using System.Diagnostics.Metrics;
using System.Linq;
using StellaOps.Router.Common.Abstractions;

namespace StellaOps.Gateway.WebService.Services;

public sealed class GatewayMetrics
{
    public const string MeterName = "StellaOps.Gateway.WebService";

    private static readonly Meter Meter = new(MeterName, "1.0.0");
    private readonly IGlobalRoutingState _routingState;

    public GatewayMetrics(IGlobalRoutingState routingState)
    {
        _routingState = routingState;

        Meter.CreateObservableGauge(
            "gateway_active_connections",
            () => GetActiveConnections(),
            description: "Number of active microservice connections.");

        Meter.CreateObservableGauge(
            "gateway_registered_endpoints",
            () => GetRegisteredEndpoints(),
            description: "Number of registered endpoints across all connections.");
    }

    public long GetActiveConnections()
    {
        return _routingState.GetAllConnections().Count;
    }

    public long GetRegisteredEndpoints()
    {
        return _routingState.GetAllConnections().Sum(c => c.Endpoints.Count);
    }
}