AnyGood MovieMatcher -- http://anygood.heroku.com

movie_matcher.rb

require 'digest'

module AnyGood
  class MovieMatcher

    def add_movie(movie_hash)
      prefixes    = prefixes_for(movie_hash[:name])
      hashed_name = data_hash_key_for(movie_hash)

      prefixes.each do |prefix|
        score = REDIS.zscore(index_key_for(prefix), hashed_name).to_i || 0
        REDIS.zadd(index_key_for(prefix), score, hashed_name)
      end

      REDIS.hset(data_key, hashed_name, movie_hash.to_json)
    end

    def find_by_prefixes(prefixes)
      intersection_key = index_key_for(prefixes)
      index_keys       = prefixes.map {|prefix| index_key_for(prefix)}

      REDIS.multi do
        REDIS.zinterstore(intersection_key, index_keys)
        REDIS.expire(intersection_key, 7200)
      end

      data_hash_keys  = REDIS.zrevrange(intersection_key, 0, -1)
      matching_movies = REDIS.hmget(data_key, *data_hash_keys)

      matching_movies.map {|movie| JSON.parse(movie, symbolize_names: true)}
    end

    def incr_score_for(movie_hash)
      prefixes    = prefixes_for(movie_hash[:name])
      hashed_name = data_hash_key_for(movie_hash)

      REDIS.multi do
        prefixes.each {|prefix| REDIS.zincrby(index_key_for(prefix), 1, hashed_name)}
      end
    end

    private

      def data_key
        'moviesearch:data'
      end

      def prefixes_for(string)
        prefixes = []
        words    = string.downcase.split(' ')

        words.each do |word|
          (1..word.length).each {|i| prefixes << word[0...i] unless i == 1}
        end

        prefixes
      end

      def index_key_for(*prefixes)
        "moviesearch:index:#{prefixes.join('|').downcase}"
      end

      def data_hash_key_for(movie_hash)
        Digest::MD5.hexdigest(movie_hash[:name] + movie_hash[:year].to_s)
      end
  end
end