def findNextInvoiceDate()

in src/main/scala/com/gu/invoicing/preview/Impl.scala [173:192]

• 19 lines of code
• 2 McCabe index (conditional complexity)

  def findNextInvoiceDate(
      items: List[InvoiceItem],
      today: LocalDate = LocalDate.now(),
  ): Option[LocalDate] = {
    def verifyNextInvoiceDate(nextInvoiceDate: LocalDate): Unit =
      assert(
        nextInvoiceDate >= today,
        s"nextInvoiceDate $nextInvoiceDate should not be before today $today for ${items.headOption
            .map(_.subscriptionName)}",
      )

    val sortedItems = items.sortBy(_.serviceStartDate)
    sortedItems
      .find(item => today.inClosedInterval(item.serviceStartDate, item.serviceEndDate))
      .map(_.serviceEndDate.plusDays(1))
      .orElse(
        sortedItems.headOption.map(_.serviceStartDate),
      ) // first invoice item might be in the future
      .tap(_.map(verifyNextInvoiceDate))
  }