Task #155 — TagService + TagsTab CRUD UI for Modbus tags

Closes the remaining loop on user-visible Modbus tag editing. Pre-#155 tags
arrived only via SQL seeding or runtime ITagDiscovery; the Admin UI had no
interactive surface for creating / editing / deleting tag rows.

Changes:

- TagService.cs (Admin/Services/) — CRUD wrapper around OtOpcUaConfigDbContext.Tags.
  ListAsync supports optional driver / equipment filters; CreateAsync auto-derives
  TagId; UpdateAsync persists editable fields; DeleteAsync removes the row. Mirrors
  the EquipmentService shape.
- TagsTab.razor (Components/Pages/Clusters/) — list + filter + add/edit/remove form.
  The address/config editor is conditional: when the selected DriverInstance is
  Modbus, ModbusAddressEditor (#145) renders with live-parse preview; otherwise a
  generic JSON textarea (matches the DriversTab pattern from #147). Save-side
  serializes the address-string into TagConfig as `{"addressString":"..."}` JSON.
- ClusterDetail.razor — new "Tags" tab in the cluster-detail nav strip + the routing
  switch.
- Program.cs — TagService registered as a scoped DI service.

Drive-by fix: ModbusDriverFactoryExtensions.CreateInstance promoted from internal
to public — Admin.Tests was using it via reflection-friendly internal access that
broke under the #153 logger overload addition. Public is the right access modifier
anyway since the Server-side bootstrapper calls it from a different assembly.

Drive-by fix #2: ModbusDriverConfigDto was missing MaxReadGap (#143) — surfaced by
the #147 round-trip test that flips MaxReadGap=12 in the view model and asserts
it lands on the resolved options. Added the field + binding line. Confirms #143's
DriverConfig JSON binding was incomplete since the original commit; no production
deployment configured this knob through JSON until now so the gap stayed hidden.

Tests (4 new TagServiceTests):
- Create_And_List_Surfaces_The_Tag — CreateAsync auto-assigns TagId; list returns
  the row.
- List_Filters_By_DriverInstance — driver-scoped filter works.
- Update_Persists_Editable_Fields — Name / DataType / AccessLevel / TagConfig all
  persist through Update.
- Delete_Removes_The_Row — basic delete verification.

113 + 4 (TagService) + 2 (DriversTab round-trip restored after compile fix) = 119
Admin tests green. Solution build clean.

Caveat: bUnit-style render tests for TagsTab still aren't included — Admin.Tests
doesn't have bUnit set up. The TagService logic is fully covered; the razor
component's parser/save glue is exercised by hand at runtime for now.

src/ZB.MOM.WW.OtOpcUa.Admin/Components/Pages/Clusters/ClusterDetail.razor

@@ -51,6 +51,7 @@ else
         <li class="nav-item"><button class="nav-link @Tab("uns")" @onclick='() => _tab = "uns"'>UNS Structure</button></li>
         <li class="nav-item"><button class="nav-link @Tab("namespaces")" @onclick='() => _tab = "namespaces"'>Namespaces</button></li>
         <li class="nav-item"><button class="nav-link @Tab("drivers")" @onclick='() => _tab = "drivers"'>Drivers</button></li>
+        <li class="nav-item"><button class="nav-link @Tab("tags")" @onclick='() => _tab = "tags"'>Tags</button></li>
         <li class="nav-item"><button class="nav-link @Tab("acls")" @onclick='() => _tab = "acls"'>ACLs</button></li>
         <li class="nav-item"><button class="nav-link @Tab("redundancy")" @onclick='() => _tab = "redundancy"'>Redundancy</button></li>
         <li class="nav-item"><button class="nav-link @Tab("audit")" @onclick='() => _tab = "audit"'>Audit</button></li>
@@ -89,6 +90,10 @@ else
     {
         <DriversTab GenerationId="@_currentDraft.GenerationId" ClusterId="@ClusterId"/>
     }
+    else if (_tab == "tags" && _currentDraft is not null)
+    {
+        <TagsTab GenerationId="@_currentDraft.GenerationId" ClusterId="@ClusterId"/>
+    }
     else if (_tab == "acls" && _currentDraft is not null)
     {
         <AclsTab GenerationId="@_currentDraft.GenerationId" ClusterId="@ClusterId"/>

