#!/usr/bin/perl -w
# timediff.pl - outputs a time difference respecting sig figs and grammar
# Author: Jed Yang (htam)
# Date: 2005.08.24
# I _might_ add a -v option to print words that indicate past or future if requested.

use strict;
use Time::Local;
my $show = 0;
my $count = 0;

# this outputs a number with units
# it is called `grammar' because half of the lines (6/12) deal with English grammar
sub grammar
{
   my ($num, $word) = @_;
   $count--;
   return if (!$show && !$num); # skip initial 0's, but not middle ones
   $show = 1;
   print "$num $word";
   print "s" unless (1 == $num);
   exit if ($count <= 0);
   if ($count == 1) {
      print " and ";
   } else {
      print ", ";
   }
}

# program starts here
if (!@ARGV)
{
   print "Usage: countdown.pl year [month [date [hour [min [sec]]]]]\n";
   exit 1;
}
$count = @ARGV; # how many sig figs should the output have? no more than the input, of course
if ($count > 6) # why would any one be naughty?
{
   $#ARGV = 5; # this is NECESSARY as we do a reverse on @ARGV later, it should have precisely 6 elements
   $count = 6; # this is to prevent a trailing comma (and a space) in the output
}
my $now = time(); # on extremely slow systems, a second or two might elapse, rendering our feature useless
my (@now) = localtime $now;

# now begins a block of code to make clarify fuzzy timestamps in such a way to make rounding less critical
$now[4]++; # use 1-based month for user friendliness
for (my $i = @ARGV; $i < 6; $i++)
{
   $ARGV[$i] = $now[5-$i];
}
$ARGV[1]--; # use 1-based month for user friendliness
# so I know this is VERY hackish, but I don't really care right now

my $diff = timelocal(reverse @ARGV) - $now;

# hey, why not?
if ($diff == 0)
{
   print "now";
   exit;
}

my $sec = abs($diff); # no need to restrict to only counting down, really
my $min = int($sec / 60);
$sec %= 60;
my $hour = int($min / 60);
$min %= 60;
my $day = int($hour / 24);
$hour %= 24;
my $month = int($day / 30);
my $year = int($day / 365);
$day %= 365; # get rid of year
$day %= 30; # get rid of month
$month %= 12;

grammar($year, "year");
grammar($month, "month");
grammar($day, "day");
grammar($hour, "hour");
grammar($min, "minute");
grammar($sec, "second");