A very naive graph implementation in ruby

graph.rb

require 'pp'

class Graph
  def initialize(graph = {})
    @hash = graph.freeze
  end

  def add_vertex(node)
    Graph.new(@hash.merge(Hash[node, { edges: {}.freeze }]).freeze)
  end

  def remove_vertex(node)
    Graph.new(@hash.reject { |key, _| key == node })
  end

  def add_edge(start_node, end_node)
    return unless @hash.key?(start_node) && @hash.key?(end_node)

    Graph.new(@hash.merge(Hash[
                            start_node, { edges: @hash[start_node][:edges].merge(Hash[end_node, true]).freeze },
                            end_node, { edges: @hash[end_node][:edges].merge(Hash[start_node, true]).freeze }
                          ]))
  end

  def remove_edge(start_node, end_node)
    return unless @hash.key?(start_node) && @hash.key?(end_node)

    Graph.new(@hash.merge(Hash[
                            start_node, { edges: Hash[@hash[start_node][:edges].reject { |key, _| key == end_node }].freeze },
                            end_node, { edges: Hash[@hash[end_node][:edges].reject { |key, _| key == start_node }].freeze }
                          ]))
  end
end

dev_book = Graph.new
             .add_vertex('James Gosling')
             .add_vertex('Guido Rossum')
             .add_vertex('Linus Torvalds')
             .add_vertex('Michael Olorunnisola')
             .add_edge('James Gosling', 'Guido Rossum')
             .add_edge('Linus Torvalds', 'Michael Olorunnisola')
             .remove_edge('Linus Torvalds', 'Michael Olorunnisola')
             .remove_vertex('Linus Torvalds')

pp dev_book