Table node (using Tabulator) for Node-RED Dashboard 2.0

A short summary of the node's design concepts, functionality & configuration options. Complete, detailed usage reference is provided in the node's on-line help, available in the Node-RED editor.

ui-tabulator

!example-pic

The ui-tabulator custom node uses the popular Tabulator JavaScript package, for updating, presenting & querying UI tables.
> Note: the node comes in addition to, not replacing, dashboard V2.0's native vue-based table node.

#### General Overview
* The node serves as a smart wrapper containing a Tabulator (table) object. For the most part, it calls the Tabulator API as-is (as defined in the Tabulator Documentation.
* The table table structure & data can be pre-configure in the node configuration, as well as dynamically created/modified/destroyed in runtime.
* Interface to the node is through messages (Node-RED msg objects). The message specifies a command (with arguments), and returns the table's response
* The table accepts data-setting commands (e.g. setData, addData, updateData, deleteData etc.) as well as data-query commands (getData, searchData etc.), and in-cell data edit (from the UI).
* In addition, the node can send unsolicited notifications on selected table events (e.g. cell & row click/double-click, cell edit etc.)
* By default, the table operates in _shared_ mode, i.e. a common table image (data + styling) in all concurrent dashboard clients. The table image is also cached in the Node-RED datastore, and reloaded upon browser open, refresh etc.
The node also supports a _Multi-User_ mode, which maintains independent, client-specific table data without a centralized datastore.

#### Message Examples
* Data-setting command example
``
msg.tbCmd = "addData";
msg.tbArgs = [
[
{id:1, name:"bob", gender:"male"},
{id:2, name:"Jenny", gender:"female"}
],
true
];
`
* Data-retrieval command example
`
msg.tbCmd = "searchData";
msg.tbArgs = [ "age", ">", 12 ];
`
* Event example
`
{
tbName: "myTable1234",
msgType: "tbNotification",
event: "cellEdited",
payload: {
id: 2,
field: "name",
newValue: "Jack Brown",
oldValue: "John Doe"
},
_client: {
socketId: "uXRxjY9yO-Hya1vtAAAB"
},
_msgid:"6d9d7a97666f2783"
}
``
#### Node Configuration
The node configuration properties (in the editor):
* Name, Group, Size: - same as in all dashboard 2.0 nodes
* Initial Table Configuration: JSON object with all table & column definitions, and (optional) initial data
* Custom Functions: logical expressions for custom or dynamic table settings, e.g. conditional formatting, user-defined filters/validators etc.
* Allow functions in messages: (Y/N) - security option to block function injection in runtime
* Max Width: sets the maximum visible width of the table
* Notifications: selection of table events which trigger notification messages
* Multi-user mode: (Y/N)
* Row-Id validation/duplication check (Y/N)
* CSS theme: selection of an optional tabulator CSS Stylesheet (e.g. _Midnight_, _Modern_ etc.)
* DIV Override: optional: enables to specify the HTML DIV Id in which the table will be created, overriding the default auto-allocated DIV

#### Architectural Concepts in Multi-Client Environment
Tables are created as _widgets_ on the client (browser) page. Hence, in case of multiple dashboard clients, a single _ui-tabulator_ node will be associated to multiple table widgets. Per Node-RED's framework, every message sent to a _ui-tabulator_ node in a flow, is broadcasted to all of its respecive widgets. If the table object responds, the flow will receive multiple, identical responses (one per client). In _Shared_ mode we do the following:
* Data-setting & styling commands sent from the _ui-tabulator_ node in flow to all table widgets in parallel, thus applying the same changes on the widgets
* The (identical) table responses to command messages are grouped by _msgid_, and only a single response is returned to the flow
* When a user changes table data directly on the UI of any client, an update notification is automatically sent to all other clients
* The current table data image is always saved in the Node-RED datastore, automatically restoring the table image upon client open/refresh.

Having said the above, some table presentation aspects (on top of the common data image) are user-related by nature, and are not synchronized. For example, users may want to set their own filtering/sorting, or select specific rows for further actions. In such cases, each client table may return a different response to data query commands. For this, the command should be scoped to a specific table widget (by specifying the client Id, or initiating the command from a dashboard objet, e.g. button, on the same client)

#### Known Issues
When the node is started (e.g. upon server restart or full deploy), sometimes its connectivity with existing clients is not restored properly. As a temporary workaround (until fixed in Node-RED), each client automatically reloads itself once upon reconnection (showing a little "flicker").

#### Node Dependencies
* Node-JS version >= 18
* Node-red version >= 3.10
* Node-red dashboard 2.0, version >= 1.22.0
* Tabulator version >= 6.3 (comes bundled in the node installation)