using System.Collections.Immutable;
using System.Reflection;
using Akka.Actor;
using Akka.Cluster;
using Akka.Configuration;
using Akka.Util;
using Microsoft.Extensions.Logging.Abstractions;
using Shouldly;
using Xunit;
using ZB.MOM.WW.Audit;
using ZB.MOM.WW.OtOpcUa.Cluster;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Redundancy;
using ZB.MOM.WW.OtOpcUa.ControlPlane.Fleet;
using ZB.MOM.WW.OtOpcUa.ControlPlane.Redundancy;

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

/// <summary>
///     R3-04 (01/C-9, census rows 17/20-24/30): a PEER gossiping a miscased plain role (a
///     rolling-upgrade-window peer running an older build — <see cref="EffectiveRoles"/> (T1) already
///     means a node on the FIXED build cannot gossip a miscased role itself) must not read as a
///     stranger to the six production predicates this plan names.
/// </summary>
/// <remarks>
///     <para>
///         <b>Deviation from the plan's stated T5 test (recorded per the execution brief):</b> the
///         plan asked for "a <c>RedundancyStateActor</c> selection case where the member gossips
///         'Driver' and a Primary IS elected". That is not achievable from this repo.
///         <see cref="RedundancyStateActor.SelectOldestUpMemberOfRole"/> /
///         <see cref="RedundancyStateActor.SelectDriverPrimary"/> delegate to
///         <c>ZB.MOM.WW.Health.Akka</c>'s <c>ClusterActiveNode.OldestUpMember</c>, which matches via
///         Akka's OWN <c>Member.HasRole</c> — an ordinal comparison this repo does not own, the exact
///         same class of "not ours to change" the plan itself already carves out for
///         <c>ClusterSingletonOptions.Role</c> (rows 18/19). <see cref="Primary_election_itself_remains_ordinal_and_still_elects_no_one_for_an_all_miscased_pair"/>
///         below pins that TRUE (negative) outcome instead of asserting a false positive.
///     </para>
///     <para>
///         What R3-04 DOES fix and this file proves: every consumer that reads gossiped roles
///         DIRECTLY (not through that external oldest-member helper) is now case-insensitive, so an
///         individual miscased member is no longer invisible to failover candidacy, address
///         reconciliation, or the redundancy snapshot's own role classification.
///     </para>
/// </remarks>
public sealed class GossipedRoleCaseInsensitivityTests
{
    // ---- Pure-unit: ClusterNodeAddressReconcilerActor.FilterOwnClusterDriverMembers ---------------
    // (public static over IEnumerable<Member> — no live cluster needed)

    private static int _memberUid;

    // Akka's Member.Create factories are internal — same reflection idiom as
    // ClusterNodeAddressReconcilerTests.UpMember.
    private static readonly MethodInfo MemberCreate = typeof(Member).GetMethod(
        "Create",
        BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.Public,
        binder: null,
        types:
        [
            typeof(UniqueAddress), typeof(int), typeof(MemberStatus),
            typeof(ImmutableHashSet<string>), typeof(AppVersion),
        ],
        modifiers: null)
        ?? throw new InvalidOperationException("Akka.Cluster.Member.Create(5-arg) not found — Akka API changed");

    private static Member UpMember(string host, int port, params string[] roles) =>
        (Member)MemberCreate.Invoke(null,
        [
            new UniqueAddress(new Address("akka.tcp", "otopcua", host, port), Interlocked.Increment(ref _memberUid)),
            1,
            MemberStatus.Up,
            roles.ToImmutableHashSet(),
            AppVersion.Zero,
        ])!;

    [Fact]
    public void FilterOwnClusterDriverMembers_recognises_a_miscased_driver_role()
    {
        var members = new[] { UpMember("site-a-1", 4053, "Driver", "cluster-SITE-A") };

        var result = ClusterNodeAddressReconcilerActor.FilterOwnClusterDriverMembers(members, "cluster-SITE-A");

        result.ShouldHaveSingleItem();
    }

    [Fact]
    public void FilterOwnClusterDriverMembers_recognises_a_miscased_cluster_role()
    {
        var members = new[] { UpMember("site-a-1", 4053, "driver", "Cluster-SITE-A") };

