using Akka.Actor;
using Akka.TestKit.Xunit2;
using NSubstitute;
using Opc.Ua;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Protocol;
using ZB.MOM.WW.ScadaBridge.Commons.Messages.DataConnection;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
using ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Actors;
using ZB.MOM.WW.ScadaBridge.HealthMonitoring;

namespace ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests.Actors;

/// <summary>
/// Arch-review 2026-08-19 <b>P2-4</b> (classification half) — how a thrown
/// <see cref="ServiceResultException"/> out of a batch subscribe is classified.
///
/// <para>
/// <b>The gap these pin.</b> <c>IsConnectionLevelFailure</c> knew only about
/// <c>InvalidOperationException</c> / socket / timeout / IO faults, so the OPC UA SDK's own way of
/// reporting a dead session — a <c>ServiceResultException</c> carrying a bad-session status —
/// was treated as a per-tag resolution failure for the WHOLE chunk. Every tag went unresolved and
/// the backoff probe re-issued the same batch against the same dead session forever, growing the
/// adapter's monitored-item bookkeeping each round, instead of reconnecting once.
/// </para>
///
/// <para>
/// The classification must stay narrow: a per-node status (<c>BadNodeIdUnknown</c>) is exactly the
/// "device still booting / wrong tag path" case the resolution timer exists for, and must NOT put
/// the connection into a reconnect loop.
/// </para>
/// </summary>
public class DataConnectionOpcUaFaultClassificationTests : TestKit
{
    private readonly ISiteHealthCollector _health = Substitute.For<ISiteHealthCollector>();
    private readonly IDataConnectionFactory _factory = Substitute.For<IDataConnectionFactory>();

    private static DataConnectionOptions Options() => new()
    {
        ReconnectInterval = TimeSpan.FromMilliseconds(100),
        TagResolutionRetryInterval = TimeSpan.FromMilliseconds(150),
        TagResolutionRetryMaxInterval = TimeSpan.FromMilliseconds(600),
        WriteTimeout = TimeSpan.FromSeconds(5),
        SeedReadMaxAttempts = 1,
        SeedReadRetryDelay = TimeSpan.FromMilliseconds(10),
        SubscribeBatchSize = 5,
        SubscribeBatchDelay = TimeSpan.FromMilliseconds(50),
        SeedReadBatchSize = 4,
        SeedReadMaxParallelism = 2,
        SeedOverallTimeout = TimeSpan.FromSeconds(30),
        QualityFlushInterval = TimeSpan.FromMilliseconds(200)
    };

    private IActorRef CreateActor(FakeBatchDataConnection adapter, string name) =>
        Sys.ActorOf(Props.Create(() => new DataConnectionActor(
            name, adapter, Options(), _health, _factory, "OpcUa")), name);

    private int HealthTransitions(string connectionName, ConnectionHealth health) =>
        _health.ReceivedCalls().Count(c =>
            c.GetMethodInfo().Name == nameof(ISiteHealthCollector.UpdateConnectionHealth) &&
            c.GetArguments() is [string name, ConnectionHealth reported, ..] &&
            name == connectionName && reported == health);

    /// <summary>
    /// A bad-session fault is a CONNECTION fault: the request fails and the actor enters
    /// Reconnecting (which pushes bad quality for the connection).
    ///
    /// <para><b>Fails before the fix:</b> the chunk was treated per-tag, so the request was acked
    /// Success and the connection stayed nominally up on a dead session.</para>
    /// </summary>
    [Fact]
    public void BadSessionServiceResultException_IsConnectionLevel_AndDrivesReconnect()
    {
        const string name = "opcua-bad-session";
        var adapter = new FakeBatchDataConnection
        {
            BatchSubscribeThrows = () =>
                new ServiceResultException(StatusCodes.BadSessionIdInvalid, "session is no longer valid")
        };
        var actor = CreateActor(adapter, name);

        actor.Tell(new SubscribeTagsRequest("c1", "inst1", name, ["tag1", "tag2"], DateTimeOffset.UtcNow));

        ExpectMsg<SubscribeTagsResponse>(m => !m.Success && m.ErrorMessage != null, TimeSpan.FromSeconds(5));
        ExpectMsg<ConnectionQualityChanged>(q => q.Quality == QualityCode.Bad, TimeSpan.FromSeconds(5));
    }

    /// <summary>
    /// The narrowness control. <c>BadNodeIdUnknown</c> is a per-node fault: the tags go unresolved
    /// (bad quality, retried on the backoff timer) and the connection is NOT torn down.
    /// </summary>
    [Fact]
    public void BadNodeIdServiceResultException_StaysPerTag_AndDoesNotTearDownTheConnection()
    {
        const string name = "opcua-bad-nodeid";
        var adapter = new FakeBatchDataConnection
        {
            BatchSubscribeThrows = () =>
                new ServiceResultException(StatusCodes.BadNodeIdUnknown, "no such node")
        };
        var actor = CreateActor(adapter, name);

        actor.Tell(new SubscribeTagsRequest("c1", "inst1", name, ["tag1", "tag2"], DateTimeOffset.UtcNow));

        // Per-tag treatment: bad quality per tag, and the request itself is still acked Success
        // (the tags are registered and retried, exactly as an unresolved tag path is).
        FishForMessage<SubscribeTagsResponse>(m => m.Success, TimeSpan.FromSeconds(5));
        Assert.Equal(0, HealthTransitions(name, ConnectionHealth.Disconnected));
    }
}