How to get a string before the last occurrence of a specific character before a maximum character count? - regex

Question

I have some long but variable-length texts that are divided into sections marked by ********************. I need to post those texts into a field that only accepts 2048 characters, so I will need to divide that text into groups of no more than 2048 characters but which do not contain an incomplete section.
My regex so far is ^([\s\S]{1,2048})([\s\S]{1,2048})([\s\S]{1,2048})
However, this has two problems:
1) It divides the text into groups that can include an incomplete section. What I want is a complete section, even if it is not a full 2048 characters. Assume the example below is at the end of 2048 characters.
Here's my actual result. Notice that the "7 Minute Workout" section is cut off mid-section
********************
Maybe Baby™ Period & Fertility (📱)
Popular app for tracking your periods and predicting times of fertility; recommended; avg 4.5/5 stars (3,500+ ratings); 50% off, $3.99 ↘️ $1.99!
https://example.com/2019/07/29/maybe-baby-period-fertility-7-29-19/
********************
7 Minute Workout: Lose Weight (📱)
Scientifically-proven and featured by the New York Times, a 7-minute high intensity workout proven to lose weig
Here's my desired result. Notice that the "7 Minute Workout" section is entirely omitted because it could not be included in its entirety while staying under the 2048 character limit.
********************
Maybe Baby™ Period & Fertility (📱)
Popular app for tracking your periods and predicting times of fertility; recommended; avg 4.5/5 stars (3,500+ ratings); 50% off, $3.99 ↘️ $1.99!
https://example.com/2019/07/29/maybe-baby-period-fertility-7-29-19/
2) The second problem with this regex is that the text I need to input varies greatly in length; it may be less than 2048 or it could be 10,000+ characters. My regex obviously only works for texts up to 6,144 characters long. Do I just keep duplicating the regex a crazy number of times to get longer than the longest text I could enter, or is there a way to get it to repeat?
Addendum: Several asked about the use case/environment for this question. No, it’s not a spambot 🙂. Rather, I’m trying to use Apple’s Shortcuts app to cross-post items from my website to followers on Kik. Unfortunately, Kik has a 2048 character limit, so I can’t post it all at once. I’m trying to use regex to split the text into appropriate sections so I can copy them from Shortcuts and paste them one at a time into Kik.

Answer 1

Couple Notes:
No need to use groups at all, just use match results directly as each match represent one section.
Use lazy quantifier instead of greedy by adding ? after {1,2048} to make the match cut in the right place.
In my regex, I used only Global g without the multiline m.
The code below will work only with sections that have 2048 characters or less. If the section has more than 2048 characters, it will be skipped.
The regex below uses Positive Lookahead to signal the end of the section without matching.
Here is the regex:
^|\*[\s\S]{1,2048}?(?=\n\*|$)
Example: https://regex101.com/r/hezvu5/1/
==== Update ====
To make the results greedy, to match as many sections as possible without splitting the last section, use this regex:
^|\*[\s\S]{1,2048}(?=\n\*|$)