package gw.lang.enhancements

uses gw.api.financials.CurrencyAmount

/**
 * The overloaded versions of the sum() method had to be moved to separate enhancements due to the way block type erasure
 * works (all blocks with the same arity have the same erasure).  Splitting the methods up into different enhancements
 * prevents them from conflicting, since they become part of different Java classes.
 *
 *  Copyright 2010 Guidewire Software, Inc.
 */
@ReadOnly
enhancement GWCoreArrayCurrencyAmountSumEnhancement<T> : T[] {
  /**
   * Sums up the values of the target of the mapper argument.
   * Returns null if the array is empty, since the currency cannot be determined.
   * Note: this behavior is different from that of other sum methods, where zero is returned.
   * @throws IllegalStateException if all mapped amounts are not in the same currency
   */
  function sum( mapper(elt:T):CurrencyAmount ) : CurrencyAmount {
    if (not this.HasElements) {
      return null
    }

    var sum : CurrencyAmount = null
    for (elem in this) {
      var val = mapper(elem)
      sum = sum == null ? val : sum.add(val)
    }
    return sum
  }
}