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

/// <summary>
///     Where compiled scripts run (<c>Scripting:Runner</c>, lmxopcua#780). <see cref="InProcess"/> is the default
///     and the documented rollback: it is today's <see cref="ScriptRunGuard"/> path, unchanged.
/// </summary>
public enum ScriptRunnerMode
{
    /// <summary>Compiled scripts run in the host process under <see cref="ScriptRunGuard"/> (the default).</summary>
    InProcess = 0,

    /// <summary>
    ///     Run in process — that result is the one published — AND mirror each evaluation of the selected seams to the
    ///     worker pool, comparing the two (design P2, <see cref="ShadowScriptRunner"/>). A time-boxed diagnostic: it
    ///     doubles script CPU and keeps the in-process risk. Nothing on the shadow side reaches a published value or
    ///     readiness.
    /// </summary>
    Shadow = 1,

    /// <summary>
    ///     Compiled scripts of the selected seams run in the pre-emptible <c>ScriptWorker</c> process pool. The
    ///     runner fails closed: a worker that cannot start makes the script Bad
    ///     (<c>BadResourceUnavailable</c>), never an in-process run.
    /// </summary>
    OutOfProcess = 2,
}

/// <summary>The three host seams that run operator-authored C# (<c>Scripting:Runner:Seams</c>).</summary>
public enum ScriptSeam
{
    /// <summary>Virtual tags (<c>RoslynVirtualTagEvaluator</c>).</summary>
    VirtualTag = 0,

    /// <summary>Calculation tags (<c>CalculationEvaluator</c>).</summary>
    Calculation = 1,

    /// <summary>
    ///     Scripted-alarm predicates (<c>ScriptedAlarmEngine</c>). Last in the rollout (design §14 #10): out of process only
    ///     when <c>Scripting:Runner:Seams</c> lists it — an unset list does not select it.
    /// </summary>
    ScriptedAlarm = 2,
}

/// <summary>
///     The out-of-process worker pool's knobs (the <c>Scripting:Worker</c> section). Every value is clamped by
///     <see cref="Sanitized"/>, which reports each out-of-range key as a startup Warning, like the rest of the
///     <c>Scripting</c> section. Only consulted when <see cref="ScriptingOptions.Runner"/> is not
///     <see cref="ScriptRunnerMode.InProcess"/>.
/// </summary>
public sealed class ScriptWorkerOptions
{
    /// <summary>Default <see cref="Shards"/>: 2 (design §14 #1).</summary>
    public const int DefaultShards = 2;

    /// <summary>Upper bound of <see cref="Shards"/>.</summary>
    public const int MaxShards = 8;

    /// <summary>Default <see cref="HeapLimitBytes"/>: 512 MiB.</summary>
    public const long DefaultHeapLimitBytes = 512L * 1024 * 1024;

    /// <summary>Lower bound of <see cref="HeapLimitBytes"/>: 64 MiB (a worker below this cannot host Roslyn).</summary>
    public const long MinHeapLimitBytes = 64L * 1024 * 1024;

    /// <summary>Default <see cref="QuarantineAfterKills"/>: 2.</summary>
    public const int DefaultQuarantineAfterKills = 2;

    /// <summary>Default <see cref="UnavailableGrace"/>: 5 s.</summary>
    public static readonly TimeSpan DefaultUnavailableGrace = TimeSpan.FromSeconds(5);

    /// <summary>Lower bound of an explicit <see cref="HardGrace"/>: 250 ms.</summary>
    public static readonly TimeSpan MinHardGrace = TimeSpan.FromMilliseconds(250);

    /// <summary>Upper bound of an explicit <see cref="HardGrace"/>: 30 s.</summary>
    public static readonly TimeSpan MaxHardGrace = TimeSpan.FromSeconds(30);

    /// <summary>Upper bound of <see cref="UnavailableGrace"/>: 60 s.</summary>
    public static readonly TimeSpan MaxUnavailableGrace = TimeSpan.FromSeconds(60);

    /// <summary>Default <see cref="IsolationProbationRuns"/>: 20.</summary>
    public const int DefaultIsolationProbationRuns = 20;

    /// <summary>Default <see cref="IsolationIdleTimeout"/>: 10 min (design §3.3).</summary>
    public static readonly TimeSpan DefaultIsolationIdleTimeout = TimeSpan.FromMinutes(10);

    /// <summary>Default <see cref="CircuitOpenAfter"/>: 2 min (design §5.3.6).</summary>
    public static readonly TimeSpan DefaultCircuitOpenAfter = TimeSpan.FromMinutes(2);