src/ZB.MOM.WW.OtOpcUa.Admin/Components/Pages/Clusters/TagsTab.razor

@@ -0,0 +1,271 @@
+@using System.Text.Json
+@using ZB.MOM.WW.OtOpcUa.Admin.Components.Pages.Modbus
+@using ZB.MOM.WW.OtOpcUa.Admin.Services
+@using ZB.MOM.WW.OtOpcUa.Configuration.Entities
+@using ZB.MOM.WW.OtOpcUa.Configuration.Enums
+@using ZB.MOM.WW.OtOpcUa.Driver.Modbus
+@inject TagService TagSvc
+@inject DriverInstanceService DriverSvc
+@inject EquipmentService EquipmentSvc
+
+@*
+    #155 — interactive Tag CRUD scoped to a draft generation. Conditional editor: when the
+    selected DriverInstance is Modbus, the address input switches to ModbusAddressEditor (#145)
+    so users get the live-parse preview + grammar validation. Other driver types fall back to
+    a generic JSON textarea, matching the DriversTab pattern from #147.
+*@
+
+<div class="d-flex justify-content-between mb-3">
+    <h4>Tags (draft gen @GenerationId)</h4>
+    <button class="btn btn-primary btn-sm" @onclick="StartAdd">Add tag</button>
+</div>
+
+<div class="row g-3 mb-3">
+    <div class="col-md-4">
+        <label class="form-label small text-muted">Filter by driver</label>
+        <select class="form-select form-select-sm" @bind="_filterDriverId" @bind:after="ReloadAsync">
+            <option value="">— all drivers —</option>
+            @if (_drivers is not null)
+            {
+                @foreach (var d in _drivers)
+                {
+                    <option value="@d.DriverInstanceId">@d.Name (@d.DriverType)</option>
+                }
+            }
+        </select>
+    </div>
+</div>
+
+@if (_tags is null) { <p>Loading…</p> }
+else if (_tags.Count == 0 && !_showForm) { <p class="text-muted">No tags in this filter.</p> }
+else if (_tags.Count > 0)
+{
+    <table class="table table-sm">
+        <thead>
+            <tr><th>Name</th><th>Driver</th><th>Equipment</th><th>DataType</th><th>Access</th><th>TagConfig</th><th></th></tr>
+        </thead>
+        <tbody>
+        @foreach (var t in _tags)
+        {
+            <tr>
+                <td>@t.Name</td>
+                <td><code>@t.DriverInstanceId</code></td>
+                <td>@(t.EquipmentId ?? "—")</td>
+                <td>@t.DataType</td>
+                <td>@t.AccessLevel</td>
+                <td class="font-monospace small text-truncate" style="max-width:18rem">@t.TagConfig</td>
+                <td>
+                    <button class="btn btn-sm btn-outline-secondary me-1" @onclick="() => StartEdit(t)">Edit</button>
+                    <button class="btn btn-sm btn-outline-danger" @onclick="() => DeleteAsync(t.TagRowId)">Remove</button>
+                </td>
+            </tr>
+        }
+        </tbody>
+    </table>
+}
+
+@if (_showForm)
+{
+    <div class="card mt-3">
+        <div class="card-body">
+            <h5>@(_editMode ? "Edit tag" : "New tag")</h5>
+            <div class="row g-3">
+                <div class="col-md-4">
+                    <label class="form-label">Name</label>
+                    <input class="form-control" @bind="_draft.Name"/>
+                </div>
+                <div class="col-md-4">
+                    <label class="form-label">DriverInstance</label>
+                    <select class="form-select" @bind="_draft.DriverInstanceId" @bind:after="OnDriverChanged">
+                        <option value="">— select driver —</option>
+                        @if (_drivers is not null)
+                        {
+                            @foreach (var d in _drivers) { <option value="@d.DriverInstanceId">@d.Name (@d.DriverType)</option> }
+                        }
+                    </select>
+                </div>
+                <div class="col-md-4">
+                    <label class="form-label">Equipment (optional)</label>
+                    <select class="form-select" @bind="_draft.EquipmentId">
+                        <option value="">— none (folder-path mode) —</option>
+                        @if (_equipment is not null)
+                        {
+                            @foreach (var e in _equipment) { <option value="@e.EquipmentId">@e.Name</option> }
+                        }
+                    </select>
+                </div>
+                <div class="col-md-4">
+                    <label class="form-label">DataType</label>
+                    <input class="form-control" @bind="_draft.DataType" placeholder="Boolean / Int32 / Float / etc."/>
+                </div>
+                <div class="col-md-4">
+                    <label class="form-label">AccessLevel</label>
+                    <select class="form-select" @bind="_draft.AccessLevel">
+                        @foreach (var a in Enum.GetValues<TagAccessLevel>())
+                        {
+                            <option value="@a">@a</option>
+                        }
+                    </select>
+                </div>
+                <div class="col-md-4">
+                    <div class="form-check mt-4">
+                        <input type="checkbox" class="form-check-input" @bind="_draft.WriteIdempotent"/>
+                        <label class="form-check-label">WriteIdempotent</label>
+                    </div>
+                </div>
+            </div>
+
+            <div class="mt-3">
