feat(CUB-55): add SignalR broadcast state method with AgentStatusHub and DTO

backend/Hubs/AgentStatusHub.cs

@@ -0,0 +1,155 @@
+using ControlCenter.Api.Dtos;
+using Microsoft.AspNetCore.SignalR;
+
+namespace ControlCenter.Api.Hubs;
+
+/// <summary>
+/// SignalR hub for broadcasting agent status updates to connected clients.
+///
+/// <para>
+/// Clients call <see cref="SendStatusUpdate"/> to broadcast a status change,
+/// and the hub relays it to all connected clients via the
+/// <see cref="IAgentStatusClient.AgentStatusChanged"/> callback.
+/// </para>
+///
+/// <para>
+/// Server-side code should use <see cref="AgentStatusHubExtensions.PushStatusUpdateAsync"/>
+/// via <c>IHubContext&lt;AgentStatusHub, IAgentStatusClient&gt;</c> for background-service broadcasts.
+/// </para>
+///
+/// <para>
+/// Architecture note: This hub bridges OpenClaw Gateway events to SignalR clients.
+/// A background service subscribes to Gateway events and pushes them through
+/// this hub's extension methods.
+/// </para>
+/// </summary>
+public class AgentStatusHub : Hub<IAgentStatusClient>
+{
+    private readonly ILogger<AgentStatusHub> _logger;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AgentStatusHub"/> class.
+    /// </summary>
+    /// <param name="logger">Logger for diagnostic output.</param>
+    public AgentStatusHub(ILogger<AgentStatusHub> logger)
+    {
+        _logger = logger;
+    }
+
+    /// <summary>
+    /// Broadcasts an agent status update to all connected clients.
+    ///
+    /// <para>
+    /// Any connected client (or server-side caller) can invoke this method
+    /// to push a status update to every subscriber. The update is relayed
+    /// through the <see cref="IAgentStatusClient.AgentStatusChanged"/> callback.
+    /// </para>
+    /// </summary>
+    /// <param name="update">The agent status update payload to broadcast.</param>
+    public async Task SendStatusUpdate(AgentStatusUpdateDto update)
+    {
+        _logger.LogInformation(
+            "Broadcasting status update for agent {AgentId}: {Status}",
+            update.AgentId, update.Status);
+
+        await Clients.All.AgentStatusChanged(update);
+    }
+
+    /// <summary>
+    /// Adds the calling connection to the fleet group.
+    /// Once joined, the client will receive all agent status updates.
+    /// </summary>
+    public async Task JoinFleet()
+    {
+        await Groups.AddToGroupAsync(Context.ConnectionId, FleetGroupName);
+        _logger.LogDebug("Connection {ConnectionId} joined fleet group", Context.ConnectionId);
+    }
+
+    /// <summary>
+    /// Removes the calling connection from the fleet group.
+    /// </summary>
+    public async Task LeaveFleet()
+    {
+        await Groups.RemoveFromGroupAsync(Context.ConnectionId, FleetGroupName);
+        _logger.LogDebug("Connection {ConnectionId} left fleet group", Context.ConnectionId);
+    }
+
+    /// <summary>
+    /// Overrides <see cref="Hub{T}.OnDisconnectedAsync"/> to log disconnections.
+    /// SignalR automatically removes disconnected connections from all groups.
+    /// </summary>
+    /// <param name="exception">Exception that caused the disconnection, if any.</param>
+    public override Task OnDisconnectedAsync(Exception? exception)
+    {
+        _logger.LogDebug("Connection {ConnectionId} disconnected", Context.ConnectionId);
+        return base.OnDisconnectedAsync(exception);
+    }
+
+    /// <summary>
+    /// The SignalR group name for the entire fleet (all agents).
+    /// </summary>
+    internal const string FleetGroupName = "fleet";
+}
+
+/// <summary>
+/// Strongly-typed client interface for the AgentStatus SignalR hub.
+/// Defines the methods the server can invoke on connected clients
+/// to push real-time agent status updates.
+/// </summary>
+public interface IAgentStatusClient
+{
+    /// <summary>
+    /// Pushes an agent status change to all subscribed clients.
+    /// Fired whenever an agent's operational status changes
+    /// (e.g., idle → active, active → thinking, active → error).
+    /// </summary>
+    /// <param name="update">The full status update payload.</param>
+    /// <returns>A Task that completes when the client has processed the update.</returns>
+    Task AgentStatusChanged(AgentStatusUpdateDto update);
+}
+
+/// <summary>
+/// Extension methods for pushing real-time agent updates through
+/// the <see cref="IHubContext{T}"/> of <see cref="AgentStatusHub"/>.
+///
+/// <para>
+/// These methods are intended to be called from background services
+/// or other server-side code that detects an agent state change,
+/// using the injected <c>IHubContext&lt;AgentStatusHub, IAgentStatusClient&gt;</c>.
+/// </para>
+/// </summary>
+public static class AgentStatusHubExtensions
+{
+    /// <summary>
+    /// Pushes an agent status update to all connected clients.
+    ///
+    /// <para>
+    /// Call this from any background service when an agent's
+    /// operational status changes (e.g., the Gateway reports a
+    /// session transition from "running" to "done").
+    /// </para>
+    /// </summary>
+    /// <param name="hubContext">The hub context injected via DI.</param>
+    /// <param name="update">The agent status update payload.</param>
+    /// <returns>A Task that completes when the message has been sent to all clients.</returns>
+    public static async Task PushStatusUpdateAsync(
+        this IHubContext<AgentStatusHub, IAgentStatusClient> hubContext,
+        AgentStatusUpdateDto update)
+    {
+        await hubContext.Clients.All.AgentStatusChanged(update);
+    }
+
+    /// <summary>
+    /// Pushes an agent status update to clients subscribed to the fleet group.
+    /// </summary>
+    /// <param name="hubContext">The hub context injected via DI.</param>
+    /// <param name="update">The agent status update payload.</param>
+    /// <returns>A Task that completes when the message has been sent to the fleet group.</returns>
+    public static async Task PushStatusUpdateToFleetAsync(
+        this IHubContext<AgentStatusHub, IAgentStatusClient> hubContext,
+        AgentStatusUpdateDto update)
+    {
+        await hubContext.Clients.Group(AgentStatusHub.FleetGroupName)
+            .AgentStatusChanged(update);
+    }
+}