    /// <summary>Shard workers per node; a script is placed by a stable hash of its key. Clamped to 1–8.</summary>
    public int Shards { get; set; } = DefaultShards;

    /// <summary>
    ///     Grace after the soft deadline <c>T</c> before the worker running the script is killed. Null (the default)
    ///     means <c>max(1 s, T)</c> per run (design §14 #2); an explicit value is clamped to 250 ms – 30 s.
    /// </summary>
    public TimeSpan? HardGrace { get; set; }

    /// <summary>The worker's <c>DOTNET_GCHeapHardLimit</c>. Default 512 MiB, minimum 64 MiB.</summary>
    public long HeapLimitBytes { get; set; } = DefaultHeapLimitBytes;

    /// <summary>Hard-deadline kills (within one hour) after which a script is quarantined. Default 2; 1–100.</summary>
    public int QuarantineAfterKills { get; set; } = DefaultQuarantineAfterKills;

    /// <summary>
    ///     How long an evaluation waits for its shard to become ready (a restart, a backoff) before it reports
    ///     <c>script runner unavailable</c>. Default 5 s; 0–60 s.
    /// </summary>
    public TimeSpan UnavailableGrace { get; set; } = DefaultUnavailableGrace;

    /// <summary>
    ///     Successful runs a suspect script must complete in the isolation worker before it returns to its shard.
    ///     Default 20; 1–10 000.
    /// </summary>
    public int IsolationProbationRuns { get; set; } = DefaultIsolationProbationRuns;

    /// <summary>
    ///     How long the isolation worker may sit with nothing to run before it is stopped (it is started again by the
    ///     next suspect). Default 10 min; 1 s – 24 h.
    /// </summary>
    public TimeSpan IsolationIdleTimeout { get; set; } = DefaultIsolationIdleTimeout;

    /// <summary>
    ///     The crash-loop circuit (design §5.3.6): when every shard worker has been down for this long, the runner
    ///     reports <c>Unavailable</c>, logs one Error and answers evaluations at once (no <see cref="UnavailableGrace"/>
    ///     wait) while it keeps retrying at the backoff cap. Default 2 min; 1 s – 1 h.
    /// </summary>
    public TimeSpan CircuitOpenAfter { get; set; } = DefaultCircuitOpenAfter;

    /// <summary>
    ///     Directory of the node-local compiled-PE cache (design §7): HMAC-authenticated PE images, so a worker restart
    ///     does not re-enter Roslyn. Must be absolute and outside the content root when set; startup fails otherwise
    ///     (the family's fail-closed path rule). Null (the default) runs without a cache: every worker start recompiles.
    /// </summary>
    public string? PeCacheDir { get; set; }

    /// <summary>
    ///     Path of the worker entry assembly (<c>ZB.MOM.WW.OtOpcUa.ScriptWorker.dll</c>). Null (the default) means
    ///     <c>script-worker/</c> under the host's base directory, where the Host build places it.
    /// </summary>
    public string? ExecutablePath { get; set; }

    /// <summary>
    ///     The worker's identity on Windows (design §6, owner decision §14 #5): <c>NT SERVICE\&lt;name&gt;</c> — the virtual
    ///     account <c>scripts/install/Install-ScriptWorkerIsolation.ps1</c> registers, by default
    ///     <c>NT SERVICE\OtOpcUaScriptWorker</c> — or a SID string. When set, each worker starts under a restricted token
    ///     derived from the host's (see <see cref="ScriptWorkerIdentity"/>): every privilege removed, and every access check
    ///     must ALSO pass for this identity, <c>Everyone</c>, <c>BUILTIN\Users</c> or <c>RESTRICTED</c>. The pipe ACL then
    ///     admits the host account and this identity only. Null (the default) keeps the host's own token. Windows only:
    ///     startup refuses it elsewhere.
    /// </summary>
    public string? Identity { get; set; }

    /// <summary>The hard grace that applies to a run with soft budget <paramref name="softTimeout"/>.</summary>
    /// <param name="softTimeout">The run's soft deadline <c>T</c>.</param>
    /// <returns><see cref="HardGrace"/> when set, otherwise <c>max(1 s, T)</c>.</returns>
    public TimeSpan EffectiveHardGrace(TimeSpan softTimeout)
        => HardGrace ?? (softTimeout > TimeSpan.FromSeconds(1) ? softTimeout : TimeSpan.FromSeconds(1));

