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>
///     The bridge that carries the Primary-gate decision out of the actor and into
///     <see cref="IRedundancyRoleView"/>, where the alarm store-and-forward drain can read it.
/// </summary>
/// <remarks>
///     <para>
///         The drain runs on a timer owned by the sink, not on a mailbox, so it cannot receive
///         <see cref="RedundancyStateChanged"/> itself — but it must be Primary-scoped, because
///         the queue it drains replicates to the pair peer and two draining nodes would deliver
///         every alarm event twice.
///     </para>
///     <para>
///         These cases mirror <see cref="DriverHostActorPrimaryGateTests"/>'s matrix on purpose:
///         the view must reach exactly the same verdict as the inbound-write and native-ack gates,
///         because a second, subtly different notion of "am I the Primary" is how a pair ends up
///         with one node writing and neither draining.
///     </para>
/// </remarks>
public sealed class DriverHostActorRoleViewTests : RuntimeActorTestBase
{
    private static readonly NodeId TestNode = NodeId.Parse("driver-roleview-test");
    private static readonly TimeSpan Timeout = TimeSpan.FromSeconds(5);

    /// <summary>
    ///     Before any snapshot arrives the view must read open, not closed.
    /// </summary>
    /// <remarks>
    ///     A deployment that runs no redundancy never publishes here at all. Defaulting closed
    ///     would silently stop its alarm history forever — the exact failure the drain gate exists
    ///     to avoid causing.
    /// </remarks>
    [Fact]
    public void An_unpublished_view_reads_as_primary()
    {
        new RedundancyRoleView().ShouldServiceAsPrimary.ShouldBeTrue();
    }

    [Fact]
    public void Secondary_role_closes_the_view()
    {
        var view = SpawnAndTellRole(RedundancyRole.Secondary, driverMemberCount: 2);

        AwaitAssert(() => view.ShouldServiceAsPrimary.ShouldBeFalse(), duration: Timeout);
    }

    [Fact]
    public void Primary_role_opens_the_view()
    {
        var view = SpawnAndTellRole(RedundancyRole.Primary, driverMemberCount: 2);

        AwaitAssert(() => view.ShouldServiceAsPrimary.ShouldBeTrue(), duration: Timeout);
    }

    /// <summary>Unknown role + a real driver peer ⇒ closed, matching the write gate's default-DENY.</summary>
    [Fact]
    public void Unknown_role_with_a_driver_peer_closes_the_view()
    {
        // A snapshot that never names this node is how the role stays unknown in practice — the
        // documented identity-mismatch shape, not a contrived case.
        var view = SpawnAndTellForeignSnapshot(driverMemberCount: 2);

        AwaitAssert(() => view.ShouldServiceAsPrimary.ShouldBeFalse(), duration: Timeout);
    }

    /// <summary>Unknown role + no driver peer ⇒ open, preserving the single-node posture.</summary>
    [Fact]
    public void Unknown_role_without_a_driver_peer_leaves_the_view_open()
    {
        var view = SpawnAndTellForeignSnapshot(driverMemberCount: 1);

        AwaitAssert(() => view.ShouldServiceAsPrimary.ShouldBeTrue(), duration: Timeout);
    }

    /// <summary>A demotion must move the view, not just an initial promotion.</summary>
    [Fact]
    public void A_demotion_closes_a_previously_open_view()
    {
        var view = new RedundancyRoleView();
        var host = SpawnHost(view, driverMemberCount: 2);

        host.Tell(Snapshot(TestNode, RedundancyRole.Primary));
        AwaitAssert(() => view.ShouldServiceAsPrimary.ShouldBeTrue(), duration: Timeout);

        host.Tell(Snapshot(TestNode, RedundancyRole.Secondary));
        AwaitAssert(() => view.ShouldServiceAsPrimary.ShouldBeFalse(), duration: Timeout);
    }

    // ---------------- helpers ----------------

    private RedundancyRoleView SpawnAndTellRole(RedundancyRole role, int driverMemberCount)
    {
        var view = new RedundancyRoleView();
        SpawnHost(view, driverMemberCount).Tell(Snapshot(TestNode, role));
        return view;
    }

    private RedundancyRoleView SpawnAndTellForeignSnapshot(int driverMemberCount)
    {
        var view = new RedundancyRoleView();
        SpawnHost(view, driverMemberCount).Tell(Snapshot(NodeId.Parse("some-other-node"), RedundancyRole.Primary));
        return view;
    }

    private IActorRef SpawnHost(IRedundancyRoleView view, int driverMemberCount) =>
        Sys.ActorOf(DriverHostActor.Props(
            NewInMemoryDbFactory(),
            TestNode,
            coordinator: null,
            driverMemberCountProvider: () => driverMemberCount,
            redundancyRoleView: view));

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