How can you return a list for both found records and not found

Question

I'm new to programming so I apologize if I a missing a the concept here. I'm trying to respect bulkification when writing this class and was curious how you can do so given this scenario.

What I am going to do is feed a list of leadIds into the method and I want to do create a record if no record was found and use an existing an record if one was found. I know I need to query the existing record, but how do I go about adding those leads who did not have an existing record while still respecting bulk?

I understand that what I have below is not allowed but this is where my head went...

public class createLNBRecords {

private List<Lead_Not_Booked_Summary__c> createSummaryRecord(List<Lead> leadIds){
    List<Lead_Not_Booked_Summary__c> foundSummaries = [SELECT Id
                                                       FROM Lead_Not_Booked_Summary__c
                                                       Where Lead__c IN :leadIds];
    
    List<Lead> noSummary = [SELECT Id
                            FROM leadIds
                            Where NOT IN :foundSummaries];
    
}

}

Answer 1

You can in a variety of ways. You could create a wrapper:

class SummarySearchResults {
  Lead_Not_Booked_Summary__c[] foundSummaries;
  Lead[] noSummaries;
}
SummarySearchResults createSummaryRecord(Lead[] leadIds) {
  SummarySearchResults results = new SummarySearchResults();
  results.foundSummaries = [SELECT ... ];
  results.noSummaries = [SELECT ... ];
  return results;
}

Or just return a list of lists:

return List<List<sObject>> createSummaryRecord(Lead[] leadIds) {
  Lead_Not_Booked_Summary__c[] foundSummaries = [SELECT ... ];
  Lead[] noSummaries = [SELECT ... ];
  return new List<sObject> { foundSummaries, noSummaries };
}

Or a Map, or any other alternative structure you want.