use v5.26; use strict;
use feature qw[ signatures ]; no warnings qw[ experimental::signatures ];


# From https://perlmonks.org/index.pl?node_id=11137457

use Astro::Coords;
use Astro::MoonPhase qw[ phasehunt ];
use DateTime;
use DateTime::Format::ISO8601;

# Not want to divine the configuration file for Log::Log4perl, module used in
# the query.
{
   package Log::Log4perl;
   sub get_logger( $pkg ) { return bless [], $pkg; }

   sub show( @arg ) { warn @arg, "\n"; }
   sub debug( $ignore, @rest ) { show( 'DEBUG: ', @rest ); }
   sub info(  $ignore, @rest ) { show( 'INFO: ', @rest ); }
   sub warn(  $ignore, @rest ) { show( 'WARNING: ', @rest ); }

   sub error( $ignore, @rest ) { die 'ERROR: ', @rest, "\n"; }
}

my $logger = Log::Log4perl->get_logger();
my $now   = DateTime->now( time_zone => 'UTC' );
$logger->info( "$0 start time: $now" );

# Juilan date: 2459496.96802.
my $isostr = '2021-10-09T11:13:57';
my $dt     = DateTime::Format::ISO8601->parse_datetime($isostr);

show_moon_phases( $dt );

show_moon_venus_travel( $dt, my $show_march = 0 );

my $later = DateTime->now( time_zone => 'UTC' );
my $seconds_dur = $later->subtract_datetime_absolute($now )->in_units( q[seconds] );
my $mess = sprintf q[program run time: %d s], $seconds_dur;
$logger->info( $mess );
exit;


sub show_moon_venus_travel( $dt, $show_travel = undef ) {
   my $moon_coord = Astro::Coords->new( planet => 'Moon' );
   my $venus_coord = Astro::Coords->new( planet => 'Venus' );
   my $jup_coord = Astro::Coords->new( planet => 'Jupiter' );

   # NOTE: Need to get the RA based on time, so $coord->datetime_is_unsafe() is
   # not called.
   for ( $moon_coord, $venus_coord, $jup_coord ) {
      # Observation is location dependent.
      $_->telescope( 'JCMT' );
   }

   # values make initial while condition true
   my $moon_ra  = 4.15;
   my $venus_ra = 4.2;
   my $jup_ra = 7;

   my $adjust_ra = sub { my ( $dt, $coord ) = @_;
                         $coord->datetime( $dt );
                         return $coord->ra( 'format' => q[deg] );
                       };

   my @march;
   while ( $moon_ra < $venus_ra ) {
      ( $moon_ra, $venus_ra ) = map $adjust_ra->( $dt, $_ ),
                                     $moon_coord, $venus_coord;

      if ( $show_travel ) {
         my $random = rand();
         if ( $random > .99 ) {
            push @march, sprintf qq[- dt: %s  Moon RA: %f  Venus RA: %f],
                                 $dt,
                                 $moon_ra, $venus_ra ;
         }
      }

      $dt->add( seconds => 1 );
   }

   my $et = $dt->clone->subtract( seconds => 1 );
   my @mess = ( q[March of Moon & Venus ...],
                @march,
                sprintf( qq[final dt: $dt  et: $et  Julian equality: %f], $et->jd() ),
                sprintf( q[final Moon RA: %f  Venus RA: %f], $moon_ra, $venus_ra )
              );
   $logger->info( join qq[\n  ], @mess );

   return;
}


sub show_moon_phases( $dt ) {
   my @phases = phasehunt( $dt->epoch() );

   my ( $start_epoch, $end_epoch ) = @phases[0,4];
   my $diff     = $end_epoch - $start_epoch;
   my $lunation = $diff / ( 24 * 60 * 60 );
   my $deg_covered_per_day = 360 / ( $diff / ( 24 * 60 * 60 ) );

   my @mess = ( qq[Phasing of the Moon ...],
                sprintf( "phase epoch: %s", join q[, ], @phases ),
                sprintf( "integer bottom of first phase: %d", int( $start_epoch ) ),
                sprintf( "lunation: %f days", $lunation ),
                sprintf( "degrees covered per day: %f", $deg_covered_per_day )
              );
   $logger->info( join qq[\n  ], @mess );
   return;
}


__END__

INFO: 11137457-program.pl start time: 2021-10-14T05:55:20
INFO: Phasing of the Moon ...
  phase epoch: 1633518344.15928, 1634095655.87543, 1634741861.07993, 1635451604.37235, 1636060526.50686
  integer bottom of first phase: 1633518344
  lunation: 29.423407 days
  degrees covered per day: 12.235157
INFO: March of Moon & Venus ...
  final dt: 2021-10-09T20:25:47  et: 2021-10-09T20:25:46  Julian equality: 2459497.351227
  final Moon RA: 239.630096  Venus RA: 239.630026
INFO: program run time: 59 s