import M2._

// first test 

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

              m: Map[String, List[String]]) : Map[String, List[String]] = ratings match {

  case Nil => m

  case (id, mov) :: rest => {

    val old_ratings = m.getOrElse (id, Nil)

    val new_ratings = m + (id -> (mov :: old_ratings))

    urban_groupById(rest, new_ratings)

  }

}

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

//  ratings.groupBy(_._1).view.mapValues(_.map(_._2)).toMap 

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

  import io.Source

  import scala.util._

  val csv = Source.fromFile(name)("ISO-8859-1")

  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).toInt >= 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 = urban_process_ratings(urban_get_csv_file("ratings.csv"))

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

val urban_ratings_map = urban_groupById(urban_good_ratings, Map())

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))