#!/usr/local/bin/perl
#
# Rock Scissors Paper
# a basic artificial life demo
# using the unix file system as "environ"
#
# by miff, 3/2000
# 
# written for the "Creative Perl Daemon" contest.
#
# here's the scoop:
# -we spawn 3 daemons, rock, scissors, and paper
# -given a base dir, and using all the dirs below it
#  that we dont specifically exclude in @nouse, we will
#  allow rock, scissors, and paper to "claim" any dir.
#  as its territory.  NOTE! make sure you have write access
#  to all subdirs in question!  (you can use root user and /
#  if you like - or use someuser and ~someuser)
# -rock will determine its own life force by the number of
#  .rocks that are existing at the beginning of any cycle;
#  rock then tries to write more .rocks - it succeeds if
#  the dir is empty of (.rock/.scissors/.paper) and gets
#  one more ".rock" territory.  if it encounters ".scissors"
#  rock gets the terrirory and an extra life point bonus.
#  If it encounters ".paper" in a dir, rock loses a life point
#  and moves on.
# -the other elements behave similarly
# -the number of life points determines the number of "turns"
#  an element has before a mandatory sleep event.
# -if any element has no territories left, it dies.
# -to watch what is going on, tail -f /tmp/RSPlog
# -use ps aux | grep ROCK to see a process, killall -9 rsp to 
#  stop them all!
#
# mad shouts and 40z to all my homiez
# and
# the obligatory plug:  mike patton rules.
#
# EFNet #perl sucks.
#
# miff@9mm.com
#

#use NOTHING.    we aint submitting other ppl's code...

my $life = 4;   #set an initial life to 4 - meaning we will be able to 
		#write 4 of "me" (rock/scis/pap) initially.
my $alive = 1;  #lets hope we stay alive!

#put the dir that you want to be "root" of your env here:
my $basedir = '/home/miff';

#PUT ALL DIRS YOU DONT WANT TO USE HERE -->
my @nouse = ('/dev','/proc','/cdrom','/floppy','/usr/src','/var/lib');  

my $sleeptime = 5;  #sleep for 5 seconds between cycles
my $logfile = '/tmp/RSPlog'; # lets all write to the same log

my $this_rsp;  #which rock/scis/paper are we?
my $this_desc;  #R/S/P description (for log)?
my $we_beat;   #which rock/scis/paper do we beat?
my $beats_us;  #which rock/scis/paper beats us
my @elements = ('ROCK','PAPER','SCISSORS');

#and, to comply with the "rules", we have to set umask and set initial working dir:
# damn rules.  rules are not for perl people.  i'll comply so my entry doesnt get
# booted out of the contest, but under strong protest.
chdir ("/");  
umask 0;      

my @alldirs;
my @tmpdirs = split "\n", `find '$basedir' -type d `;
my $d,$nu;
#now remove the no use dirs:
foreach $d (@tmpdirs) {
	my $ok = 1;
	foreach $nu (@nouse) {
		if ($d =~ /$nu/) {
			$ok = 0;
		}
	}
	if ($ok) {
		push @alldirs, $d;
	}
}

#lets clear the logfile and some old rsps if they exist!
print "Clearing prior environment\n";
system ("cat /dev/null > $logfile");
system ("rm `find '$basedir' -name .rock` ");
system ("rm `find '$basedir' -name .scissors` ");
system ("rm `find '$basedir' -name .paper` ");

#TIME TO SPAWN OUR ROCK, SCISSORS, AND PAPER!!
# note to judge:  we use a double fork.
my $element;
foreach $element (@elements) {
	print "forking for $element \n";
	my $spawn_id = fork();
	die "fork failed: $!" unless defined $spawn_id;
	if ($spawn_id) {
        	#we are the parent 
        	waitpid($spawn_id,0);
	} else { 
		#we are the child
		my $dfork = fork();
		die "double fork failed $!" unless defined $dfork;
		if ($dfork)  {
		  	#we are the intermediary - must die!!!
			exit 0; 
		}
		#critical!  clear out @elements!
		$this_desc = $element;
		@elements = '';
	}
}

#now we are a happily forked rock, scissor, or paper!
#(defined by $element)
if ($this_desc eq "ROCK") {
	$this_rsp = ".rock";
	$we_beat = ".scissors";
	$beats_us = ".paper";
} elsif ($this_desc eq "PAPER") {
	$this_rsp = ".paper";
	$we_beat = ".rock";
	$beats_us = ".scissors";
} elsif ($this_desc eq "SCISSORS") {
	$this_rsp = ".scissors";
	$we_beat = ".paper";
	$beats_us = ".rock";
} else {
	print "all processes launched;  tail -f $logfile for progress! \n";
	exit(0); #parent exits here.
}
$0 = $this_desc;  #set our proc name!

open STDIN,  '/dev/null' or die "Can't read /dev/null: $!";
open STDOUT, '>/dev/null';
open STDERR, '>/dev/null';

#do an initial write:
open LOGFILE, ">>$logfile";
print LOGFILE "$this_desc born with $life life points. \n";
close LOGFILE;

#set up randomizer
srand(time ^ $$);

my @provinces;  #the dirs that i have staked a claim to
my $loops;  #how many "turns" did we stay alive?

#MASTER LOOP!!
while ($alive) {
	$loops++;
	my $added = 0;
	my $rejected = 0;
	my $converted = 0;
	my @nprov = '';
	#check how many dirs we still claim:
	foreach $d (@provinces) {
		if (-e $d) {
			#ok!
			push @nprov, $d;
			$life++;
		}
	}
	@provinces = @nprov; #trim out the lost territories
	if ($life < 1) { 
		$alive = 0; #im slain!
	}
	#NOW WE LIVE AND TAKE ACTION!
	while ($life > 0) {
		#pick a random dir:
		my $randdir = @alldirs[int(rand($#alldirs))];
		my $newrsp = "$randdir/$this_rsp";
		#now check what is in it!:
		if (-e "$newrsp") {
			#do nothing.
		} elsif (-e "$randdir/$we_beat") { 
			#we found someone we can beat: 
			my $removal = "$randdir/$we_beat";
			unlink $removal;
			system ("touch '$newrsp' ");
			push @provinces, $newrsp;
			$added++;
			$converted++;
			$life++;  # a little life bonus!
		} elsif (-e "$randdir/$beats_us") { 
			#we got beat down!
			$rejected++;
			$life--;
		} else {
			#we found an empty dir!
			system ("touch '$newrsp' ");
			push @provinces, $newrsp;
			$added++;
		}
		$life--;
	}
	#do a quick log write...
	open LOGFILE, ">>$logfile";
	my $message = "$this_desc has run $loops loops. \n" .
		"	added $added territories,\n".
		"	beat down $converted enemies,\n".
		"	and got rejected $rejected times.\n";
	print LOGFILE "$message";
	close LOGFILE;

	#now sleep and recover some energy:
	sleep ($sleeptime + int(rand(4))); # add some randomness
}

#the only way to get out of the loop is to be dead.:
open LOGFILE, ">>$logfile";
print LOGFILE "*******$this_desc has died after $loops iterations. **********\n";
close LOGFILE;
exit(0);