+                @if (_isModbus)
+                {
+                    <ModbusAddressEditor @bind-AddressString="_modbusAddress"
+                                         @bind-AddressString:after="OnAddressChanged"/>
+                }
+                else
+                {
+                    <label class="form-label">TagConfig (driver-specific JSON or string)</label>
+                    <textarea class="form-control font-monospace" rows="3" @bind="_draft.TagConfig"
+                              placeholder='@("{\"address\": ...}")'></textarea>
+                }
+            </div>
+
+            @if (_error is not null) { <div class="alert alert-danger mt-3">@_error</div> }
+
+            <div class="mt-3">
+                <button class="btn btn-sm btn-primary" @onclick="SaveAsync">Save</button>
+                <button class="btn btn-sm btn-secondary ms-2" @onclick="Cancel">Cancel</button>
+            </div>
+        </div>
+    </div>
+}
+
+@code {
+    [Parameter] public long GenerationId { get; set; }
+    [Parameter] public string ClusterId { get; set; } = string.Empty;
+
+    private List<Tag>? _tags;
+    private List<DriverInstance>? _drivers;
+    private List<Equipment>? _equipment;
+    private string _filterDriverId = string.Empty;
+
+    private bool _showForm;
+    private bool _editMode;
+    private Tag _draft = NewBlankDraft();
+    private string? _error;
+    private bool _isModbus;
+    private string? _modbusAddress;
+
+    private static Tag NewBlankDraft() => new()
+    {
+        TagId = string.Empty, DriverInstanceId = string.Empty, Name = string.Empty,
+        DataType = "Int32", AccessLevel = TagAccessLevel.Read, TagConfig = string.Empty,
+    };
+
+    protected override async Task OnParametersSetAsync()
+    {
+        _drivers = await DriverSvc.ListAsync(GenerationId, CancellationToken.None);
+        _equipment = await EquipmentSvc.ListAsync(GenerationId, CancellationToken.None);
+        await ReloadAsync();
+    }
+
+    private async Task ReloadAsync()
+    {
+        _tags = await TagSvc.ListAsync(GenerationId,
+            string.IsNullOrWhiteSpace(_filterDriverId) ? null : _filterDriverId,
+            equipmentId: null,
+            CancellationToken.None);
+    }
+
+    private void StartAdd()
+    {
+        _draft = NewBlankDraft();
+        _editMode = false;
+        _modbusAddress = null;
+        _isModbus = false;
+        _error = null;
+        _showForm = true;
+    }
+
+    private void StartEdit(Tag row)
+    {
+        _draft = new Tag
+        {
+            TagRowId = row.TagRowId,
+            GenerationId = row.GenerationId,
+            TagId = row.TagId,
+            DriverInstanceId = row.DriverInstanceId,
+            DeviceId = row.DeviceId,
+            EquipmentId = row.EquipmentId,
+            Name = row.Name,
+            FolderPath = row.FolderPath,
+            DataType = row.DataType,
+            AccessLevel = row.AccessLevel,
+            WriteIdempotent = row.WriteIdempotent,
+            PollGroupId = row.PollGroupId,
+            TagConfig = row.TagConfig,
+        };
+        _editMode = true;
+        OnDriverChanged();
+        // Try to extract addressString from existing JSON config so the Modbus editor pre-fills.
+        if (_isModbus) _modbusAddress = TryExtractAddressString(row.TagConfig);
+        _error = null;
+        _showForm = true;
+    }
+
+    private void OnDriverChanged()
+    {
+        var driver = _drivers?.FirstOrDefault(d => d.DriverInstanceId == _draft.DriverInstanceId);
+        _isModbus = driver is not null
+            && string.Equals(driver.DriverType, "Modbus", StringComparison.OrdinalIgnoreCase);
+    }
+
+    private void OnAddressChanged()
+    {
+        // Sync the address string into TagConfig as a JSON object the factory consumes.
+        if (string.IsNullOrWhiteSpace(_modbusAddress)) return;
+        _draft.TagConfig = JsonSerializer.Serialize(new { addressString = _modbusAddress });
+    }
+
+    private static string? TryExtractAddressString(string tagConfig)
+    {
+        try
+        {
+            using var doc = JsonDocument.Parse(tagConfig);
+            return doc.RootElement.TryGetProperty("addressString", out var v) ? v.GetString() : null;
+        }
+        catch { return null; }
+    }
+
+    private void Cancel()
+    {
+        _showForm = false;
+        _editMode = false;
+    }
+
+    private async Task SaveAsync()
+    {
+        _error = null;
+        try
+        {
+            if (string.IsNullOrWhiteSpace(_draft.Name) || string.IsNullOrWhiteSpace(_draft.DriverInstanceId))
+            {
+                _error = "Name and DriverInstance are required.";
+                return;
+            }
+            if (_editMode)
+                await TagSvc.UpdateAsync(_draft, CancellationToken.None);
+            else
+                await TagSvc.CreateAsync(GenerationId, _draft, CancellationToken.None);
+            _showForm = false;
+            _editMode = false;
+            await ReloadAsync();
+        }
+        catch (Exception ex) { _error = ex.Message; }
+    }
+
+    private async Task DeleteAsync(Guid id)
+    {
+        await TagSvc.DeleteAsync(id, CancellationToken.None);
+        await ReloadAsync();
+    }
+}

