package object collection {

  /**
   * Provides extra util methods for the [[Traversable]] class.
   *
   * @param traversable The [[Traversable]] to enrich.
   * @tparam A The [[Traversable]] type parameter.
   */
  implicit class RichTraversable[+A](traversable: Traversable[A]) {

    /**
     * Groups the traversable by the criteria specified by ``groupBy`` and then filters each
     * group by the minimum element according to ``minBy``.
     *
     * @param groupBy The group by function.
     * @param minBy The min by function.
     * @param cmp An implicit ordering for ``B``.
     * @tparam K The type for the groups keys.
     * @tparam B The resulting type of the min by function.
     * @return The traversable with the minimum elements of each group.
     */
    def groupByAndFilterMin[K, B](groupBy: A => K, minBy: A => B)
                                 (implicit cmp: Ordering[B]): Traversable[A] =
      traversable.groupBy(groupBy).mapValues(_.minBy(minBy)).values.toSeq

  }

}