lmxopcua/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Drivers/DeploymentArtifact.cs

using System.Text.Json;
using System.Text.Json.Nodes;
using ZB.MOM.WW.OtOpcUa.Commons.Types;
using ZB.MOM.WW.OtOpcUa.Configuration.Enums;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.OpcUaServer;

namespace ZB.MOM.WW.OtOpcUa.Runtime.Drivers;

/// <summary>
///     Minimal driver-side view of the deployment artifact emitted by
///     <c>ConfigComposer.SnapshotAndFlattenAsync</c>. The artifact JSON is the full snapshot —
///     for driver spawning we only need the <c>DriverInstances</c> array. Reading just the
///     subset keeps allocations cheap on every deploy.
/// </summary>
public sealed record DriverInstanceSpec(
    Guid DriverInstanceRowId,
    string DriverInstanceId,
    string Name,
    string DriverType,
    bool Enabled,
    string DriverConfig,
    string? ClusterId = null,
    string? ResilienceConfig = null);

/// <summary>How a node should scope a deployment artifact to its own ClusterId.</summary>
public enum ClusterFilterMode
{
    /// <summary>Apply everything (single-cluster / legacy deployments).</summary>
    None,

    /// <summary>Filter the artifact to the node's own ClusterId.</summary>
    ScopeTo,

    /// <summary>Apply nothing (node's cluster row not found in a multi-cluster artifact).</summary>
    Suppress,
}

/// <summary>Resolved scoping decision for a node against an artifact.</summary>
/// <param name="Mode">
///     None = apply everything (single-cluster / legacy); ScopeTo = filter to <paramref name="ClusterId"/>;
///     Suppress = apply nothing.
/// </param>
/// <param name="ClusterId">The node's ClusterId when <paramref name="Mode"/> is ScopeTo; otherwise null.</param>
public readonly record struct ClusterScope(ClusterFilterMode Mode, string? ClusterId);

public static class DeploymentArtifact
{
    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        PropertyNameCaseInsensitive = true,
    };

    /// <summary>
    ///     Parse a deployment artifact blob into the list of driver-instance specs to spawn.
    ///     Empty / malformed blobs return an empty list — callers log + treat as "no drivers".
    /// </summary>
    /// <param name="blob">The deployment artifact blob to parse.</param>
    /// <returns>The parsed driver-instance specs, or an empty list for empty/malformed blobs.</returns>
    public static IReadOnlyList<DriverInstanceSpec> ParseDriverInstances(ReadOnlySpan<byte> blob)
    {
        if (blob.IsEmpty) return Array.Empty<DriverInstanceSpec>();

        try
        {
            using var doc = JsonDocument.Parse(blob.ToArray());
            var root = doc.RootElement;
            if (!root.TryGetProperty("DriverInstances", out var arr)
                || arr.ValueKind != JsonValueKind.Array)
            {
                return Array.Empty<DriverInstanceSpec>();
            }

            // v3: each spec's DriverConfig is the MERGED config the driver factory binds from —
            // DriverConfig (protocol/channel) + per-Device DeviceConfig (endpoint) + the driver's authored
            // raw tags (RawTags array, keyed by RawPath) — folded once here via DriverDeviceConfigMerger so
            // both spawn (TryCreate) and redeploy (ApplyDelta) hand the driver the same shape.
            var rawTagsByDriver = BuildRawTagsByDriver(root);
            var deviceRowsByDriver = BuildDeviceRowsByDriver(root);

            var result = new List<DriverInstanceSpec>(arr.GetArrayLength());
            foreach (var el in arr.EnumerateArray())
            {
                if (el.ValueKind != JsonValueKind.Object) continue;
                var spec = TryReadSpec(el, rawTagsByDriver, deviceRowsByDriver);
                if (spec is not null) result.Add(spec);
            }
            return result;
        }
        catch (JsonException)
        {
            return Array.Empty<DriverInstanceSpec>();
        }
    }

    /// <summary>Flatten the artifact's raw topology (RawFolders / DriverInstances / Devices / TagGroups /
    /// Tags) into each driver's authored <see cref="RawTagEntry"/> list, keyed by DriverInstanceId. Each
    /// tag's RawPath is computed via the shared <see cref="RawPathResolver"/> (the single identity authority),
    /// so the deploy-decode side agrees byte-for-byte with the authoring/validation side. A tag whose
    /// device/driver chain is broken (unknown link) is dropped.</summary>
    /// <param name="root">The artifact root element.</param>
    /// <returns>DriverInstanceId → authored raw tags (RawPath + TagConfig + WriteIdempotent + DeviceName).</returns>
    private static Dictionary<string, List<RawTagEntry>> BuildRawTagsByDriver(JsonElement root)
    {
        var byDriver = new Dictionary<string, List<RawTagEntry>>(StringComparer.Ordinal);

        var folders = new Dictionary<string, (string? ParentId, string Name)>(StringComparer.Ordinal);
        foreach (var el in EnumerateArray(root, "RawFolders"))
        {
            var id = ReadString(el, "RawFolderId");
            if (string.IsNullOrWhiteSpace(id)) continue;
            folders[id!] = (ReadNullableString(el, "ParentRawFolderId"), ReadString(el, "Name") ?? id!);
        }

        var drivers = new Dictionary<string, (string? RawFolderId, string Name)>(StringComparer.Ordinal);
        foreach (var el in EnumerateArray(root, "DriverInstances"))
        {
            var id = ReadString(el, "DriverInstanceId");
            if (string.IsNullOrWhiteSpace(id)) continue;
            drivers[id!] = (ReadNullableString(el, "RawFolderId"), ReadString(el, "Name") ?? id!);
        }

        var deviceToDriver = new Dictionary<string, string>(StringComparer.Ordinal);
        var devices = new Dictionary<string, (string DriverInstanceId, string Name)>(StringComparer.Ordinal);
        foreach (var el in EnumerateArray(root, "Devices"))
        {
            var id = ReadString(el, "DeviceId");
            var di = ReadString(el, "DriverInstanceId");
            if (string.IsNullOrWhiteSpace(id) || string.IsNullOrWhiteSpace(di)) continue;
            var name = ReadString(el, "Name") ?? id!;
            devices[id!] = (di!, name);
            deviceToDriver[id!] = di!;
        }

        var groups = new Dictionary<string, (string? ParentId, string Name)>(StringComparer.Ordinal);
        foreach (var el in EnumerateArray(root, "TagGroups"))
        {
            var id = ReadString(el, "TagGroupId");
            if (string.IsNullOrWhiteSpace(id)) continue;
            groups[id!] = (ReadNullableString(el, "ParentTagGroupId"), ReadString(el, "Name") ?? id!);
        }

        var resolver = new RawPathResolver(folders, drivers, devices, groups);

