gibberish.rb

VOWELS = ['a', 'e', 'i', 'o', 'u']

word = gets.chomp.chars.map(&:downcase)

def modify_vowel(char)
  VOWELS.include?(@previous_char) ? char : "idig#{char}"
end

def is_vowel?(char)
  VOWELS.include?(char)
end

def replace_eligible_vowel(char)
  is_vowel?(char) ? modify_vowel(char) : char
end

gibberish = word.each_with_object([]).with_index do |(char, new_word), index|
  @previous_char = word[index - 1] unless index.zero?
  new_word << replace_eligible_vowel(char)
end

puts gibberish.join