class ParallelTests::Grouper

def self.add_to_group(group, item, size)
  group[:items] << item
  group[:size] += size
end

def self.build_features_with_steps(tests)
  require 'parallel_tests/cucumber/gherkin_listener'
  listener = Cucumber::GherkinListener.new
  parser = Gherkin::Parser::Parser.new(listener, true, 'root')
  tests.each{|file|
    parser.parse(File.read(file), file, 0)
  }
  listener.collect.sort_by{|_,value| -value }
end

def self.by_steps(tests, num_groups)
  features_with_steps = build_features_with_steps(tests)
  in_even_groups_by_size(features_with_steps, num_groups)
end

def self.in_even_groups_by_size(items_with_sizes, num_groups, options={})
  groups = Array.new(num_groups){{:items => [], :size => 0}}
  # add all files that should run in a single process to one group
  (options[:single_process]||[]).each do |pattern|
    matched, items_with_sizes = items_with_sizes.partition{|item, size| item =~ pattern }
    smallest = smallest_group(groups)
    matched.each{|item,size| add_to_group(smallest, item, size) }
  end
  # add all other files
  largest_first(items_with_sizes).each do |item, size|
    smallest = smallest_group(groups)
    add_to_group(smallest, item, size)
  end
  groups.map!{|g| g[:items].sort }
end

def self.in_groups(items, num_groups)
  groups = Array.new(num_groups){ [] }
  until items.empty?
    num_groups.times do |group_number|
      if item = items.shift
        groups[group_number] << item
      end
    end
  end
  groups.map!(&:sort!)
end

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

def self.smallest_group(groups)
  groups.min_by{|g| g[:size] }
end