# Component: Central UI

## Purpose

The Central UI is a web-based management interface hosted on the central cluster. It provides all configuration, deployment, monitoring, and troubleshooting workflows for the SCADA system. There is no live machine data visualization — the UI is focused on system management, with the exception of on-demand debug views.

## Location

Central cluster only. Sites have no user interface.

## Technology

- **Framework**: Blazor Server (ASP.NET Core). UI logic executes on the server, updates pushed to the browser via SignalR.
- Keeps the entire stack in C#/.NET, consistent with the rest of the system (Akka.NET, EF Core).
- SignalR provides built-in support for real-time UI updates.

## Failover Behavior

- A **load balancer** sits in front of the central cluster and routes to the active node.
- On central failover, the Blazor Server SignalR circuit is interrupted. The browser automatically attempts to reconnect via SignalR's built-in reconnection logic.
- Since sessions use **authentication cookies** carrying an embedded JWT (not server-side state), the user's authentication survives failover — the new active node validates the same cookie-embedded JWT. No re-login required if the token is still valid.
- Active debug view streams and in-progress deployment status subscriptions are lost on failover and must be re-opened by the user.
- Both central nodes share the same **ASP.NET Data Protection keys** (stored in the configuration database or shared configuration) so that tokens and anti-forgery tokens remain valid across failover.

## Real-Time Updates

- **Debug view**: Real-time display of attribute values and alarm states via **gRPC streaming**. When the user opens a debug view, a `DebugStreamBridgeActor` on the central side opens a gRPC server-streaming subscription to the site's `SiteStreamGrpcServer` for the selected instance, then requests an initial `DebugViewSnapshot` via ClusterClient. Ongoing `AttributeValueChanged` and `AlarmStateChanged` events flow via the gRPC stream (not through ClusterClient) to the bridge actor, which delivers them to the Blazor component via callbacks that call `InvokeAsync(StateHasChanged)` to push UI updates through the built-in SignalR circuit.
- **Health dashboard**: Site status, connection health, error rates, and buffer depths update via a **10-second auto-refresh timer**. Since health reports arrive from sites every 30 seconds, a 10s poll interval catches updates within one reporting cycle without unnecessary overhead.
- **Deployment status**: Pending/in-progress/success/failed transitions **push to the UI immediately** via SignalR (built into Blazor Server). No polling required for deployment tracking.

## Responsibilities

- Provide authenticated access to all management workflows.
- Enforce role-based access control in the UI (Admin, Design, Deployment with site scoping).
- Present data from the configuration database, and from site clusters via remote queries.

## Workflows / Pages

### Template Authoring (Design Role)
- The `/design/templates` page uses a **split-pane layout**: a folder/template tree sidebar on the left and the editor on the right.
- The tree shows nested `TemplateFolder` entities with their templates underneath; composition children render inline as leaf nodes beneath their owning template (right-click "Open composed template" reveals and selects the target).
- **Per-kind context menus** on folder, template, and composition nodes expose the relevant operations (new folder, new template, rename, move, delete, move to folder). Native HTML5 **drag-drop** reorganizes templates between folders and reparents folders, with cycle detection rejected via toast on drop. Tree expansion state persists in `sessionStorage`, and deep links (`/design/templates/{id}`) reveal and select the target node.
- Create, edit, and delete templates.
- **Template deletion** is blocked if any instances or child templates reference the template. The UI displays the references preventing deletion.
- Manage template hierarchy (inheritance) — visual tree of parent/child relationships.
- Manage composition — add/remove feature module instances within templates. **Naming collision detection** provides immediate feedback if composed modules introduce duplicate attribute, alarm, or script names.
- Define and edit attributes, alarms, and scripts on templates.
- Set lock flags on attributes, alarms, and scripts.
- Visual indicator showing inherited vs. locally defined vs. overridden members.
- **On-demand validation**: A "Validate" action allows Design users to run comprehensive pre-deployment validation (flattening, naming collisions, script compilation, trigger references) without triggering a deployment. Provides early feedback during authoring.
- **Last-write-wins** editing — no pessimistic locks or conflict detection on templates.

### Shared Script Management (Design Role)
- Create, edit, and delete shared (global) scripts.
- Shared scripts are not associated with any template.
- On-demand validation (compilation check) available.

