ScadaBridge/tests/ZB.MOM.WW.ScadaBridge.ClusterInfrastructure.Tests/ClusterOptionsValidatorTests.cs

using Microsoft.Extensions.Options;

namespace ZB.MOM.WW.ScadaBridge.ClusterInfrastructure.Tests;

/// <summary>
/// CI-004: Tests that <see cref="ClusterOptionsValidator"/> rejects the
/// catastrophic misconfigurations the design doc warns against — a
/// <c>MinNrOfMembers</c> other than 1, an unsupported split-brain strategy,
/// empty seed nodes, and timings where the heartbeat is not below the
/// failure-detection threshold.
/// </summary>
public class ClusterOptionsValidatorTests
{
    private static ClusterOptions ValidOptions() => new()
    {
        SeedNodes = new List<string> { "akka.tcp://scadabridge@node1:8081", "akka.tcp://scadabridge@node2:8081" },
        SplitBrainResolverStrategy = "keep-oldest",
        StableAfter = TimeSpan.FromSeconds(15),
        HeartbeatInterval = TimeSpan.FromSeconds(2),
        FailureDetectionThreshold = TimeSpan.FromSeconds(10),
        MinNrOfMembers = 1,
        DownIfAlone = true
    };

    [Fact]
    public void DefaultOptions_AreValid()
    {
        var result = new ClusterOptionsValidator().Validate(null, ValidOptions());

        Assert.True(result.Succeeded, result.FailureMessage);
    }

    [Fact]
    public void MinNrOfMembers_NotOne_FailsValidation()
    {
        var options = ValidOptions();
        options.MinNrOfMembers = 2;

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Failed);
        Assert.Contains("MinNrOfMembers", result.FailureMessage);
    }

    [Theory]
    [InlineData("keep-majority")]
    [InlineData("static-quorum")]
    [InlineData("nonsense")]
    public void UnsupportedSplitBrainStrategy_FailsValidation(string strategy)
    {
        var options = ValidOptions();
        options.SplitBrainResolverStrategy = strategy;

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Failed);
        Assert.Contains("SplitBrainResolverStrategy", result.FailureMessage);
    }

    [Fact]
    public void EmptySeedNodes_FailsValidation()
    {
        var options = ValidOptions();
        options.SeedNodes = new List<string>();

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Failed);
        Assert.Contains("SeedNodes", result.FailureMessage);
    }

    [Fact]
    public void SingleSeed_WithoutAcknowledgement_Fails()
    {
        var options = ValidOptions();
        options.SeedNodes = new List<string> { "akka.tcp://scadabridge@h:8081" };

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Failed);
        Assert.Contains("AllowSingleNodeCluster", result.FailureMessage);
    }

    [Fact]
    public void SingleSeed_WithAllowSingleNodeCluster_Passes()
    {
        // Review 01 [Low]: the shipped single-node artifact satisfied the 2-seed
        // rule with a phantom seed the node dials forever. An explicit
        // acknowledgement flag replaces the fiction.
        var options = ValidOptions();
        options.SeedNodes = new List<string> { "akka.tcp://scadabridge@h:8081" };
        options.AllowSingleNodeCluster = true;

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Succeeded, result.FailureMessage);
    }

    [Fact]
    public void EmptySeeds_FailsEvenWithFlag()
    {
        // Zero seeds is always invalid — the flag lowers the floor to 1, not 0.
        var options = ValidOptions();
        options.SeedNodes = new List<string>();
        options.AllowSingleNodeCluster = true;

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Failed);
        Assert.Contains("SeedNodes", result.FailureMessage);
    }

    [Fact]
    public void SingleSeedNode_FailsValidation()
    {
        // CI-012: design doc says "both nodes are seed nodes" — a single-seed
        // configuration defeats the no-startup-ordering-dependency guarantee and
        // must be rejected by the contract owner's validator, not just by the
        // Host's startup validator.
        var options = ValidOptions();
        options.SeedNodes = new List<string> { "akka.tcp://scadabridge@node1:8081" };

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Failed);
        Assert.Contains("SeedNodes", result.FailureMessage);
        Assert.Contains("2", result.FailureMessage);
    }

    [Fact]
    public void HeartbeatNotBelowFailureThreshold_FailsValidation()
    {
        var options = ValidOptions();
        options.HeartbeatInterval = TimeSpan.FromSeconds(10);
        options.FailureDetectionThreshold = TimeSpan.FromSeconds(10);

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Failed);
        Assert.Contains("HeartbeatInterval", result.FailureMessage);
    }

    [Fact]
    public void NonPositiveStableAfter_FailsValidation()
    {
        var options = ValidOptions();
        options.StableAfter = TimeSpan.Zero;

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Failed);
        Assert.Contains("StableAfter", result.FailureMessage);
    }

    [Fact]
    public void DownIfAloneFalse_UnderKeepOldest_FailsValidation()
    {
        var options = ValidOptions();
        options.SplitBrainResolverStrategy = "keep-oldest";
        options.DownIfAlone = false;

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Failed);
        Assert.Contains("DownIfAlone", result.FailureMessage);
    }

    [Fact]
    public void AutoDownStrategy_Passes()
    {
        // Decision 2026-07-21: 'auto-down' is the supported availability-first
        // posture — either-node crash fails over; dual-active on a real partition
        // is the accepted trade.
        var options = ValidOptions();
        options.SplitBrainResolverStrategy = "auto-down";

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Succeeded, result.FailureMessage);
    }

    [Fact]
    public void DownIfAloneFalse_UnderAutoDown_Passes()
    {
        // DownIfAlone is a keep-oldest knob; under auto-down it is inert and must
        // not block startup.
        var options = ValidOptions();
        options.SplitBrainResolverStrategy = "auto-down";
        options.DownIfAlone = false;

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Succeeded, result.FailureMessage);
    }

    [Fact]
    public void Validate_AccumulatesAllFailures()
    {
        var options = new ClusterOptions
        {
            SeedNodes = new List<string>(),
            SplitBrainResolverStrategy = "keep-majority",
            MinNrOfMembers = 2,
            StableAfter = TimeSpan.Zero,
            HeartbeatInterval = TimeSpan.FromSeconds(20),
            FailureDetectionThreshold = TimeSpan.FromSeconds(10)
        };

        var result = new ClusterOptionsValidator().Validate(null, options);

        Assert.True(result.Failed);
        Assert.Contains("SeedNodes", result.FailureMessage);
        Assert.Contains("SplitBrainResolverStrategy", result.FailureMessage);
        Assert.Contains("MinNrOfMembers", result.FailureMessage);
        Assert.Contains("StableAfter", result.FailureMessage);
        Assert.Contains("HeartbeatInterval", result.FailureMessage);
    }
}