using ScadaLink.AuditLog.Payload;

namespace ScadaLink.AuditLog.Central;

/// <summary>
/// Audit Log (#23) M6 Bundle E (T9) — bridges
/// <see cref="IAuditRedactionFailureCounter"/> (incremented by
/// <see cref="DefaultAuditPayloadFilter"/> every time a header / body / SQL
/// parameter redactor stage throws and the filter has to over-redact the
/// offending field) into <see cref="AuditCentralHealthSnapshot"/> so the
/// failure surfaces on the central health surface as
/// <c>AuditCentralHealthSnapshot.AuditRedactionFailure</c>.
/// </summary>
/// <remarks>
/// <para>
/// <b>Site vs central.</b> M5 Bundle C wired the SITE-side bridge
/// (<see cref="ScadaLink.AuditLog.Site.HealthMetricsAuditRedactionFailureCounter"/>),
/// which routes increments into the site health report payload's
/// <c>AuditRedactionFailure</c> field. That handles redactor failures on the
/// site SQLite hot-path (FallbackAuditWriter). M6 Bundle E (T9) adds the
/// MIRROR bridge here so the same payload filter — when it runs on the
/// central <see cref="CentralAuditWriter"/> /
/// <see cref="AuditLogIngestActor"/> paths — surfaces its failures on the
/// central dashboard rather than disappearing into a NoOp.
/// </para>
/// <para>
/// <b>Registration shape.</b> Site composition roots call
/// <see cref="ServiceCollectionExtensions.AddAuditLogHealthMetricsBridge"/>,
/// which overrides the binding with the site bridge. Central composition
/// roots call <see cref="ServiceCollectionExtensions.AddAuditLogCentralMaintenance"/>,
/// which overrides with this central bridge. A node never wears both hats —
/// site and central are distinct host roles — so the two bridges never
/// fight over the same binding at runtime.
/// </para>
/// <para>
/// <b>Why not a thin wrapper around the snapshot directly?</b> The snapshot
/// itself <i>could</i> be the bound implementation (it already implements
/// <see cref="IAuditRedactionFailureCounter"/>), but a dedicated class makes
/// the central-vs-site asymmetry explicit at the DI boundary — readers of
/// <see cref="ServiceCollectionExtensions.AddAuditLogCentralMaintenance"/>
/// see "site → site bridge, central → central bridge", matching the
/// <see cref="ScadaLink.AuditLog.Site.HealthMetricsAuditRedactionFailureCounter"/>
/// shape one-for-one.
/// </para>
/// </remarks>
public sealed class CentralAuditRedactionFailureCounter : IAuditRedactionFailureCounter
{
    private readonly AuditCentralHealthSnapshot _snapshot;

    public CentralAuditRedactionFailureCounter(AuditCentralHealthSnapshot snapshot)
    {
        _snapshot = snapshot ?? throw new ArgumentNullException(nameof(snapshot));
    }

    /// <inheritdoc/>
    public void Increment() => ((IAuditRedactionFailureCounter)_snapshot).Increment();
}