how to stream user query instead of awaiting it - multithreading

Question

so, I am using a search Delegate to allow user search, however, when user is inputting data, it's really slow, it lags and skips frames as they type, because my search delegate loops through a list that contains about 2000 objects and checks user query against each object's title and main text, making about 4000 search criteria in total, this was causing the lag, so to solve this, I simply spawned a new isolate to handle the suggestions building, as such
Future<List<Data>> allData(String query) async {
List<Data> suggestions;
List<Data> myData(String message) {
return allData.where((data) {
final result = data.dataText.replaceAll(RegExp('[^A-Za-z0-9 ]'), '').toLowerCase();
final result1 = data.dataText.replaceAll(RegExp('[^A-Za-z0-9]'), '').toLowerCase();
final result2 = data.dataText.toLowerCase();
final result3 = data.dataText.replaceAll("th'incarnate", "the incarnate").toLowerCase();
final input = query.toLowerCase();
final result4 = data.dataTitle.toLowerCase();
final result5 = data.dataTitle.replaceAll(RegExp('[^A-Za-z0-9 ]'), '').toLowerCase();
final result6 =data.dataTitle.replaceAll(RegExp('[^A-Za-z0-9]'), '').toLowerCase();
return result.contains(input) ||
result1.contains(input) ||
result2.contains(input) ||
result3.contains(input) ||
result4.contains(input) ||
result5.contains(input) ||
result6.contains(input);
}).toList();
}
query.isEmpty
? suggestions = []
: suggestions = await compute<String, List<Data>>(
myData,
"",
);
if (query.isNotEmpty && suggestions.isEmpty) {
return [
Data(
DataTitle: "No Results",
DataText: "No Results",
),
];
} else {
return suggestions;
}
}
then in buildSuggestions I did this
#override
Widget buildSuggestions(BuildContext context) {
return FutureBuilder<List<Data>>(
future: DataBrain().allData(query),
builder: (context, snapshot) {
List<Data> suggestions;
query.isEmpty ? suggestions = [] : suggestions = snapshot.data!;
return ListView.builder(
itemCount: suggestions.length,
itemBuilder: (context, suggestIndex) {
final suggestion = suggestions[suggestIndex];
if (snapshot.connectionState == ConnectionState.done) {
if (suggestion.dataText.toLowerCase() == "no results") {
return const ListTile(
title: Text("No results"),
subtitle: Text("Please check for spelling mistakes"),
);
} else {
return ListTile(
title: Text(suggestion.dataTitle),
trailing: Text(
'${suggestion.dataBookName} ${suggestion.dataBookNumber == 0 ? '30a' : suggestion.dataBookNumber}',
style: const TextStyle(
fontStyle: FontStyle.italic,
fontWeight: FontWeight.w300,
),
),
onTap: () {
close(context, suggestion);
},
);
}
} else {
return const ListTile(
title: Text('Loading...'),
);
}
});
});
}
it works fine without lags, however now, the suggestions don't build as user types, it waits till user is no longer typing, for like 2 seconds, then it builds suggestions, I think this is because it's a future and in a future builder, I'm not sure why. I'm thinking of turning it into a stream rather and listen to query change and build immediately instead of awaiting for two seconds after user stops querying, is there any workaround, what's a good way to eliminate the delay, i need it to filter the list and build suggestions with each keystroke, as it used to do before i moved it to a new isolate and made it a future