        // The caller's OWN cluster role names the canonical spelling; the member gossips a different
        // casing ("Cluster-SITE-A") — GossipedRolesHave must still match the two as the same role.
        var result = ClusterNodeAddressReconcilerActor.FilterOwnClusterDriverMembers(members, "cluster-site-a");

        result.ShouldHaveSingleItem();
    }

    // ---- Live single-node cluster: BuildSnapshot classification + ManualFailoverService -----------

    private const int Port = 19_560;

    private static Config NodeConfig(int port) => ConfigurationFactory.ParseString($$"""
        akka {
            loglevel = "WARNING"
            actor.provider = "Akka.Cluster.ClusterActorRefProvider, Akka.Cluster"
            remote.dot-netty.tcp {
                hostname = "127.0.0.1"
                port = {{port}}
            }
            cluster {
                seed-nodes = ["akka.tcp://gossip-case-test@127.0.0.1:{{port}}"]
                roles = ["Driver"]
                min-nr-of-members = 1
                run-coordinated-shutdown-when-down = off
                downing-provider-class = ""
            }
        }
        """);

    private static async Task<ActorSystem> StartSingleNodeAsync()
    {
        var system = ActorSystem.Create("gossip-case-test", NodeConfig(Port));
        var cluster = Akka.Cluster.Cluster.Get(system);
        var deadline = DateTime.UtcNow + TimeSpan.FromSeconds(30);
        while (DateTime.UtcNow < deadline)
        {
            if (cluster.State.Members.Any(m => m.Status == MemberStatus.Up)) return system;
            await Task.Delay(100);
        }

        await system.Terminate();
        throw new TimeoutException("node never came Up");
    }

    [Fact]
    public async Task A_member_gossiping_a_miscased_driver_role_classifies_Secondary_not_Detached()
    {
        // Pins the fix that IS achievable: BuildSnapshot's own role classification (member.Roles
        // Contains -> GossipedRolesHave) no longer reads a genuinely-driver-but-miscased member as
        // Detached, even though (see class remarks) it can never be named Primary by itself.
        var system = await StartSingleNodeAsync();
        try
        {
            var tcs = new TaskCompletionSource<RedundancyStateChanged>(
                TaskCreationOptions.RunContinuationsAsynchronously);
            system.ActorOf(
                RedundancyStateActor.Props(broadcast: msg =>
                {
                    if (msg is RedundancyStateChanged changed) tcs.TrySetResult(changed);
                }),
                $"redundancy-{Guid.NewGuid():N}");

            var snapshot = await tcs.Task.WaitAsync(TimeSpan.FromSeconds(15));

            var node = snapshot.Nodes.ShouldHaveSingleItem();
            node.Role.ShouldBe(
                RedundancyRole.Secondary,
                "gossiping 'Driver' must not read as Detached — it is a real driver member, just "
                + "miscased; BEFORE R3-04 this was Detached (ordinal Contains(\"driver\") on \"Driver\")");
        }
        finally
        {
            await system.Terminate();
        }
    }

    /// <summary>
    ///     THE recorded deviation: proves the residual gap is real, not assumed. A pair (here,
    ///     trivially, a single node) that gossips ONLY 'Driver' still elects no Primary — because that
    ///     decision runs through Akka's own ordinal <c>Member.HasRole</c> inside the vendored
    ///     <c>ClusterActiveNode.OldestUpMember</c>, which this repo cannot patch. Tracked as a
    ///     follow-up against <c>ZB.MOM.WW.Health.Akka</c>, not closed by R3-04.
    /// </summary>
    [Fact]
    public async Task Primary_election_itself_remains_ordinal_and_still_elects_no_one_for_an_all_miscased_pair()
    {
        var system = await StartSingleNodeAsync();
        try
        {
            var members = Akka.Cluster.Cluster.Get(system).State.Members;

            RedundancyStateActor.SelectOldestUpMemberOfRole(members, "driver").ShouldBeNull(
                "known residual (R3-04 execution notes): SelectOldestUpMemberOfRole delegates to "
                + "ClusterActiveNode.OldestUpMember -> Akka's own ordinal Member.HasRole, which this "
                + "repo does not own — GossipedRolesHave cannot reach inside it");
        }
        finally
        {
            await system.Terminate();
        }
    }

    [Fact]
    public async Task ManualFailoverService_recognises_a_miscased_driver_node_as_a_candidate()
    {
        // FailOverCore refuses below 2 driver members (nothing to fail over TO), so this single-node
        // fixture exercises GetSnapshot()'s PrimaryAddress instead — which shares the same
        // OrderedDrivers candidate selection this test is actually about.
        var system = await StartSingleNodeAsync();
        try
        {
            var service = new ManualFailoverService(
                () => system, new RecordingAuditWriter(), NullLogger<ManualFailoverService>.Instance);

            var snapshot = service.GetSnapshot();

            snapshot.PrimaryAddress.ShouldNotBeNull();
            snapshot.PrimaryAddress!.ShouldContain(Port.ToString());
        }
        finally
        {
            await system.Terminate();
        }
    }

    private sealed class RecordingAuditWriter : IAuditWriter
    {
        public Task WriteAsync(AuditEvent auditEvent, CancellationToken cancellationToken = default) =>
            Task.CompletedTask;
    }
}