Final result: FromAttachment

from_attachment.rb

class PouchOrder::FromAttachment
  include DatetimeChange

  def initialize(attachment: attachment)
    @attachment = attachment
    @pouch_order = PouchOrder.new(
      number:       @attachment.header.order_number,
      phone_number: @attachment.contact_telephone,
      issued_at:    @attachment.issued_at,
      delivery_at:  @attachment.delivery_at,
    )
  end

  def parse
    parse_patient && parse_ward && parse_items
    @pouch_order
  end

  private

  def parse_patient
    patient = Patient.where(ssn: @attachment.patient_ssn).first_or_initialize
    patient.first_name = @attachment.patient_first_name
    patient.last_name = @attachment.patient_last_name
    @pouch_order.patient = patient
  end

  def parse_ward
    @pouch_order.ward = Ward.find_by_consignee_gln!(gln: @attachment.delivery_customer_gln)
  end

  def parse_items
    items_grouped_by_date.each do |date, items|
      intakes_grouped_by_time(items: items).each do |time_string, intakes|
        time = Time.zone.parse(time_string)
        admin_time = datetime_change(datetime: date, time: time)
        intakes.each do |intake|
          build_line(admin_time: admin_time, intake: intake)
        end
      end
    end
  end

  def items_grouped_by_date
    @attachment.items.group_by(&:periodic_start)
  end

  def intakes_grouped_by_time(items: items)
    items.flat_map(&:intakes).group_by(&:time)
  end

  def build_line(admin_time: admin_time, intake: intake)
    @pouch_order.lines.build(
      item:             Item.find_by!(npl_id: intake.item.npl_id),
      prescriber_name:  intake.item.prescriber_name,
      admin_time:       admin_time,
      quantity:         intake.quantity,
    )
  end
end