package Graph::Attribute;

use strict;
use warnings;

my @API = qw(get_attribute
	     get_attributes
	     set_attribute
	     set_attributes
	     has_attribute
	     has_attributes
	     delete_attribute
	     delete_attributes
	     get_attribute_names
	     get_attribute_values);

sub import {
    my $package = shift;
    my %attr = @_;
    my $caller = caller(0);
    if (exists $attr{array}) {
	my $i = $attr{array};
	no strict 'refs';
	*{"${caller}::_g_get_attributes"} = sub { $_[0]->[ $i ] };
	*{"${caller}::_g_set_attributes"} =
	    sub { $_[0]->[ $i ] ||= { };
		  $_[0]->[ $i ] = $_[1] if @_ == 2;
		  $_[0]->[ $i ] };
	*{"${caller}::_g_has_attributes"} = sub { defined $_[0]->[ $i ] };
	*{"${caller}::_g_delete_attributes"} = sub { undef $_[0]->[ $i ]; 1 };
    } elsif (exists $attr{hash}) {
	my $k = $attr{hash};
	no strict 'refs';
	*{"${caller}::_g_get_attributes"} = sub { $_[0]->{ $k } };
	*{"${caller}::_g_set_attributes"} =
	    sub { $_[0]->{ $k } ||= { };
		  $_[0]->{ $k } = $_[1] if @_ == 2;
		  $_[0]->{ $k } };
	*{"${caller}::_g_has_attributes"} = sub { defined $_[0]->{ $k } };
	*{"${caller}::_g_delete_attributes"} = sub { delete $_[0]->{ $k } };
    } else {
	# uncoverable statement
	die "Graph::Attribute::import($package @_) caller $caller\n";
    }
    if (exists $attr{map}) {
	my $map = $attr{map};
	for my $api (@API) {
	    my ($first, $rest) = ($api =~ /^(\w+?)_(.+)/);
	    no strict 'refs';
	    *{"${caller}::${first}_${map}_${rest}"} = \&$api;
	}
    }
}

sub set_attribute {
    my $g = shift;
    my $v = pop;
    my $a = pop;
    my $p = $g->_g_set_attributes;
    $p->{ $a } = $v;
    return 1;
}

sub set_attributes {
    my $g = shift;
    my $a = pop;
    my $p = $g->_g_set_attributes( $a );
    return 1;
}

sub has_attribute {
    my $g = shift;
    my $a = pop;
    my $p = $g->_g_get_attributes;
    $p ? exists $p->{ $a } : 0;
}

sub has_attributes {
    my $g = shift;
    $g->_g_get_attributes ? 1 : 0;
}

sub get_attribute {
    my $g = shift;
    my $a = pop;
    my $p = $g->_g_get_attributes;
    $p ? $p->{ $a } : undef;
}

sub delete_attribute {
    my $g = shift;
    my $a = pop;
    return 0 unless defined(my $p = $g->_g_get_attributes);
    delete $p->{ $a };
    return 1;
}

sub delete_attributes {
    my $g = shift;
    return 0 if !$g->_g_has_attributes;
    $g->_g_delete_attributes;
    return 1;
}

sub get_attribute_names {
    my $g = shift;
    my $p = $g->_g_get_attributes;
    defined $p ? keys %{ $p } : ( );
}

sub get_attribute_values {
    my $g = shift;
    my $p = $g->_g_get_attributes;
    defined $p ? values %{ $p } : ( );
}

sub get_attributes {
    $_[0]->_g_get_attributes;
}

1;