class Seeker(object):
    """This class implements a pointer for ZukeBox playlist
    A seeker response to a request about the current position, next
    or previous.
    """
    def __init__(self, playlist):
        if playlist is not None:
            self.playlist = playlist
            # the first time the previous position is the current
            self.current = playlist.current
            self.previous = self.current
            self.next = None

    def get_next_pos(self):
        next = self.current + 1
        self.next = next

    def get_previous_pos(self):
        prev = self.previous
        if prev != 0:
            prev = prev - 1
            self.previous = prev

    def get_next(self):
        self.get_next_pos()
        return self.playlist.pop(self.next)

    def get_prev(self):
        self.get_previous_pos()
        return self.playlist.pop(self.previous)