+sub invoice_type {
+ my ($self) = @_;
+
+ return 'ar_transaction' if !$self->invoice;
+ return 'credit_note' if $self->type eq 'credit_note' && $self->amount < 0 && !$self->storno;
+ return 'invoice_storno' if $self->type ne 'credit_note' && $self->amount < 0 && $self->storno;
+ return 'credit_note_storno' if $self->type eq 'credit_note' && $self->amount > 0 && $self->storno;
+ return 'invoice';
+}
+
+sub displayable_state {
+ my $self = shift;
+
+ return $self->closed ? $::locale->text('closed') : $::locale->text('open');
+}
+