refactor: Centralize constants and improve error handling

src/main/java/ru/cathub/telegabot/service/impl/BookEditingServiceImpl.java

@@ -41,10 +41,10 @@ public class BookEditingServiceImpl implements BookEditingService {
                 log.info("Found book with id {}", bookId);
                 telegramClientService.sendMessage(user, "Выберите поле для редактирования:", getEditOptions(user));
             } else {
-                telegramClientService.sendMessage(user, "Книга не найдена");
+                telegramClientService.sendMessage(user, Constants.ERROR_BOOK_NOT_FOUND);
             }
         } catch (NumberFormatException e) {
-            telegramClientService.sendMessage(user, "Некорректный ID книги");
+            telegramClientService.sendMessage(user, Constants.ERROR_INVALID_BOOK_ID);
         }
     }
 

src/main/java/ru/cathub/telegabot/service/impl/BookListingServiceImpl.java

@@ -25,13 +25,11 @@ public class BookListingServiceImpl implements BookListingService {
     private final TelegramClientService telegramClientService;
     private final BookRepository bookRepository;
 
-    private static final String FULL_STAR = "⭐"; // Эмодзи U+2B50
-    private static final String EMPTY_STAR = "☆"; // Символ U+2606
 
     @Override
     public void showPaginatedBookList(BotUser botUser, int page, Integer messageId, Boolean forEdit) {
         try {
-            Pageable pageable = PageRequest.of(page, 5);
+            Pageable pageable = PageRequest.of(page, Constants.PAGE_SIZE);
             Page<Book> books = bookRepository.findByBotUserOrderByIdAsc(botUser, pageable);
 
             StringBuilder sb = new StringBuilder();
@@ -57,8 +55,8 @@ public class BookListingServiceImpl implements BookListingService {
                 bookCacheService.updateBookEditCache(botUser.getId(), BookEditStateCache.builder().bookEditState(BookEditStateCache.BookEditState.CHOOSING_FIELD).build());
             }
         } catch (Exception e) {
-            log.error("Error loading book list", e);
-            telegramClientService.sendMessage(botUser, "❌ Ошибка при загрузке списка книг");
+            log.error("Error loading book list for user {}", botUser.getId(), e);
+            telegramClientService.sendMessage(botUser, Constants.ERROR_LOADING_BOOKS);
         }
     }
 
@@ -72,8 +70,7 @@ public class BookListingServiceImpl implements BookListingService {
     }
 
     private String getBookIcon(int index) {
-        String[] icons = {"📘", "📙", "📕", "📗", "📓"};
-        return icons[index % icons.length];
+        return Constants.BOOK_ICONS[index % Constants.BOOK_ICONS.length];
     }
 
     private String escapeMarkdown(String text) {

src/main/java/ru/cathub/telegabot/service/impl/BookManageServiceImpl.java

@@ -25,8 +25,6 @@ import static ru.cathub.telegabot.utils.Constants.*;
 @Slf4j
 public class BookManageServiceImpl implements BookManageService {
 
-    private static final String FULL_STAR = "⭐"; // Эмодзи U+2B50
-    private static final String EMPTY_STAR = "☆"; // Символ U+2606
     private final BookCreationService bookCreationService;
     private final BookEditingService bookEditingService;
     private final BookListingService bookListingService;
@@ -38,7 +36,7 @@ public class BookManageServiceImpl implements BookManageService {
 
     public static String formatRating(int rating) {
         // Ограничиваем рейтинг в диапазоне 0-10
-        int validatedRating = Math.min(10, Math.max(0, rating));
+        int validatedRating = Math.min(Constants.MAX_RATING, Math.max(Constants.MIN_RATING, rating));
 
         StringBuilder sb = new StringBuilder();
 
@@ -83,7 +81,7 @@ public class BookManageServiceImpl implements BookManageService {
                 break;
             default:
                 if (editCache == null || editCache.getBookEditState() == BookEditStateCache.BookEditState.NONE) {
-                    telegramClientService.sendMessage(user, "❌ Нет текущего действия. Выберете действие из меню или перейдите в начальное меню командой /start");
+                    telegramClientService.sendMessage(user, Constants.ERROR_NO_ACTION);
                     return;
                 }
                 switch (editCache.getBookEditState()) {

src/main/java/ru/cathub/telegabot/utils/Constants.java

@@ -1,14 +1,35 @@
 package ru.cathub.telegabot.utils;
 
-public class Constants{
+public class Constants {
+    // Commands
     public static final String START = "/start";
-
-    public static final String BOOK_CACHE_NAME = "bookCache";
+    
+    // Menu options
     public static final String ADD_BOOK = "Добавить книгу";
     public static final String LIST_BOOKS = "Список книг";
     public static final String BACK = "Назад";
     public static final String EDIT_BOOKS = "Редактировать книги";
+    
+    // Cache names
+    public static final String BOOK_CACHE_NAME = "bookCache";
     public static final String BOOK_CACHE_LIST = "bookListCache";
     public static final String BOOK_CACHE_EDIT = "bookEditCache";
-
+    
+    // Rating constants
+    public static final String FULL_STAR = "⭐";
+    public static final String EMPTY_STAR = "☆";
+    public static final int MAX_RATING = 10;
+    public static final int MIN_RATING = 0;
+    
+    // Pagination
+    public static final int PAGE_SIZE = 5;
+    
+    // Book icons
+    public static final String[] BOOK_ICONS = {"📘", "📙", "📕", "📗", "📓"};
+    
+    // Error messages
+    public static final String ERROR_BOOK_NOT_FOUND = "Книга не найдена";
+    public static final String ERROR_INVALID_BOOK_ID = "Некорректный ID книги";
+    public static final String ERROR_LOADING_BOOKS = "❌ Ошибка при загрузке списка книг";
+    public static final String ERROR_NO_ACTION = "❌ Нет текущего действия. Выберите действие из меню или перейдите в начальное меню командой /start";
 }