/*
 * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
 * Date: 2022-04-25
 * Description: This is the Library class.
 */

import java.util.ArrayList;

public class Library {
	private String name;
	private ArrayList<IUser> users;
	private ArrayList<ModelListener> listeners;

	/**
	 * Constructor.
	 *
	 * @param name
	 */
	public Library(String name) {
		this.name = name;

		// init array list
		this.users = new ArrayList<IUser>();
		this.listeners = new ArrayList<ModelListener>();
	}

	// GUI Related
	public void addListener(ModelListener listener) {
		listeners.add(listener);
	}

	// GUI Related
	private void notifyListeners() {
		for (ModelListener listener : listeners) {
			listener.update();
		}
	}

	/**
	 * Add the user to the array list.
	 *
	 * @param user The user to be added
	 */
	public void addUser(IUser user) {
		users.add(user);
		notifyListeners();
	}

	/**
	 * The total number of bookds borrowed by all users.
	 *
	 * @return the number of books.
	 */
	public int totalBorrowedBooks() {
		int total = 0;
		for (IUser user : users) {
			total += user.getBook();
		}
		return total;
	}

	/**
	 * Get the number of books borrowed by this user.
	 *
	 * @param name the name of the query user
	 * @return the number of books
	 * @throws UnknownUserException if user not found
	 */
	public int getBook(String name) throws UnknownUserException {
		for (IUser user : users) {
			if (user.getName().equals(name)) {
				return user.getBook();
			}
		}
		// user not found
		throw new UnknownUserException("User " + name + " unknown.");
	}

	/**
	 * Change the number of books currently borrowed by that user.
	 *
	 * @param name   the user's name
	 * @param number the number of books
	 * @throws UnknownUserException user not found
	 * @throws NotALenderException  can not lend book
	 */
	public void moreBook(String name, int number) throws UnknownUserException, NotALenderException {
		for (IUser user : users) {
			if (user.getName().equals(name)) {
				user.moreBook(number);
				notifyListeners();
				return;
			}
		}
		// user not found
		throw new UnknownUserException("User " + name + " unknown.");
	}

	/**
	 * Test.
	 */
	public static void testLibrary() {
		Library li = new Library("UIC Library");
		System.out.println(li.totalBorrowedBooks() == 0);
		li.addUser(new Lender("L1", 10));
		try {
			System.out.println(li.getBook("L1") == -10);
			System.out.println(li.totalBorrowedBooks() == -10);
			li.addUser(new Borrower("B1", 20));
			System.out.println(li.getBook("L1") == -10);
			System.out.println(li.getBook("B1") == 20);
			System.out.println(li.totalBorrowedBooks() == 10);
			li.getBook("B2");
		} catch (UnknownUserException ex) {
			System.out.println(ex.getMessage().equals("User B2 unknown."));
		} catch (NotALenderException ex) {
			// This should never happen!
			System.out.println(false);
		}
		// More test cases are needed
	}
}