package DBIx::Custom::Order;
use Object::Simple -base;
use overload
  'bool'   => sub {1},
  '""'     => sub { shift->to_string },
  fallback => 1;

has 'dbi',
  orders => sub { [] };

sub prepend {
  my $self = shift;
  
  for my $order (reverse @_) {
    if (ref $order eq 'ARRAY') {
      warn "prepend method receiving array reference is DEPRECATED! " .
           "use q method to quote column name.";
      my $column = shift @$order;
      $column = $self->dbi->q($column) if defined $column;
      my $derection = shift @$order;
      $order = $column;
      $order .= " $derection" if $derection;
    }
    unshift @{$self->orders}, $order;
  }
  
  return $self;
}

sub to_string {
  my $self = shift;
  
  my $exists = {};
  my @orders;
  for my $order (@{$self->orders}) {
    next unless defined $order;
    $order =~ s/^\s+//;
    $order =~ s/\s+$//;
    my ($column, $direction) = split /\s+/, $order;
    push @orders, $order unless $exists->{$column};
    $exists->{$column} = 1;
  }
  
  return '' unless @orders;
  return 'order by ' . join(', ', @orders);
}

1;

=head1 NAME

DBIx::Custom::Order - Order by

=head1 SYNOPSIS

  # Result
  my $order = DBIx::Custom::Order->new;
  $order->prepend('title', 'author desc');
  my $order_by = "$order";
  
=head1 ATTRIBUTES

=head2 C<dbi>

  my $dbi = $order->dbi;
  $order = $order->dbi($dbi);

L<DBIx::Custom> object.

=head2 C<orders>

  my $orders = $result->orders;
  $result = $result->orders(\%orders);

Parts of order by clause

=head1 METHODS

L<DBIx::Custom::Result> inherits all methods from L<Object::Simple>
and implements the following new ones.

=head2 C<prepend>

  $order->prepend('title', 'author desc');

Prepend order parts to C<orders>.

=head2 C<to_string>

  my $order_by = $order->to_string;

Create order by clause. If column name is duplicated, First one is used.
C<to_string> override stringification. so you can write the follwoing way.

  my $order_by = "$order";

=cut