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L<Algorithm::Dependency::Source::DBI> extends L<Algorithm::Dependency>
by providing a simple way to create dependency objects that pull their
data from a database directly.

=head1 METHODS

=cut

use 5.005;
use strict;
use Params::Util qw{  _STRING _ARRAY _INSTANCE };
use Algorithm::Dependency::Item   ();
use Algorithm::Dependency::Source ();

use vars qw{$VERSION @ISA};
BEGIN {
	$VERSION = '1.06';
	@ISA     = 'Algorithm::Dependency::Source';
}





#####################################################################
# Constructor and Accessors

=pod

=head2 new

  my $simple = Algorithm::Dependency::Source::DBI->new(
      dbh            => $dbi_db_handle,
      select_ids     => 'select name from stuff',
      select_depends => 'select from, to from m2m_deps',
  );
  
  my $complex = Algorithm::Dependency::Source::DBI->new(
      dbh            => $dbi_db_handle,
      select_ids     => [ 'select name from stuff where foo = ?',         'bar' ],
      select_depends => [ 'select from, to from m2m_deps where from = ?', 'bar' ],
  );

The C<new> constructor takes three named named params.

The C<dbh> param should be a standard L<DBI> database connection.

The C<select_ids> param is either a complete SQL string, or a reference to
an C<ARRAY> containing a SQL string with placeholders and matching
variables.

When executed on the database, it should return a single column containing
the complete set of all item identifiers.

The C<select_depends> param is either a complete SQL string, or a reference
to an C<ARRAY> containing a SQL string with placeholders and matching
variables.

When executed on the database, it should return two columns containing
the complete set of all dependencies, where identifiers in the first-column
depends on identifiers in the second-column.

Returns a new L<Algorithm::Dependency::Source::DBI> object, or dies on
error.

=cut

sub new {
	my $class = shift;

	# Create the object
	my $self = bless { @_ }, $class;

	# Apply defaults
	if ( _STRING($self->{select_ids}) ) {
		$self->{select_ids} = [ $self->{select_ids} ];
	}
	if ( _STRING($self->{select_depends}) ) {
		$self->{select_depends} = [ $self->{select_depends} ];
	}

	# Check params
	unless ( _INSTANCE($self->dbh, 'DBI::db') ) {
		Carp::croak("The dbh param is not a DBI database handle");
	}
	unless ( _ARRAY($self->select_ids) and _STRING($self->select_ids->[0]) ) {
		Carp::croak("Missing or invalid select_ids param");
	}
	unless ( _ARRAY($self->select_depends) and _STRING($self->select_depends->[0]) ) {
		Carp::croak("Did not provide the select_depends query");
	}

	return $self;
}

=pod

=head2 dbh

The C<dbh> accessor returns the database handle provided to the constructor.

=cut

sub dbh {
	$_[0]->{dbh};
}

=pod

=head2 select_ids

The C<select_ids> accessor returns the SQL statement provided to the
constructor. If a raw string was provided, it will be returned as a
reference to an C<ARRAY> containing the SQL string and no params.

=cut

sub select_ids {
	$_[0]->{select_ids};
}