/*
 * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
 * Date: 2022-04-18
 * Description: This is the Course class.
 */

public abstract class Course {
	/**
	 * The code of the course.
	 */
	private String code;

	/**
	 * The title of the course.
	 */
	private String title;

	/**
	 * The pre-requisite of the course.
	 *
	 * A course always has only one pre-requisite course and the pre-requisite
	 * course cannot be null.
	 *
	 * @see Course
	 */
	private Course preRequisite;

	/**
	 * Constructor.
	 *
	 * @param code         The code of the course.
	 * @param title        The title of the course.
	 * @param preRequisite The pre-requisite of the course. If the pre-requisite
	 *                     course is null, the constructor will print a message of
	 *                     "pre-requisite course cannot be null!" and return
	 *                     directly.
	 */
	public Course(String code, String title, Course preRequisite) {
		if (preRequisite == null) {
			System.out.println("pre-requisite course cannot be null!");
			return;
		}

		this.code = code;
		this.title = title;
		this.preRequisite = preRequisite;
	}

	/**
	 * Get the code of the course.
	 *
	 * @return The code of the course.
	 */
	public String getCode() {
		return code;
	}

	/**
	 * Get the title of the course.
	 *
	 * @return The title of the course.
	 */
	public String getTitle() {
		return title;
	}

	/**
	 * Get the pre-requisite of the course.
	 *
	 * @return The pre-requisite of the course.
	 */
	public Course getPreRequisite() {
		return preRequisite;
	}

	/**
	 * Indicate whether a course is required or not.
	 *
	 * One course could either be a required course or a elective course. Some
	 * courses are required, while the others are not required.
	 *
	 * @return True if the course is required, false if the course is not required.
	 */
	public abstract boolean isRequired();

	/**
	 * Test.
	 */
	public static void testCourse() {
		Course mr = new Course("CS101", "Intro to Java", null) {
			@Override
			public boolean isRequired() {
				return true;
			}
		};
		System.out.println(mr.getCode() == null);
		System.out.println(mr.getTitle() == null);
		System.out.println(mr.getPreRequisite() == null);
		System.out.println(mr.isRequired() == true);

		Course me = new Course("CS102", "Intro to Python", mr) {
			@Override
			public boolean isRequired() {
				return false;
			}
		};
		System.out.println(me.getCode() == "CS102");
		System.out.println(me.getTitle() == "Intro to Python");
		System.out.println(me.getPreRequisite() == mr);
		System.out.println(me.isRequired() == false);

	}
}