use strict;
use warnings;

use DateTime;
use DateTime::Format::ISO8601;
use DateTime::TimeZone;
use Data::Dumper;
use Try::Tiny;

use Astro::MoonPhase;

######
# Calculate the moon phase of an event in time.
# Required is the date (time defaults to 00:00:01) of the event
# The moon-phase calculator does not need a location
# since moon phase is the same across the planet (more-or-less)
# with the usual antipodean side-effects
# However, by specifying a timezone or even coordinates of the
# event conversion of event's time to UTC is more accurate
# (else UTC time is assumed)
# author: bliako
# date: 2021-10-07
######

my $debug = 0;

my @events = (
#  {
#    # example event specification
#    "name" => "a name for reference, required",
#    "date" => "date of the event in YYYY-MM-DD",
#    "time" => "optional time as hh:mm:ss, default is 00:00:01",
#    #specify optional location using one of these for calculating
#    #epoch which uses UTC time,
#    #otherwise, UTC timezone will be assumed for event's time:
#    "timezone" => "standard timezone name, e.g. America/Havana",
#    "location" => "cuba",
#    "location" => {lon=>-81.1376, lat=>22.17927},
#  },

  {
    "name" => "Normandy Landing",
    "date" => "1944-06-06",
    "time" => "05:00:00",
    #"timezone" => "Europe/Paris",
    "location" => {lat=>49.180000, lon=>-0.370000}
  },
  {
    "name" => "US Invasion of Cuba, Bay of Pigs",
    "date" => "1961-04-15",
    "time" => "05:00:00",
    "timezone" => "America/Havana",
    #"location" => {lon=>-81.1376, lat=>22.17927}
  },
  {
    "name" => "Invasion of Libya",
    "date" => "2011-03-19",
    "time" => "05:00:00",
    "timezone" => "Africa/Tripoli",
  },
  {
    "name" => "Invasion of Iraq",
    "date" => "2003-03-19",
    "time" => "05:00:00",
    "timezone" => "Asia/Baghdad",
  },
);

for my $event (@events){
	my $epoch = parse_event($event);

	print event2str($event) . "\n";

	my (	$MoonPhase,
		$MoonIllum,
		$MoonAge,
		$MoonDist,
		$MoonAng,
		$SunDist,
		$SunAng
	) = phase($epoch);
	print "Moon age: $MoonAge days\n";
	print "Moon phase: ".sprintf("%.1f", 100.0*$MoonPhase)." % of cycle (birth-to-death)\n";
	print "Moon's illuminated fraction: ",sprintf("%.1f", 100.0*$MoonIllum)." % of full disc\n";

	print "important moon phases around the event:\n";
	my @phases = phasehunt($epoch);
	print "  New Moon      = ", scalar(localtime($phases[0])), "\n";
	print "  First quarter = ", scalar(localtime($phases[1])), "\n";
	print "  Full moon     = ", scalar(localtime($phases[2])), "\n";
	print "  Last quarter  = ", scalar(localtime($phases[3])), "\n";
	print "  New Moon      = ", scalar(localtime($phases[4])), "\n";
	print "end event.\n\n"
}

sub event2str {
	my $event = shift;

	if( ! exists $event->{_is_parsed} ){
		warn "event has not been parsed, just dumping it...";
		print Dump($event);
	}
	my $str = $event->{name}
	 . " on ".$event->{datetime}
	 . " (".$event->{datetime}->epoch." seconds unix-epoch)"
	 . " timezone: ".$event->{datetime}->time_zone->name
	;
	if( exists $event->{location} ){
		if( ref($event->{location}) eq 'HASH' ){
			$str .= " (lat: ".$event->{location}->{lat}.", lon: ".$event->{location}->{lon}.")"
		} else { $str .= "(".$event->{location}.")" }
	}
	return $str
}

sub parse_event {
	my $event = shift;

	if( ! exists $event->{date} ){ die "date field is missing from event." }

	my $datestr = $event->{date};

	die "event does not have a 'name' field, please specify one, anything really."
		unless exists $event->{name};

	my $timestr = "00:00:01";
	if( exists $event->{time} ){
		$timestr = $event->{time};
		print "event2epoch(): setting time to '$timestr' ...\n"
			if $debug > 0;
		die "time '$timestr' is not valid, it must be in the form 'hh:mm:ss'."
			unless $timestr =~ /^\d{2}:\d{2}:\d{2}$/;
	} else { $event->{time} = $timestr }

	my $isostr = $datestr . 'T' . $timestr;
	my $dt = DateTime::Format::ISO8601->parse_datetime($isostr);
	die "failed to parse date '$isostr', check date and time fields."
		unless defined $dt;
	$event->{datetime} = $dt;

	my $tzstr = 'UTC';
	if( exists $event->{timezone} ){
		$tzstr = $event->{timezone};
		print "event2epoch(): found a timezone via 'timezone' field as '$tzstr' (that does not mean it is valid) ...\n"
			if $debug > 0;
	} elsif( exists $event->{location} ){
		my $loc = $event->{location};
		if( (ref($loc) eq '') && ($loc =~ /^[a-zA-Z]$/) ){
			# we have a location string
			my @alltzs = DateTime::TimeZone->all_names;
			my $tzstr;
			for (@alltzs){ if( $_ =~ /$loc/i  ){ $tzstr = $_; last } }
			die "event's location can not be converted to a timezone, consider specifying the 'timezone' directly or setting 'location' coordinates with: \[lat,lon\]."
				unless $tzstr;
			print "event2epoch(): setting timezone via 'location' name to '$timestr' ...\n"
				if $debug > 0;
		} elsif( (ref($loc) eq 'HASH') && (exists $loc->{lat}) && (exists $loc->{lon}) ){
			# we have a [lat,lon] array for location
			require Geo::Location::TimeZone;
			my $gltzobj = Geo::Location::TimeZone->new();
			$tzstr = $gltzobj->lookup(lat => $loc->{lat}, lon => $loc->{lon});
			if( ! $tzstr ){ die "timezone lookup from location coordinates lat:".$loc->{lat}.", lon:".$loc->{lon}." has failed." }
			print "event2epoch(): setting timezone via 'location' coordinates lat:".$loc->{lat}.", lon:".$loc->{lon}." ...\n"
				if $debug > 0
		}
	}
	if( $tzstr ){
		print "event2epoch(): deduced timezone to '$tzstr' and setting it ...\n"
			if $debug > 0;
		try {
			$dt->set_time_zone($tzstr)
		} catch {
			die "$_\n failed to set the timezone '$tzstr', is it valid?"
		}
	}

	$event->{_is_parsed} = 1;
	$event->{epoch} = $dt->epoch;
	return $event->{epoch}
}