import java.io.*;
import java.util.*;

public class BookDAOImpl implements BookDAO {

    private final String filePath;
    private final List<Book> books = new ArrayList<>();

    public BookDAOImpl(String filePath) {
        this.filePath = filePath;
        load();
    }

    private void load() {
        try (BufferedReader br = new BufferedReader(new FileReader(filePath))) {
            br.readLine(); // skip header
            String line;
            while ((line = br.readLine()) != null) {
                String[] arr = line.split(",");
                books.add(new Book(arr[0], arr[1]));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public List<Book> getAllBooks() {
        return books;
    }

    @Override
    public Book getByISBN(String isbn) {
        return books.stream()
                .filter(b -> b.getIsbn().equals(isbn))
                .findFirst().orElse(null);
    }

    @Override
    public void addBook(Book book) {
        books.add(book);
    }

    @Override
    public void saveAll() {
        try (PrintWriter pw = new PrintWriter(new FileWriter(filePath))) {
            pw.println("ISBN,Title");
            for (Book b : books) {
                pw.println(b.getIsbn() + "," + b.getTitle());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}