using Akka.Actor;
using Akka.Cluster;
using ZB.MOM.WW.ScadaBridge.Communication.ClusterState;

namespace ZB.MOM.WW.ScadaBridge.IntegrationTests.Cluster;

/// <summary>
/// Real-cluster proof for the central→site failover relay. The unit tests in
/// <c>SiteCommunicationActorTests</c> pin the routing and guard logic with the failover action
/// stubbed out; this pins the part they cannot — that the shared
/// <see cref="ClusterFailoverCoordinator"/> actually moves a SITE pair when scoped to the
/// site-specific role.
///
/// <para>The site-specific role scope is the load-bearing detail: site singletons (the
/// Deployment Manager) are placed on <c>site-{SiteId}</c>, not on the base <c>Site</c> role, so
/// failing over the wrong scope would move the wrong node.</para>
/// </summary>
public sealed class SiteFailoverRelayTests
{
    /// <summary>Verifies that failing over a site pair moves the oldest node and the survivor takes over.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task Failing_over_a_site_pair_moves_the_oldest_and_the_survivor_takes_over()
    {
        // A site pair, both nodes carrying the site-specific role.
        await using var f = await TwoNodeClusterFixture.StartAsync(role: "site-SiteA");
        var oldest = Akka.Cluster.Cluster.Get(f.NodeA);
        Assert.True(ActiveNodeEvaluator.SelfIsOldestUp(oldest, "site-SiteA"),
            "precondition: NodeA must be the active (oldest Up) site node");

        // Issued from the other node, as the relay does when contact rotation lands there.
        var target = ClusterFailoverCoordinator.FailOverOldest(f.NodeB, "site-SiteA");

        Assert.Equal(oldest.SelfAddress, target);
        await f.NodeA.WhenTerminated.WaitAsync(TimeSpan.FromSeconds(30));
        await TwoNodeClusterFixture.WaitForMemberRemoved(f.NodeB, oldest.SelfAddress, TimeSpan.FromSeconds(30));
        Assert.True(ActiveNodeEvaluator.SelfIsOldestUp(Akka.Cluster.Cluster.Get(f.NodeB), "site-SiteA"));
    }

    /// <summary>Verifies that a site role scope matching no member is refused.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task A_site_role_scope_that_matches_no_member_is_refused()
    {
        // Guards the role-scoping mistake directly: asking for a site that isn't this pair
        // must find no members and refuse, rather than falling back to some other node.
        await using var f = await TwoNodeClusterFixture.StartAsync(role: "site-SiteA");

        var target = ClusterFailoverCoordinator.FailOverOldest(f.NodeB, "site-SiteB");

        Assert.Null(target);
        // Positive control: the pair is untouched and still fully formed.
        await TwoNodeClusterFixture.WaitForMembersUp(f.NodeB, 2, TimeSpan.FromSeconds(10));
    }
}