# NAME

IRC::Server::Tree - Manipulate an IRC "spanning tree"

# SYNOPSIS

   ## Basic path-tracing usage:
   my $tree = IRC::Server::Tree->new;

   $tree->add_node_to_top($_) for qw/ peerA peerB /;

   $tree->add_node_to_name('peerA', 'leafA');
   $tree->add_node_to_name('peerA', 'leafB');

   $tree->add_node_to_name('peerB', 'hubA');
   $tree->add_node_to_name('hubA', 'peerB');

   ## ARRAY of hop names between root and peerB:
   my $hop_names = $tree->trace( 'peerB' );

See [IRC::Server::Tree::Network](https://metacpan.org/pod/IRC::Server::Tree::Network) for a simpler and more specialized
interface to the tree.

See the DESCRIPTION for a complete method list.

# DESCRIPTION

An IRC network is defined as a 'spanning tree' per RFC1459; this module
is an array-type object representing such a tree, with convenient path
resolution methods for determining route "hops" and extending or shrinking
the tree.

See [IRC::Server::Tree::Network](https://metacpan.org/pod/IRC::Server::Tree::Network) for higher-level
(and simpler) methods pertaining to manipulation of an IRC network
specifically; a Network instance also provides an optional
memory-for-speed tradeoff via memoization of traced paths.

An IRC network tree is essentially unordered; any node can have any
number of child nodes, with the only rules being that:

- The tree remains a tree (it is acyclic; there is only one route between
any two nodes, and no node has more than one parent)
- No two nodes can share the same name.

Currently, this module doesn't enforce the listed rules for performance
reasons, but things will break if you add non-uniquely-named nodes. Be
warned. In fact, this module doesn't sanity
check very much of anything; an [IRC::Server::Tree::Network](https://metacpan.org/pod/IRC::Server::Tree::Network) does much
more to validate the tree and passed arguments.

A new Tree can be created from an existing Tree:

   my $new_tree = IRC::Server::Tree->new( $old_tree );

In principle, the general structure of the tree is your average deep
array-of-arrays:

   $self => [
     hubA => [
       leafA => [],
       leafB => [],
     ],

     hubB => [
       leafC => [],
       leafD => [],
     ],
   ],

The methods provided below can be used to manipulate the tree and
determine hops in a path to an arbitrary node using either breadth-first
or depth-first search.

Currently routes are not memoized; that's left to a higher layer or
subclass.

## new

Create a new network tree:

   my $tree = IRC::Server::Tree->new;

Create a new network tree from an old one or part of one (see
["child\_node\_for"](#child_node_for) and ["del\_node\_by\_name"](#del_node_by_name)):

   my $tree = IRC::Server::Tree->new( $old_tree );

(Note that this will clone the old Tree object.)

Optionally create a tree from an ARRAY, if you really know what
you're doing:

   my $tree = IRC::Server::Tree->new(
     [
       hubA => [
         hubB => [
           hubBleaf1 => [],
         ],
         leaf1 => [],
         leaf2 => [],
       ],
     ],
   );

## add\_node\_to\_parent\_ref

   ## Add empty node to parent ref:
   $tree->add_node_to_parent_ref( $parent_ref, $new_name );
   ## Add existing node to parent ref:
   $tree->add_node_to_parent_ref( $parent_ref, $new_name, $new_ref );

Adds an empty or preexisting node to a specified parent reference.

Also see ["add\_node\_to\_top"](#add_node_to_top), ["add\_node\_to\_name"](#add_node_to_name)

## add\_node\_to\_top

   $tree->add_node_to_top( $new_name );
   $tree->add_node_to_top( $new_name, $new_ref );

Also see ["add\_node\_to\_parent\_ref"](#add_node_to_parent_ref), ["add\_node\_to\_name"](#add_node_to_name)

## add\_node\_to\_name

   $tree->add_node_to_name( $parent_name, $name );
   $tree->add_node_to_name( $parent_name, $name, $new_ref );

Adds an empty or specified node to the specified parent name.

For example:

   $tree->add_node_to_top( 'MyHub1' );
   $tree->add_node_to_name( 'MyHub1', 'MyLeafA' );

   ## Existing nodes under our new node
   my $new_node = [ 'MyLeafB' => [] ];
   $tree->add_node_to_name( 'MyHub1', 'MyHub2', $new_node );

## as\_hash

   my $hash_ref = $tree->as_hash;
   my $hash_ref = $tree->as_hash( $parent_ref );

Get a (possibly deep) HASH describing the state of the tree underneath
the specified parent reference, or the entire tree if none is specified.

For example:

   my $hash_ref = $tree->as_hash( $self->child_node_for('MyHub1') );

Also see ["child\_node\_for"](#child_node_for)

## as\_list

   my @tree = $tree->as_list;
   my @tree = $tree->as_list( $parent_ref );

Returns the tree in list format.

(["as\_hash"](#as_hash) is likely to be more useful.)

## child\_node\_for

   my $child_node = $tree->child_node_for( $parent_name );
   my $child_node = $tree->child_node_for( $parent_name, $start_ref );

Finds and returns the named child node from the tree.

Starts at the root of the tree or the specified parent reference.

## del\_node\_by\_name

   $tree->del_node_by_name( $parent_name );
   $tree->del_node_by_name( $parent_name, $start_ref );

Finds and deletes the named child from the tree.

Returns the deleted node.

## names\_beneath

   my $names = $tree->names_beneath( $parent_name );
   my $names = $tree->names_beneath( $parent_ref );

Return an ARRAY of all names in the tree beneath the specified parent
node.

Takes either the name of a node in the tree or a reference to a node.

## path\_by\_indexes

   my $names = $tree->path_by_indexes( $index_route );
   my $names = $tree->path_by_indexes( $index_route, $parent_ref );

Given an array of index hops as retrieved by ["trace\_indexes"](#trace_indexes), retrieve
the name for each hop.

This is mostly used internally by ["trace"](#trace).

## print\_map

   $tree->print_map;
   $tree->print_map( $start_ref );

Prints a visualization of the network map to STDOUT.

## trace

   my $names = $tree->trace( $parent_name );
   my $names = $tree->trace( $parent_name, $start_ref );
   my $names = $tree->trace( $parent_name, $start_ref, 'dfs' );

Returns an ARRAY of the names of every hop in the path to the
specified parent name.

Starts tracing from the root of the tree unless a parent node reference
is also specified.

The last hop returned is the target's name.

Specifying a true value as a third argument is the same as calling
["trace\_dfs"](#trace_dfs). Defaults to breadth-first as described in
["trace\_indexes"](#trace_indexes).

## trace\_dfs

A convenience method for using depth-first tracing. This is likely to be less
efficient than the default breadth-first approach for most network layouts.

This is the same as specifying a true third argument to ["trace"](#trace).

## trace\_indexes

Primarily intended for internal use. This is the BFS/DFS search
that other methods use to find a node. There is nothing very
useful you can do with this externally except count hops; it is documented
here to show how path resolution works.

Returns an ARRAY consisting of the index of every hop taken to get to
the node reference belonging to the specified node name starting from
the root of the tree or the specified parent node reference.

Given a network:

   hubA
     leafA
     leafB
     hubB
       leafC
       leafD

`trace_indexes(**'leafD'**)` would return:

   [ 1, 5, 1 ]

These are the indexes into the node references (arrays) owned by each
hop, including the last hop. Retrieving their names requires
subtracting one from each index; ["trace"](#trace) handles this.

# AUTHOR

Jon Portnoy <[email protected]>

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