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 cycl
+e (birth-to-death)\n";
    print "Moon's illuminated fraction: ",sprintf("%.1f", 100.0*$MoonI
+llum)." % 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: ".$eve
+nt->{location}->{lon}.")"
        } else { $str .= "(".$event->{location}.")" }
    }
    return $str
}

sub parse_event {
    my $event = shift;

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

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

    die "event does not have a 'name' field, please specify one, anyth
+ing 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' coo
+rdinates 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}) && (exi
+sts $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( ! $tzstr ){ die "timezone lookup from location coordin
+ates lat:".$loc->{lat}.", lon:".$loc->{lon}." has failed." }
            print "event2epoch(): setting timezone via 'location' coor
+dinates lat:".$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}
}
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