package Env;
use strict;

sub new {
    bless {
        pads => [
            sub { eval $_[0] },
        ], 
        variable_names => [
            [ ],
        ], 
    }, $_[0];
}

sub get_levels {
    my $self = shift;
    scalar @{$self->{pads}};
}

sub eval {
    my $self = shift;
    $self->{pads}[-1]( $_[0] );
}

sub get_variables {
    my $self = shift;
    $self->eval(
        join ',', map {
            ( "'$_'", $_ )
        } @{$self->{variable_names}[-1]} 
    );
}

sub add_pad {
    my $self = shift;
    push @{$self->{variable_names}}, [@_]; 
    push @{$self->{pads}}, $self->eval( 
           (scalar @_ ? 'my (' . (join ',', @_ ) . '); ' : '')
        .  'sub { ' . (join ',', @_ ) . '; eval $_[0] } '
    );
}

sub drop_pad {
    my $self = shift;
    pop @{$self->{pads}};
    pop @{$self->{variable_names}};
}

1;