        // scriptId → SourceCode, from the artifact's Scripts array — the same join the VirtualTag plan
        // builder uses. A calc tag's TagConfig carries a scriptId (not the source); the calc driver is
        // host-blind and can't resolve it, so we inject the resolved `scriptSource` into the delivered
        // TagConfig here (the deploy-side counterpart of the Calculation driver). Tags with no scriptId
        // are untouched.
        var scriptSourceById = BuildScriptSourceMap(root);

        foreach (var el in EnumerateArray(root, "Tags"))
        {
            var deviceId = ReadString(el, "DeviceId");
            var name = ReadString(el, "Name");
            if (string.IsNullOrWhiteSpace(deviceId) || string.IsNullOrWhiteSpace(name)) continue;
            if (!deviceToDriver.TryGetValue(deviceId!, out var driverInstanceId)) continue;
            var tagGroupId = ReadNullableString(el, "TagGroupId");
            var rawPath = resolver.TryBuildTagPath(deviceId!, tagGroupId, name!);
            if (rawPath is null) continue; // broken chain — dropped (deploy gate rejects invalid names)
            var tagConfig = el.TryGetProperty("TagConfig", out var tcEl) && tcEl.ValueKind == JsonValueKind.String
                ? tcEl.GetString() ?? "{}" : "{}";
            tagConfig = InjectScriptSource(tagConfig, scriptSourceById);
            // WriteIdempotent (bool; non-bool/absent ⇒ false — the safe R2 default: writes are non-idempotent).
            var writeIdempotent = el.TryGetProperty("WriteIdempotent", out var wiEl)
                && wiEl.ValueKind is JsonValueKind.True or JsonValueKind.False && wiEl.GetBoolean();
            var deviceName = devices.TryGetValue(deviceId!, out var dev) ? dev.Name : string.Empty;

            if (!byDriver.TryGetValue(driverInstanceId, out var list))
                byDriver[driverInstanceId] = list = new List<RawTagEntry>();
            list.Add(new RawTagEntry(rawPath, tagConfig, writeIdempotent, deviceName));
        }

        // Deterministic ordering per driver (ordinal RawPath) so the injected config is byte-stable.
        foreach (var list in byDriver.Values)
            list.Sort((a, b) => string.CompareOrdinal(a.RawPath, b.RawPath));
        return byDriver;
    }

    /// <summary>
    ///     Build the per-equipment <c>{{equip}}/&lt;RefName&gt;</c> reference map — <c>equipmentId →
    ///     (effectiveName → backing-tag RawPath)</c> — from the artifact's raw topology + <c>Tags</c> +
    ///     <c>UnsTagReferences</c> via the shared <see cref="EquipmentReferenceMap"/> + <see cref="RawPathResolver"/>.
    ///     The JSON-side mirror of <c>AddressSpaceComposer.BuildEquipmentReferenceMap</c> (entity side), so
    ///     both compose seams resolve <c>{{equip}}</c> script paths to byte-identical RawPaths. Empty when
    ///     the artifact carries no references / tags.
    /// </summary>
    /// <param name="root">The artifact root element.</param>
    /// <returns><c>equipmentId → (effectiveName → RawPath)</c>.</returns>
    private static IReadOnlyDictionary<string, IReadOnlyDictionary<string, string>> BuildEquipmentReferenceMap(JsonElement root)
    {
        var folders = new Dictionary<string, (string? ParentId, string Name)>(StringComparer.Ordinal);
        foreach (var el in EnumerateArray(root, "RawFolders"))
        {
            var id = ReadString(el, "RawFolderId");
            if (string.IsNullOrWhiteSpace(id)) continue;
            folders[id!] = (ReadNullableString(el, "ParentRawFolderId"), ReadString(el, "Name") ?? id!);
        }

        var drivers = new Dictionary<string, (string? RawFolderId, string Name)>(StringComparer.Ordinal);
        foreach (var el in EnumerateArray(root, "DriverInstances"))
        {
            var id = ReadString(el, "DriverInstanceId");
            if (string.IsNullOrWhiteSpace(id)) continue;
            drivers[id!] = (ReadNullableString(el, "RawFolderId"), ReadString(el, "Name") ?? id!);
        }

        var devices = new Dictionary<string, (string DriverInstanceId, string Name)>(StringComparer.Ordinal);
        foreach (var el in EnumerateArray(root, "Devices"))
        {
            var id = ReadString(el, "DeviceId");
            var di = ReadString(el, "DriverInstanceId");
            if (string.IsNullOrWhiteSpace(id) || string.IsNullOrWhiteSpace(di)) continue;
            devices[id!] = (di!, ReadString(el, "Name") ?? id!);
        }

        var groups = new Dictionary<string, (string? ParentId, string Name)>(StringComparer.Ordinal);
        foreach (var el in EnumerateArray(root, "TagGroups"))
        {
            var id = ReadString(el, "TagGroupId");
            if (string.IsNullOrWhiteSpace(id)) continue;
            groups[id!] = (ReadNullableString(el, "ParentTagGroupId"), ReadString(el, "Name") ?? id!);
        }

        var resolver = new RawPathResolver(folders, drivers, devices, groups);

        var tagsById = new Dictionary<string, EquipmentReferenceMap.TagRow>(StringComparer.Ordinal);
        foreach (var el in EnumerateArray(root, "Tags"))
        {
            var tagId = ReadString(el, "TagId");
            var deviceId = ReadString(el, "DeviceId");
            var name = ReadString(el, "Name");
            if (string.IsNullOrWhiteSpace(tagId) || string.IsNullOrWhiteSpace(deviceId) || string.IsNullOrWhiteSpace(name))
                continue;
            tagsById[tagId!] = new EquipmentReferenceMap.TagRow(name!, deviceId!, ReadNullableString(el, "TagGroupId"));
        }

        var references = new List<EquipmentReferenceMap.ReferenceRow>();
        foreach (var el in EnumerateArray(root, "UnsTagReferences"))
        {
            var refId = ReadString(el, "UnsTagReferenceId");
            var equipmentId = ReadString(el, "EquipmentId");
            var tagId = ReadString(el, "TagId");
            if (string.IsNullOrWhiteSpace(refId) || string.IsNullOrWhiteSpace(equipmentId) || string.IsNullOrWhiteSpace(tagId))
                continue;
            references.Add(new EquipmentReferenceMap.ReferenceRow(
                refId!, equipmentId!, tagId!, ReadNullableString(el, "DisplayNameOverride")));
        }

