#!/usr/bin/perl
use constant DEBUG => undef;
use warnings;
use strict;
use POSIX qw/strftime/;
use Cwd;

my $this = "perl " . getcwd . "/$0";
my $list = getcwd . "list";

if (@ARGV) {
  my $opt = shift @ARGV;
  if ($opt eq "stop") {
    # there's really no point in using this from crontab, it'll shut the whole
    # thing off and eat your crontab.  for breakfast.  with hot sauce.
    print "Removing crontab entries matching $this.\n";

    eval { open CRONTAB, "crontab -l |" };
    if ($@) {
      die "Couldn't list from crontab -l: $@\n"
	unless $@ =~ /^no crontab/i;
    } else { # if there's no crontab, there's no need to save it.
      my @lines = grep {!m($0)o} <CRONTAB>; # simple but weedy
      close CRONTAB;

      open CRONTAB, "| crontab -";
      print CRONTAB for @lines;
      close CRONTAB;
    }
    exit 0;

  } elsif ($opt eq "run") {

    open LIST, "< $list" or die "Couldn't open file `$list': $!\n";

    my $toread = <LIST>;
    my @lines = <LIST>;
    close LIST;

    my $comm = "bsetbg '" .  $lines[$toread] . "'";
    system $comm;

    open LIST, "> $list" or die "Couldn't open file `$list': $!\n";
    print LIST ++$toread, "\n";
    print LIST join "\n", @lines;
    print LIST "\n";
    close LIST;

    exit 0;

  } elsif ($opt eq "create") {
    die "Not enough arguments to script!\n" unless @ARGV;

    my $base = shift @ARGV;
    my @pics;
    my @exts = ("bmp", "jpg", "gif", "png");
    my $extlist = join "|", @exts;
    my $re = qr/$extlist$/io;

    sub dodir ($\$) {
      my $basedir = shift;
      my $refarr = shift;

      opendir my $dir, $basedir or die "Couldn't opendir $basedir: $!\n";

      while (my $f = readdir($dir)) {
	&dodir("$basedir/$f", $refarr)
	  if (-d "$basedir/$f" and $f !~ /^\.\.?$/);
	if (-f "$basedir/$f") {
	  # symbolic links get it in the shorts.  boo hoo.
	  print "pushing file $basedir/$f onto \$refarr\n" if DEBUG;
	  push(@$refarr, "$basedir/$f") if $f =~ $re;
	}
      }

      closedir $dir;
    }

    sub randarr ($) {
      my @arr;
      my $len = shift;

      sub inarr ($@) {
	my $val = shift;
	my @arr = shift;

	foreach my $i (@arr) {
	  return not undef if $val == $i;
	}
      }

      push @arr, int rand $len;

      for (1..$len) {
	my $i;
	do {
	  $i = int rand $len;
	} while inarr($i, @arr);
	push @arr, $i;
      }

      return @arr;
    }

    my $ref = \@pics;
    &dodir($base, $ref);

    print "\@pics exist\n" if DEBUG && @pics;

    my $mins = 5 + strftime '%M', localtime;
    my $hour = strftime '%H', localtime;


    my @cron;
    eval { open CRONTAB, "crontab -l |" };
    if ($@) {
      die "Couldn't pipe from crontab: $!\n"
	unless $@ =~ m/^no crontab/i;
      @cron = ();
    } else {
      @cron = grep {!m($0)} <CRONTAB>;
    }

    close CRONTAB;

    open CRONTAB, "| crontab -";
    print CRONTAB for @cron;
    print CRONTAB "\n";

    @pics = @pics[randarr @pics];

    for (@pics) {
      ++$mins;
      $hour++ if $mins > 60;
      $mins %= 60;
      $hour %= 24;

      print CRONTAB "$mins $hour * * * $this run\n";
    }

    print CRONTAB "$mins $hour * * * $this create\n";
    close CRONTAB;

    open LIST, "> $list" or die "Couldn't open file `$list': $!\n";
    print LIST "0\n";
    print LIST join("\n", @pics);
    print LIST "\n";
    close LIST;

  } else {
    die "Invalid argument: $opt!\n";
  }

} else {
  die "Not enough arguments!\n";
}