class WindowGrouper(Grouper):
    """
    A grouper used to create a grouping of students according to their
    answers to a survey. This grouper uses a window search algorithm to create
    groups.

    === Public Attributes ===
    group_size: the ideal number of students that should be in each group

    === Representation Invariants ===
    group_size > 1
    """

    group_size: int


    def make_grouping(self, course: Course, survey: Survey) -> Grouping:
        """
        Return a grouping for all students in <course>.

        Starting with a tuple of all students in <course> obtained by calling
        the <course>.get_students() method, create groups of students using the
        following algorithm:

        1. Get the windows of the list of students who have not already been
           put in a group.
        2. For each window in order, calculate the current window's score as
           well as the score of the next window in the list. If the current
           window's score is greater than or equal to the next window's score,
           make a group out of the students in current window and start again at
           step 1. If the current window is the last window, compare it to the
           first window instead.

        In step 2 above, use the <survey>.score_students to determine the score
        of each window (list of students).

        In step 1 and 2 above, use the windows function to get the windows of
        the list of students.

        If there are any remaining students who have not been put in a group
        after repeating steps 1 and 2 above, put the remaining students into a
        new group.
        """
        students = list(course.get_students())
        s = students.copy()
        master = Grouping()

        while not not s:
            window = windows(s, self.group_size)
            for i in range(len(window)):
                if i + 1 != len(window):
                    if survey.score_students(window[i]) > \
                            survey.score_students(window[i+1]):
                        x = []
                        for lst in window[i:i+2]:
                            for student in lst:
                                x.append(student)
                                s.remove(student)
                        master.add_group(Group(x))

                else:
                    if survey.score_students(window[i]) > \
                            survey.score_students(window[0]):
                        x = []
                        for lst in window[i] + window[0]:
                            for student in lst:
                                x.append(student)
                                s.remove(student)
                        master.add_group(Group(x))
        return master