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+# This file is part of Config::AST -*- perl -*-
+# Copyright (C) 2017-2019 Sergey Poznyakoff <gray@gnu.org>
+#
+# Config::AST is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+#
+# Config::AST is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Config::AST. If not, see <http://www.gnu.org/licenses/>.
+
+package Config::AST::Root;
+use strict;
+use warnings;
+
+=head1 NAME
+
+Config::AST::Root - root of the abstract syntax tree
+
+=head1 DESCRIPTION
+
+An auxiliary class representing the root of the abstract syntax tree.
+It is necessary because the tree itself forms a circular structure
+(due to the B<root> attribute of B<Config::AST::Node::Section>). Without
+this intermediate class (if B<root> pointed to B<Config::AST> itself),
+the structure would have never been destroyed, because each element
+would remain referenced at least once.
+
+=head1 CONSTRUCTOR
+
+=head2 $obj = new($ci)
+
+I<$ci> is one to enable case-insensitive keyword lookup, and 0 otherwise.
+
+=cut
+
+sub new {
+ my ($class, $ci) = @_;
+ bless { _ci => $ci }, $class;
+}
+
+=head1 METHODS
+
+=head2 $s = $r->mangle_key($name)
+
+Converts the string I<$name> to a form suitable for lookups, in accordance
+with the _ci attribute.
+
+=cut
+
+sub mangle_key {
+ my ($self, $key) = @_;
+ $self->{_ci} ? lc($key) : $key;
+}
+
+=head2 $r->reset
+
+Destroys the underlying syntax tree.
+
+=cut
+
+sub reset { delete shift->{_tree} }
+
+
+=head2 $t = $r->tree
+
+Returns the root node of the tree, initializing it if necessary.
+
+=cut
+
+sub tree {
+ my $self = shift;
+
+ return $self->{_tree} //=
+ new Config::AST::Node::Section($self,
+ locus => new Text::Locus);
+}
+
+=head2 $bool = $r->empty
+
+Returns true if the tree is empty.
+
+=cut
+
+sub empty {
+ my $self = shift;
+ return !($self->{_tree} && $self->{_tree}->keys > 0);
+}
+
+=head1 SEE ALSO
+
+L<Config::AST>.
+
+=cut
+
+1;

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