package Tree::Template::Declare;
use strict;
use warnings;
use Sub::Exporter;
use Devel::Caller 'caller_args';
use Carp;
use Data::Dumper;

our $VERSION='0.1';

Sub::Exporter::setup_exporter({
    groups => {
        default => \&_build_group,
    },
    collectors => [ INIT => \&_init_args, 'options' ],
});

sub _init_args {
    my (undef,$args)=@_;

    @{$args->{import_args}}=( [ -default => undef] )
        unless @{$args->{import_args}};

    return 1;
}

sub _build_group {
    my ($class,$name,$args,$coll)=@_;

    my $builder=$args->{builder} || $coll->{options}{builder};

    if (!ref($builder)) {
        my $builder_pkg=$builder;
        if ($builder_pkg=~m{\A \+(\w+) \z}smx) {
            $builder_pkg="Tree::Template::Declare::$1";
        }
        eval "require $builder_pkg";
        croak "Can't load $builder_pkg: $@" if $@;

        if ($builder_pkg->can('new')) {
            $builder=$builder_pkg->new();
        }
        else {
            $builder=$builder_pkg;
        }
    }

    my @current_node=(undef);

    return {
        tree => sub(&) {
            local $current_node[0]=undef;
            my ($ret)=$_[0]->(caller_args(1));
            return $ret;
        },
        node => sub (&) {
            my $node=$builder->new_node();
            {
                local $current_node[0]=$node;
                $_[0]->(caller_args(1));
            }
            if ($current_node[0]) {
                $builder->add_child_node($current_node[0],$node);
            }
            return $node;
        },
        name => sub ($) {
            $builder->set_node_name($current_node[0],$_[0]);
            return;
        },
        attribs => sub {
            my %attrs=@_;
            $builder->set_node_attributes($current_node[0],\%attrs);
            return;
        },
    };
}

1;