feat: add jetstream stream lifecycle api

src/NATS.Server/JetStream/StreamManager.cs

@@ -0,0 +1,78 @@
+using System.Collections.Concurrent;
+using NATS.Server.JetStream.Api;
+using NATS.Server.JetStream.Models;
+using NATS.Server.JetStream.Storage;
+using NATS.Server.Subscriptions;
+
+namespace NATS.Server.JetStream;
+
+public sealed class StreamManager
+{
+    private readonly ConcurrentDictionary<string, StreamHandle> _streams =
+        new(StringComparer.Ordinal);
+
+    public IReadOnlyCollection<string> StreamNames => _streams.Keys.ToArray();
+
+    public JetStreamApiResponse CreateOrUpdate(StreamConfig config)
+    {
+        if (string.IsNullOrWhiteSpace(config.Name))
+            return JetStreamApiResponse.ErrorResponse(400, "stream name required");
+
+        var normalized = NormalizeConfig(config);
+        var handle = _streams.AddOrUpdate(
+            normalized.Name,
+            _ => new StreamHandle(normalized, new MemStore()),
+            (_, existing) => existing with { Config = normalized });
+
+        return BuildStreamInfoResponse(handle);
+    }
+
+    public JetStreamApiResponse GetInfo(string name)
+    {
+        if (_streams.TryGetValue(name, out var stream))
+            return BuildStreamInfoResponse(stream);
+
+        return JetStreamApiResponse.NotFound($"$JS.API.STREAM.INFO.{name}");
+    }
+
+    public bool TryGet(string name, out StreamHandle handle) => _streams.TryGetValue(name, out handle!);
+
+    public StreamHandle? FindBySubject(string subject)
+    {
+        foreach (var stream in _streams.Values)
+        {
+            if (stream.Config.Subjects.Any(p => SubjectMatch.MatchLiteral(subject, p)))
+                return stream;
+        }
+
+        return null;
+    }
+
+    private static StreamConfig NormalizeConfig(StreamConfig config)
+    {
+        var copy = new StreamConfig
+        {
+            Name = config.Name,
+            Subjects = config.Subjects.Count == 0 ? [] : [.. config.Subjects],
+            MaxMsgs = config.MaxMsgs,
+            Replicas = config.Replicas,
+        };
+
+        return copy;
+    }
+
+    private static JetStreamApiResponse BuildStreamInfoResponse(StreamHandle handle)
+    {
+        var state = handle.Store.GetStateAsync(default).GetAwaiter().GetResult();
+        return new JetStreamApiResponse
+        {
+            StreamInfo = new JetStreamStreamInfo
+            {
+                Config = handle.Config,
+                State = state,
+            },
+        };
+    }
+}
+
+public sealed record StreamHandle(StreamConfig Config, IStreamStore Store);