Fun with Palindromes

palindrome.rb

KNOWN_PLANINDROMES = %w(racecar hannah).freeze

def unique_palindrome(books)
  palindromes_per_book = {}
  books.each do |book_name, book_words|
    palindromes_per_book[book_name] = {}

    # filter out any unknown palindromes
    book_words.split(" ").each do |word|
      next unless KNOWN_PLANINDROMES.include?(word)
      current_value = palindromes_per_book[book_name][word]

      palindromes_per_book[book_name][word] = current_value.nil? ? 1 : current_value + 1
    end
  end

  palindromes_per_book
end

all_books = {
    book: "a racecar string of racecar and hannah"
}

puts unique_palindrome(all_books)