#!/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/>.
#
# ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '
#
#                         rollingstone.py
#                     --------------------
#       date created : Tue Aug 7 2012
#          copyright : (C) 2012 Niels G. W. Serup
#      maintained by : Niels G. W. Serup <ns@metanohi.name>

"""Logic for rolling."""

from __future__ import print_function

class RollingStoneError(Exception):
    pass

class Field(object):
    def next_posdir(self):
        raise NotImplementedError

class Start(Field):
    def __init__(self, direction):
        self.direction = direction

    def next_posdir(self, pos, direc):
        return self.direction.next_pos(pos), self.direction

class Turn(Field):
    def __init__(self, direction):
        self.direction = direction

    def next_posdir(self, pos, direc):
        return self.direction.next_pos(pos), self.direction

class Goal(Field):
    def next_posdir(self, pos, direc):
        return pos, direc

class Stone(Field):
    def next_posdir(self, pos, direc):
        return pos, direc


def step(playfield, pos, direc):
    field = _at(playfield, pos)
    if field is not None:
        return field.next_posdir(pos, direc)
    return direc.next_pos(pos), direc

def reaches_goal(playfield, max_steps):
    pos = _find_start(playfield)
    direc = None
    for i in range(max_steps):
        pos, direc = step(playfield, pos, direc)
        if isGoal(playfield, pos):
            return True
        if isStone(playfield, pos):
            return False
    return False

def _find_start(playfield):
    for y in range(len(playfield)):
        for x in range(len(playfield[y])):
            if isStart(playfield, (x, y)):
                return (x, y)
    raise RollingStoneError("Missing Start field")

def _at(playfield, pos):
    x, y = pos
    return playfield[y][x]

_is = lambda t: lambda playfield, pos: isinstance(_at(playfield, pos), t)

(isGoal, isTurn, isStart, isStone) = (_is(Goal), _is(Turn), _is(Start), _is(Stone))



def generate_playfield():