class Money::Splitter

def [](index)
  offset = 0
  split.each do |money, count|
    offset += count
    if index < offset
      return money
    end
  end
  nil
end

def each(&block)
  split.each do |money, count|
    count.times do
      yield money
    end
  end
end

def first(count = (count_undefined = true))
  if count_undefined
    each do |money|
      return money
    end
  elsif count >= size
    to_a
  else
    result = Array.new(count)
    index = 0
    each do |money|
      result[index] = money
      index += 1
      break if index == count
    end
    result
  end
end

def initialize(money, num)
  @num = Integer(num)
  raise ArgumentError, "need at least one party" if num < 1
  @money = money
  @split = nil
end

def last(count = (count_undefined = true))
  if count_undefined
    reverse_each do |money|
      return money
    end
  elsif count >= size
    to_a
  else
    result = Array.new(count)
    index = 0
    reverse_each do |money|
      result[index] = money
      index += 1
      break if index == count
    end
    result.reverse!
    result
  end
end

def reverse
  copy = dup
  copy.split = split.reverse_each.to_h.freeze
  copy
end

def reverse_each(&block)
  split.reverse_each do |money, count|
    count.times do
      yield money
    end
  end
end

def size
  count = 0
  split.each_value { |c| count += c }
  count
end

def split
  @split ||= begin
    subunits = @money.subunits
    low = Money.from_subunits(subunits / @num, @money.currency)
    high = Money.from_subunits(low.subunits + 1, @money.currency)
    num_high = subunits % @num
    split = {}
    split[high] = num_high if num_high > 0
    split[low] = @num - num_high
    split.freeze
  end
end