lmxopcua/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/DriverTestConnectButton.razor

@using ZB.MOM.WW.OtOpcUa.AdminUI.Clients
@using ZB.MOM.WW.OtOpcUa.Commons.Messages.Admin
@inject AdminProbeService Probe
@implements IAsyncDisposable

<div class="d-inline-flex align-items-center gap-2">
    <button type="button" class="btn btn-outline-primary btn-sm" disabled="@_busy" @onclick="OnClickAsync"
            title="@(_lastBudgetSeconds is { } b ? $"Probe budget: {b} s" : "Probe budget: the driver's configured probe timeout")">
        @if (_busy) { <span class="spinner-border spinner-border-sm me-1"></span> }
        Test Connect
    </button>

    @if (_result is not null)
    {
        @if (_result.Ok)
        {
            <span class="chip chip-ok" title="@($"Probe succeeded in {_result.LatencyMs:F0} ms")">
                OK &middot; @_result.LatencyMs?.ToString("F0") ms
            </span>
        }
        else
        {
            <span class="chip chip-bad" title="@_result.Message">
                Failed &middot; @DisplayText.Abbreviate(_result.Message, 60)
            </span>
        }
    }
</div>

@code {
    /// <summary>Driver type key — must match an installed <c>IDriverProbe.DriverType</c>.</summary>
    [Parameter, EditorRequired] public string DriverType { get; set; } = "";

    /// <summary>Callback that returns the current form config as JSON. Called at click time.</summary>
    [Parameter, EditorRequired] public Func<string> GetConfigJson { get; set; } = () => "{}";

    /// <summary>
    ///     Fallback probe budget, used only when the config JSON carries no positive
    ///     <c>ProbeTimeoutSeconds</c> and the driver has no documented default (<c>TestConnectBudget.DriverDefaults</c>). The configured value wins (it is every driver's documented "Test Connect
    ///     probe timeout"), so it can lengthen the budget as well as shorten it. Clamped to [1, 60] s.
    /// </summary>
    [Parameter] public int TimeoutSeconds { get; set; } = TestConnectBudget.DefaultSeconds;

    private const int ClearAfterMs = 30_000;

    private bool _busy;
    private int? _lastBudgetSeconds;
    private TestDriverConnectResult? _result;

    // System.Threading.Timer (it replaced an Elapsed-event timer with an async void lambda): DisposeAsync awaits an
    // in-flight callback, and the callback body never throws onto the thread pool (R04 L2). The generation
    // makes a superseded timer's late fire a no-op, so it cannot clear a newer result.
    private System.Threading.Timer? _clearTimer;
    private int _resultGeneration;
    private volatile bool _disposed;

    private async Task OnClickAsync()
    {
        _busy = true;
        _result = null;
        StateHasChanged();
        try
        {
            var json = GetConfigJson() ?? "{}";
            var budget = TestConnectBudget.Resolve(json, TimeoutSeconds, DriverType);
            _lastBudgetSeconds = budget;
            _result = await Probe.TestAsync(DriverType, json, budget);
        }
        catch (Exception ex)
        {
            _result = new TestDriverConnectResult(false, ex.Message, null, Guid.Empty);
        }
        finally
        {
            _busy = false;
            ScheduleClear();
            if (!_disposed) StateHasChanged();
        }
    }

    private void ScheduleClear()
    {
        if (_disposed) return;
        var generation = ++_resultGeneration;
        _clearTimer?.Dispose();
        _clearTimer = new System.Threading.Timer(_ => _ = ClearAsync(generation), null, ClearAfterMs, Timeout.Infinite);
    }

    private async Task ClearAsync(int generation)
    {
        try
        {
            await InvokeAsync(() =>
            {
                if (_disposed || generation != _resultGeneration) return;
                _result = null;
                StateHasChanged();
            });
        }
        catch (Exception ex) when (ex is ObjectDisposedException or InvalidOperationException)
        {
            // The circuit went away between the fire and the render — nothing to clear.
        }
    }

    /// <inheritdoc />
    public async ValueTask DisposeAsync()
    {
        _disposed = true;
        if (_clearTimer is not null) await _clearTimer.DisposeAsync();
    }
}