lib/tree/utils/hash_converter.rb
# hash_converter.rb - This file is part of the RubyTree package.
#
# = hash_converter.rb - Provides utility methods for converting between
# {Tree::TreeNode} and Ruby's native +Hash+.
#
# Author:: Jen Hamon (http://www.github.com/jhamon)
#
# Time-stamp: <2022-06-20 22:16:39 anupam>
#
# Copyright (C) 2014, 2015, 2022, 2022 Jen Hamon (http://www.github.com/jhamon) and
# Anupam Sengupta <anupamsg@gmail.com>
#
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# - Redistributions of source code must retain the above copyright notice, this
# list of conditions and the following disclaimer.
#
# - Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
#
# - Neither the name of the organization nor the names of its contributors may
# be used to endorse or promote products derived from this software without
# specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
# frozen_string_literal: true
module Tree
module Utils
# Provides a utility for marshalling/unmarshalling TreeNode objects to Ruby
# +hash+ objects.
#
# @author Jen Hamon (https://www.github.com/jhamon)
module HashConverter
def self.included(base)
base.extend(ClassMethods)
end
# Methods in {Tree::Utils::HashConverter::ClassMethods} will be added as
# class methods on any class mixing in the {Tree::Utils::HashConverter}
# module.
module ClassMethods
# Factory method builds a {Tree::TreeNode} from a +Hash+.
#
# This method will interpret each key of your +Hash+ as a {Tree::TreeNode}.
# Nested hashes are expected and child nodes will be added accordingly. If
# a hash key is a single value that value will be used as the name for the
# node. If a hash key is an Array, both node name and content will be
# populated.
#
# A leaf element of the tree should be represented as a hash key with
# corresponding value +nil+ or +{}+.
#
# @example
# TreeNode.from_hash({:A => {:B => {}, :C => {:D => {}, :E => {}}}})
# # would be parsed into the following tree structure:
# # A
# # / \
# # B C
# # / \
# # D E
#
# # The same tree would result from this nil-terminated Hash
# {:A => {:B => nil, :C => {:D => nil, :E => nil}}}
#
# # A tree with equivalent structure but with content present for
# # nodes A and D could be built from a hash like this:
# {[:A, "A content"] => {:B => {},
# :C => { [:D, "D content"] => {},
# :E => {} }}}
#
# @author Jen Hamon (http://www.github.com/jhamon)
# @param [Hash] hash Hash to build tree from.
#
# @return [Tree::TreeNode] The {Tree::TreeNode} instance representing the
# root of your tree.
#
# @raise [ArgumentError] This exception is raised if a non-Hash is passed.
#
# @raise [ArgumentError] This exception is raised if the hash has multiple
# top-level elements.
#
# @raise [ArgumentError] This exception is raised if the hash contains
# values that are not hashes or nils.
def from_hash(hash)
raise ArgumentError, 'Argument must be a type of hash'\
unless hash.is_a?(Hash)
raise ArgumentError, 'Hash must have one top-level element'\
if hash.size != 1
root, children = hash.first
raise ArgumentError, 'Invalid child. Must be nil or hash.' unless [Hash, NilClass].include?(children.class)
node = new(*root)
node.add_from_hash(children) unless children.nil?
node
end
end
# Instantiate and insert child nodes from data in a Ruby +Hash+
#
# This method is used in conjunction with from_hash to provide a
# convenient way of building and inserting child nodes present in a Ruby
# hashes.
#
# This method will instantiate a node instance for each top-
# level key of the input hash, to be inserted as children of the receiver
# instance.
#
# Nested hashes are expected and further child nodes will be created and
# added accordingly. If a hash key is a single value that value will be
# used as the name for the node. If a hash key is an Array, both node
# name and content will be populated.
#
# A leaf element of the tree should be represented as a hash key with
# corresponding value +nil+ or {}.
#
# @example
# root = Tree::TreeNode.new(:A, "Root content!")
# root.add_from_hash({:B => {:D => {}}, [:C, "C content!"] => {}})
#
# @author Jen Hamon (http://www.github.com/jhamon)
# @param [Hash] children The hash of child subtrees.
# @raise [ArgumentError] This exception is raised if a non-hash is passed.
# @return [Array] Array of child nodes added
# @see ClassMethods#from_hash
def add_from_hash(children)
raise ArgumentError, 'Argument must be a type of hash'\
unless children.is_a?(Hash)
child_nodes = []
children.each do |child, grandchildren|
child_node = self.class.from_hash({ child => grandchildren })
child_nodes << child_node
self << child_node
end
child_nodes
end
# Convert a node and its subtree into a Ruby hash.
#
# @example
# root = Tree::TreeNode.new(:root, "root content")
# root << Tree::TreeNode.new(:child1, "child1 content")
# root << Tree::TreeNode.new(:child2, "child2 content")
# root.to_h # => {[:root, "root content"] =>
# { [:child1, "child1 content"] =>
# {}, [:child2, "child2 content"] => {}}}
# @author Jen Hamon (http://www.github.com/jhamon)
# @return [Hash] Hash representation of tree.
def to_h
key = content? ? [name, content] : name
children_hash = {}
children do |child|
children_hash.merge! child.to_h
end
{ key => children_hash }
end
end
end
end