package gw.currency

uses gw.pl.currency.MonetaryAmount

uses java.lang.Iterable
uses java.math.BigDecimal

@ReadOnly
enhancement GWIterableMonetaryAmountSumCoreEnhancement<T> : Iterable<T> {

  /**
   * Return the average of the values of the target of the mapper argument,
   *   which must all be of the same currency as specified.
   */
  reified function average( currency : Currency, select:block(elt:T):MonetaryAmount) : MonetaryAmount {
    return this.sum(currency, \ elt -> select(elt) ) / (this.Count as BigDecimal)
  }


  /**
   * Sums up the values of the target of the mapper argument,
   *   which must all be of the same currency as specified.
   */
  function sum( currency : Currency, mapper(elt:T) : MonetaryAmount ) : MonetaryAmount {
    var sum = new MonetaryAmount(0, currency)//TODO: 0bd.ofCurrency(currency)
    for (elt in this) {
      sum = sum.add(mapper( elt ))
    }
    return sum
  }
}