package Config::HAProxy::Node;
use strict;
use warnings;
use Carp;
use Config::HAProxy::Iterator;

sub new {
    my $class = shift;
    local %_ = @_;
    bless {
	_kw => $_{kw},
	_argv => $_{argv} // [],
	_orig => $_{orig},
	_locus => $_{locus},
	_parent => $_{parent},
	_index => -1
    }, $class;
}

my @ATTRIBUTES = qw(kw orig locus parent index);

{
    no strict 'refs';
    foreach my $attribute (@ATTRIBUTES) {
	*{ __PACKAGE__ . '::' . $attribute } = sub {
	    my $self = shift;
	    if (defined(my $val = shift)) {
		croak "too many arguments" if @_;
		$self->{'_'.$attribute} = $val;
	    }
	    return $self->{'_'.$attribute};
	}
    }
}

sub argv {
    my $self = shift;
    if (my $val = shift) {
	croak "too many arguments" if @_;
	$self->{_argv} = $val;
    }
    return @{$self->{_argv}};
}

sub arg {
    my $self = shift;
    my $n = shift;
    if (my $val = shift) {
	croak "too many arguments" if @_;
	$self->{_argv}[$n] = $val;
    }
    return $self->{_argv}[$n];
}

sub drop {
    my $self = shift;
    $self->parent->delete_node($self->index);
}

sub iterator {
    return new Config::HAProxy::Iterator(@_);
}

sub depth {
    my $self = shift;
    my $n = 0;
    while ($self = $self->parent) {
	$n++;
    }
    return $n - 1;
}

sub root {
    my $self = shift;
    while ($self->parent()) {
	$self = $self->parent();
    }
    return $self;
}

sub as_string {
    my $self = shift;
    if (defined(my $v = $self->orig)) {
	return $v;
    }
    return '' unless $self->kw;
    return $self->orig(join(' ', ($self->kw, $self->argv())));
}

# use overload
#     '""' => sub { shift->as_string };

sub is_root { 0 }
sub is_section { 0 }
sub is_statement { 0 }
sub is_empty { 0 }
sub is_comment { 0 }

1;
__END__

=head1 NAME

Config::HAProxy::Node - Abstract HAProxy configuration node

=head1 DESCRIPTION

The class B<Config::HAProxy::Node> represents an abstract node in the
HAProxy configuration parse tree. It serves as a base class for classes
representing configuration tree, section, simple statement, comment and
empty line.

=head1 CONSTRUCTOR

    $obj = new Config::HAProxy::Node(%args);

Returns new object. B<%args> can contain the following keys:

=over 4

=item B<kw>

Configuration keyword (string),

=item B<argv>

Reference to the list of arguments.
    
=item B<orig>

Original text as read from the configuration file.

=item B<locus>

Locus (a B<Text::Locus> object) where this statement occurred.

=item B<parent>

Parent node.

=back

=head1 METHODS

=head2 B<kw>, B<argv>, B<orig>, B<locus>, B<parent>

These methods return the corresponding field of the node. When called
with an argument, they set the field prior to returning it. The B<argv>
method returns array of strings and takes as its argument a reference to
the array of strings:

    @a = $node->argv;

    $node->argv([@a]);

=head2 index  

Index (0-based) of this node in the parent node.
    
=head2 arg

    $a = $node->arg($n)

Returns the B<$n>th argument (0-based) from the argument list.

=head2 drop

    $node->drop;

Removes this node and destroys it.

=head2 iterator

    $itr = $node->iterator(@args);

Returns the iterator for this node. See B<Config::HAProxy::Iterator> for
a detailed discussion.

=head2 depth

    $n = $node->depth;

Returns the depth of this node in the configuration tree. Depth is the
number of parent nodes between the root of tree and this node. Top-level
nodes have depth 0.

=head2 root

    $root_node = $node->root;

Returns the root node of the parse tree this node belongs to.

=head2 as_string

    $s = $node->as_string;

Returns canonical string representation of this node. The canonical
representation consists of the keyword followed by arguments delimited
with horizontal space characters.

=head1 ABSTRACT METHODS

Derived classes must overload at least one of the following methods:
    
=head2 is_root

True if the node is a root node, false otherwise.
    
=head2 is_section

True if the node represents a section (i.e. contains subnodes).
    
=head2 is_statement

True if the node is a simple statement.
    
=head2 is_empty

True if the node represents an empty line.
    
=head2 is_comment

True if the node represents a comment.

=head1 SEE ALSO

B<Config::HAProxy::Node::Comment>,    
B<Config::HAProxy::Node::Empty>,    
B<Config::HAProxy::Node::Root>,    
B<Config::HAProxy::Node::Section>,    
B<Config::HAProxy::Node::Statement>,    
B<Config::HAProxy::Iterator>,
B<Config::HAProxy>,
B<Text::Locus>.
    
=cut