feat: add StreamRelayActor bridging Akka events to gRPC proto channel

src/ScadaLink.Communication/Actors/StreamRelayActor.cs

@@ -0,0 +1,90 @@
+using System.Threading.Channels;
+using Akka.Actor;
+using Akka.Event;
+using Google.Protobuf.WellKnownTypes;
+using ScadaLink.Commons.Messages.Streaming;
+using ScadaLink.Communication.Grpc;
+using AlarmState = ScadaLink.Commons.Types.Enums.AlarmState;
+
+namespace ScadaLink.Communication.Actors;
+
+/// <summary>
+/// Lightweight relay actor that bridges Akka domain events (AttributeValueChanged,
+/// AlarmStateChanged) to a System.Threading.Channels.Channel of protobuf SiteStreamEvent
+/// messages. The gRPC server method reads from the channel's reader side.
+/// </summary>
+public class StreamRelayActor : ReceiveActor
+{
+    private readonly ILoggingAdapter _log = Context.GetLogger();
+    private readonly string _correlationId;
+    private readonly ChannelWriter<SiteStreamEvent> _channelWriter;
+
+    public StreamRelayActor(string correlationId, ChannelWriter<SiteStreamEvent> channelWriter)
+    {
+        _correlationId = correlationId;
+        _channelWriter = channelWriter;
+
+        Receive<AttributeValueChanged>(HandleAttributeValueChanged);
+        Receive<AlarmStateChanged>(HandleAlarmStateChanged);
+    }
+
+    private void HandleAttributeValueChanged(AttributeValueChanged msg)
+    {
+        var protoEvent = new SiteStreamEvent
+        {
+            CorrelationId = _correlationId,
+            AttributeChanged = new AttributeValueUpdate
+            {
+                InstanceUniqueName = msg.InstanceUniqueName,
+                AttributePath = msg.AttributePath,
+                AttributeName = msg.AttributeName,
+                Value = msg.Value?.ToString() ?? "",
+                Quality = MapQuality(msg.Quality),
+                Timestamp = Timestamp.FromDateTimeOffset(msg.Timestamp)
+            }
+        };
+
+        WriteToChannel(protoEvent);
+    }
+
+    private void HandleAlarmStateChanged(AlarmStateChanged msg)
+    {
+        var protoEvent = new SiteStreamEvent
+        {
+            CorrelationId = _correlationId,
+            AlarmChanged = new AlarmStateUpdate
+            {
+                InstanceUniqueName = msg.InstanceUniqueName,
+                AlarmName = msg.AlarmName,
+                State = MapAlarmState(msg.State),
+                Priority = msg.Priority,
+                Timestamp = Timestamp.FromDateTimeOffset(msg.Timestamp)
+            }
+        };
+
+        WriteToChannel(protoEvent);
+    }
+
+    private void WriteToChannel(SiteStreamEvent protoEvent)
+    {
+        if (!_channelWriter.TryWrite(protoEvent))
+        {
+            _log.Warning("Channel full, dropping event for correlation {0}", _correlationId);
+        }
+    }
+
+    private static Quality MapQuality(string quality) => quality switch
+    {
+        "Good" => Quality.Good,
+        "Uncertain" => Quality.Uncertain,
+        "Bad" => Quality.Bad,
+        _ => Quality.Unspecified
+    };
+
+    private static AlarmStateEnum MapAlarmState(AlarmState state) => state switch
+    {
+        AlarmState.Normal => AlarmStateEnum.AlarmStateNormal,
+        AlarmState.Active => AlarmStateEnum.AlarmStateActive,
+        _ => AlarmStateEnum.AlarmStateUnspecified
+    };
+}