#!/usr/local/bin/perl

# Display Sun and Moon rise and set for a pre-programmed position. The
# -help option gets you help.

use 5.006002;

use strict;
use warnings;

use Astro::Coord::ECI;
use Astro::Coord::ECI::Sun;
use Astro::Coord::ECI::Moon;
use Astro::Coord::ECI::Utils qw{deg2rad};
use Getopt::Long 2.33;
use Pod::Usage;
use POSIX qw{strftime};
use Time::Local;

our $VERSION = '0.119';

Getopt::Long::Configure( 'pass_through' );	# Numbers may be negative.

my %opt = (
    format => '%d-%b-%Y %H:%M:%S',
);

GetOptions( \%opt,
    qw{ date=s format=s moon! sun! tomorrow! },
    help => sub { pod2usage( { -verbose => 2 } ) },
) or pod2usage( { -verbose => 0 } );

my @args = @ARGV;
@args
    or not defined $ENV{ALMANAC_POSITION}
    or @args = split '\s+', $ENV{ALMANAC_POSITION};
@args
    or @args = ( 38.898748, -77.037684, 16.68 );

$opt{sun}
    or $opt{moon}
    or $opt{sun} = $opt{moon} = 1;

#	Stash position where it's convenient.

my ( $lat, $lon, $hgt ) = @args;

#	Start time is the previous midnight. Unless -tomorrow is
#	set, in which case it's the next midnight.

my $start;
if ( defined $opt{date} ) {
    require Date::Manip;
    $start = Date::Manip::UnixDate( $opt{date}, '%s' )
	or die "Invalid date $opt{date}\n";
} else {
    $start = timelocal (0, 0, 0, (localtime)[3 .. 5]);
    $start += 86400 if $opt{tomorrow};
}

#	The end time is the start time + 1 day.

my $end = $start + 86400;

#	Create an object representing our location. Remember that
#	angles are in radians, and distance in kilometers.

my $loc = Astro::Coord::ECI->geodetic(
    deg2rad( $lat ), deg2rad( $lon ), $hgt/1000 );

#	Generate the almanac data for the Sun and Moon if each is
#	desired. We instantiate the luminary, call almanac() on it, and
#	then throw it away.

my @almanac;
foreach my $luminary ( qw{ sun moon } ) {
    $opt{$luminary}
	or next;
    my $class = 'Astro::Coord::ECI::' . ucfirst $luminary;
    push @almanac, $class->new( station => $loc )->almanac(
	$start, $end );
}

#	Display the time and the text description of the events, in
#	order of increasing time.

foreach (sort {$a->[0] <=> $b->[0]} @almanac) {
    print strftime ($opt{format}, localtime $_->[0]), '  ',
	ucfirst ($_->[3]), "\n";
}

__END__

=head1 TITLE

almanac - Generate almanac data for a given location

=head1 SYNOPSIS

 almanac       # The White House by default
 almanac 52.07 4.29 4   # The Hague
 almanac -help
 almanac -version

=head1 OPTIONS

=head2 -date=date_string

This option specifies the date as a string that can be parsed by
L<Date::Manip|Date::Manip>. If L<Date::Manip|Date::Manip> can not be
loaded an error occurs. If this option is specified, C<-tomorrow> is
ignored.

=head2 -format=strftime_format

This option specifies the C<strftime> format used to display dates and
times. The default is C<'%d-%b-%Y %H:%M:%S'>.

=head2 -help

This option displays the documentation for this script. The script then
exits.

=head2 -moon

Display data for the Moon. Defaults to C<-nomoon> if C<-sun> is
asserted.

=head2 -sun

Display data for the Sun. Defaults to C<-nosun> if C<-moon> is asserted.

=head2 -tomorrow

Display data for tomorrow, rather than today.

=head2 -version

This option displays the version of this script. The script then exits.

=head1 DETAILS

This Perl script displays today's almanac for the position given on the
command line, in latitude north of the Equator, longitude east of the
prime meridian, and meters above sea level. If no position is given on
the command line, the contents of environment variable
C<ALMANAC_POSITION> are broken on spaces and used as the posiiton. If
this environment variable is not found, the position of the White House
in Washington DC USA is used.

By default, data for both the Sun and Moon are displayed. If you
explicitly assert either C<-sun> or C<-moon>, only the selected luminary
will be displayed.

You can look a day ahead by specifying C<-tomorrow>.

The format of the time output can be specified using the C<-format>
option.

=head1 AUTHOR

Thomas R. Wyant, III F<wyant at cpan dot org>

=head1 COPYRIGHT AND LICENSE

Copyright (C) 2012-2021 by Thomas R. Wyant, III

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl 5.10.0. For more details, see the full text
of the licenses in the directory LICENSES.

This program is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of
merchantability or fitness for a particular purpose.

=cut

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