package studentDB;
/**
 *	The student data base.
 */
public class StudentDB {
    private StudentList ugStudents = new StudentListImpl();
    private StudentList gradStudents = new StudentListImpl();
    private CourseList courses = new CourseListImpl();

    // Looks up the given student in the given student list. If
    // the student isn't in the list, returns null.
    private Student getStudent (StudentList s, int studentNumber) {
	for (int i=0; i<s.numElements(); i++) {
	    if (s.get(i).getStudentNumber() == studentNumber) {
		return s.get(i);
	    }
	}
	// We didn't find this student
	return null;
    }

    public void load (String dataBaseFile) {
	StudentDBFile db = new StudentDBFile (dataBaseFile);
	String[] line;
	while ((line = db.getNextLine()) != null) {
	    // Echo the line
	    for (int i=0; i<line.length; i++) {
		System.out.print (line [i] + " ");
	    }
	    System.out.println("");

	    // Determine what kind of line this is, and take the
	    // appropriate action to add it to the data base

	    String entryKind = line [0];

	    if (entryKind.equals ("gradStudent")) {
		// Create a grad student object, and add
		// into the list of grad students.
		String name = line [1];
		int studentNumber = Util.strint (line [2]);
		String thesisTitle = line [3];
		GraduateStudent g
		    = new GraduateStudent (name, studentNumber, thesisTitle);

		// Add to list of grad students
		gradStudents.add (g);

	    } else if (entryKind.equals ("ugStudent")) {
		// Create an undergrad student object, and add
		// into the list of undergrad students

		String name = line [1];
		int studentNumber = Util.strint (line [2]);
		CourseList courses = new CourseListImpl();
		UndergraduateStudent s
		    = new UndergraduateStudent (name, studentNumber, courses);

		// Add to list of undergrad students
		ugStudents.add (s);

	    } else if (entryKind.equals ("course")) {
		// Create a course object. Add the course to the
		// list of courses.  Add the enrolled students to
		// the course.  Add the course to the list of courses
		// taken by each of those students.

		String title = line [1];
		Course c = new CourseImpl (title);
		courses.add (c);

		// Add each student to the course, and add the course
		// to each of the students' course list
		StudentList studentsInCourse = c.getEnrolledStudents();
		for (int i=2; i<line.length; i++) {
		    // Get the next student from the list of undergrads
		    // by looking him/her up by student number
		    int studentNumber = Util.strint (line [i]);
		    UndergraduateStudent s = 
			(UndergraduateStudent)
			    getStudent (ugStudents, studentNumber);
		    if (s == null) {
			System.out.println ("Student " + studentNumber
			    + " enrolled in course " + title
			    + " does not exist");
		    } else {
			// Add the student to the list of students
			studentsInCourse.add(s);

			// Add the course to this student's list of courses
			s.getCourses().add (c);
		    }
		}

	    } else {
		// This is an illegal line in the file
		System.out.println ("Error in student data base: " + entryKind);;
	    }

	}
    }


    // Returns the course with the given title in the given list of
    // courses. If the course is not in the list, returns null.
    private Course getCourse (CourseList c, String title) {
	for (int i=0; i<c.numElements(); i++) {
	    if (c.get(i).getTitle().equals (title)) {
		return c.get(i);
	    }
	}
	// We didn't find the course
	return null;
    }

    // Rule 1:  CISC 121 and CISC 124 cannot be taken at the same time
    private void checkRule1() {
	// Go through each students choice of courses, and determine
	// whether that student is enrolled in both cisc121 and cisc124
	for (int i=0; i<ugStudents.numElements(); i++) {
	    // Perform the check for student i
	    UndergraduateStudent s = (UndergraduateStudent) ugStudents.get(i);

	    // Get this student's courses
	    CourseList cl = s.getCourses();

	    // Check if this student is enrolled in both 121 and 124
	    if (getCourse (cl, "cisc121") != null
		    && getCourse (cl, "cisc124") != null) {
		System.out.println ("Student " + s
		    + " is enrolled in both cisc121 and cisc124");
	    }
	}
    }

    // Rule 2:  Students may be enrolled in at most 5 courses at a time
    private void checkRule2() {
	// Go through each students choice of courses, and determine
	// whether that student is enrolled in both cisc121 and cisc124
	for (int i=0; i<ugStudents.numElements(); i++) {
	    // Perform the check for student i
	    UndergraduateStudent s = (UndergraduateStudent) ugStudents.get(i);

	    // Get this student's courses
	    CourseList cl = s.getCourses();

	    // Check if this student is enrolled in more than 5 courses
	    if (cl.numElements() > 5) {
		System.out.println ("Student " + s
		    + " is enrolled in " + cl.numElements() + " courses");
	    }
	}
    }

    // Rule 3:  Courses must have an enrollment of at least 3 students
    private void checkRule3() {
	for (int i=0; i<courses.numElements(); i++) {
	    // Perform the check for course i
	    Course c = courses.get(i);
	    int numStudents = c.getEnrolledStudents().numElements();
	    if (numStudents < 3) {
		System.out.println ("Course " + c
		    + " has only " + numStudents + " student(s).");
	    }
	}
    }

    //  Checks for errors in the data base and displays errors
    //  that are found.
    public void check() {
	// There are three rules -- check them successively, and
	// print appropriate error messages.
	checkRule1();
	checkRule2();
	checkRule3();
    }
}