        if (references.Count == 0 || tagsById.Count == 0)
            return new Dictionary<string, IReadOnlyDictionary<string, string>>(StringComparer.Ordinal);

        return EquipmentReferenceMap.Build(references, tagsById, resolver);
    }

    /// <summary>Build the <c>scriptId → SourceCode</c> map from the artifact's <c>Scripts</c> array (mirrors
    /// the VirtualTag plan builder's join). Empty when the artifact carries no Scripts.</summary>
    private static Dictionary<string, string> BuildScriptSourceMap(JsonElement root)
    {
        var byId = new Dictionary<string, string>(StringComparer.Ordinal);
        foreach (var el in EnumerateArray(root, "Scripts"))
        {
            var sid = ReadString(el, "ScriptId");
            if (string.IsNullOrWhiteSpace(sid)) continue;
            byId[sid!] = el.TryGetProperty("SourceCode", out var srcEl) && srcEl.ValueKind == JsonValueKind.String
                ? srcEl.GetString() ?? string.Empty : string.Empty;
        }
        return byId;
    }

    /// <summary>
    ///     When <paramref name="tagConfig"/> carries a <c>scriptId</c> (a calc tag), inject the resolved
    ///     <c>scriptSource</c> so the host-blind Calculation driver can compile + evaluate it. Identity for
    ///     tags with no <c>scriptId</c> (every other driver's tags), an unresolvable id, or malformed JSON —
    ///     so no existing tag's blob changes. The pre-existing <c>scriptId</c>/trigger fields are preserved.
    /// </summary>
    /// <param name="tagConfig">The tag's raw <c>TagConfig</c> JSON.</param>
    /// <param name="scriptSourceById">The <c>scriptId → SourceCode</c> map from the artifact.</param>
    /// <returns>The TagConfig with <c>scriptSource</c> injected, or the original when nothing to inject.</returns>
    private static string InjectScriptSource(string tagConfig, IReadOnlyDictionary<string, string> scriptSourceById)
    {
        if (scriptSourceById.Count == 0 || string.IsNullOrWhiteSpace(tagConfig)) return tagConfig;
        JsonNode? node;
        try { node = JsonNode.Parse(tagConfig); }
        catch (JsonException) { return tagConfig; }
        if (node is not JsonObject obj) return tagConfig;

        var scriptId = obj.TryGetPropertyValue("scriptId", out var sidNode) && sidNode is JsonValue sv
            && sv.TryGetValue<string>(out var sid) ? sid : null;
        if (string.IsNullOrWhiteSpace(scriptId) || !scriptSourceById.TryGetValue(scriptId!, out var source))
            return tagConfig;

        obj["scriptSource"] = source;
        return obj.ToJsonString();
    }

    /// <summary>Group the artifact's Devices into per-driver <see cref="DriverDeviceConfigMerger.DeviceRow"/>
    /// lists (entity Name + schemaless DeviceConfig), ordered by DeviceId for a stable merge.</summary>
    /// <param name="root">The artifact root element.</param>
    /// <returns>DriverInstanceId → ordered device rows.</returns>
    private static Dictionary<string, List<DriverDeviceConfigMerger.DeviceRow>> BuildDeviceRowsByDriver(JsonElement root)
    {
        var byDriver = new Dictionary<string, List<(string DeviceId, DriverDeviceConfigMerger.DeviceRow Row)>>(StringComparer.Ordinal);
        foreach (var el in EnumerateArray(root, "Devices"))
        {
            var id = ReadString(el, "DeviceId");
            var di = ReadString(el, "DriverInstanceId");
            if (string.IsNullOrWhiteSpace(id) || string.IsNullOrWhiteSpace(di)) continue;
            var name = ReadString(el, "Name") ?? id!;
            var deviceConfig = ReadString(el, "DeviceConfig");
            if (!byDriver.TryGetValue(di!, out var list))
                byDriver[di!] = list = new List<(string, DriverDeviceConfigMerger.DeviceRow)>();
            list.Add((id!, new DriverDeviceConfigMerger.DeviceRow(name, deviceConfig)));
        }

        return byDriver.ToDictionary(
            kv => kv.Key,
            kv => kv.Value.OrderBy(x => x.DeviceId, StringComparer.Ordinal).Select(x => x.Row).ToList(),
            StringComparer.Ordinal);
    }

    /// <summary>Enumerate an artifact array property's object elements (empty when absent/non-array).</summary>
    private static IEnumerable<JsonElement> EnumerateArray(JsonElement root, string property)
    {
        if (!root.TryGetProperty(property, out var arr) || arr.ValueKind != JsonValueKind.Array)
            yield break;
        foreach (var el in arr.EnumerateArray())
            if (el.ValueKind == JsonValueKind.Object)
                yield return el;
    }

    /// <summary>Reads a string property, coalescing a JSON <c>null</c> (or wrong type) to <see langword="null"/>.</summary>
    private static string? ReadNullableString(JsonElement el, string property) =>
        el.TryGetProperty(property, out var p) && p.ValueKind == JsonValueKind.String ? p.GetString() : null;

    /// <summary>
    ///     Resolve how a node should scope a deployment artifact to its own ClusterId. Single-cluster
    ///     (or legacy) artifacts resolve to <see cref="ClusterFilterMode.None"/> so every existing
    ///     deployment applies unchanged. In a multi-cluster artifact the node's <c>ClusterNode</c> row
    ///     (matched by <paramref name="nodeId"/>) selects <see cref="ClusterFilterMode.ScopeTo"/> its
    ///     ClusterId; a missing row resolves to <see cref="ClusterFilterMode.Suppress"/>. Empty /
    ///     malformed blobs resolve to <see cref="ClusterFilterMode.None"/> (lenient, matching the
    ///     other parsers).
    /// </summary>
    /// <param name="blob">The deployment artifact blob to inspect.</param>
    /// <param name="nodeId">The node's identity (e.g. a "host:port" string) to match against <c>Nodes</c>.</param>
    /// <returns>The resolved <see cref="ClusterScope"/> decision for this node.</returns>
    public static ClusterScope ResolveClusterScope(ReadOnlySpan<byte> blob, string nodeId)
    {
        if (blob.IsEmpty) return new ClusterScope(ClusterFilterMode.None, null);
        try
        {
            using var doc = JsonDocument.Parse(blob.ToArray());
            var root = doc.RootElement;
            var clusterCount = root.TryGetProperty("Clusters", out var cl) && cl.ValueKind == JsonValueKind.Array
                ? cl.GetArrayLength() : 0;
            if (clusterCount <= 1) return new ClusterScope(ClusterFilterMode.None, null);

