rest api, get ticket categories: remove n+1 query when fetching ticket category configuration

src/main/java/alfio/controller/api/v2/user/EventApiV2Controller.java

@@ -295,6 +295,8 @@ public ResponseEntity<ItemsByCategory> getTicketCategories(@PathVariable("eventN
         //
         return eventRepository.findOptionalByShortName(eventName).filter(e -> e.getStatus() != Event.Status.DISABLED).map(event -> {
 
+            var configurations = configurationManager.getFor(List.of(DISPLAY_TICKETS_LEFT_INDICATOR, MAX_AMOUNT_OF_TICKETS_BY_RESERVATION), ConfigurationLevel.event(event));
+            var ticketCategoryLevelConfiguration = configurationManager.getAllCategoriesAndValueWith(event, MAX_AMOUNT_OF_TICKETS_BY_RESERVATION);
             var messageSource = messageSourceManager.getMessageSourceForEvent(event);
             var appliedPromoCode = checkCode(event, code);
 
@@ -309,7 +311,7 @@ public ResponseEntity<ItemsByCategory> getTicketCategories(@PathVariable("eventN
             List<SaleableTicketCategory> saleableTicketCategories = ticketCategories.stream()
                 .filter((c) -> !c.isAccessRestricted() || shouldDisplayRestrictedCategory(specialCode, c, promoCodeDiscount))
                 .map((m) -> {
-                    int maxTickets = configurationManager.getFor(ConfigurationKeys.MAX_AMOUNT_OF_TICKETS_BY_RESERVATION, ConfigurationLevel.ticketCategory(event, m.getId())).getValueAsIntOrDefault(5); //<- TODO: N+1, find a better way
+                    int maxTickets = getMaxAmountOfTicketsPerReservation(configurations, ticketCategoryLevelConfiguration, m.getId());
                     PromoCodeDiscount filteredPromoCode = promoCodeDiscount.filter(promoCode -> shouldApplyDiscount(promoCode, m)).orElse(null);
                     if (specialCode.isPresent()) {
                         maxTickets = Math.min(1, maxTickets);
@@ -330,7 +332,7 @@ public ResponseEntity<ItemsByCategory> getTicketCategories(@PathVariable("eventN
             var ticketCategoryIds = valid.stream().map(SaleableTicketCategory::getId).collect(Collectors.toList());
             var ticketCategoryDescriptions = ticketCategoryDescriptionRepository.descriptionsByTicketCategory(ticketCategoryIds);
 
-            boolean displayTicketsLeft = configurationManager.getFor(DISPLAY_TICKETS_LEFT_INDICATOR, ConfigurationLevel.event(event)).getValueAsBooleanOrDefault(false);
+            boolean displayTicketsLeft = configurations.get(DISPLAY_TICKETS_LEFT_INDICATOR).getValueAsBooleanOrDefault(false);
             var converted = valid.stream()
                 .map(stc -> {
                     var description = applyCommonMark(ticketCategoryDescriptions.getOrDefault(stc.getId(), Collections.emptyMap()));
@@ -385,6 +387,16 @@ public ResponseEntity<ItemsByCategory> getTicketCategories(@PathVariable("eventN
         });
     }
 
+    private static int getMaxAmountOfTicketsPerReservation(Map<ConfigurationKeys, ConfigurationManager.MaybeConfiguration> eventLevelConf,
+                                                           Map<Integer, String> ticketCategoryLevelConf,
+                                                           int ticketCategory) {
+
+        if (ticketCategoryLevelConf.containsKey(ticketCategory)) {
+            return Integer.parseInt(ticketCategoryLevelConf.get(ticketCategory));
+        }
+        return eventLevelConf.get(MAX_AMOUNT_OF_TICKETS_BY_RESERVATION).getValueAsIntOrDefault(5);
+    }
+
     @GetMapping("event/{eventName}/calendar/{locale}")
     public void getCalendar(@PathVariable("eventName") String eventName,
                             @PathVariable("locale") String locale,

src/main/java/alfio/manager/system/ConfigurationManager.java

@@ -597,4 +597,15 @@ public String getRequiredValue() {
         }
     }
 
+    /**
+     * Fetch all ticket_category_id, value that are present at the ticket category level with a given configuration key
+     *
+     * @param event
+     * @param key
+     * @return
+     */
+    public Map<Integer, String> getAllCategoriesAndValueWith(EventAndOrganizationId event, ConfigurationKeys key) {
+        return configurationRepository.getAllCategoriesAndValueWith(event.getOrganizationId(), event.getId(), key);
+    }
+
 }

src/main/java/alfio/model/system/Configuration.java

@@ -178,10 +178,6 @@ private ConfigurationPathKey(ConfigurationPath path, ConfigurationKeys key) {
     }
     //
 
-    public static ConfigurationPathKey getSystemConfiguration(ConfigurationKeys configurationKey) {
-        return new ConfigurationPathKey(system(), configurationKey);
-    }
-
     private static ConfigurationPathKey getOrganizationConfiguration(int organizationId, ConfigurationKeys configurationKey) {
         return new ConfigurationPathKey(organization(organizationId), configurationKey);
     }

src/main/java/alfio/repository/system/ConfigurationRepository.java

@@ -19,14 +19,18 @@
 import alfio.model.support.JSONData;
 import alfio.model.system.Configuration;
 import alfio.model.system.ConfigurationKeyValuePathLevel;
+import alfio.model.system.ConfigurationKeys;
 import ch.digitalfondue.npjt.Bind;
 import ch.digitalfondue.npjt.Query;
 import ch.digitalfondue.npjt.QueryRepository;
+import ch.digitalfondue.npjt.ConstructorAnnotationRowMapper.Column;
+import lombok.Getter;
 
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 @QueryRepository
 public interface ConfigurationRepository {
@@ -50,6 +54,24 @@ public interface ConfigurationRepository {
     @Query(SELECT_FROM_TICKET_CATEGORY)
     List<Configuration> findCategoryConfiguration(@Bind("organizationId") int organizationId, @Bind("eventId") int eventId, @Bind("ticketCategoryId") int categoryId);
 
+    @Query("SELECT ticket_category_id_fk, c_value FROM configuration_ticket_category where organization_id_fk = :organizationId and event_id_fk = :eventId and c_key = :key")
+    List<CategoryAndValue> findAllCategoriesAndValueWith(@Bind("organizationId") int organizationId, @Bind("eventId") int eventId, @Bind("key") String key);
+
+    @Getter
+    class CategoryAndValue {
+        final int ticketCategoryId;
+        final String value;
+
+        public CategoryAndValue(@Column("ticket_category_id_fk") int ticketCategoryId, @Column("c_value") String value) {
+            this.ticketCategoryId = ticketCategoryId;
+            this.value = value;
+        }
+    }
+
+    default Map<Integer, String> getAllCategoriesAndValueWith(int organizationId, int eventId, ConfigurationKeys key) {
+        return findAllCategoriesAndValueWith(organizationId, eventId, key.name()).stream().collect(Collectors.toMap(CategoryAndValue::getTicketCategoryId, CategoryAndValue::getValue));
+    }
+
     String SYSTEM_FIND_BY_KEY = SELECT_FROM_SYSTEM + " where c_key = :key";
     String ORGANIZATION_FIND_BY_KEY = SELECT_FROM_ORGANIZATION + " and c_key = :key ";
     String EVENT_FIND_BY_KEY = SELECT_FROM_EVENT + " and c_key = :key ";