using Akka.Actor;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Redundancy;
using ZB.MOM.WW.OtOpcUa.ControlPlane.Redundancy;
using ZB.MOM.WW.OtOpcUa.ControlPlane.Tests.Harness;

namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Tests;

/// <summary>
/// Verifies <see cref="RedundancyStateActor"/> publishes a <see cref="RedundancyStateChanged"/>
/// snapshot in response to cluster events, and that the 250ms debounce coalesces bursts.
/// The actor accepts an <c>Action&lt;object&gt;</c> broadcast override so tests can use a
/// TestProbe sink instead of bootstrapping DistributedPubSub (which is flaky single-node).
/// </summary>
public sealed class RedundancyStateActorTests : ControlPlaneActorTestBase
{
    /// <summary>Verifies that a self-join event triggers RedundancyStateChanged through the broadcast override.</summary>
    [Fact]
    public void Self_join_triggers_RedundancyStateChanged_via_broadcast_override()
    {
        var probe = CreateTestProbe("redundancy-listener");
        Sys.ActorOf(RedundancyStateActor.Props(broadcast: msg => probe.Ref.Tell(msg)),
            "redundancy-actor");

        var msg = probe.ExpectMsg<RedundancyStateChanged>(TimeSpan.FromSeconds(3));
        msg.Nodes.ShouldNotBeNull();
        msg.CorrelationId.Value.ShouldNotBe(Guid.Empty);
    }

    /// <summary>Verifies that multiple back-to-back events debounce to a single RedundancyStateChanged publication.</summary>
    [Fact]
    public void Multiple_back_to_back_events_debounce_to_single_publish()
    {
        var probe = CreateTestProbe("dedup-listener");
        Sys.ActorOf(RedundancyStateActor.Props(broadcast: msg => probe.Ref.Tell(msg)),
            "redundancy-debounce");

        // First publish should arrive within the debounce window.
        probe.ExpectMsg<RedundancyStateChanged>(TimeSpan.FromSeconds(3));

        // After debounce settles, no more events are fired by a quiescent cluster.
        probe.ExpectNoMsg(TimeSpan.FromMilliseconds(500));
    }

    /// <summary>
    /// Verifies the periodic heartbeat re-publishes the CURRENT snapshot even when no new cluster
    /// events arrive — so a late subscriber that missed the change-driven publish converges within
    /// the heartbeat interval. The first message is the self-join publish; the second proves the
    /// recurring heartbeat fires with no intervening cluster event.
    /// </summary>
    [Fact]
    public void Heartbeat_republishes_current_snapshot_without_cluster_events()
    {
        var probe = CreateTestProbe("heartbeat-listener");
        Sys.ActorOf(
            RedundancyStateActor.Props(
                broadcast: msg => probe.Ref.Tell(msg),
                heartbeatInterval: TimeSpan.FromMilliseconds(300)),
            "redundancy-heartbeat");

        // First publish: the change-driven self-join snapshot.
        probe.ExpectMsg<RedundancyStateChanged>(TimeSpan.FromSeconds(2));

        // Second publish: the periodic heartbeat re-publish, with NO new cluster event sent.
        probe.ExpectMsg<RedundancyStateChanged>(TimeSpan.FromSeconds(2));
    }

    /// <summary>
    /// Regression guard: the snapshot node id MUST be the canonical <c>host:port</c> form (matching
    /// ClusterRoleInfo.LocalNode/ToNodeId), or every consumer's
    /// <c>n.NodeId == _localNode.Value</c> match fails and no node ever learns its role.
    /// </summary>
    [Fact]
    public void ToNodeId_uses_canonical_host_and_port()
    {
        var nodeId = RedundancyStateActor.ToNodeId(
            new Address("akka.tcp", "otopcua", "central-2", 4053));

        nodeId.Value.ShouldBe("central-2:4053");
    }

    /// <summary>
    /// Documents the host-less/port-less fallback (<c>:0</c>). Such members are skipped by
    /// BuildSnapshot's guard, but the helper must still format deterministically.
    /// </summary>
    [Fact]
    public void ToNodeId_handles_missing_port()
    {
        var nodeId = RedundancyStateActor.ToNodeId(new Address("akka.tcp", "otopcua"));

        nodeId.Value.ShouldBe(":0");
    }
}
