Programmatically changing TextSpans in the selected text of a SelectableText.rich - flutter

Question

I have a SelectableText.rich widget in flutter where the usecase requires each word within the text to be its own TextSpan.
The app currently parses the text into words and sets up the list of TextSpans. I want the user to be able to select text and then trigger a modification to the styling of all TextSpans touched by the selection.
For example, let’s say the SelectableText.rich has the following text where each word is its own TextSpan:
The boy went to the store. He went to the store every day.
If the user selects “went to the store” in the first sentence and then taps on a ‘bold’ button, how can I identify which spans should be affected? Note that “went to the store” is in the source text twice but only the first instance should be modified (so I can’t simply search the source text).
Here's a stripped-down example (using only the first sentence):
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'RichText Selection Issue',
home: MyHomePage(),
);
}
}
class MyHomePage extends StatelessWidget {
const MyHomePage({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: const Text('Selectable Text Problem')),
body: Padding(
padding: const EdgeInsets.all(30),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
const SelectableText.rich(
TextSpan(text: 'The ', style: TextStyle(fontSize: 20), children: [
TextSpan(text: 'boy '),
TextSpan(text: 'went '),
TextSpan(text: 'to '),
TextSpan(text: 'the '),
TextSpan(text: 'store '),
TextSpan(text: '.'),
])),
const SizedBox(height: 20),
// Add button to trigger selection
ElevatedButton(
onPressed: () {},
child: const Text('Select'),
),
],
),
),
);
}
}
What would I do in the ElevatedButton's onPressed callback to trigger a rebuild that modified the style associated with the TextSpans for 'went to the store'? I can't take the example further than this because I don't know how to associate the selected text with the spans (which obviously would need 'style' properties and presumably some sort of state logic relating to whether or not they should be rendered as bold).
Any suggestions on how this could be handled (or pointers to any online articles covering this sort of topic)?
Thanks in advance!
Note : For the purposes of this question, please ignore the fact that the user could select partial words using the SelectableText widget. I haven’t thought through that issue yet (the objective would be that a partially selected word would be treated as the full word).
Edited to add an example.