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') {

            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>.

You can pass array reference, which contain column name and direction.

Column name is quoted properly

    # Column name and direction

    $order->prepend(['book-title']);

    $order->prepend([qw/book-title desc/]);

This is expanded to the following way.

    "book-title"

    "book-title" desc

=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