experimental_parser.rb

require 'gherkin'

class TableListener
  attr_reader :rows
  def table(rows, line_number)
    @rows = rows
  end
end

class Parser
  def initialize(state)
    table_listener = TableListener.new
    @parser = Gherkin::Parser['en'].new(table_listener)
    @parser.scan(File.read('./root.txt'))
    @state_machine = state_machine(table_listener.rows)
    @current = state
  end

  def state_machine(table)
    events = table.shift[1..-1]
    table.inject({}) do |machine, actions|
      state = actions.shift
      machine[state] = Hash[*events.zip(actions).flatten]
      machine
    end
  end
  
  # Doesn't yet fall back to super
  def method_missing(meth, *args)
    meth = meth.to_s
    case @state_machine[@current][meth]
    when "E"
      raise "Oh noes! #{expected.join(' ')}"
    when "-"
      # @listener.send(meth, *args)
    else
      @current = meth
      # @listener.send(meth, *args)
    end
  end

  def expected
    allowed = @state_machine[@current].find_all { |_, action| action != "E" }
    allowed.collect { |state| state[0] } 
  end
end