lmxopcua/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Hubs/AlertSignalRBridge.cs

using Akka.Actor;
using Akka.Cluster.Tools.PublishSubscribe;
using Akka.Event;
using Microsoft.AspNetCore.SignalR;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Alerts;

namespace ZB.MOM.WW.OtOpcUa.AdminUI.Hubs;

/// <summary>
/// Akka actor that subscribes to the <c>alerts</c> DistributedPubSub topic and forwards each
/// <see cref="AlarmTransitionEvent"/> to every SignalR client connected to <see cref="AlertHub"/>.
/// Mirrors <c>FleetStatusSignalRBridge</c>'s design — one bridge per admin node, hub fan-out is
/// per-node, no cluster-singleton needed.
/// </summary>
public sealed class AlertSignalRBridge : ReceiveActor
{
    public const string TopicName = "alerts";

    private readonly IHubContext<AlertHub> _hub;
    private readonly IInProcessBroadcaster<AlarmTransitionEvent> _broadcaster;
    private readonly ILoggingAdapter _log = Context.GetLogger();

    /// <summary>
    /// Creates actor props for the AlertSignalRBridge.
    /// </summary>
    /// <param name="hub">The SignalR hub context to send alerts to.</param>
    /// <param name="broadcaster">In-process fan-out read directly by the Blazor Server Alerts page.</param>
    /// <returns>The Akka <see cref="Akka.Actor.Props"/> for creating this actor.</returns>
    public static Props Props(IHubContext<AlertHub> hub, IInProcessBroadcaster<AlarmTransitionEvent> broadcaster) =>
        Akka.Actor.Props.Create(() => new AlertSignalRBridge(hub, broadcaster));

    /// <summary>
    /// Initializes a new instance of the AlertSignalRBridge actor.
    /// </summary>
    /// <param name="hub">The SignalR hub context to send alerts to.</param>
    /// <param name="broadcaster">In-process fan-out read directly by the Blazor Server Alerts page.</param>
    public AlertSignalRBridge(IHubContext<AlertHub> hub, IInProcessBroadcaster<AlarmTransitionEvent> broadcaster)
    {
        _hub = hub;
        _broadcaster = broadcaster;
        ReceiveAsync<AlarmTransitionEvent>(ForwardAsync);
        // DPS subscription is now live — mark the feed connected so the Blazor "live" pill lights up.
        Receive<SubscribeAck>(_ => _broadcaster.SetConnected(true));
    }

    /// <inheritdoc />
    protected override void PreStart() =>
        DistributedPubSub.Get(Context.System).Mediator.Tell(new Subscribe(TopicName, Self));

    /// <inheritdoc />
    protected override void PostStop()
    {
        // Bridge stopping — the feed is no longer live, drop the "live" pill.
        _broadcaster.SetConnected(false);
        base.PostStop();
    }

    private async Task ForwardAsync(AlarmTransitionEvent msg)
    {
        // In-process fan-out first — this is what the Blazor Server Alerts page reads. The hub push
        // is kept for any out-of-process (e.g. WASM) SignalR client.
        _broadcaster.Publish(msg);
        try
        {
            await _hub.Clients.All.SendAsync(AlertHub.MethodName, msg);
        }
        catch (Exception ex)
        {
            _log.Warning(ex, "AlertSignalRBridge: SignalR push failed for {AlarmId}", msg.AlarmId);
        }
    }
}