feat: add jetstream stream lifecycle api

src/NATS.Server/JetStream/Api/Handlers/StreamApiHandlers.cs

@@ -0,0 +1,91 @@
+using System.Text.Json;
+using NATS.Server.JetStream.Models;
+
+namespace NATS.Server.JetStream.Api.Handlers;
+
+public static class StreamApiHandlers
+{
+    private const string CreatePrefix = "$JS.API.STREAM.CREATE.";
+    private const string InfoPrefix = "$JS.API.STREAM.INFO.";
+
+    public static JetStreamApiResponse HandleCreate(string subject, ReadOnlySpan<byte> payload, StreamManager streamManager)
+    {
+        var streamName = ExtractTrailingToken(subject, CreatePrefix);
+        if (streamName == null)
+            return JetStreamApiResponse.NotFound(subject);
+
+        var config = ParseConfig(payload);
+        if (string.IsNullOrWhiteSpace(config.Name))
+            config.Name = streamName;
+
+        if (config.Subjects.Count == 0)
+            config.Subjects.Add(streamName.ToLowerInvariant() + ".>");
+
+        return streamManager.CreateOrUpdate(config);
+    }
+
+    public static JetStreamApiResponse HandleInfo(string subject, StreamManager streamManager)
+    {
+        var streamName = ExtractTrailingToken(subject, InfoPrefix);
+        if (streamName == null)
+            return JetStreamApiResponse.NotFound(subject);
+
+        return streamManager.GetInfo(streamName);
+    }
+
+    private static string? ExtractTrailingToken(string subject, string prefix)
+    {
+        if (!subject.StartsWith(prefix, StringComparison.Ordinal))
+            return null;
+
+        var token = subject[prefix.Length..].Trim();
+        return token.Length == 0 ? null : token;
+    }
+
+    private static StreamConfig ParseConfig(ReadOnlySpan<byte> payload)
+    {
+        if (payload.IsEmpty)
+            return new StreamConfig();
+
+        try
+        {
+            using var doc = JsonDocument.Parse(payload.ToArray());
+            var root = doc.RootElement;
+            var config = new StreamConfig();
+
+            if (root.TryGetProperty("name", out var nameEl))
+                config.Name = nameEl.GetString() ?? string.Empty;
+
+            if (root.TryGetProperty("subjects", out var subjectsEl))
+            {
+                if (subjectsEl.ValueKind == JsonValueKind.Array)
+                {
+                    foreach (var item in subjectsEl.EnumerateArray())
+                    {
+                        var value = item.GetString();
+                        if (!string.IsNullOrWhiteSpace(value))
+                            config.Subjects.Add(value);
+                    }
+                }
+                else if (subjectsEl.ValueKind == JsonValueKind.String)
+                {
+                    var value = subjectsEl.GetString();
+                    if (!string.IsNullOrWhiteSpace(value))
+                        config.Subjects.Add(value);
+                }
+            }
+
+            if (root.TryGetProperty("max_msgs", out var maxMsgsEl) && maxMsgsEl.TryGetInt32(out var maxMsgs))
+                config.MaxMsgs = maxMsgs;
+
+            if (root.TryGetProperty("replicas", out var replicasEl) && replicasEl.TryGetInt32(out var replicas))
+                config.Replicas = replicas;
+
+            return config;
+        }
+        catch (JsonException)
+        {
+            return new StreamConfig();
+        }
+    }
+}