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

/// <summary>
///     ⚠️ DEPRECATED compatibility path (lmxopcua#815) — the ONE switch between "enforce" and "warn-only" credential
///     resolution, and it is chosen by CALL SITE, never by a global flag: a deployed, running driver (Galaxy
///     <c>InitializeAsync</c>/<c>ReopenAsync</c> + ack fallback, OpcUaClient session open) passes its instance's tracker
///     and so keeps resolving a pre-#815 out-of-namespace reference with its OLD semantics, warning instead of
///     faulting; every admin-node path (Test Connect probe, AdminUI live browse) and Heidenhain pass
///     <see langword="null"/> and stay hard-fail.
/// </summary>
/// <remarks>
///     <para>
///         Why it is safe to keep for running drivers: the AdminUI save path and the deploy gate refuse every
///         out-of-namespace reference, so a Designer can no longer CREATE one — what remains are configs deployed
///         before the upgrade, whose endpoint and reference an administrator already deployed. Such a config runs
///         only until its next deploy (which the gate refuses until it is migrated).
///     </para>
///     <para>
///         Removing it (the planned hard-fail release): delete this type, the per-driver <c>Legacy…</c> resolve
///         methods it gates and the <c>legacy</c> parameters; every caller then takes the enforce branch it already
///         has. Nothing else changes.
///     </para>
///     <para>
///         Each use is reported through <paramref name="warn"/> at most once per <see cref="WarnInterval"/> per field
///         (a Galaxy gateway reconnect re-resolves every time), and is exposed as <see cref="Diagnostics"/> so the
///         driver's <see cref="IDriverDiagnostics"/> bag carries it to the AdminUI (<c>/hosts</c> and the <c>/raw</c>
///         credential banner). Messages name the driver, field and allowed forms — never the value.
///     </para>
/// </remarks>
/// <param name="scope">The driver's scope (for the allowed forms).</param>
/// <param name="driverInstanceId">The driver instance (for messages).</param>
/// <param name="warn">Sink for a rate-limited warning line.</param>
/// <param name="clock">Clock (tests); null ⇒ <see cref="DateTime.UtcNow"/>.</param>
public sealed class LegacyCredentialReferenceTracker(
    CredentialScope scope, string driverInstanceId, Action<string> warn, Func<DateTime>? clock = null)
{
    /// <summary>The <see cref="Diagnostics"/> key prefix (one entry per field).</summary>
    public const string DiagnosticsKeyPrefix = "credential-compat:";

    /// <summary>Minimum spacing between two warnings for the same field.</summary>
    public static readonly TimeSpan WarnInterval = TimeSpan.FromHours(1);

    private readonly object _gate = new();
    private readonly Dictionary<string, DateTime> _lastWarned = new(StringComparer.Ordinal);
    private readonly SortedDictionary<string, string> _diagnostics = new(StringComparer.Ordinal);

    /// <summary>The scope this tracker reports against.</summary>
    public CredentialScope Scope => scope;

    /// <summary>The current legacy uses, keyed <c>credential-compat:&lt;field&gt;</c>.</summary>
    public IReadOnlyDictionary<string, string> Diagnostics
    {
        get
        {
            lock (_gate) return new Dictionary<string, string>(_diagnostics, StringComparer.Ordinal);
        }
    }

    /// <summary>Records that <paramref name="field"/> was resolved through the legacy path (warns, rate-limited).</summary>
    /// <param name="field">The field label.</param>
    public void Report(string field)
    {
        var forms = $"secret:{scope.SecretNamespaces[0]}<name> or env:{scope.EnvVariablePrefixes[0]}<NAME>";
        Record(
            field,
            $"out-of-namespace ref still resolved (#815 warn-only, deprecated); next deploy refuses it — use {forms}",
            $"{scope.Label} driver '{driverInstanceId}': {field} is a credential reference outside the {scope.Label} "
            + $"namespace. It is still resolved for this already-deployed driver (lmxopcua#815 warn-only "
            + $"compatibility — deprecated, a later release fails closed) but the deploy gate refuses it: migrate "
            + $"it to {forms} before the next deploy. See docs/security.md §\"Credential references are namespaced per driver\".");
    }

    /// <summary>
    ///     Records that the key-material file field <paramref name="field"/> (lmxopcua#836, e.g. OpcUaClient
    ///     <c>UserCertificatePath</c>) was loaded from a path outside the node's certificate directory through the same
    ///     warn-only window (warns, rate-limited). Never carries the path.
    /// </summary>
    /// <param name="field">The field label.</param>
    /// <param name="directoryDescription">How the operator configures the directory.</param>
    public void ReportPath(string field, string directoryDescription) =>
        Record(
            field,
            $"path outside the certificate directory still loaded (#836 warn-only, deprecated); next deploy refuses it — "
            + $"move the file under {directoryDescription} and author it as a relative path",
            $"{scope.Label} driver '{driverInstanceId}': {field} is not a relative path inside the node's certificate "
            + $"directory ({directoryDescription}). It is still loaded for this already-deployed driver (lmxopcua#836 "
            + "warn-only compatibility — deprecated, a later release fails closed) but the deploy gate refuses it: move "
            + "the file into that directory and set the field to its relative path before the next deploy. See "
            + "docs/security.md §\"Key-material file paths are confined to a node directory\".");

    private void Record(string field, string diagnostic, string warning)
    {
        var now = (clock ?? (() => DateTime.UtcNow))();
        bool log;
        lock (_gate)
        {
            _diagnostics[DiagnosticsKeyPrefix + field] = diagnostic;
            log = !_lastWarned.TryGetValue(field, out var last) || now - last >= WarnInterval;
            if (log) _lastWarned[field] = now;
        }

        if (log) warn(warning);
    }
}