#!/usr/bin/env python

# This file is part of ROBOTGAME
#
# ROBOTGAME is free software: you can redistribute it and/or modify it under the
# terms of the GNU General Public License as published by the Free Software
# Foundation, either version 3 of the License, or (at your option) any later
# version.
#
# ROBOTGAME is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along with
# ROBOTGAME.  If not, see <http://www.gnu.org/licenses/>.
#
# ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '
#
#                         direction.py
#                     --------------------
#       date created : Tue Aug 7 2012
#          copyright : (C) 2012 Niels G. W. Serup
#      maintained by : Niels G. W. Serup <ns@metanohi.name>

"""Directions."""

class Direction(object):
    @staticmethod
    def next_pos(pos):
        raise NotImplementedError

class Up(Direction):
    @staticmethod
    def next_pos(pos):
        x, y = pos
        return x, y - 1

class Right(Direction):
    @staticmethod
    def next_pos(pos):
        x, y = pos
        return x + 1, y

class Down(Direction):
    @staticmethod
    def next_pos(pos):
        x, y = pos
        return x, y + 1

class Left(Direction):
    @staticmethod
    def next_pos(pos):
        x, y = pos
        return x - 1, y

succ = {Up:    Right,
        Right: Down,
        Down:  Left,
        Left:  Up}.__getitem__

pred = {Right: Up,
        Down:  Right,
        Left:  Down,
        Up:    Left}.__getitem__