            string? myCluster = null;
            if (root.TryGetProperty("Nodes", out var nodes) && nodes.ValueKind == JsonValueKind.Array)
            {
                foreach (var el in nodes.EnumerateArray())
                {
                    if (el.ValueKind != JsonValueKind.Object) continue;
                    var nid = el.TryGetProperty("NodeId", out var nEl) ? nEl.GetString() : null;
                    if (!string.Equals(nid, nodeId, StringComparison.OrdinalIgnoreCase)) continue;
                    myCluster = el.TryGetProperty("ClusterId", out var cEl) ? cEl.GetString() : null;
                    break;
                }
            }
            return string.IsNullOrWhiteSpace(myCluster)
                ? new ClusterScope(ClusterFilterMode.Suppress, null)
                : new ClusterScope(ClusterFilterMode.ScopeTo, myCluster);
        }
        catch (JsonException)
        {
            return new ClusterScope(ClusterFilterMode.None, null);
        }
    }

    /// <summary>
    ///     Parse a deployment artifact blob into the driver-instance specs a specific node should
    ///     spawn, scoped to its own ClusterId via <see cref="ResolveClusterScope"/>. Single-cluster /
    ///     legacy artifacts return every spec; a multi-cluster artifact returns only the matching
    ///     cluster's specs (or none when the node's row is absent).
    /// </summary>
    /// <param name="blob">The deployment artifact blob to parse.</param>
    /// <param name="nodeId">The node's identity (e.g. a "host:port" string) used to resolve cluster scope.</param>
    /// <returns>The driver-instance specs this node should spawn.</returns>
    public static IReadOnlyList<DriverInstanceSpec> ParseDriverInstances(ReadOnlySpan<byte> blob, string nodeId)
    {
        var scope = ResolveClusterScope(blob, nodeId);
        if (scope.Mode == ClusterFilterMode.Suppress) return Array.Empty<DriverInstanceSpec>();
        var all = ParseDriverInstances(blob);
        return scope.Mode == ClusterFilterMode.ScopeTo
            ? all.Where(s => string.Equals(s.ClusterId, scope.ClusterId, StringComparison.OrdinalIgnoreCase)).ToArray()
            : all;
    }

    /// <summary>Reads a string property, tolerating a wrong JSON type: a property that is present but
    /// NOT a JSON string (number / bool / object / array) yields null rather than throwing
    /// <see cref="InvalidOperationException"/> from <c>GetString()</c>. Keeps the artifact-decode lenient
    /// — a wrong-typed field degrades to the field default / a skipped row, matching the documented
    /// "malformed blobs return an empty list/composition" contract.</summary>
    private static string? ReadString(JsonElement el, string property) =>
        el.TryGetProperty(property, out var p) && p.ValueKind == JsonValueKind.String ? p.GetString() : null;

    private static DriverInstanceSpec? TryReadSpec(
        JsonElement el,
        IReadOnlyDictionary<string, List<RawTagEntry>> rawTagsByDriver,
        IReadOnlyDictionary<string, List<DriverDeviceConfigMerger.DeviceRow>> deviceRowsByDriver)
    {
        var rowId = el.TryGetProperty("DriverInstanceRowId", out var rowEl)
            && rowEl.TryGetGuid(out var rid) ? rid : Guid.Empty;
        var id = ReadString(el, "DriverInstanceId");
        var name = ReadString(el, "Name");
        var type = ReadString(el, "DriverType");
        // A non-bool Enabled token degrades to the field default (true = "desired here"), never throws.
        var enabled = !el.TryGetProperty("Enabled", out var enEl)
            || enEl.ValueKind is not (JsonValueKind.True or JsonValueKind.False)
            || enEl.GetBoolean();
        var driverConfig = ReadString(el, "DriverConfig");
        var clusterId = ReadString(el, "ClusterId");
        // Per-instance resilience overrides (DriverInstance.ResilienceConfig column). Optional/nullable —
        // absent means tier defaults; layered onto the tier by DriverResilienceOptionsParser at spawn.
        var resilienceConfig = ReadString(el, "ResilienceConfig");

        if (string.IsNullOrWhiteSpace(id) || string.IsNullOrWhiteSpace(type)) return null;

        // v3 endpoint→DeviceConfig + RawTags injection: fold DriverConfig + per-device DeviceConfig + the
        // driver's authored raw tags into the single config the factory binds from (single-endpoint drivers
        // get their sole DeviceConfig merged up; multi-device drivers get a reconstructed Devices[] array).
        var devices = deviceRowsByDriver.TryGetValue(id!, out var dr) ? dr : (IReadOnlyList<DriverDeviceConfigMerger.DeviceRow>)Array.Empty<DriverDeviceConfigMerger.DeviceRow>();
        var rawTags = rawTagsByDriver.TryGetValue(id!, out var rt) ? rt : (IReadOnlyList<RawTagEntry>)Array.Empty<RawTagEntry>();
        var mergedConfig = DriverDeviceConfigMerger.Merge(driverConfig, devices, rawTags);

        return new DriverInstanceSpec(
            DriverInstanceRowId: rowId,
            DriverInstanceId: id!,
            Name: name ?? id!,
            DriverType: type!,
            Enabled: enabled,
            DriverConfig: mergedConfig,
            ClusterId: clusterId,
            ResilienceConfig: resilienceConfig);
    }

    /// <summary>
    ///     Parse the artifact into the projected <see cref="AddressSpaceComposition"/> used by
    ///     <c>AddressSpacePlanner</c> + <c>AddressSpaceApplier</c>. Returns an empty composition for empty/
    ///     malformed blobs so callers can treat parse failure as a no-op deploy.
    ///
    ///     The artifact JSON is produced by <c>ConfigComposer.SnapshotAndFlattenAsync</c> in the
    ///     ControlPlane — its Pascal-case property names match the EF entities. We only need a
    ///     subset of fields per entity class to drive the address-space rebuild on driver-role
    ///     nodes.
    /// </summary>
    /// <param name="blob">The deployment artifact blob to parse.</param>
    /// <returns>The projected <see cref="AddressSpaceComposition"/>, or an empty composition for empty/malformed blobs.</returns>
    public static AddressSpaceComposition ParseComposition(ReadOnlySpan<byte> blob)
    {
        if (blob.IsEmpty) return Empty();

        try
        {
            using var doc = JsonDocument.Parse(blob.ToArray());
            var root = doc.RootElement;