### External System Management (Design Role)
- Define external system contracts: connection details, API method definitions (parameters, return types).
- Define retry settings per external system (max retry count, fixed time between retries).
- The external system detail page includes a **"Recent activity"** link that opens the Audit Log page pre-filtered to `Channel = ApiOutbound` and `Target` starts-with the system name — surfacing the system's recent outbound API audit history.

### Database Connection Management (Design Role)
- Define named database connections: server, database, credentials.
- Define retry settings per connection (max retry count, fixed time between retries).

### Notification List Management (Design Role)
- Create, edit, and delete notification lists.
- Each notification list has a **`Type`** — `Email` now, with `Teams` and other types planned. The type determines the type-specific targets a list carries.
- Manage recipients (name + email) within each `Email` list.
- Configure SMTP settings.

### Site & Data Connection Management (Admin Role)
- Create, edit, and delete site definitions, including Akka node addresses (NodeA/NodeB) and gRPC node addresses (GrpcNodeA/GrpcNodeB).
- Define data connections and assign them to sites (name, protocol type, connection details).
- **Data connection form**: "Primary Endpoint Configuration" (required JSON text area) and optional "Backup Endpoint Configuration" (collapsible section, hidden by default, revealed via "Add Backup Endpoint" button; "Remove Backup" button when editing an existing backup). "Failover Retry Count" numeric input (default 3, min 1, max 20) is visible only when a backup endpoint is configured.
- **Data connection list page**: Shows Primary Config and Backup Config columns. Active Endpoint column populated from health reports.
- The site detail page exposes a new **"Audit feed"** tab that hosts the Audit Log page pre-filtered to `Site = <site>` — an in-context view of every operational audit event for that site.

### Inbound API Management (Admin Role for keys, Design Role for methods)
- Manage inbound API keys (create, enable / disable, delete) and define API methods (name, parameters, return values, approved keys, implementation script).
- The API key detail page includes a **"Recent calls"** link that opens the Audit Log page pre-filtered to `Actor = <key name>` and `Channel = ApiInbound` — surfacing the key's recent inbound-call audit history.

### Area Management (Admin Role)
- Define hierarchical area structures per site.
- Parent-child area relationships.
- Assign areas when managing instances.

### Instance Management (Deployment Role)
- Create instances from templates at a specific site.
- Assign instances to areas.
- Bind data connections — **per-attribute binding** where each attribute with a data source reference individually selects its data connection from the site's available connections. **Bulk assignment** supported: select multiple attributes and assign a data connection to all of them at once.
- Set instance-level attribute overrides (non-locked attributes only).
- Filter/search instances by site, area, template, or status.
- **Disable** instances — stops data collection, script triggers, and alarm evaluation at the site while retaining the deployed configuration.
- **Enable** instances — re-activates a disabled instance.
- **Delete** instances — removes the running configuration from the site. Blocked if the site is unreachable. Store-and-forward messages are not cleared.
- The instance detail page exposes a new **"Audit feed"** tab that hosts the Audit Log page pre-filtered to the instance (`Site = <site>` and the `Instance / Script` filter set to the instance unique name) — an in-context view of every operational audit event involving that instance.

### Deployment (Deployment Role)
- View list of instances with staleness indicators (deployed config differs from template-derived config).
- Filter by site, area, template.
- View diff between deployed and current template-derived configuration.
- Deploy updated configuration to individual instances. **Pre-deployment validation** runs automatically before any deployment is sent — validation errors are displayed and block deployment.
- Track deployment status (pending, in-progress, success, failed).

### System-Wide Artifact Deployment (Deployment Role)
- Explicitly deploy shared scripts, external system definitions, database connection definitions, and data connection definitions to all sites or to an individual site. (Notification lists and SMTP configuration are central-only and are not deployed.)
- **Per-site deployment**: A "Deploy Artifacts" button on the Sites admin page allows deploying all artifacts to an individual site.
- **Deploy all**: A bulk action deploys artifacts to all sites at once.
- This is a **separate action** from instance deployment — system-wide artifacts are not automatically pushed when definitions change.
- Track per-site deployment status.

