using ScadaLink.Communication.Grpc;

namespace ScadaLink.AuditLog.Site.Telemetry;

/// <summary>
/// Default <see cref="ISiteStreamAuditClient"/> registered by
/// <see cref="ScadaLink.AuditLog.ServiceCollectionExtensions.AddAuditLog"/>.
/// It is a no-op binding for composition roots that have no
/// <c>SiteCommunicationActor</c> — central and test roots. Site roles override
/// it in the Host with the ClusterClient-based
/// <see cref="ClusterClientSiteAuditClient"/>, which actually forwards audit
/// telemetry to central.
/// </summary>
/// <remarks>
/// <para>
/// Returns an empty <see cref="IngestAck"/> so the
/// <see cref="SiteAuditTelemetryActor"/> doesn't flip any rows to
/// <c>Forwarded</c> when this NoOp is in effect — rows stay <c>Pending</c>
/// until a real client (or a test stub) takes over.
/// </para>
/// <para>
/// Audit-write paths are best-effort by contract: a NoOp client keeps the
/// host running cleanly and is consistent with "audit-write failures never
/// abort the user-facing action".
/// </para>
/// </remarks>
public sealed class NoOpSiteStreamAuditClient : ISiteStreamAuditClient
{
    private static readonly IngestAck EmptyAck = new();

    /// <inheritdoc/>
    public Task<IngestAck> IngestAuditEventsAsync(AuditEventBatch batch, CancellationToken ct)
    {
        ArgumentNullException.ThrowIfNull(batch);
        // Empty ack — no EventIds will be flipped to Forwarded, so rows stay
        // Pending until the real ClusterClientSiteAuditClient (or a test stub)
        // takes over.
        return Task.FromResult(EmptyAck);
    }

    /// <inheritdoc/>
    public Task<IngestAck> IngestCachedTelemetryAsync(CachedTelemetryBatch batch, CancellationToken ct)
    {
        ArgumentNullException.ThrowIfNull(batch);
        // Empty ack — same rationale as IngestAuditEventsAsync. The site still
        // writes the audit + tracking rows to its SQLite stores authoritatively;
        // central-side state only materialises once the real
        // ClusterClientSiteAuditClient (or a test stub) is wired in.
        return Task.FromResult(EmptyAck);
    }
}