            var areas = ReadArray(root, "UnsAreas", ReadAreaProjection);
            var lines = ReadArray(root, "UnsLines", ReadLineProjection);
            var equipment = ReadArray(root, "Equipment", ReadEquipmentNode);
            var drivers = ReadArray(root, "DriverInstances", ReadDriverPlan);
            var alarms = ReadArray(root, "ScriptedAlarms", ReadAlarmPlan);
            // v3 DARK address space (Batch 1): NO equipment-tag variable plans materialize — the raw + UNS
            // variable nodes are lit up in Batch 4 (the dual namespace + UNS fan-out). EquipmentTags is
            // deliberately empty; {{equip}} substitution therefore has no per-equipment tag base (empty).
            // The retained per-equipment plans (folder hierarchy + VirtualTags + ScriptedAlarms) still exist.
            var equipmentTags = Array.Empty<EquipmentTagPlan>();
            // Per-equipment {{equip}}/<RefName> reference map (effectiveName → RawPath), shared by the
            // VirtualTag + ScriptedAlarm plan builders so both substitute against the same resolved paths.
            var referenceMapByEquip = BuildEquipmentReferenceMap(root);
            var equipmentVirtualTags = BuildEquipmentVirtualTagPlans(root, referenceMapByEquip);
            var equipmentScriptedAlarms = BuildEquipmentScriptedAlarmPlans(root, referenceMapByEquip);

            return new AddressSpaceComposition(areas, lines, equipment, drivers, alarms)
            {
                EquipmentTags = equipmentTags,
                EquipmentVirtualTags = equipmentVirtualTags,
                EquipmentScriptedAlarms = equipmentScriptedAlarms,
            };
        }
        catch (JsonException)
        {
            return Empty();
        }
    }

    /// <summary>Cluster-scoped overload: the address-space composition a node should materialise given
    /// its NodeId. Filters every projection to the node's own ClusterId (see <see cref="ResolveClusterScope"/>).
    /// Equipment attribution is dual-path: driver-bound equipment (non-null DriverInstanceId) is kept when
    /// its driver is in-cluster; driver-less equipment (null DriverInstanceId) is kept when its UNS line's
    /// area is in-cluster.
    /// When <paramref name="onInconsistency"/> is supplied it is invoked with a human-readable message for each
    /// kept driver-bound equipment whose owning UNS line is NOT in the node's cluster — a cross-cluster binding
    /// that violates the same-cluster invariant and would orphan the equipment folder. This is
    /// detection only (observability); the equipment is still returned, since the upstream draft validator
    /// is the authority that should prevent the binding in the first place.</summary>
    /// <param name="blob">The deployment artifact blob.</param>
    /// <param name="nodeId">This node's identity in "host:port" form.</param>
    /// <param name="onInconsistency">Optional diagnostic callback for cross-cluster orphan bindings; null disables the check.</param>
    /// <returns>The filtered composition per the node's scoping decision.</returns>
    public static AddressSpaceComposition ParseComposition(
        ReadOnlySpan<byte> blob, string nodeId, Action<string>? onInconsistency = null)
    {
        var scope = ResolveClusterScope(blob, nodeId);
        if (scope.Mode == ClusterFilterMode.None) return ParseComposition(blob);
        if (scope.Mode == ClusterFilterMode.Suppress) return Empty();

        var full = ParseComposition(blob);
        var sets = BuildClusterSets(blob, scope.ClusterId!);

        var keptLines = full.UnsLines.Where(l => sets.AreaIds.Contains(l.UnsAreaId)).ToArray();
        var keptEquipment = full.EquipmentNodes.Where(e => sets.EquipmentIds.Contains(e.EquipmentId)).ToArray();

        if (onInconsistency is not null)
        {
            var keptLineIds = keptLines.Select(l => l.UnsLineId).ToHashSet(StringComparer.OrdinalIgnoreCase);
            // This cross-cluster check only fires for DRIVER-BOUND equipment. Driver-less equipment
            // is attributed by its UNS line's area cluster, so by construction its line is always in
            // keptLines — the condition `!keptLineIds.Contains(e.UnsLineId)` is never true for it.
            foreach (var e in keptEquipment)
            {
                if (!string.IsNullOrEmpty(e.UnsLineId) && !keptLineIds.Contains(e.UnsLineId))
                    onInconsistency(
                        $"equipment '{e.EquipmentId}' is in cluster '{scope.ClusterId}' (by its driver) but its " +
                        $"UNS line '{e.UnsLineId}' is not — a cross-cluster binding violates the same-cluster " +
                        "invariant (decision #122) and would orphan the equipment folder.");
            }
        }

        return new AddressSpaceComposition(
            full.UnsAreas.Where(a => sets.AreaIds.Contains(a.UnsAreaId)).ToArray(),
            keptLines,
            keptEquipment,
            full.DriverInstancePlans.Where(d => sets.DriverIds.Contains(d.DriverInstanceId)).ToArray(),
            full.ScriptedAlarmPlans.Where(a => sets.EquipmentIds.Contains(a.EquipmentId)).ToArray())
        {
            EquipmentTags = full.EquipmentTags.Where(t => sets.DriverIds.Contains(t.DriverInstanceId)).ToArray(),
            EquipmentVirtualTags = full.EquipmentVirtualTags.Where(v => sets.EquipmentIds.Contains(v.EquipmentId)).ToArray(),
            EquipmentScriptedAlarms = full.EquipmentScriptedAlarms.Where(a => sets.EquipmentIds.Contains(a.EquipmentId)).ToArray(),
        };
    }

    /// <summary>The in-cluster id sets used to filter a composition.</summary>
    /// <param name="DriverIds">DriverInstanceIds whose row carries the in-scope ClusterId.</param>
    /// <param name="AreaIds">UnsAreaIds whose row carries the in-scope ClusterId.</param>
    /// <param name="EquipmentIds">In-cluster EquipmentIds: driver-bound equipment is attributed by its
    /// driver's cluster; driver-less equipment (null DriverInstanceId) by its UNS line's area cluster.</param>
    private sealed record ClusterSets(HashSet<string> DriverIds, HashSet<string> AreaIds, HashSet<string> EquipmentIds);

