Design an Editor with a plain-rich text mode toggle

[pavel-karpovich]

Hi guys, appretiate your attention!

I would like to get an expert advise on how to better implement one not-so-ordinary editor feature.
I have a task to create an editor which will have a toggle control to switch between plain and rich text modes.
The simplest implementation would be to switch between RichTextPlugin and PlainTextPlugin and by rich-to-plain mode transition to clear editor and insert the previous content stripped of all tags. This solution is no brainer, but it will have too many drawbacks and I want to acheive more.
Look at what I want to achieve with plain-rich mode transition:

1. Preserve Undo-Redo history with respect of the selected mode.
2. Option to switch plain text to rich text with restoration of its original form (and more than that, restore it with changes made in a plain text).
   Let me explain it with an example:
   Given editor is set to rich text mode and we entered such content:

• list item 1
• list item 2

So there is an image and bullet list.
Then I toggle rich text mode into plain text mode and my editor content changes to:

image.jpg
- list item 1
- list item 2

Basically all nodes HTML content turned into plain text. Alt text instead of pictue, dashes instead of bullets.
After that I want to edit plain text, say, like that:

- list item A
- list item B

I removed image alt text and modified list items.
And now I want to switch my editor back to rich text mode.

• list item A
• list item B

And I get the bullet list displayed as a bullet list again with modified text. And no image as I deleted corresponding alt text.
Let's assume that my last action in the plain mode editor was removal of "image.jpg" line. And now in the rich text mode I will press Undo action:

• list item A
• list item B

There it is - I restore deleted image while it was deleted in the plain text mode being displayed as alt text.

It is how I want it to work.

It seems not an ordinary behavior and I would like to get some advise on implementation from experienced lexical developers.
As I see it right now, I will have to replace ALL default lexical nodes with extended classes with custom createDOM implemenation which will look at some global mode parameter and return either rich text DOM element or plain text node.
One thing which I'm not sure to understand is where to define global mode parameter so it will be accessible from every node and how to make the editor to react on mode change and reset DOM for all displayed nodes.

Any advice and suggestions will be appreciated!