namespace ZB.MOM.WW.OtOpcUa.AdminUI.Components.Shared.Drivers.Forms;

/// <summary>
///     The rule deciding which primary-host advisory <c>MqttDriverForm</c> shows when
///     <c>Act as Primary Host</c> is on.
/// </summary>
/// <remarks>
///     <para>
///         <b>A plain static rather than markup logic, because this repo has no bUnit.</b> A condition
///         written inline in a <c>.razor</c> file is unreachable from any test, and the failure mode
///         here is specific: an operator who ticks the box with a blank host id must see a
///         <i>refusal</i>, not the ordinary "here is what will happen" note. Getting that backwards
///         tells them a claim is being made when the driver is in fact declining to make one.
///     </para>
///     <para>
///         Deliberately mirrors <c>SparkplugPrimaryHost.DescribeUnusable</c>'s blank-host-id arm. The
///         mode arm is not duplicated: this panel only renders inside the SparkplugB branch of the
///         form, so mode cannot be wrong here.
///     </para>
/// </remarks>
public static class SparkplugPrimaryHostAdvice
{
    /// <summary>
    ///     Describes why a primary-host claim cannot be made for <paramref name="hostId"/>, or
    ///     <see langword="null"/> when it can.
    /// </summary>
    /// <param name="hostId">The Sparkplug host id as typed into the form.</param>
    /// <returns>An operator-facing reason, or <see langword="null"/>.</returns>
    public static string? DescribeBlockingProblem(string? hostId) =>
        string.IsNullOrWhiteSpace(hostId)
            ? "A Sparkplug host claim is published on spBv1.0/STATE/{hostId}, so it needs a Host ID. "
              + "Set one above, or turn this off — the driver will otherwise log a warning at startup "
              + "and publish nothing."
            : null;
}