src/ZB.MOM.WW.OtOpcUa.Admin/Program.cs

@@ -41,6 +41,7 @@ builder.Services.AddDbContext<OtOpcUaConfigDbContext>(opt =>
 builder.Services.AddScoped<ClusterService>();
 builder.Services.AddScoped<GenerationService>();
 builder.Services.AddScoped<EquipmentService>();
+builder.Services.AddScoped<TagService>();
 builder.Services.AddScoped<UnsService>();
 builder.Services.AddScoped<NamespaceService>();
 builder.Services.AddScoped<DriverInstanceService>();

src/ZB.MOM.WW.OtOpcUa.Admin/Services/TagService.cs

@@ -0,0 +1,71 @@
+using Microsoft.EntityFrameworkCore;
+using ZB.MOM.WW.OtOpcUa.Configuration;
+using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
+
+namespace ZB.MOM.WW.OtOpcUa.Admin.Services;
+
+/// <summary>
+///     #155 — Tag CRUD scoped to a draft generation. Tags are the canonical signal definitions
+///     (one row per OPC UA variable) the Server materialises into the address space at startup.
+///     Mirrors the shape of <see cref="EquipmentService"/>; writes are restricted to draft
+///     generations only (published generations are immutable per the validation pipeline).
+/// </summary>
+public sealed class TagService(OtOpcUaConfigDbContext db)
+{
+    /// <summary>Lists all tags in a generation, ordered by name. Optional driver / equipment filter.</summary>
+    public Task<List<Tag>> ListAsync(long generationId,
+        string? driverInstanceId = null,
+        string? equipmentId = null,
+        CancellationToken ct = default)
+    {
+        var query = db.Tags.AsNoTracking().Where(t => t.GenerationId == generationId);
+        if (!string.IsNullOrWhiteSpace(driverInstanceId))
+            query = query.Where(t => t.DriverInstanceId == driverInstanceId);
+        if (!string.IsNullOrWhiteSpace(equipmentId))
+            query = query.Where(t => t.EquipmentId == equipmentId);
+        return query.OrderBy(t => t.Name).ToListAsync(ct);
+    }
+
+    /// <summary>
+    ///     Creates a new tag row in the given draft. TagId is auto-derived as a GUID — the
+    ///     human-friendly Name is the user-facing identifier.
+    /// </summary>
+    public async Task<Tag> CreateAsync(long draftId, Tag input, CancellationToken ct)
+    {
+        input.GenerationId = draftId;
+        if (string.IsNullOrWhiteSpace(input.TagId))
+            input.TagId = Guid.NewGuid().ToString("N");
+        db.Tags.Add(input);
+        await db.SaveChangesAsync(ct);
+        return input;
+    }
+
+    public async Task UpdateAsync(Tag updated, CancellationToken ct)
+    {
+        var existing = await db.Tags
+            .FirstOrDefaultAsync(t => t.TagRowId == updated.TagRowId, ct)
+            ?? throw new InvalidOperationException($"Tag row {updated.TagRowId} not found");
+
+        // Editable fields. TagId / GenerationId are immutable; the Validation pipeline rejects
+        // changes that would break referential integrity (sp_ValidateDraft per decision #110).
+        existing.Name = updated.Name;