    /// <summary>Build the in-cluster id sets used to filter a composition: DriverInstanceIds + UnsAreaIds
    /// that directly carry the ClusterId, plus in-cluster EquipmentIds — driver-bound equipment attributed
    /// by its driver's cluster, and driver-less equipment (null DriverInstanceId) attributed by its UNS
    /// line's area cluster.</summary>
    /// <param name="blob">The deployment artifact blob.</param>
    /// <param name="clusterId">The node's ClusterId to scope to.</param>
    /// <returns>The resolved in-cluster id sets (empty on parse failure => empty composition).</returns>
    private static ClusterSets BuildClusterSets(ReadOnlySpan<byte> blob, string clusterId)
    {
        var driverIds = new HashSet<string>(StringComparer.Ordinal);
        var areaIds = new HashSet<string>(StringComparer.Ordinal);
        var equipmentIds = new HashSet<string>(StringComparer.Ordinal);
        try
        {
            using var doc = JsonDocument.Parse(blob.ToArray());
            var root = doc.RootElement;
            CollectIdsWhereCluster(root, "DriverInstances", "DriverInstanceId", clusterId, driverIds);
            CollectIdsWhereCluster(root, "UnsAreas", "UnsAreaId", clusterId, areaIds);
            // Map each UnsLine to its owning UnsArea so driver-less equipment can be attributed via
            // its line's area cluster (Equipment -> UnsLine.UnsAreaId -> UnsArea.ClusterId).
            var lineToArea = new Dictionary<string, string>(StringComparer.Ordinal);
            if (root.TryGetProperty("UnsLines", out var lines) && lines.ValueKind == JsonValueKind.Array)
            {
                foreach (var el in lines.EnumerateArray())
                {
                    if (el.ValueKind != JsonValueKind.Object) continue;
                    var lineId = el.TryGetProperty("UnsLineId", out var lEl) ? lEl.GetString() : null;
                    var areaId = el.TryGetProperty("UnsAreaId", out var aEl) ? aEl.GetString() : null;
                    if (!string.IsNullOrWhiteSpace(lineId) && !string.IsNullOrWhiteSpace(areaId))
                        lineToArea[lineId!] = areaId!;
                }
            }
            // v3: Equipment carries no ClusterId AND no driver binding — it is attributed solely by its
            // UNS line's area cluster (Equipment -> UnsLine.UnsAreaId -> UnsArea.ClusterId).
            if (root.TryGetProperty("Equipment", out var eq) && eq.ValueKind == JsonValueKind.Array)
            {
                foreach (var el in eq.EnumerateArray())
                {
                    if (el.ValueKind != JsonValueKind.Object) continue;
                    var id = el.TryGetProperty("EquipmentId", out var idEl) ? idEl.GetString() : null;
                    var lineId = el.TryGetProperty("UnsLineId", out var luEl) ? luEl.GetString() : null;
                    if (string.IsNullOrWhiteSpace(id)) continue;
                    if (lineId is not null && lineToArea.TryGetValue(lineId, out var areaOfLine) && areaIds.Contains(areaOfLine))
                        equipmentIds.Add(id!);
                }
            }
        }
        catch (JsonException) { /* empty sets => nothing matches => empty composition */ }
        return new ClusterSets(driverIds, areaIds, equipmentIds);
    }

    /// <summary>Collect each row's <paramref name="idField"/> value from <paramref name="arrayName"/> whose
    /// ClusterId equals <paramref name="clusterId"/> (case-insensitive, matching the codebase convention).</summary>
    /// <param name="root">The artifact root element.</param>
    /// <param name="arrayName">The array property name to scan (e.g. "DriverInstances").</param>
    /// <param name="idField">The id field to collect from each in-cluster row.</param>
    /// <param name="clusterId">The ClusterId rows must match.</param>
    /// <param name="into">The set to collect matching ids into.</param>
    private static void CollectIdsWhereCluster(
        JsonElement root, string arrayName, string idField, string clusterId, HashSet<string> into)
    {
        if (!root.TryGetProperty(arrayName, out var arr) || arr.ValueKind != JsonValueKind.Array) return;
        foreach (var el in arr.EnumerateArray())
        {
            if (el.ValueKind != JsonValueKind.Object) continue;
            var cid = el.TryGetProperty("ClusterId", out var cEl) ? cEl.GetString() : null;
            if (!string.Equals(cid, clusterId, StringComparison.OrdinalIgnoreCase)) continue;
            var id = el.TryGetProperty(idField, out var idEl) ? idEl.GetString() : null;
            if (!string.IsNullOrWhiteSpace(id)) into.Add(id!);
        }
    }

    private static AddressSpaceComposition Empty() => new(
        Array.Empty<UnsAreaProjection>(),
        Array.Empty<UnsLineProjection>(),
        Array.Empty<EquipmentNode>(),
        Array.Empty<DriverInstancePlan>(),
        Array.Empty<ScriptedAlarmPlan>());

    /// <summary>
    ///     Join the artifact's VirtualTags array to its Scripts array (by ScriptId) to emit one
    ///     <see cref="EquipmentVirtualTagPlan"/> per VirtualTag. The artifact-decode mirror of
    ///     <c>AddressSpaceComposer.Compose</c>'s VirtualTag producer — so the compose-side + artifact-decode
    ///     plans agree. Each <c>{{equip}}/&lt;RefName&gt;</c> in the joined Script's <c>SourceCode</c> is
    ///     substituted with the owning equipment's backing RawPath (via <paramref name="referenceMapByEquip"/>)
    ///     BEFORE refs are extracted, byte-parity with the composer. <c>Expression</c> = the substituted
    ///     source (empty when the ScriptId is absent); <c>DependencyRefs</c> = the distinct
    ///     <c>ctx.GetTag("…")</c> literals in that source; <c>FolderPath</c> is always "" (VirtualTag has
    ///     no FolderPath today). Ordered by EquipmentId then Name to match the composer's deterministic
    ///     ordering.
    /// </summary>
    private static IReadOnlyList<EquipmentVirtualTagPlan> BuildEquipmentVirtualTagPlans(
        JsonElement root, IReadOnlyDictionary<string, IReadOnlyDictionary<string, string>> referenceMapByEquip)
    {
        if (!root.TryGetProperty("VirtualTags", out var vtArr) || vtArr.ValueKind != JsonValueKind.Array)
            return Array.Empty<EquipmentVirtualTagPlan>();

        var emptyRefMap = (IReadOnlyDictionary<string, string>)
            new Dictionary<string, string>(StringComparer.Ordinal);

