sequentialFutures.scala

package utils

import scala.concurrent.{ExecutionContext, Future}

object FutureExt {

  /**
    * For each item in items, sequentially generate a future using futureGenerator to create a future for an item.
    *
    * @param items           initial items
    * @param futureGenerator function to generate a future for one item
    * @param ec              execution context
    * @tparam T item type
    * @tparam U future type
    * @return a future containing the sequence of results
    */
  def sequentially[T, U](items: Seq[T])(futureGenerator: T => Future[U])(implicit ec: ExecutionContext): Future[Seq[U]] = {
    items.foldLeft(Future.successful(Seq[U]())) { (acc, item) =>
      acc.flatMap { seq =>
        futureGenerator(item).map(seq :+ _)
      }
    }
  }

}