class ParallelTests::Grouper

def self.in_even_groups_by_size(items_with_sizes, num_groups)
  items_with_size = smallest_first(items_with_sizes)
  groups = Array.new(num_groups){{:items => [], :size => 0}}
  items_with_size.each do |item, size|
    # always add to smallest group
    smallest = groups.sort_by{|g| g[:size] }.first
    smallest[:items] << item
    smallest[:size] += size
  end
  groups.map{|g| g[:items] }
end

def self.in_groups(items, num_groups)
  [].tap do |groups|
    while ! items.empty?
      (0...num_groups).map do |group_number|
        groups[group_number] ||= []
        groups[group_number] << items.shift
      end
    end
  end
end

def self.smallest_first(files)
  files.sort_by{|item, size| size }.reverse
end