namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;

/// <summary>
///     Health snapshot a driver returns to the Core. Drives the status dashboard,
///     ServiceLevel computation, and Bad-quality fan-out decisions.
/// </summary>
/// <param name="State">Current driver-instance state.</param>
/// <param name="LastSuccessfulRead">Timestamp of the most recent successful equipment read; null if never.</param>
/// <param name="LastError">Most recent error message; null when state is Healthy.</param>
/// <param name="Diagnostics">
///     Optional driver-attributable counters/metrics surfaced for the <c>driver-diagnostics</c>
///     RPC (introduced for Modbus task #154). Drivers populate the dictionary with stable,
///     well-known keys (e.g. <c>PublishRequestCount</c>, <c>NotificationsPerSecond</c>);
///     Core treats it as opaque metadata. Defaulted to an empty read-only dictionary so
///     existing drivers and call-sites that don't construct this field stay back-compat.
/// </param>
public sealed record DriverHealth(
    DriverState State,
    DateTime? LastSuccessfulRead,
    string? LastError,
    IReadOnlyDictionary<string, double>? Diagnostics = null)
{
    /// <summary>Driver-attributable counters, empty when the driver doesn't surface any.</summary>
    public IReadOnlyDictionary<string, double> DiagnosticsOrEmpty
        => Diagnostics ?? EmptyDiagnostics;

    private static readonly IReadOnlyDictionary<string, double> EmptyDiagnostics
        = new Dictionary<string, double>(0);
}

/// <summary>Driver-instance lifecycle state.</summary>
public enum DriverState
{
    /// <summary>Driver has not been initialized yet.</summary>
    Unknown,

    /// <summary>Driver is in the middle of <see cref="IDriver.InitializeAsync"/> or <see cref="IDriver.ReinitializeAsync"/>.</summary>
    Initializing,

    /// <summary>Driver is connected and serving data.</summary>
    Healthy,

    /// <summary>Driver is connected but reporting degraded data (e.g. some equipment unreachable, some tags Bad).</summary>
    Degraded,

    /// <summary>Driver lost connection to its data source; reconnecting in the background.</summary>
    Reconnecting,

    /// <summary>
    ///     Driver hit an unrecoverable error and stopped trying.
    ///     Operator must reinitialize via Admin UI; nodes report Bad quality.
    /// </summary>
    Faulted,
}