        // scriptId → SourceCode (the expression source the VirtualTagActor evaluates).
        var scriptSourceById = new Dictionary<string, string>(StringComparer.Ordinal);
        if (root.TryGetProperty("Scripts", out var scriptsArr) && scriptsArr.ValueKind == JsonValueKind.Array)
        {
            foreach (var el in scriptsArr.EnumerateArray())
            {
                if (el.ValueKind != JsonValueKind.Object) continue;
                var sid = el.TryGetProperty("ScriptId", out var sidEl) ? sidEl.GetString() : null;
                if (string.IsNullOrWhiteSpace(sid)) continue;
                var src = el.TryGetProperty("SourceCode", out var srcEl) && srcEl.ValueKind == JsonValueKind.String
                    ? srcEl.GetString() : null;
                scriptSourceById[sid!] = src ?? string.Empty;
            }
        }

        var result = new List<EquipmentVirtualTagPlan>(vtArr.GetArrayLength());
        foreach (var el in vtArr.EnumerateArray())
        {
            if (el.ValueKind != JsonValueKind.Object) continue;
            var virtualTagId = el.TryGetProperty("VirtualTagId", out var vidEl) ? vidEl.GetString() : null;
            var equipmentId = el.TryGetProperty("EquipmentId", out var eqEl) ? eqEl.GetString() : null;
            var name = el.TryGetProperty("Name", out var nmEl) ? nmEl.GetString() : null;
            var dataType = el.TryGetProperty("DataType", out var dtEl) ? dtEl.GetString() : null;
            var scriptId = el.TryGetProperty("ScriptId", out var sidEl) ? sidEl.GetString() : null;

            if (string.IsNullOrWhiteSpace(virtualTagId) || string.IsNullOrWhiteSpace(equipmentId)
                || string.IsNullOrWhiteSpace(name)) continue;

            var source = scriptId is not null && scriptSourceById.TryGetValue(scriptId, out var src)
                ? src : string.Empty;

            // Historize: the artifact carries a Pascal-case "Historize" bool (ConfigComposer serialises
            // the whole VirtualTag entity with DefaultIgnoreCondition.Never). Robust parse — default
            // false; only honoured when the JSON value is an actual boolean — so absent/non-bool ⇒ false,
            // byte-parity with AddressSpaceComposer's entity-default-false behaviour.
            var historize = el.TryGetProperty("Historize", out var hEl)
                && (hEl.ValueKind == JsonValueKind.True || hEl.ValueKind == JsonValueKind.False)
                && hEl.GetBoolean();

            // Substitute each {{equip}}/<RefName> with the owning equipment's backing RawPath BEFORE
            // extracting refs, so both Expression and DependencyRefs are machine-specific — byte-parity
            // with AddressSpaceComposer.Compose.
            var expanded = EquipmentScriptPaths.SubstituteEquipmentToken(
                source, referenceMapByEquip.GetValueOrDefault(equipmentId!, emptyRefMap));

            result.Add(new EquipmentVirtualTagPlan(
                VirtualTagId: virtualTagId!,
                EquipmentId: equipmentId!,
                FolderPath: string.Empty,
                Name: name!,
                DataType: dataType ?? "BaseDataType",
                Expression: expanded,
                DependencyRefs: EquipmentScriptPaths.ExtractDependencyRefs(expanded),
                Historize: historize));
        }

        result.Sort((a, b) =>
        {
            var byEquipment = string.CompareOrdinal(a.EquipmentId, b.EquipmentId);
            return byEquipment != 0 ? byEquipment : string.CompareOrdinal(a.Name, b.Name);
        });
        return result;
    }

    /// <summary>
    ///     Join the artifact's ScriptedAlarms array to its Scripts array (by PredicateScriptId) to emit
    ///     one <see cref="EquipmentScriptedAlarmPlan"/> per alarm. The artifact-decode mirror of
    ///     <c>AddressSpaceComposer.Compose</c>'s scripted-alarm producer — so the compose-side + artifact-decode
    ///     plans agree byte-for-byte. An alarm whose <c>PredicateScriptId</c> has no matching Script row is
    ///     SKIPPED (matching the composer's skip behaviour) to preserve parity. <c>PredicateSource</c> = the
    ///     joined script source ("" when missing — but such alarms are skipped above); <c>DependencyRefs</c>
    ///     = the shared <see cref="EquipmentScriptPaths.ExtractAlarmDependencyRefs"/> merge of the predicate's
    ///     distinct <c>ctx.GetTag("…")</c> reads UNION the message template's <c>{TagPath}</c> tokens. The
    ///     predicate source's <c>{{equip}}/&lt;RefName&gt;</c> paths are substituted with the owning equipment's
    ///     backing RawPath (via <paramref name="referenceMapByEquip"/>) BEFORE the merge — byte-parity with
    ///     the composer. Ordered by EquipmentId then ScriptedAlarmId to match the composer's deterministic order.
    /// </summary>
    private static IReadOnlyList<EquipmentScriptedAlarmPlan> BuildEquipmentScriptedAlarmPlans(
        JsonElement root, IReadOnlyDictionary<string, IReadOnlyDictionary<string, string>> referenceMapByEquip)
    {
        if (!root.TryGetProperty("ScriptedAlarms", out var alarmsArr) || alarmsArr.ValueKind != JsonValueKind.Array)
            return Array.Empty<EquipmentScriptedAlarmPlan>();

        // scriptId → SourceCode (the predicate source the alarm host evaluates). Same join the
        // VirtualTag builder uses; an alarm whose PredicateScriptId is absent here is skipped below.
        var scriptSourceById = new Dictionary<string, string>(StringComparer.Ordinal);
        if (root.TryGetProperty("Scripts", out var scriptsArr) && scriptsArr.ValueKind == JsonValueKind.Array)
        {
            foreach (var el in scriptsArr.EnumerateArray())
            {
                if (el.ValueKind != JsonValueKind.Object) continue;
                var sid = el.TryGetProperty("ScriptId", out var sidEl) ? sidEl.GetString() : null;
                if (string.IsNullOrWhiteSpace(sid)) continue;
                var src = el.TryGetProperty("SourceCode", out var srcEl) && srcEl.ValueKind == JsonValueKind.String
                    ? srcEl.GetString() : null;
                scriptSourceById[sid!] = src ?? string.Empty;
            }
        }

