using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.AdminUI.Hosts;

namespace ZB.MOM.WW.OtOpcUa.AdminUI.Tests.Hosts;

/// <summary>
///     R04 P4: a driver health publish only marks <c>/hosts</c> dirty; the page's 5 s tick rebuilds and
///     renders at most once, however many publishes arrived.
/// </summary>
[Trait("Category", "Unit")]
public sealed class HostsRenderCoalescingTests
{
    [Fact]
    public void Many_marks_coalesce_into_one_consume()
    {
        var flag = new CoalescingDirtyFlag();
        for (var i = 0; i < 200; i++) flag.Mark();

        flag.TryConsume().ShouldBeTrue();
        flag.TryConsume().ShouldBeFalse();
    }

    [Fact]
    public void A_fresh_flag_is_clean_and_a_mark_after_consume_is_seen()
    {
        var flag = new CoalescingDirtyFlag();
        flag.TryConsume().ShouldBeFalse();

        // Positive control: the flag is not stuck clean.
        flag.Mark();
        flag.TryConsume().ShouldBeTrue();
    }

    [Fact]
    public void Concurrent_marks_are_never_lost()
    {
        var flag = new CoalescingDirtyFlag();
        Parallel.For(0, 1000, _ => flag.Mark());

        flag.TryConsume().ShouldBeTrue();
    }

    /// <summary>Source pin (no bUnit): the snapshot handler must not render or rebuild.</summary>
    [Fact]
    public void Snapshot_handler_only_marks_and_the_tick_consumes()
    {
        var src = AdminUiSource.Read("Components", "Pages", "Hosts.razor");

        src.ShouldContain("private void OnSnapshotChanged(DriverHealthChanged _) => _driversDirty.Mark();");
        src.ShouldContain("if (_driversDirty.TryConsume() | configChanged) RebuildDriverGroups();");
    }
}