Find words that sorta rhyme with the input

slantrhyme.rb

#! /usr/bin/env ruby

def words
  @_words ||= open 'cmudict.dict' do |f|
    f.each_line.with_object({}) do |line, acc|
      word, *phonemes = line.strip.split ' '
      acc[word] = phonemes
    end
  end
rescue Errno::ENOENT
  download_dict and retry
end

def download_dict
  require 'open-uri'
  download = open 'https://raw.githubusercontent.com/cmusphinx/cmudict/master/cmudict.dict'
  IO.copy_stream download, 'cmudict.dict'
end

def vowel_key phonemes
  phonemes.select { |ph| ph[0] =~ /[AEIOU]/ }
end

def rhymes
  @_rhymes ||= Hash.new { |h, k| h[k] = [] }.tap do |h|
    words.each do |k, v| h[vowel_key(v)] << k end
  end
end

def common? word
  %w[that this with from your have will you're i've].include? word
end

def simple? word
  word.length < 4 || common?(word) || !words.key?(word)
end

def rhyme_for word
  return word if simple?(lword = word.downcase)

  rhyme = rhymes[vowel_key(words[lword])]
    .sample
    .sub %r[\(\d+\)\z], ''

  word.capitalize == word ? rhyme.capitalize : rhyme
end

def rhyme_each_word line
  line.strip.gsub(/[\w']+/) { |w| rhyme_for w }
end

if __FILE__ == $0
  puts rhyme_each_word gets until STDIN.eof?
end