        var emptyRefMap = (IReadOnlyDictionary<string, string>)
            new Dictionary<string, string>(StringComparer.Ordinal);
        var result = new List<EquipmentScriptedAlarmPlan>(alarmsArr.GetArrayLength());
        foreach (var el in alarmsArr.EnumerateArray())
        {
            if (el.ValueKind != JsonValueKind.Object) continue;
            var scriptedAlarmId = el.TryGetProperty("ScriptedAlarmId", out var idEl) ? idEl.GetString() : null;
            var equipmentId = el.TryGetProperty("EquipmentId", out var eqEl) ? eqEl.GetString() : null;
            var name = el.TryGetProperty("Name", out var nmEl) ? nmEl.GetString() : null;
            var alarmType = el.TryGetProperty("AlarmType", out var atEl) ? atEl.GetString() : null;
            var severity = el.TryGetProperty("Severity", out var svEl) && svEl.TryGetInt32(out var sv) ? sv : 0;
            var messageTemplate = el.TryGetProperty("MessageTemplate", out var mtEl) ? mtEl.GetString() : null;
            var predicateScriptId = el.TryGetProperty("PredicateScriptId", out var psEl) ? psEl.GetString() : null;
            // Booleans default to the entity defaults (true) when absent / null / non-boolean, so a
            // partial blob decodes the same as the composer's view of a default-constructed
            // ScriptedAlarm — preserving byte-parity. GetBoolean only runs for a genuine true/false
            // token (a non-bool token would otherwise throw InvalidOperationException, uncaught here).
            bool ReadBool(string prop, bool dflt) =>
                el.TryGetProperty(prop, out var b) && b.ValueKind is JsonValueKind.True or JsonValueKind.False
                    ? b.GetBoolean() : dflt;
            var historize = ReadBool("HistorizeToAveva", true);
            var retain = ReadBool("Retain", true);
            var enabled = ReadBool("Enabled", true);

            if (string.IsNullOrWhiteSpace(scriptedAlarmId)) continue;

            // Skip alarms whose predicate script is missing — matching AddressSpaceComposer's skip behaviour
            // so both sides emit the same set (byte-parity).
            if (predicateScriptId is null || !scriptSourceById.TryGetValue(predicateScriptId, out var rawSource))
                continue;

            // Substitute each {{equip}}/<RefName> with the owning equipment's backing RawPath BEFORE the
            // dependency merge — byte-parity with AddressSpaceComposer.Compose.
            var source = EquipmentScriptPaths.SubstituteEquipmentToken(
                rawSource, referenceMapByEquip.GetValueOrDefault(equipmentId ?? string.Empty, emptyRefMap));

            result.Add(new EquipmentScriptedAlarmPlan(
                ScriptedAlarmId: scriptedAlarmId!,
                EquipmentId: equipmentId ?? string.Empty,
                Name: name ?? string.Empty,
                AlarmType: alarmType ?? string.Empty,
                Severity: severity,
                MessageTemplate: messageTemplate ?? string.Empty,
                PredicateScriptId: predicateScriptId,
                PredicateSource: source,
                DependencyRefs: EquipmentScriptPaths.ExtractAlarmDependencyRefs(source, messageTemplate),
                HistorizeToAveva: historize,
                Retain: retain,
                Enabled: enabled));
        }

        result.Sort((a, b) =>
        {
            var byEquipment = string.CompareOrdinal(a.EquipmentId, b.EquipmentId);
            return byEquipment != 0 ? byEquipment : string.CompareOrdinal(a.ScriptedAlarmId, b.ScriptedAlarmId);
        });
        return result;
    }

    private static IReadOnlyList<T> ReadArray<T>(JsonElement root, string propertyName, Func<JsonElement, T?> reader)
        where T : class
    {
        if (!root.TryGetProperty(propertyName, out var arr) || arr.ValueKind != JsonValueKind.Array)
            return Array.Empty<T>();

        var result = new List<T>(arr.GetArrayLength());
        foreach (var el in arr.EnumerateArray())
        {
            if (el.ValueKind != JsonValueKind.Object) continue;
            var item = reader(el);
            if (item is not null) result.Add(item);
        }
        // Match AddressSpaceComposer's natural-key sort so plan diffs are deterministic across
        // artifact-decode + composer-compose passes.
        return result.OrderBy(IdentityOf, StringComparer.Ordinal).ToList();
    }

    private static string IdentityOf<T>(T item) where T : class => item switch
    {
        UnsAreaProjection a => a.UnsAreaId,
        UnsLineProjection l => l.UnsLineId,
        EquipmentNode e => e.EquipmentId,
        DriverInstancePlan d => d.DriverInstanceId,
        ScriptedAlarmPlan a => a.ScriptedAlarmId,
        _ => string.Empty,
    };

    private static UnsAreaProjection? ReadAreaProjection(JsonElement el)
    {
        var id = ReadString(el, "UnsAreaId");
        var name = ReadString(el, "Name");
        if (string.IsNullOrWhiteSpace(id)) return null;
        return new UnsAreaProjection(id!, name ?? id!);
    }

    private static UnsLineProjection? ReadLineProjection(JsonElement el)
    {
        var id = ReadString(el, "UnsLineId");
        var areaId = ReadString(el, "UnsAreaId");
        var name = ReadString(el, "Name");
        if (string.IsNullOrWhiteSpace(id) || string.IsNullOrWhiteSpace(areaId)) return null;
        return new UnsLineProjection(id!, areaId!, name ?? id!);
    }

    private static EquipmentNode? ReadEquipmentNode(JsonElement el)
    {
        var id = ReadString(el, "EquipmentId");
        // DisplayName = the UNS Name segment (friendly browse name, matching UnsArea/UnsLine
        // + the live rebuild's source of truth) — NOT the colloquial MachineCode. NodeId stays the
        // logical EquipmentId.
        var displayName = ReadString(el, "Name");
        var lineId = ReadString(el, "UnsLineId");
        if (string.IsNullOrWhiteSpace(id)) return null;
        // v3: Equipment no longer binds a driver/device — it references raw tags via UnsTagReference.
        // The EquipmentNode's DriverInstanceId/DeviceId/DeviceHost hooks (used by the multi-device FixedTree
        // partition path) are therefore always null now; Batch 4 owns the UNS↔Raw fan-out that lights them up.
        return new EquipmentNode(id!, displayName ?? id!, lineId ?? string.Empty);
    }

    private static DriverInstancePlan? ReadDriverPlan(JsonElement el)
    {
        var id = ReadString(el, "DriverInstanceId");
        var type = ReadString(el, "DriverType");
        var config = ReadString(el, "DriverConfig");
        if (string.IsNullOrWhiteSpace(id) || string.IsNullOrWhiteSpace(type)) return null;
        return new DriverInstancePlan(id!, type!, config ?? "{}");
    }

    private static ScriptedAlarmPlan? ReadAlarmPlan(JsonElement el)
    {
        var id = ReadString(el, "ScriptedAlarmId");
        var equipmentId = ReadString(el, "EquipmentId");
        var script = ReadString(el, "PredicateScriptId");
        var template = ReadString(el, "MessageTemplate");
        if (string.IsNullOrWhiteSpace(id)) return null;
        return new ScriptedAlarmPlan(id!, equipmentId ?? string.Empty, script ?? string.Empty, template ?? string.Empty);
    }
}