module Hashie::Extensions::DeepMerge

def _recursive_merge(hash, other_hash, &block)
  other_hash.each do |k, v|
    hash[k] =
      if hash.key?(k) && hash[k].is_a?(::Hash) && v.is_a?(::Hash)
        _recursive_merge(hash[k], v, &block)
      elsif hash.key?(k) && block_given?
        yield(k, hash[k], v)
      else
        v.respond_to?(:deep_dup) ? v.deep_dup : v
      end
  end
  hash
end

def deep_merge(other_hash, &block)
  copy = dup
  copy.extend(Hashie::Extensions::DeepMerge) unless copy.respond_to?(:deep_merge!)
  copy.deep_merge!(other_hash, &block)
end

def deep_merge!(other_hash, &block)
  return self unless other_hash.is_a?(::Hash)
  _recursive_merge(self, other_hash, &block)
  self
end