+        existing.DriverInstanceId = updated.DriverInstanceId;
+        existing.DeviceId = updated.DeviceId;
+        existing.EquipmentId = updated.EquipmentId;
+        existing.FolderPath = updated.FolderPath;
+        existing.DataType = updated.DataType;
+        existing.AccessLevel = updated.AccessLevel;
+        existing.WriteIdempotent = updated.WriteIdempotent;
+        existing.PollGroupId = updated.PollGroupId;
+        existing.TagConfig = updated.TagConfig;
+        await db.SaveChangesAsync(ct);
+    }
+
+    public async Task DeleteAsync(Guid tagRowId, CancellationToken ct)
+    {
+        var existing = await db.Tags.FirstOrDefaultAsync(t => t.TagRowId == tagRowId, ct);
+        if (existing is null) return;
+        db.Tags.Remove(existing);
+        await db.SaveChangesAsync(ct);
+    }
+}

src/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusDriverFactoryExtensions.cs

@@ -28,10 +28,12 @@ public static class ModbusDriverFactoryExtensions
         registry.Register(DriverTypeName, (id, json) => CreateInstance(id, json, loggerFactory));
     }
 
-    internal static ModbusDriver CreateInstance(string driverInstanceId, string driverConfigJson)
+    /// <summary>Public for the Server-side bootstrapper + test consumers (Admin.Tests, etc.).</summary>
+    public static ModbusDriver CreateInstance(string driverInstanceId, string driverConfigJson)
         => CreateInstance(driverInstanceId, driverConfigJson, loggerFactory: null);
 
-    internal static ModbusDriver CreateInstance(string driverInstanceId, string driverConfigJson, ILoggerFactory? loggerFactory)
+    /// <summary>Logger-aware overload — used by <see cref="Register"/>'s closure when wired through DI.</summary>
+    public static ModbusDriver CreateInstance(string driverInstanceId, string driverConfigJson, ILoggerFactory? loggerFactory)
     {
         ArgumentException.ThrowIfNullOrWhiteSpace(driverInstanceId);
         ArgumentException.ThrowIfNullOrWhiteSpace(driverConfigJson);
@@ -57,6 +59,7 @@ public static class ModbusDriverFactoryExtensions
             UseFC16ForSingleRegisterWrites = dto.UseFC16ForSingleRegisterWrites ?? false,
             DisableFC23 = dto.DisableFC23 ?? false,
             WriteOnChangeOnly = dto.WriteOnChangeOnly ?? false,
+            MaxReadGap = dto.MaxReadGap ?? 0,
             Family = dto.Family is null ? ModbusFamily.Generic
                 : ParseEnum<ModbusFamily>(dto.Family, "<driver-level>", driverInstanceId, "Family"),
             MelsecSubFamily = dto.MelsecSubFamily is null ? MelsecFamily.Q_L_iQR
@@ -188,6 +191,7 @@ public static class ModbusDriverFactoryExtensions
         public bool? UseFC16ForSingleRegisterWrites { get; init; }
         public bool? DisableFC23 { get; init; }
         public bool? WriteOnChangeOnly { get; init; }
+        public ushort? MaxReadGap { get; init; }
         public string? Family { get; init; }
         public string? MelsecSubFamily { get; init; }
         public int? AutoProhibitReprobeMs { get; init; }