module ViewModel::Utils::Collections

def self.count_by(enumerable)
  enumerable.each_with_object({}) do |el, counts|
    key = yield(el)
    unless key.nil?
      counts[key] = (counts[key] || 0) + 1
    end
  end
end

def contains_exactly?(other)
  mine   = count_by { |x| x }
  theirs = other.count_by { |x| x }
  mine == theirs
end

def count_by(&by)
  Collections.count_by(self, &by)
end

def count_by(&by)
  Collections.count_by(self, &by)
end

def duplicates
  duplicates_by { |x| x }
end

def duplicates
  duplicates_by { |x| x }
end

def duplicates_by(&by)
  count_by(&by).delete_if { |_, count| count == 1 }
end

def duplicates_by(&by)
  count_by(&by).delete_if { |_, count| count == 1 }
end