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

namespace ZB.MOM.WW.OtOpcUa.Runtime.Tests.Drivers;

/// <summary>
///     Gitea #674 review — the OPC UA HistoryUpdate verdict (<see cref="IHistoryUpdateRoleView"/>) is the Primary
///     data-plane verdict but CLOSED until this node's first redundancy snapshot, so both nodes of a pair cannot accept a
///     HistoryUpdate during the pre-join boot window (where the data-plane verdict allows: member count 0/1). A single node
///     still opens — its own redundancy singleton names it Primary in its first snapshot.
/// </summary>
/// <remarks>
///     Assertions are on what was PUBLISHED, in order, so a missing publish cannot pass for a closed seed.
/// </remarks>
public sealed class DriverHostActorHistoryUpdateRoleViewTests : RuntimeActorTestBase
{
    private static readonly NodeId TestNode = NodeId.Parse("driver-history-update-test");
    private static readonly TimeSpan Timeout = PresenceBudget;

    /// <summary>The boot window: a single-driver node (data-plane verdict ALLOW) publishes CLOSED for HistoryUpdate until
    /// a snapshot arrives; its first snapshot naming it Primary opens it.</summary>
    [Fact]
    public void A_single_node_is_closed_until_its_first_snapshot_then_opens()
    {
        var view = new RecordingHistoryUpdateRoleView();
        var host = SpawnHost(view, () => 1);

        AwaitAssert(() => view.Published.ShouldBe([false]), duration: Timeout);

        host.Tell(Snapshot(RedundancyRole.Primary));
        AwaitAssert(() => view.Published[^1].ShouldBeTrue(), duration: Timeout);
    }

    /// <summary>Once a snapshot has arrived, an unknown role on a single-driver cluster (a snapshot that omits this
    /// node) follows the data-plane rule and opens — a real verdict exists, it just does not name us.</summary>
    [Fact]
    public void After_a_snapshot_an_unknown_role_follows_the_data_plane_rule()
    {
        var view = new RecordingHistoryUpdateRoleView();
        var host = SpawnHost(view, () => 1);
        AwaitAssert(() => view.Published.ShouldBe([false]), duration: Timeout);

        host.Tell(new RedundancyStateChanged([], CorrelationId.NewId()));
        AwaitAssert(() => view.Published[^1].ShouldBeTrue(), duration: Timeout);
    }

    /// <summary>A Secondary stays closed after its snapshot; becoming Primary opens it.</summary>
    [Fact]
    public void A_secondary_stays_closed_and_a_promotion_opens()
    {
        var view = new RecordingHistoryUpdateRoleView();
        var host = SpawnHost(view, () => 2);
        AwaitAssert(() => view.Published.ShouldBe([false]), duration: Timeout);

        host.Tell(Snapshot(RedundancyRole.Secondary));
        AwaitAssert(() => view.Published.Count.ShouldBeGreaterThanOrEqualTo(2), duration: Timeout);
        view.Published.ShouldAllBe(v => !v);

        host.Tell(Snapshot(RedundancyRole.Primary));
        AwaitAssert(() => view.Published[^1].ShouldBeTrue(), duration: Timeout);
    }

    /// <summary>The policy itself: no snapshot ⇒ closed whatever the role/count; with one ⇒ the data-plane verdict.</summary>
    [Theory]
    [InlineData(false, null, 0, false)]
    [InlineData(false, null, 1, false)]
    [InlineData(false, RedundancyRole.Primary, 1, false)]
    [InlineData(true, null, 1, true)]
    [InlineData(true, null, 2, false)]
    [InlineData(true, RedundancyRole.Primary, 2, true)]
    [InlineData(true, RedundancyRole.Secondary, 2, false)]
    [InlineData(true, RedundancyRole.Detached, 1, false)]
    public void Policy_is_the_data_plane_verdict_gated_on_a_snapshot(
        bool snapshot, RedundancyRole? role, int members, bool expected) =>
        PrimaryGatePolicy.ShouldServeHistoryUpdate(snapshot, role, members).ShouldBe(expected);

    /// <summary>The production view is seeded CLOSED (unlike the data-plane verdict's allow seed).</summary>
    [Fact]
    public void The_role_view_is_seeded_closed()
    {
        var view = new RedundancyRoleView();
        view.ShouldServeHistoryUpdate.ShouldBeFalse();
        view.ShouldActAsPrimary.ShouldBeTrue("control: the data-plane seed is the single-node allow");
        view.PublishHistoryUpdateRole(true);
        view.ShouldServeHistoryUpdate.ShouldBeTrue();
    }

    private IActorRef SpawnHost(IHistoryUpdateRoleView view, Func<int> driverMemberCount) =>
        Sys.ActorOf(DriverHostActor.Props(
            NewInMemoryDbFactory(),
            TestNode,
            ackRouter: null,
            driverMemberCountProvider: driverMemberCount,
            historyUpdateRoleView: view));

    private static RedundancyStateChanged Snapshot(RedundancyRole role) =>
        new(
            [
                new NodeRedundancyState(TestNode, role,
                    IsClusterLeader: role == RedundancyRole.Primary,
                    IsDriverPrimary: role == RedundancyRole.Primary,
                    AsOfUtc: DateTime.UtcNow),
            ],
            CorrelationId.NewId());

    /// <summary>Remembers every published verdict, in order.</summary>
    private sealed class RecordingHistoryUpdateRoleView : IHistoryUpdateRoleView
    {
        private readonly List<bool> _published = [];
        private readonly Lock _gate = new();

        public IReadOnlyList<bool> Published
        {
            get { lock (_gate) return _published.ToArray(); }
        }

        public bool ShouldServeHistoryUpdate
        {
            get { lock (_gate) return _published.Count > 0 && _published[^1]; }
        }

        public void PublishHistoryUpdateRole(bool shouldServeHistoryUpdate)
        {
            lock (_gate) _published.Add(shouldServeHistoryUpdate);
        }
    }
}