### Debug View (Deployment Role)
- Select a deployed instance and open a live debug view.
- Real-time streaming of all attribute values (with quality and timestamp) and alarm states for that instance.
- The `DebugStreamService` creates a `DebugStreamBridgeActor` on the central side. The bridge actor opens a **gRPC server-streaming subscription** to the site's `SiteStreamGrpcServer` for the selected instance, then requests an initial `DebugViewSnapshot` via ClusterClient.
- Ongoing events (`AttributeValueChanged`, `AlarmStateChanged`) flow via the gRPC stream directly to the bridge actor — they do not pass through ClusterClient.
- Events are delivered to the Blazor component via callbacks, which call `InvokeAsync(StateHasChanged)` to push UI updates through the built-in SignalR circuit.
- A pulsing "Live" indicator replaces the static "Connected" badge when streaming is active.
- Stream includes attribute values formatted as `[InstanceUniqueName].[AttributePath].[AttributeName]` and alarm states formatted as `[InstanceUniqueName].[AlarmName]`.
- Subscribe-on-demand — stream starts when opened, stops when closed.

### Parked Message Management (Deployment Role)
- Query sites for parked messages (external system calls, cached DB writes). (Parked notifications are managed centrally on the Notification Outbox page, not here.)
- View message details (target, payload, retry count, timestamps).
- Retry or discard individual parked messages.

### Notification Outbox (Deployment Role)
- Monitor and manage centrally-delivered notifications. The Notification Outbox dispatches every notification store-and-forwarded from sites and logs each one to the central `Notifications` table.
- **KPI tiles** at the top of the page: queue depth (`Pending` + `Retrying`), stuck count, parked count, delivered in the last interval, and oldest pending age. The KPIs are central-computed on demand from the `Notifications` table.
- A **queryable notification list** filterable by status, type, source site, notification list, and time range, with a **stuck-only toggle** and keyword search on subject. Each row shows the notification's status, retry count, last error, and key timestamps.
- **Retry** and **Discard** actions are available on parked notifications: Retry returns the notification to `Pending` and resets `RetryCount` / `NextAttemptAt`; Discard moves it to `Discarded`. The row is retained either way so the table stays a complete audit record.
- Each row exposes a **"View audit history"** action that opens the Audit Log page pre-filtered to `CorrelationId = NotificationId`, surfacing every operational audit event recorded for that notification.
- **Stuck rows are visually badged** — a notification is stuck if it is `Pending` or `Retrying` and older than the configurable stuck-age threshold. Stuck detection is display-only; there is no automated escalation or alerting.
- All queries are served from the central `Notifications` table — no remote per-site queries are needed, unlike the Parked Message Management page.

### Site Calls (Deployment Role)
- Monitor cached calls store-and-forwarded from sites — `ExternalSystem.CachedCall()` and `Database.CachedWrite()` operations. Scoped to the `ExternalCall` and `DatabaseWrite` kinds only; notifications keep their separate Notification Outbox page and are not merged here.
- A **queryable cached-call list** filterable by site, kind, status, and time range. Each row shows the call's timestamp, site, kind, target summary, status badge, retry count, and last error.
- **Retry** and **Discard** actions are available on `Parked` rows only — `Failed` rows are not actionable, since a permanent failure would simply fail again and its error was already returned synchronously to the calling script. The actions issue central→site commands to the owning site; if the site is offline the UI surfaces a "site unreachable" message.
- Each row exposes a **"View audit history"** action that opens the Audit Log page pre-filtered to `CorrelationId = TrackedOperationId`, showing every operational audit event recorded for that cached call.
- Data is served from the central Site Call Audit component's `SiteCalls` table. The page is **read-mostly** — an eventually-consistent mirror of site state; the site remains the source of truth.

### Health Monitoring Dashboard (All Roles)
- Overview of all sites with online/offline status.
- Per-site detail: active/standby node status, data connection health, script error rates, alarm evaluation error rates, store-and-forward buffer depths.
- Headline **Notification Outbox KPI tiles** — queue depth, stuck count, and parked count. These are central-computed by the Notification Outbox from the central `Notifications` table (not part of any site health report). The full outbox view is on the dedicated Notification Outbox page.
- Headline **Site Call Audit KPI tiles** — buffered count, parked count, and failed-last-interval. These are central-computed by the Site Call Audit component from the central `SiteCalls` table (not part of any site health report). The full cached-call view is on the dedicated Site Calls page.
- Headline **Audit KPI tiles** — three tiles in a new "Audit" KPI group: **Audit volume**, **Audit error rate**, and **Audit backlog**. These are sourced from the Audit Log component (#23) and Health Monitoring per the metric definitions in Component-HealthMonitoring.md; the dashboard simply surfaces them. The full audit query view is on the dedicated Audit Log page.

