using ZB.MOM.WW.OtOpcUa.Commons.Messages.Drivers;

namespace ZB.MOM.WW.OtOpcUa.AdminUI.Hubs;

/// <summary>
///     Singleton last-snapshot-per-<c>(instance, host)</c> cache of driver resilience status
///     (breaker open / consecutive failures / in-flight depth). Populated by
///     <c>DriverResilienceStatusBridge</c> as it forwards <c>driver-resilience-status</c> DPS
///     messages; read in-process by the driver status panel's resilience section via
///     <see cref="SnapshotChanged"/> + <see cref="GetForInstance"/>. Mirrors
///     <see cref="IDriverStatusSnapshotStore"/> — the panel reads this singleton directly instead of
///     opening a self-targeted SignalR connection (which a server-side Blazor component cannot reach
///     behind a reverse proxy).
/// </summary>
public interface IDriverResilienceStatusStore
{
    /// <summary>Stores or replaces the last-known resilience snapshot for a <c>(instance, host)</c> pair.</summary>
    /// <param name="snapshot">The resilience status snapshot to store.</param>
    void Upsert(DriverResilienceStatusChanged snapshot);

    /// <summary>Returns every stored host snapshot for one driver instance (empty if none).</summary>
    /// <param name="driverInstanceId">The driver instance's stable logical ID.</param>
    /// <returns>The per-host resilience snapshots for that instance.</returns>
    IReadOnlyList<DriverResilienceStatusChanged> GetForInstance(string driverInstanceId);

    /// <summary>Returns a point-in-time snapshot of every tracked <c>(instance, host)</c> pair.</summary>
    /// <returns>A read-only collection of the last-known resilience snapshot for each pair.</returns>
    IReadOnlyCollection<DriverResilienceStatusChanged> GetAll();

    /// <summary>
    ///     Evicts every snapshot whose driver instance is not in <paramref name="configuredInstanceIds"/>
    ///     <b>and</b> whose last publish is older than <paramref name="olderThanUtc"/>. The stores have no other
    ///     removal path, so a deleted (or re-created under a new id) driver would otherwise keep its last
    ///     snapshot until the process restarts. Both conditions are required: the configured set comes from
    ///     the AUTHORED (draft) table, so a driver deleted in <c>/raw</c> but not yet deployed is still
    ///     running and still publishing — it must stay visible until a deploy actually stops it and its
    ///     snapshot goes stale. The <c>/hosts</c> page calls this after each successful config load; a failed
    ///     load must never call it.
    /// </summary>
    /// <param name="configuredInstanceIds">The configured driver-instance ids to keep. The set's own
    ///     comparer decides matching.</param>
    /// <param name="olderThanUtc">Only an unconfigured entry published before this instant is evicted.</param>
    /// <returns>The number of entries removed.</returns>
    int EvictUnconfiguredStale(IReadOnlySet<string> configuredInstanceIds, DateTime olderThanUtc);

    /// <summary>
    ///     Raised after every <see cref="Upsert"/> with the just-stored snapshot. Lets the Blazor Server
    ///     driver status panel receive live updates by reading this singleton directly. Handlers run on
    ///     the caller's thread (the bridge actor), so subscribers must marshal to their own sync context.
    /// </summary>
    event Action<DriverResilienceStatusChanged>? SnapshotChanged;
}