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#!/usr/bin/env perl
use strict;
use warnings;
use utf8;
use feature qw{ postderef say signatures state switch };
no warnings
qw{ experimental::postderef experimental::smartmatch experimental::signatures };
use Carp;
use DateTime;
use Try::Tiny;
# handle command-line input
if (@ARGV) { say date_finder( $ARGV[0] ) }
# testing data
else {
for my $string (qw{2230120 1230120 1230231}) {
say date_finder($string)
}
}
exit;
# break the date string into constituent parts, which will cause errors
# if ill-formatted, and then feed that into DateTime, for formatting, but
# also for catching non-existent dates, like 2220931, for example.
sub date_finder ( $string ) {
my ( $century, $year, $month, $day ) = $string =~ m{
^ # start of string
(\d) # century value 1-2
(\d{2}) # year value 00-99
(\d{2}) # month value 01-12
(\d{2}) # day value 01-31, plus
$ # end of string
}mx;
croak qq{Bad value: Century $century} if $century != 2 && $century != 1;
croak qq{Bad value: Month $month} if $month < 1 || $month > 12;
croak qq{Bad value: Day $day} if $day < 1 || $day > 31;
try {
# here we make a DateTime object with the values give us
# and if those values are invalid, DateTime croaks, which
# we catch
my $y = ( $century == 2 ? '19' : '20' ) . $year;
my $date = DateTime->new(
year => $y,
month => $month,
day => $day,
time_zone => 'floating'
);
return $date->ymd;
}
catch {
# catching the death of DateTime just to die our own way
# MIGHT be antisocial, but I accept it for now.
croak "Bad value: Input is not a day ($string)";
};
}
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