    /// <summary>Returns a clamped copy; one line per out-of-range key in <paramref name="adjustments"/>.</summary>
    /// <param name="adjustments">The clamps applied, naming each key.</param>
    /// <returns>A new, clamped instance.</returns>
    public ScriptWorkerOptions Sanitized(out IReadOnlyList<string> adjustments)
    {
        const string prefix = ScriptingOptions.SectionName + ":Worker:";
        var notes = new List<string>();

        var shards = Shards;
        if (shards < 1 || shards > MaxShards)
        {
            var clamped = Math.Clamp(shards, 1, MaxShards);
            notes.Add($"{prefix}{nameof(Shards)} {shards} is outside 1–{MaxShards}; clamped to {clamped}.");
            shards = clamped;
        }

        var grace = HardGrace;
        if (grace is { } g && (g < MinHardGrace || g > MaxHardGrace))
        {
            var clamped = g < MinHardGrace ? MinHardGrace : MaxHardGrace;
            notes.Add($"{prefix}{nameof(HardGrace)} {g} is outside {MinHardGrace}–{MaxHardGrace}; clamped to {clamped}.");
            grace = clamped;
        }

        var heap = HeapLimitBytes;
        if (heap < MinHeapLimitBytes)
        {
            notes.Add($"{prefix}{nameof(HeapLimitBytes)} {heap} is below the minimum; clamped to {MinHeapLimitBytes}.");
            heap = MinHeapLimitBytes;
        }

        var kills = QuarantineAfterKills;
        if (kills < 1 || kills > 100)
        {
            var clamped = Math.Clamp(kills, 1, 100);
            notes.Add($"{prefix}{nameof(QuarantineAfterKills)} {kills} is outside 1–100; clamped to {clamped}.");
            kills = clamped;
        }

        var unavailable = UnavailableGrace;
        if (unavailable < TimeSpan.Zero || unavailable > MaxUnavailableGrace)
        {
            var clamped = unavailable < TimeSpan.Zero ? TimeSpan.Zero : MaxUnavailableGrace;
            notes.Add($"{prefix}{nameof(UnavailableGrace)} {unavailable} is outside 0–{MaxUnavailableGrace}; clamped to {clamped}.");
            unavailable = clamped;
        }

        var probation = IsolationProbationRuns;
        if (probation < 1 || probation > 10_000)
        {
            var clamped = Math.Clamp(probation, 1, 10_000);
            notes.Add($"{prefix}{nameof(IsolationProbationRuns)} {probation} is outside 1–10000; clamped to {clamped}.");
            probation = clamped;
        }

        var idle = IsolationIdleTimeout;
        if (idle < TimeSpan.FromSeconds(1) || idle > TimeSpan.FromHours(24))
        {
            var clamped = idle < TimeSpan.FromSeconds(1) ? TimeSpan.FromSeconds(1) : TimeSpan.FromHours(24);
            notes.Add($"{prefix}{nameof(IsolationIdleTimeout)} {idle} is outside 00:00:01–1.00:00:00; clamped to {clamped}.");
            idle = clamped;
        }

        var circuit = CircuitOpenAfter;
        if (circuit < TimeSpan.FromSeconds(1) || circuit > TimeSpan.FromHours(1))
        {
            var clamped = circuit < TimeSpan.FromSeconds(1) ? TimeSpan.FromSeconds(1) : TimeSpan.FromHours(1);
            notes.Add($"{prefix}{nameof(CircuitOpenAfter)} {circuit} is outside 00:00:01–01:00:00; clamped to {clamped}.");
            circuit = clamped;
        }

        adjustments = notes;
        return new ScriptWorkerOptions
        {
            IsolationIdleTimeout = idle,
            CircuitOpenAfter = circuit,
            Shards = shards,
            HardGrace = grace,
            HeapLimitBytes = heap,
            QuarantineAfterKills = kills,
            UnavailableGrace = unavailable,
            IsolationProbationRuns = probation,
            PeCacheDir = PeCacheDir,
            ExecutablePath = ExecutablePath,
            Identity = Identity,
        };
    }

