1 files changed, 30 insertions, 0 deletions
diff --git a/share/json2json b/share/json2json
index 5cad10f..189ee2c 100755
--- a/share/json2json
+++ b/share/json2json
@@ -10,5 +10,35 @@ use JSON;
 my $json_str = read_file('stations.json');
 my $stations = JSON->new->utf8->decode($json_str);
 @{$stations} = sort { $a->{name} cmp $b->{name} } @{$stations};
+
+my $have_duplicates = 0;
+my @names           = map { $_->{name} } @{$stations};
+my @ds100           = map { $_->{ds100} } sort { $a->{ds100} cmp $b->{ds100} } @{$stations};
+my @uic_ids         = map { $_->{uic} } sort { $a->{uic} <=> $b->{uic} } @{$stations};
+
+for my $i ( 1 .. $#names ) {
+	if ( $names[ $i - 1 ] eq $names[$i] ) {
+		say "Duplicate station name: $names[$i]";
+		$have_duplicates = 1;
+	}
+}
+for my $i ( 1 .. $#ds100 ) {
+	if ( $ds100[ $i - 1 ] eq $ds100[$i] ) {
+		say "Duplicate DS100 code: $ds100[$i]";
+		$have_duplicates = 1;
+	}
+}
+for my $i ( 1 .. $#uic_ids ) {
+	if ( $uic_ids[ $i - 1 ] == $uic_ids[$i] ) {
+		say "Duplicate UIC ID: $uic_ids[$i]";
+		$have_duplicates = 1;
+	}
+}
+
+if ($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 );