#!/usr/bin/perl
# Copyright 2004-7, Jason Thaxter
#
# Redistribution, with or without modification, is permitted provided that the
# following condition is met:
#
# Redistribution of this code must retain the above copyright notice, this
# condition, and the following disclaimer.
#
# THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS
# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
# EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
# EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

use strict;

use DateTime::Format::ISO8601;
use DateTime::Format::Duration;
#use Smart::Comments;

my ($birthday,  $lifeday,  $alpha,   $omega,  $full,
    $time_zone, $interval, $verbose, $output, $until
);

use Getopt::Long;
GetOptions(
    'alpha|a=s'     => \$alpha,
    'birthday|b=s'  => \$birthday,
    'full|f'        => \$full,
    'help|h'        => \&usage,
    'lifeday|l=s'   => \$lifeday,
    'omega|z=s'     => \$omega,
    'time-zone|z=s' => \$time_zone,
    'until|u:s'     => \$until,
    'verbose|v'     => \$verbose,
) or usage();

if ( $alpha and $until ) {
    warn "--alpha and --until are mutually exclusive";
    usage();
}

# start
$birthday ||= '1969-09-04T03:16:00-04';
### $birthday

my $start;
if ( not $until ) {
    $start = DateTime::Format::ISO8601->parse_datetime( $alpha or $birthday );
}
else {
    $start = DateTime->now;
}
$start->set_time_zone($time_zone) if $time_zone;
#$start->truncate( to => 'day' );
### start: $start->iso8601

print "Start time:\t$start\n" if $verbose;

# end
my $end;
if ( $lifeday || $omega ) {
    $end = DateTime::Format::ISO8601->parse_datetime( $lifeday or $omega );
}
elsif ( not $until ) {
    $end = DateTime->now;
}
else {
    ### $until
    $end = DateTime::Format::ISO8601->parse_datetime($until);
}
$end->set_time_zone($time_zone) if $time_zone;
#$end->truncate( to => 'day' );
### end: $end->iso8601
print "End time:\t$end\n" if $verbose;

### Calculate the difference string...
my ( $dur, $fmtr, $output );
if ( not $full ) {
    $dur = $start->delta_days($end);
    ### $dur
    $fmtr = new DateTime::Format::Duration( pattern => '%j' );
    $output = $fmtr->format_duration($dur);
    if ($until){
        $output--;
    }
}
else {
    $dur = $end->subtract_datetime($start);
    ### $dur

    my $y = $dur->years;
    my $m = $dur->delta_months;
    my $d = $dur->delta_days;    # ->days gives zero?

    $output = sprintf '%s years, %s months, %s days', $dur->years,
        $dur->months, $dur->{days};

    # doesn't do years!
    #my $pattern =
    #'%Y years, %m months, %e days, ' . '%H hours, %M minutes, %S seconds';
    #$fmtr = new DateTime::Format::Duration( pattern => $pattern);

}

if ( not $full ) {
    if ( not $lifeday and not $until ) {
        print "You are $output days old.\n";
    }
    elsif ($alpha) {
        print "On $lifeday you were $output days old.\n";
    }
    else {
        print $output;
    }
}
else {
    if ( not $lifeday and not $until) {
        print "You are $output old.\n";
    }
    elsif ($alpha) {
        print "On $lifeday you were $output old.\n";
    }
    else {
        print $output;
    }

}

sub usage {
    print STDERR <<EOF;
Usage: lifeday.pl [OPTIONS]

This just prints out how many days you have been alive. If you don't tell it
your birthday, it will use mine. This is fun for use in .profile, .login, etc.
Or, perhaps, sobering. It can be used as a generic date-difference calculator
using alpha and omega in place of birtday and lifeday switches. Dates must be in
ISO-8601 format: YYYY-MM-DD. Times and time-zones can be used as well. It has a
special "until" mode which prints the days left until a given date, in honor of
the 43rd POTUS.

Options:
    --help,-h         Print this help message and exit.
    --lifeday,-l      Which day to count to
    --birthday,-b,    Set birthday
    --alpha,-a        Set start date
    --omega,-z        Set end date
    --until,-u        Print days from now until this date
    --verbose,-v      Print extra info to stdout.
    --full,-f         Express output in years, months, days, hours, minutes, seconds.
EOF
    exit 1;
}