module PgTrgm

# File lib/pg_trgm.rb, line 20
def self.similarity(v1, v2)
  v1_trigrams = PgTrgm.trigrams v1
  v2_trigrams = PgTrgm.trigrams v2
  return 0 if v1_trigrams.empty? and v2_trigrams.empty?
  count_dup = (v1_trigrams & v2_trigrams).length
  count_all = (v1_trigrams + v2_trigrams).length
  count_dup / count_all.to_f
end

# File lib/pg_trgm.rb, line 6
def self.trigrams(v)
  memo = Set.new
  v.to_s.split(/[\W_]+/).each do |word|
    next if word.empty?
    # Each word is considered to have two spaces prefixed and one space suffixed when determining the set of trigrams contained in the string
    word = "  #{word.downcase} "
    word.chars.each_cons(3).map do |cons|
      memo << cons.join
    end
  end
  memo
end