Simple fuzzy index with left weight

fuzzy_index.rb

class FuzzyIndex
  def initialize
    @index = Hash.new { |h, k| h[k] = Set.new }
  end
  
  def []=(key, value)
    trigrams(key).each { @index[it] << [key, value] }
  end
  
  def [](query)
    results = {}
    
    trigrams(query).each do |trigram|
      @index[trigram].each do |pair|
        results[pair] ||= 0
        results[pair] += 1
      end
    end
    
    results
      .map { |(k, v), score| [score.to_f / k.length, [k, v]] }
      .sort_by { |(weight, pair)| -weight }
      .take(10)
  end
  
  private
  
  def trigrams(word)
    padded_normalized_word = "■■#{word.downcase}"
    
    (0..padded_normalized_word.length - 3).map do |index|
      padded_normalized_word[index, 3]
    end
  end
end