 {
     private static readonly TimeSpan DefaultGatewayInterestInterval = TimeSpan.FromSeconds(1);
+    private ConsumerInfo? _initialInfo;
 
     internal bool UpdateDeliveryInterest(bool localInterest)
     {
@@ -582,4 +584,158 @@ internal sealed partial class NatsConsumer
             _mu.ExitReadLock();
         }
     }
+
+    internal void ApplyState(ConsumerState state)
+    {
+        ArgumentNullException.ThrowIfNull(state);
+        _mu.EnterWriteLock();
+        try
+        {
+            _state = new ConsumerState
+            {
+                Delivered = new SequencePair
+                {
+                    Consumer = state.Delivered.Consumer,
+                    Stream = state.Delivered.Stream,
+                },
+                AckFloor = new SequencePair
+                {
+                    Consumer = state.AckFloor.Consumer,
+                    Stream = state.AckFloor.Stream,
+                },
+                Pending = state.Pending is null ? null : new Dictionary<ulong, Pending>(state.Pending),
+                Redelivered = state.Redelivered is null ? null : new Dictionary<ulong, ulong>(state.Redelivered),
+            };
+        }
+        finally
+        {
+            _mu.ExitWriteLock();
+        }
+    }
+
+    internal void SetStoreState(ConsumerState state) => ApplyState(state);
+
+    internal ConsumerState WriteStoreState()
+    {
+        _mu.EnterWriteLock();
+        try
+        {
+            return WriteStoreStateUnlocked();
+        }
+        finally
+        {
+            _mu.ExitWriteLock();
+        }
+    }
+
+    internal ConsumerState WriteStoreStateUnlocked() => GetConsumerState();
+
+    internal ConsumerInfo InitialInfo()
+    {
+        _mu.EnterWriteLock();
+        try
+        {
+            _initialInfo ??= GetInfo();
+            return _initialInfo;
+        }
+        finally
+        {
+            _mu.ExitWriteLock();
+        }
+    }
+
+    internal void ClearInitialInfo()
+    {
+        _mu.EnterWriteLock();
+        try
+        {
+            _initialInfo = null;
+        }
+        finally
+        {
+            _mu.ExitWriteLock();
+        }
+    }
+
+    internal ConsumerInfo Info() => GetInfo();
+
+    internal ConsumerInfo InfoWithSnap(ConsumerState? snapshot = null)
+    {
+        if (snapshot is null)
+            return GetInfo();
+
+        var info = GetInfo();
+        info.Delivered = new SequenceInfo { Consumer = snapshot.Delivered.Consumer, Stream = snapshot.Delivered.Stream };
+        info.AckFloor = new SequenceInfo { Consumer = snapshot.AckFloor.Consumer, Stream = snapshot.AckFloor.Stream };
+        return info;
+    }
+
+    internal (ConsumerInfo Info, string ReplySubject) InfoWithSnapAndReply(string replySubject, ConsumerState? snapshot = null) =>
+        (InfoWithSnap(snapshot), replySubject);
+
+    internal void SignalNewMessages() => _updateChannel.Writer.TryWrite(true);
+
+    internal bool ShouldSample()
+    {
+        if (string.IsNullOrWhiteSpace(Config.SampleFrequency))
+            return false;
+
+        var token = Config.SampleFrequency!.Trim().TrimEnd('%');
+        if (!int.TryParse(token, out var percent))
+            return false;
+
+        return percent > 0;
+    }
+
+    internal bool SampleAck(string ackReply)
+    {
+        if (!ShouldSample())
+            return false;
+
+        if (string.IsNullOrWhiteSpace(ackReply))
+            return false;
+
+        AddAckReply((ulong)ackReply.Length, ackReply);
+        return true;
+    }
+
+    internal bool IsFiltered(string subject)
+    {
+        if (string.IsNullOrWhiteSpace(subject))
+            return false;
+
+        if (!string.IsNullOrWhiteSpace(Config.FilterSubject))
+            return Internal.DataStructures.SubscriptionIndex.SubjectIsSubsetMatch(subject, Config.FilterSubject!);
+
+        if (Config.FilterSubjects is not { Length: > 0 })
+            return false;
+
+        return Config.FilterSubjects.Any(filter => Internal.DataStructures.SubscriptionIndex.SubjectIsSubsetMatch(subject, filter));
+    }
+
+    internal bool NeedAck() => Config.AckPolicy != AckPolicy.AckNone;
+
+    internal static (JsApiConsumerGetNextRequest? Request, Exception? Error) NextReqFromMsg(ReadOnlySpan<byte> message)
+    {
+        if (message.Length == 0)
+            return (new JsApiConsumerGetNextRequest { Batch = 1 }, null);
+
+        try
+        {
+            var text = Encoding.UTF8.GetString(message);
+            if (int.TryParse(text, out var batch))
+                return (new JsApiConsumerGetNextRequest { Batch = Math.Max(1, batch) }, null);
+
+            var req = JsonSerializer.Deserialize<JsApiConsumerGetNextRequest>(text);
+            if (req is null)
+                return (null, new InvalidOperationException("invalid request"));
+            if (req.Batch <= 0)
+                req.Batch = 1;
+            return (req, null);
+        }
+        catch (Exception ex)
+        {
+            return (null, ex);
+        }
+    }
 }