I was intrigued enough to spend a couple of hours hardcore coding on a grey saturday afternoon...just as a "proof of concept", here's what I ended up with;
1. Hook (no core code changes as it's a hook)
This hook listens to the admin side product EDITING part of the admin page to determine if the products stock has increased.
If
YES, the stock has increased;
1a. It adds an Email to the Queue
If
NO, the stock is unchanged (or decreased)
1b. It does nothing.
Note here that the hook does not listen to the product ADDING part of the page, as a new product would, I think, have no people subscribed to its product notifications.
2. A Queued Email scheduler module (no core code changes as it's a module)
This allows shopowner to make a Email Template, as so;
q_update_stock.jpg
The result
An email is placed into the Queue automatically, as so, based on the explanation in point #1a above;
q_queue.jpg
And looking at the Debug, you can see the email (with replacements [{{FNAME}} to Mickey etc), ready to go;
q_debug.jpg
Conclusion
Wow, that is some hardcore putting together of jigsaw pieces to make a nice picture. I guess it shows the really great flexibility that Phoenix has, as this is all done with no core code changes at all!
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