import java.io.*;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;

public class BorrowingDAOImpl implements BorrowingDAO {

    private final String filePath;
    private final List<Borrowing> borrowings = new ArrayList<>();

    private final BookDAO bookDAO;
    private final MemberDAO memberDAO;

    private final SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

    public BorrowingDAOImpl(String filePath, BookDAO bookDAO, MemberDAO memberDAO) {
        this.filePath = filePath;
        this.bookDAO = bookDAO;
        this.memberDAO = memberDAO;
        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(",");

                String memberId = arr[0];
                String isbn = arr[1];
                String borrowDateStr = arr[2];
                String returnDateStr = arr.length > 3 ? arr[3] : "";

                Member m = memberDAO.getById(memberId);
                Book b = bookDAO.getByISBN(isbn);

                if (m == null || b == null) {
                    System.err.println("[WARNING] Missing book/member for borrowing: " + line);
                    continue; // skip inconsistent entry
                }

                Date borrowDate = parseDate(borrowDateStr);
                Date returnDate = parseDate(returnDateStr);

                Borrowing borrowing = new Borrowing(m, b, borrowDate, returnDate);
                borrowings.add(borrowing);
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private Date parseDate(String str) {
        if (str == null || str.isBlank()) return null;
        try {
            return sdf.parse(str);
        } catch (ParseException e) {
            System.err.println("Invalid date: " + str);
            return null;
        }
    }

    private String format(Date d) {
        return (d == null) ? "" : sdf.format(d);
    }

    // ----------------------------------------------------

    @Override
    public List<Borrowing> getAllBorrowings() {
        return borrowings;
    }

    @Override
    public List<Borrowing> getBorrowingsByMember(String memberId) {
        List<Borrowing> result = new ArrayList<>();
        for (Borrowing b : borrowings) {
            if (b.getMember().getId().equals(memberId)) {
                result.add(b);
            }
        }
        return result;
    }

    @Override
    public List<Borrowing> getBorrowingsByBook(String isbn) {
        List<Borrowing> result = new ArrayList<>();
        for (Borrowing b : borrowings) {
            if (b.getBook().getIsbn().equals(isbn)) {
                result.add(b);
            }
        }
        return result;
    }

    @Override
    public void addBorrowing(Borrowing b) {
        borrowings.add(b);
    }

    @Override
    public void saveAll() {
        try (PrintWriter pw = new PrintWriter(new FileWriter(filePath))) {

            pw.println("MemberID,ISBN,BorrowDate,ReturnDate");

            for (Borrowing b : borrowings) {
                pw.println(
                        b.getMember().getId() + "," +
                        b.getBook().getIsbn() + "," +
                        format(b.getBorrowDate()) + "," +
                        format(b.getReturnDate())
                );
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}