use strict;
use warnings;
use Geo::Gpx;
use DateTime;
# Open the GPX file
open my $fh_in, '<', 'fells_loop.gpx';
# Parse GPX
my $gpx = Geo::Gpx->new( input => $fh_in );
# Close the GPX file
close $fh_in;

# Open an output file
open my $fh_out, '>', 'fells_loop.csv';
# Print the header line to the file
print $fh_out "time,lat,lon,ele,name,sym,type,desc\n";

# The waypoints-method of the GEO::GPX-Object returns an array-ref
# which we can iterate in a foreach loop
foreach my $wp ( @{ $gpx->waypoints() } ) {
  # Some fields seem to be optional so they are missing in the hash.
  # We have to add an empty string by iterating over all the possible
  # hash keys to put '' in them. Map is like a foreach loop.
  map { $wp->{$_} ||= '' } qw( time lat lon ele name sym type desc );

  # The time is a unix timestamp, which is hard to read.
  # We can make it an ISO8601 date with the DateTime module.
  # We only do it if there already is a time, though.
  if ($wp->{'time'}) {
    $wp->{'time'} = DateTime->from_epoch( epoch => $wp->{'time'} )
                             ->iso8601();
  }
  # Join the fields with a comma and print them to the output file
  print $fh_out join(',', (
    $wp->{'time'},
    $wp->{'lat'},
    $wp->{'lon'},
    $wp->{'ele'},
    $wp->{'name'},
    $wp->{'sym'},
    $wp->{'type'},
    $wp->{'desc'},
  )), "\n"; # Add a newline at the end
}
# Close the output file
close $fh_out;