module HTTParty::HashConversions

def self.normalize_keys(key, value)
  stack = []
  normalized_keys = []
  if value.respond_to?(:to_ary)
    if value.empty?
      normalized_keys << ["#{key}[]", '']
    else
      normalized_keys = value.to_ary.flat_map do |element|
        normalize_keys("#{key}[]", element)
      end
    end
  elsif value.respond_to?(:to_hash)
    stack << [key, value.to_hash]
  else
    normalized_keys << [key.to_s, value]
  end
  stack.each do |parent, hash|
    hash.each do |child_key, child_value|
      if child_value.respond_to?(:to_hash)
        stack << ["#{parent}[#{child_key}]", child_value.to_hash]
      elsif child_value.respond_to?(:to_ary)
        child_value.to_ary.each do |v|
          normalized_keys << normalize_keys("#{parent}[#{child_key}][]", v).flatten
        end
      else
        normalized_keys << normalize_keys("#{parent}[#{child_key}]", child_value).flatten
      end
    end
  end
  normalized_keys
end