first implementation

backend/src/main/java/com/aiteacher/book/BookService.java

@@ -0,0 +1,79 @@
+package com.aiteacher.book;
+
+import org.springframework.stereotype.Service;
+import org.springframework.web.multipart.MultipartFile;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.NoSuchElementException;
+import java.util.UUID;
+
+@Service
+public class BookService {
+
+    private final BookRepository bookRepository;
+    private final BookEmbeddingService bookEmbeddingService;
+
+    public BookService(BookRepository bookRepository, BookEmbeddingService bookEmbeddingService) {
+        this.bookRepository = bookRepository;
+        this.bookEmbeddingService = bookEmbeddingService;
+    }
+
+    public Book upload(MultipartFile file) throws IOException {
+        String originalFilename = file.getOriginalFilename();
+        if (originalFilename == null || !originalFilename.toLowerCase().endsWith(".pdf")) {
+            throw new IllegalArgumentException("Only PDF files are accepted.");
+        }
+
+        String title = deriveTitle(originalFilename);
+
+        Book book = new Book(title, originalFilename, file.getSize());
+        book = bookRepository.save(book);
+
+        // Write to a temp file so the async task can read it
+        Path tempFile = Files.createTempFile("aiteacher-", "-" + book.getId() + ".pdf");
+        file.transferTo(tempFile.toFile());
+
+        UUID bookId = book.getId();
+        Path pdfPath = tempFile;
+        String bookTitle = title;
+
+        bookEmbeddingService.embedBook(bookId, bookTitle, pdfPath);
+
+        return book;
+    }
+
+    public List<Book> listAll() {
+        return bookRepository.findAll();
+    }
+
+    public Book getById(UUID id) {
+        return bookRepository.findById(id)
+            .orElseThrow(() -> new NoSuchElementException("Book not found."));
+    }
+
+    public void delete(UUID id) {
+        Book book = bookRepository.findById(id)
+            .orElseThrow(() -> new NoSuchElementException("Book not found."));
+
+        if (book.getStatus() == BookStatus.PROCESSING) {
+            throw new IllegalStateException("Cannot delete a book that is currently being processed.");
+        }
+
+        bookEmbeddingService.deleteBookChunks(id);
+        bookRepository.deleteById(id);
+    }
+
+    private String deriveTitle(String filename) {
+        // Strip .pdf extension and replace separators with spaces
+        String name = filename.replaceAll("(?i)\\.pdf$", "");
+        name = name.replaceAll("[-_]", " ");
+        // Capitalise first letter
+        if (!name.isEmpty()) {
+            name = Character.toUpperCase(name.charAt(0)) + name.substring(1);
+        }
+        return name;
+    }
+}