fix(scan-library): prevent NPE during rescan for books with missing file associations (#2429)

Signed-off-by: Balázs Szücs <bszucs1209@gmail.com>

Author: balazs-szucs

booklore-api/src/main/java/com/adityachandel/booklore/service/library/LibraryProcessingService.java

@@ -2,8 +2,8 @@
 
 import com.adityachandel.booklore.exception.ApiError;
 import com.adityachandel.booklore.model.dto.settings.LibraryFile;
-import com.adityachandel.booklore.model.entity.BookFileEntity;
 import com.adityachandel.booklore.model.entity.BookEntity;
+import com.adityachandel.booklore.model.entity.BookFileEntity;
 import com.adityachandel.booklore.model.entity.LibraryEntity;
 import com.adityachandel.booklore.model.websocket.LogNotification;
 import com.adityachandel.booklore.model.websocket.Topic;
@@ -22,7 +22,8 @@
 import java.io.UncheckedIOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.util.*;
+import java.util.List;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 @AllArgsConstructor
@@ -115,13 +116,19 @@ protected static List<Long> detectDeletedBookIds(List<LibraryFile> libraryFiles,
 
         return libraryEntity.getBookEntities().stream()
                 .filter(book -> (book.getDeleted() == null || !book.getDeleted()))
-                .filter(book -> !currentFullPaths.contains(book.getFullFilePath()))
+                .filter(book -> {
+                    if (book.getBookFiles() == null || book.getBookFiles().isEmpty()) {
+                        return true;
+                    }
+                    return !currentFullPaths.contains(book.getFullFilePath());
+                })
                 .map(BookEntity::getId)
                 .collect(Collectors.toList());
     }
 
     protected List<LibraryFile> detectNewBookPaths(List<LibraryFile> libraryFiles, LibraryEntity libraryEntity) {
         Set<String> existingKeys = libraryEntity.getBookEntities().stream()
+                .filter(book -> book.getBookFiles() != null && !book.getBookFiles().isEmpty())
                 .map(this::generateUniqueKey)
                 .collect(Collectors.toSet());
 

booklore-api/src/test/java/com/adityachandel/booklore/service/library/LibraryProcessingServiceRegressionTest.java

@@ -0,0 +1,112 @@
+package com.adityachandel.booklore.service.library;
+
+import com.adityachandel.booklore.model.entity.BookEntity;
+import com.adityachandel.booklore.model.entity.LibraryEntity;
+import com.adityachandel.booklore.model.entity.LibraryPathEntity;
+import com.adityachandel.booklore.model.enums.LibraryScanMode;
+import com.adityachandel.booklore.repository.BookAdditionalFileRepository;
+import com.adityachandel.booklore.repository.LibraryRepository;
+import com.adityachandel.booklore.service.NotificationService;
+import com.adityachandel.booklore.task.options.RescanLibraryContext;
+import jakarta.persistence.EntityManager;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.api.io.TempDir;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
+
+@ExtendWith(MockitoExtension.class)
+class LibraryProcessingServiceRegressionTest {
+
+    @Mock
+    private LibraryRepository libraryRepository;
+    @Mock
+    private NotificationService notificationService;
+    @Mock
+    private BookAdditionalFileRepository bookAdditionalFileRepository;
+    @Mock
+    private LibraryFileProcessorRegistry fileProcessorRegistry;
+    @Mock
+    private BookRestorationService bookRestorationService;
+    @Mock
+    private BookDeletionService bookDeletionService;
+    @Mock
+    private LibraryFileHelper libraryFileHelper;
+    @Mock
+    private EntityManager entityManager;
+    @Mock
+    private LibraryFileProcessor libraryFileProcessor;
+
+    private LibraryProcessingService libraryProcessingService;
+
+    @BeforeEach
+    void setUp() {
+        libraryProcessingService = new LibraryProcessingService(
+                libraryRepository,
+                notificationService,
+                bookAdditionalFileRepository,
+                fileProcessorRegistry,
+                bookRestorationService,
+                bookDeletionService,
+                libraryFileHelper,
+                entityManager
+        );
+    }
+
+    @Test
+    void rescanLibrary_shouldThrowException_whenBookHasNoFiles(@TempDir Path tempDir) throws IOException {
+        long libraryId = 1L;
+        Path accessiblePath = tempDir.resolve("accessible");
+        Files.createDirectory(accessiblePath);
+
+        LibraryEntity libraryEntity = new LibraryEntity();
+        libraryEntity.setId(libraryId);
+        libraryEntity.setName("Test Library");
+        libraryEntity.setScanMode(LibraryScanMode.FILE_AS_BOOK);
+
+        LibraryPathEntity pathEntity = new LibraryPathEntity();
+        pathEntity.setId(10L);
+        pathEntity.setPath(accessiblePath.toString());
+        libraryEntity.setLibraryPaths(List.of(pathEntity));
+
+        BookEntity bookWithNoFiles = new BookEntity();
+        bookWithNoFiles.setId(1L);
+        bookWithNoFiles.setLibraryPath(pathEntity);
+        bookWithNoFiles.setBookFiles(Collections.emptyList()); // Empty files list
+        
+        libraryEntity.setBookEntities(List.of(bookWithNoFiles));
+
+        when(libraryRepository.findById(libraryId)).thenReturn(Optional.of(libraryEntity));
+        when(fileProcessorRegistry.getProcessor(libraryEntity)).thenReturn(libraryFileProcessor);
+        // We need at least one file so it doesn't think the library is offline
+        when(libraryFileHelper.getLibraryFiles(libraryEntity, libraryFileProcessor)).thenReturn(List.of(
+            com.adityachandel.booklore.model.dto.settings.LibraryFile.builder()
+                .libraryPathEntity(pathEntity)
+                .fileName("other.epub")
+                .fileSubPath("")
+                .build()
+        ));
+
+        RescanLibraryContext context = RescanLibraryContext.builder().libraryId(libraryId).build();
+
+        // Should not throw exception anymore
+        libraryProcessingService.rescanLibrary(context);
+
+        // Verify that the book with no files (ID 1) was detected as deleted
+        verify(bookDeletionService).processDeletedLibraryFiles(
+                argThat(list -> list.contains(1L)), 
+                any()
+        );
+    }
+}