class ParallelTests::Grouper

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

def build_features_with_steps(tests, options)
  require 'gherkin/parser'
  ignore_tag_pattern = options[:ignore_tag_pattern].nil? ? nil : Regexp.compile(options[:ignore_tag_pattern])
  parser = ::Gherkin::Parser.new
  # format of hash will be FILENAME => NUM_STEPS
  steps_per_file = tests.each_with_object({}) do |file,steps|
    feature = parser.parse(File.read(file)).fetch(:feature)
    # skip feature if it matches tag regex
    next if feature[:tags].grep(ignore_tag_pattern).any?
    # count the number of steps in the file
    # will only include a feature if the regex does not match
    all_steps = feature[:children].map{|a| a[:steps].count if a[:tags].grep(ignore_tag_pattern).empty? }.compact
    steps[file] = all_steps.inject(0,:+)
  end
  steps_per_file.sort_by { |_, value| -value }
end

def by_scenarios(tests, num_groups, options={})
  scenarios = group_by_scenarios(tests, options)
  in_even_groups_by_size(scenarios, num_groups)
end

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

def group_by_scenarios(tests, options={})
  require 'parallel_tests/cucumber/scenarios'
  ParallelTests::Cucumber::Scenarios.all(tests, options)
end

def group_features_by_size(items, groups_to_fill)
  items.each do |item, size|
    size ||= 1
    smallest = smallest_group(groups_to_fill)
    add_to_group(smallest, item, size)
  end
end

def in_even_groups_by_size(items, 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 = items.partition { |item, _size| item =~ pattern }
    matched.each { |item, size| add_to_group(groups.first, item, size) }
  end
  groups_to_fill = (options[:isolate] ? groups[1..-1] : groups)
  group_features_by_size(items_to_group(items), groups_to_fill)
  groups.map! { |g| g[:items].sort }
end

def items_to_group(items)
  items.first && items.first.size == 2 ? largest_first(items) : items
end

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

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