// first test 

def urban_groupById(ratings: List[(String, String)]) = 

  ratings.groupBy(_._1).mapValues(_.map(_._2)) 

def urban_get_csv_file(name: String) : List[String] = {

  import io.Source

  import scala.util._

  val csv = Source.fromFile(name)

  csv.mkString.split("\n").toList.drop(1)

}

def urban_process_ratings(lines: List[String]) : List[(String, String)] = {

  for (cols <- lines.map(_.split(",").toList); 

       if (cols(2).toFloat >= 4)) yield (cols(0), cols(1))  

}

def urban_process_movies(lines: List[String]) : List[(String, String)] = {

  for (cols <- lines.map(_.split(",").toList)) yield (cols(0), cols(1))  

}

val urban_good_ratings = process_ratings(urban_get_csv_file("ratings.csv"))

val urban_movie_names = process_movies(urban_get_csv_file("movies.csv")).toMap

val urban_ratings_map = urban_groupById(urban_good_ratings)

assert((for (n <- List("1", "2", "3", "4", "5")) yield {

  recommendations(urban_ratings_map, urban_movie_names, n).length

}) == List(2, 2, 2, 0, 2))