public class DimensionSelector {

    @InvocableMethod(label='Get Dimensions' description='Returns available Dimension IDs' category='Scheduling')
    public static List<DimensionResult> getDimensions(List<DimensionSelector.DimensionRequest> requests) {      
        Set<Id> scopeIds = (new Map<Id,SObject>([select id from B25__Resource__c where B25__Resource_Type__r.Name = 'Personal Stylist'])).keySet();
        List<DimensionResult> allResults = new List<DimensionResult>();
        for (DimensionRequest request : requests) {
            allResults.add(DimensionSelector.getResultForRequest(request, scopeIds));
        }
        return allResults;
    }
   
    private static DimensionResult getResultForRequest(DimensionRequest request, Set<Id> scopeIds) {
        DimensionResult result = new DimensionResult();
        B25.AvailableDimensionIds.Context context = createContext(request.getReservation(), request.dimensionFieldName, scopeIds);
        result.dimensionIds = new List<Id>(B25.AvailableDimensionIds.findAvailableDimensionIds(context));
        return result;
    }

    public class DimensionResult {
        @InvocableVariable(Label='Available Dimension IDs')
        public List<Id> dimensionIds;
    }

    public class DimensionRequest {
        @InvocableVariable(Label='Start' Required=true)
        public Datetime startDateTime;
        @InvocableVariable(Label='End' Required=true)
        public Datetime endDateTime;
        @InvocableVariable(Label='Dimension Field Name' Required=true)
        public String dimensionFieldName;

        public B25__Reservation__c getReservation() {
            return new B25__Reservation__c(B25__StartLocal__c = startDateTime, B25__EndLocal__c = endDateTime);
        }
    }

    public static B25.AvailableDimensionIds.Context createContext(B25__Reservation__c reservationIn, String dimensionFieldNameIn, Set<ID> dimensionIdsIn) {
        B25.AvailableDimensionIds.Context context = new B25.AvailableDimensionIds.Context();
        context.reservation = reservationIn;
        context.dimensionFieldName = dimensionFieldNameIn;
        context.dimensionIds = dimensionIdsIn;
        return context;
    }

}