### Site Event Log Viewer (Deployment Role)
- Query site event logs remotely.
- Filter by event type, time range, instance.
- View script executions, alarm events (activations, clears, evaluation errors), deployment events (including script compilation results), connection status changes, store-and-forward activity, instance lifecycle events (enable, disable, delete).

### Audit Log (Admin / Audit Role)
- Lives under a **new top-level "Audit" nav group** (sibling to Notifications). In v1 the Audit nav group contains this single Audit Log page; the pre-existing Configuration Audit Log Viewer remains its own page below.
- Global query / filter / drilldown over the central `AuditLog` table maintained by the Audit Log component (#23). Read-only — the table is append-only, so there are no edit actions on rows.
- Per-site row scoping reuses the existing site-permission model from Security & Auth: a user sees only rows for sites they are authorized to operate. Bulk export (see below) requires the additional `AuditExport` permission.
- **Filter bar** (top of page, collapses to a single row when not focused):
  - Time range — relative (15m / 1h / 24h / 7d) or custom.
  - Channel — multi-select: `ApiOutbound`, `DbOutbound`, `Notification`, `ApiInbound`.
  - Kind — multi-select; the available options are filtered by the selected Channels.
  - Status — multi-select.
  - Site — multi-select, scoped to the user's authorized sites.
  - Instance / Script — text search with autocomplete.
  - Target — text search (system + method, DB connection, list name).
  - Actor — text search (inbound API key name).
  - CorrelationId — paste a `TrackedOperationId` / `NotificationId` / request-id to see the full event sequence for one operation.
  - "Errors only" toggle — shorthand for `Status NOT IN (Success, Delivered, Enqueued)`.
- **Results grid** (custom Blazor + Bootstrap component, consistent with the rest of the UI — no third-party grid):
  - Columns, all resizable and reorderable, persisted per user: `OccurredAtUtc`, `Site`, `Channel`, `Kind`, `Status`, `Target`, `Actor`, `DurationMs`, `HttpStatus`, `ErrorMessage`.
  - Keyset pagination ordered by `(OccurredAtUtc desc, EventId desc)`. Default page size 100.
  - Clicking a row opens the drilldown drawer.
- **Drilldown drawer**:
  - Pretty-prints `RequestSummary` / `ResponseSummary` — JSON is auto-detected and syntax-highlighted; SQL is syntax-highlighted.
  - Surfaces **redaction indicators** wherever headers or fields were stripped at write time, per the Audit Log component's "Payload Capture Policy".
  - **"Copy as cURL"** action on `ApiOutbound` and `ApiInbound` rows.
  - **"Show all events for this operation"** link — re-applies the current view filtered by the row's `CorrelationId`.
- **Export** button on the page header streams a server-side CSV of the current filter (default cap 100k rows; larger exports go through the CLI). Requires the `AuditExport` permission.

### Configuration Audit Log Viewer (Admin Role)
- Pre-existing viewer for the `IAuditService` configuration-change log (template / instance / site / etc. before-after edits). Lives under the same **Audit** nav group as the operational Audit Log above.
- Query the central configuration audit log.
- Filter by user, entity type, action type, time range.
- View before/after state for each change.

### LDAP Group Mapping (Admin Role)
- Map LDAP groups to system roles (Admin, Design, Deployment).
- Configure site-scoping for Deployment role groups.

## Dependencies

- **Template Engine**: Provides template and instance data models, flattening, diff calculation, and validation.
- **Deployment Manager**: Triggers deployments, system-wide artifact deployments, and instance lifecycle commands. Provides deployment status.
- **Communication Layer**: Routes debug view subscriptions, remote queries to sites.
- **Security & Auth**: Authenticates users and enforces role-based access.
- **Configuration Database**: All central data, including audit log data for the audit log viewer. Accessed via `ICentralUiRepository`.
- **Health Monitoring**: Provides site health data for the dashboard.
- **Notification Outbox**: Provides notification delivery KPIs and serves the `Notifications` table queries and Retry/Discard actions for the Notification Outbox page.
- **Site Call Audit**: Serves the `SiteCalls` table queries and relays Retry/Discard actions to sites for the Site Calls page.
- **Audit Log (#23)**: Serves all `AuditLog` table queries (filter / grid / drilldown / CSV export) for the new Audit Log page and the drill-in surfaces on Notifications, Site Calls, External Systems, Inbound API keys, Sites, and Instances. Payload capture, redaction, and per-site authorization follow the Audit Log component's "Payload Capture Policy" and "Security & Tamper-Evidence" sections.