    /// <summary>
    ///     Fail-closed path validation (design §7): <see cref="PeCacheDir"/>, when set, must be absolute and must not
    ///     sit inside <paramref name="contentRootPath"/>. Same rule as the family's <c>Secrets:SqlitePath</c>.
    /// </summary>
    /// <param name="contentRootPath">The host's content root.</param>
    /// <returns>The violation, or null when the options are acceptable.</returns>
    public string? ValidatePaths(string contentRootPath)
    {
        if (string.IsNullOrWhiteSpace(PeCacheDir)) return null;
        const string key = ScriptingOptions.SectionName + ":Worker:" + nameof(PeCacheDir);
        if (!Path.IsPathFullyQualified(PeCacheDir))
            return $"{key} '{PeCacheDir}' must be an absolute path.";
        var dir = Path.TrimEndingDirectorySeparator(Path.GetFullPath(PeCacheDir));
        var root = Path.TrimEndingDirectorySeparator(Path.GetFullPath(contentRootPath));
        var comparison = OperatingSystem.IsWindows() ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal;
        if (string.Equals(dir, root, comparison)
            || dir.StartsWith(root + Path.DirectorySeparatorChar, comparison)
            || dir.StartsWith(root + Path.AltDirectorySeparatorChar, comparison))
            return $"{key} '{PeCacheDir}' is inside the content root '{contentRootPath}'; it must live outside it.";
        return null;
    }

    /// <summary>
    ///     Fail-closed identity validation: <see cref="Identity"/>, when set, must be <c>NT SERVICE\&lt;name&gt;</c> or a SID
    ///     string, and the host must run on Windows.
    /// </summary>
    /// <param name="isWindows">Whether the host runs on Windows (callers pass <see cref="OperatingSystem.IsWindows"/>).</param>
    /// <returns>The violation, or null when the identity is unset or acceptable.</returns>
    public string? ValidateIdentity(bool isWindows)
    {
        if (string.IsNullOrWhiteSpace(Identity)) return null;
        const string key = ScriptingOptions.SectionName + ":Worker:" + nameof(Identity);
        if (!isWindows)
            return $"{key} '{Identity}' is only supported on Windows (it is a restricted token); unset it on this host.";
        return ScriptWorkerIdentity.TryResolveSid(Identity, out _, out var error) ? null : $"{key} '{Identity}': {error}";
    }
}

/// <summary>
///     The shadow comparison's knobs (the <c>Scripting:Shadow</c> section, lmxopcua#780 P2). Only consulted when
///     <see cref="ScriptingOptions.Runner"/> is <see cref="ScriptRunnerMode.Shadow"/>.
/// </summary>
public sealed class ScriptShadowOptions
{
    /// <summary>Default <see cref="MaxInFlight"/>: 256.</summary>
    public const int DefaultMaxInFlight = 256;

    /// <summary>Default <see cref="MismatchLogsPerMinute"/>: 20.</summary>
    public const int DefaultMismatchLogsPerMinute = 20;

    /// <summary>
    ///     Shadow runs outstanding at once (all seams). An evaluation that would exceed it is not mirrored and is counted
    ///     as dropped (<c>reason = behind</c>): the shadow is best effort and never queues without bound. Default 256;
    ///     1–100 000.
    /// </summary>
    public int MaxInFlight { get; set; } = DefaultMaxInFlight;

    /// <summary>
    ///     Mismatch Warning lines per minute (each script logs once per mismatch reason until its seam redeploys; this
    ///     caps a burst of many scripts). Default 20; 0 (counted, never logged) – 10 000.
    /// </summary>
    public int MismatchLogsPerMinute { get; set; } = DefaultMismatchLogsPerMinute;

    /// <summary>Returns a clamped copy; one line per out-of-range key in <paramref name="adjustments"/>.</summary>
    /// <param name="adjustments">The clamps applied, naming each key.</param>
    /// <returns>A new, clamped instance.</returns>
    public ScriptShadowOptions Sanitized(out IReadOnlyList<string> adjustments)
    {
        const string prefix = ScriptingOptions.SectionName + ":Shadow:";
        var notes = new List<string>();
        var inFlight = MaxInFlight;
        if (inFlight < 1 || inFlight > 100_000)
        {
            var clamped = Math.Clamp(inFlight, 1, 100_000);
            notes.Add($"{prefix}{nameof(MaxInFlight)} {inFlight} is outside 1–100000; clamped to {clamped}.");
            inFlight = clamped;
        }
        var logs = MismatchLogsPerMinute;
        if (logs < 0 || logs > 10_000)
        {
            var clamped = Math.Clamp(logs, 0, 10_000);
            notes.Add($"{prefix}{nameof(MismatchLogsPerMinute)} {logs} is outside 0–10000; clamped to {clamped}.");
            logs = clamped;
        }
        adjustments = notes;
        return new ScriptShadowOptions { MaxInFlight = inFlight, MismatchLogsPerMinute = logs };
    }
}