Help creating a rule for a last name about citrus HOT 4 CLOSED

irb> require 'citrus'
=> true
irb> rule = Citrus.rule '[A-Za-z]+ (" "* [iI]+)?'
=> /[A-Za-z]/+ (" "* /[iI]/+)?
irb> rule.test 'Love III'
=> 8
irb> rule.test 'Immelman'
=> 8
irb> rule.test 'Donald'
=> 6

grammar Name
  rule name
    first_name space middle_name space last_name |
    first_name space last_name |
    first_name
  end

  rule first_name
    [A-Za-z]+
  end

  rule last_name
    [A-Za-z]+ space [iI]+ | [iI]+ &[^iI]+ | [^iI] [A-Za-z]+
  end

  rule middle_name
    ([A-Za-z] '.') {
      delete('.')
    }
    | [A-Za-z]+
  end

  rule space
    [ \t]*
  end
end

require 'citrus'

Citrus.eval(<<CITRUS)
grammar Name
  rule name
    first_name space middle_name space last_name space suffix? |
    first_name space last_name space suffix? |
    first_name
  end

  rule first_name
    [A-Za-z]+
  end

  rule middle_name
    ([A-Za-z] '.') {
      delete('.')
    }
    | [A-Za-z]+
  end

  rule last_name
    !suffix [A-Za-z]+
  end

  rule suffix
    [iI]+ | `jr` '.'?
  end

  rule space
    [ \t]*
  end
end
CITRUS

puts Name.parse("David Love III").dump