using Akka.Cluster;
using Microsoft.Extensions.Diagnostics.HealthChecks;
using ZB.MOM.WW.ScadaBridge.Host.Actors;

namespace ZB.MOM.WW.ScadaBridge.Host.Health;

/// <summary>
/// Health check that verifies this node is an active member of the Akka.NET cluster.
/// Returns healthy only if the node's self-member status is Up or Joining.
/// </summary>
public class AkkaClusterHealthCheck : IHealthCheck
{
    private readonly AkkaHostedService _akkaService;

    /// <summary>
    /// Initializes the health check with the Akka hosted service.
    /// </summary>
    /// <param name="akkaService">The hosted service providing access to the Akka actor system.</param>
    public AkkaClusterHealthCheck(AkkaHostedService akkaService)
    {
        _akkaService = akkaService;
    }

    /// <summary>
    /// Checks that this node is an active member of the Akka.NET cluster.
    /// </summary>
    /// <param name="context">Health check context.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    public Task<HealthCheckResult> CheckHealthAsync(
        HealthCheckContext context,
        CancellationToken cancellationToken = default)
    {
        var system = _akkaService.ActorSystem;
        if (system == null)
            return Task.FromResult(HealthCheckResult.Degraded("ActorSystem not yet available."));

        var cluster = Cluster.Get(system);
        var status = cluster.SelfMember.Status;

        var result = status switch
        {
            MemberStatus.Up or MemberStatus.Joining =>
                HealthCheckResult.Healthy($"Akka cluster member status: {status}"),
            MemberStatus.Leaving or MemberStatus.Exiting =>
                HealthCheckResult.Degraded($"Akka cluster member status: {status}"),
            _ =>
                HealthCheckResult.Unhealthy($"Akka cluster member status: {status}")
        };

        return Task.FromResult(result);
    }
}