json2json: add old_stations consistency checks

@{$stations}

  = sort { $a->{name} cmp $b->{name} or $a->{eva} <=> $b->{eva} } @{$stations};

$json_str = read_file('old_stations.json');

my $old_stations = JSON->new->utf8->decode($json_str);

@{$old_stations}

  = sort { $a->{name} cmp $b->{name} or $a->{eva} <=> $b->{eva} }

  @{$old_stations};

my $have_duplicates = 0;

my @names           = map { $_->{name} } @{$stations};

my @ds100

  = map { $_->{ds100} } sort { $a->{ds100} cmp $b->{ds100} } @{$stations};

my @eva_ids = map { $_->{eva} } sort { $a->{eva} <=> $b->{eva} } @{$stations};

my %name   = map { $_ => 1 } @names;

my %ds100  = map { $_ => 1 } @ds100;

my %eva_id = map { $_ => 1 } @eva_ids;

my @old_names = map { $_->{name} } @{$old_stations};

my @old_ds100

  = map { $_->{ds100} } sort { $a->{ds100} cmp $b->{ds100} } @{$old_stations};

my @old_eva_ids

  = map { $_->{eva} } sort { $a->{eva} <=> $b->{eva} } @{$old_stations};

for my $i ( 1 .. $#ds100 ) {

	if ( $ds100[ $i - 1 ] eq $ds100[$i] ) {

		say "Duplicate DS100 code: $ds100[$i]";

	}

}

for my $old_ds100 (@old_ds100) {

	if ( $ds100{$old_ds100} ) {

		say "Old DS100 also present in new station list: $old_ds100";

	}

}

for my $old_eva (@old_eva_ids) {

	if ( $eva_id{$old_eva} ) {

		say "Old EVA also present in new station list: $old_eva";

	}

}

for my $old_name (@old_names) {

	if ( $name{$old_name} ) {

		say "Old name also present in new station list: $old_name";

	}

}

if ($have_duplicates) {

	say "Thank you for your contribution.";

	say "Please remove duplicate entries before opening a pull request.";

my $json_out = JSON->new->utf8->canonical->pretty->encode($stations);

write_file( 'stations.json', $json_out );

$json_out = JSON->new->utf8->canonical->pretty->encode($old_stations);

write_file( 'old_stations.json', $json_out );