using Akka.Cluster.Hosting;
using Akka.Cluster.Hosting.SBR;
using Shouldly;
using Xunit;

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

/// <summary>
/// Guards the split-brain-resolver ACTIVATION (arch-review 03/S1). The <c>split-brain-resolver</c>
/// HOCON block is inert on its own; the resolver only runs when the typed
/// <see cref="ClusterOptions.SplitBrainResolver"/> is set. These tests assert
/// <see cref="ServiceCollectionExtensions.BuildClusterOptions"/> registers it, so a future refactor
/// cannot silently drop back to Akka's default NoDowning (the exact "built-but-never-wired" failure
/// mode this finding described).
/// </summary>
public sealed class SplitBrainResolverActivationTests
{
    private static AkkaClusterOptions SampleOptions() => new()
    {
        SeedNodes = new[] { "akka.tcp://otopcua@127.0.0.1:4053" },
        Roles = new[] { "admin", "driver" },
    };

    /// <summary>Verifies the cluster options carry a split-brain resolver (provider gets activated).</summary>
    [Fact]
    public void BuildClusterOptions_activates_a_split_brain_resolver()
    {
        var options = ServiceCollectionExtensions.BuildClusterOptions(SampleOptions());

        options.SplitBrainResolver.ShouldNotBeNull(
            "SplitBrainResolver must be set — without it the cluster runs default NoDowning and never fails over on a hard crash.");
    }

    /// <summary>Verifies the resolver is keep-oldest with down-if-alone (correct for a 2-node pair).</summary>
    [Fact]
    public void BuildClusterOptions_uses_keep_oldest_with_down_if_alone()
    {
        var options = ServiceCollectionExtensions.BuildClusterOptions(SampleOptions());

        var keepOldest = options.SplitBrainResolver.ShouldBeOfType<KeepOldestOption>();
        keepOldest.DownIfAlone.ShouldBe(true);
    }

    /// <summary>Verifies seed nodes and roles are still threaded through unchanged.</summary>
    [Fact]
    public void BuildClusterOptions_preserves_seed_nodes_and_roles()
    {
        var input = SampleOptions();

        var options = ServiceCollectionExtensions.BuildClusterOptions(input);

        options.SeedNodes.ShouldBe(input.SeedNodes);
        options.Roles.ShouldBe(input.Roles);
    }
}