time-series-main.scala

observations.foldLeft(
  List[Observation]() -> WindowStats(0, Int.MaxValue, Int.MinValue, 0)
) {
  case ((series, stats), ob) =>

    @tailrec
    def calcStats(
      st: WindowStats, 
      obs: List[Observation]): (WindowStats, List[Observation]) = {
      
      obs match {
        case h :: t if ob.time - obs.head.time > windowSize =>
          val newStats = WindowStats(
            st.sum - h.value,
            if (t.nonEmpty) t.map(_.value).min else ob.value,
            if (t.nonEmpty) t.map(_.value).max else ob.value,
            t.length - 1
          )
          calcStats(newStats, t)
        case _ =>
          val window = obs :+ ob
          val newStats = WindowStats(
            st.sum + ob.value,
            Math.min(st.min, ob.value),
            Math.max(st.max, ob.value),
            window.length
          )
          (newStats, window)
      }
    }

    val (newStats, newSeries) = calcStats(stats, series)
    f(ob, newStats) // f is a function which captures current statistics and prints it to a file
    (newSeries, newStats)
}