using Microsoft.AspNetCore.SignalR;

namespace ZB.MOM.WW.MxGateway.Server.Dashboard.Hubs;

/// <summary>
/// Background service that subscribes to <see cref="IDashboardSnapshotService.WatchSnapshotsAsync"/>
/// and broadcasts every snapshot it produces to every connected
/// <see cref="DashboardSnapshotHub"/> client. There is one publisher per
/// gateway process; clients listen via the hub.
/// </summary>
public sealed class DashboardSnapshotPublisher(
    IDashboardSnapshotService snapshotService,
    IHubContext<DashboardSnapshotHub> hubContext,
    ILogger<DashboardSnapshotPublisher> logger) : BackgroundService
{
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        try
        {
            await foreach (DashboardSnapshot snapshot in snapshotService
                .WatchSnapshotsAsync(stoppingToken)
                .ConfigureAwait(false))
            {
                try
                {
                    await hubContext.Clients
                        .All
                        .SendAsync(DashboardSnapshotHub.SnapshotMessage, snapshot, stoppingToken)
                        .ConfigureAwait(false);
                }
                catch (Exception ex) when (ex is not OperationCanceledException)
                {
                    logger.LogWarning(ex, "Snapshot broadcast failed; will retry on the next snapshot tick.");
                }
            }
        }
        catch (OperationCanceledException)
        {
        }
    }
}