oop/finalproject/Question6/CLI.java

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

import java.util.InputMismatchException;
import java.util.Scanner;

public class CLI {
	private static Scanner input = new Scanner(System.in);

	/**
	 * Read one line from CLI.
	 *
	 * @param message Hint printed to screen
	 * @return one line input
	 */
	private static String readLine(String message) {
		System.out.print(message);
		return input.nextLine();
	}

	/**
	 * Read one positive integer.
	 *
	 * @param message HINT printed to screen
	 * @return one positive integer
	 */
	private static int readPosInt(String message) {
		while (true) {
			System.out.print(message);
			try {
				int result = input.nextInt();
				input.nextLine();
				if (result >= 0) {
					return result;
				} else {
					System.out.println("Positive integers only!");
				}
			} catch (InputMismatchException e) {
				System.out.println("You must type an integer!");
				input.nextLine();
			}
		}
	}

	public static void main(String[] args) {
		int book;
		String username;
		String menuHint = "Type an action (total:1 add:2 get:3 more:4 less:5 quit:6): ";
		String userRoleHint = "Type the user role (lender:1 borrower:2): ";

		Library library = new Library("UIC Library");
		while (true) {
			switch (readPosInt(menuHint)) {
				// total
				case 1:
					System.out.println("Total number of borrowed books: "
							+ library.totalBorrowedBooks());
					break;
				// add
				case 2:
					switch (readPosInt(userRoleHint)) {
						// lender
						case 1:
							username = readLine("Enter the name of the user: ");
							book = readPosInt(
									"Enter the initial number of borrowed books: ");
							Lender lender = new Lender(username, book);
							library.addUser(lender);
							System.out.println("Lender \"" + username + "\" lending " + book
									+ " book(s) has been added.");
							break;
						// borrower
						case 2:
							username = readLine(
									"Enter the name of the user: ");
							book = readPosInt(
									"Enter the initial number of borrowed books: ");
							try {
								library.addUser(new Borrower(username, book));
								System.out.println("Borrower \""
										+ username
										+ "\" borrowing "
										+ book
										+ " book(s) has been added.");
							} catch (NotALenderException e) {
								System.out.println("BUG! This must never happen!");
								System.exit(1);
							}
							break;
						default:
							System.out.println("Unknown user role!");
							break;
					}
					break;
				// get
				case 3:
					username = readLine("Enter the name of the user: ");
					try {
						System.out.println(username + " borrows "
								+ library.getBook(username) + " book(s).");
					} catch (UnknownUserException e) {
						System.out.println("User " + username + " unknown.");
					}
					break;
				case 4:
					username = readLine("Enter the name of the user: ");
					book = readPosInt("Enter the number of books: ");
					try {
						library.moreBook(username, book);
					} catch (NotALenderException e) {
						System.out.println("BUG! This must never happen!");
					} catch (UnknownUserException e) {
						System.out.println("User " + username + " unknown.");
					}
					break;
				case 5:
					username = readLine("Enter the name of the user: ");
					book = readPosInt("Enter the number of books: ");
					try {
						// decrease numbers
						try {
							library.moreBook(username, -book);
						} catch (NotALenderException e) {
							System.out.println("A borrower cannot lend "
									+ (-(library.getBook(username) - book))
									+ " book(s).");
						}
					} catch (UnknownUserException e) {
						System.out.println("User " + username + " unknown.");
					}
					break;
				case 6:
					System.out.println("Goodbye!");
					System.exit(0);
					break;
				default:
					System.out.println("Unknown action!");
					break;
			}
		}
	}
}