#!/usr/bin/perl -w

use strict;

use POSIX 'floor';

use constant { TRUE => 1, FALSE => 0 };

# set stdout to autoflush

select((select(STDOUT), $| = 1)[0]);

# give the $f value real meaning

my @direction = ("north", "east", "south", "west");

# read the maze data

my ($width, $height) = map { chomp; $_ } split / /, <>;

my @maze = <>;

# clear the screen

print "\e[2J\e[H";

print @maze;

sub exit_handler {

# turn the cursor back on and restore cursor position

print "\e[?25h\e[u";

exit;

}

use sigtrap 'handler', \&exit_handler, 'normal-signals';

# turn off the cursor and save cursor position for later

print "\e[?25l\e[s";

# clean up the maze data

@maze = split //, join '', map { chomp; $_ } @maze;

# find the maze entrance

sub find_entrance {

for (0 .. $height * $width) {

return ($_ % $width, floor($_ / $width)) if 'S' eq $maze[$_];

}

die "failed to find entrance\n";

}

my ($x, $y) = find_entrance;

sub print_at { print "\e[".($_[0]+1).";".($_[1]+1)."H".$_[2]; }

print_at $y, $x, '@';

# define the automaton

my $f = 0;

sub turn_left { $f = ($f + 3) % 4; }

sub turn_right { $f = ($f + 1) % 4; }

# fucking perl's modulo is unsigned. piece of shit.

my @modulo = (0, 1, 0, -1);

sub step {

my $next_y = $y + $modulo[($f + 3) % 4];

my $next_x = $x + $modulo[$f];

my $next_square = $maze[$next_y * $width + $next_x];

return FALSE if ($next_x < 0 or $next_x >= $width);

return FALSE if ($next_y < 0 or $next_y >= $height);

return FALSE if 'X' eq $maze[$next_y * $width + $next_x];

# select '', '', '', .1;

print_at $y, $x, 'o';

$y = $next_y;

$x = $next_x;

print_at $y, $x, '@';

# print "went $direction[$f], now at $x, $y\n";

return TRUE;

}

sub solved { return 'E' eq $maze[$y * $width + $x]; }

# solve the maze

until (solved) {

turn_right;

until (step) { turn_left }

}

exit_handler