module Metanorma::Utils::Hash

def deep_merge(second)
  merger = proc { |_, v1, v2|
    if ::Hash === v1 && ::Hash === v2
      v1.merge(v2, &merger)
    elsif ::Array === v1 && ::Array === v2
      v1 | v2
    elsif [:undefined].include?(v2)
      v1
    else
      v2
    end
  }
  merge(second.to_h, &merger)
end

def stringify_all_keys
  result = {}
  each do |k, v|
    result[k.to_s] = case v
                     when ::Hash, ::Array
                       v.stringify_all_keys
                     else
                       v
                     end
  end
  result
end

def symbolize_all_keys
  result = {}
  each do |k, v|
    result[k.to_sym] = case v
                       when ::Hash, ::Array
                         v.symbolize_all_keys
                       else
                         v
                       end
  end
  result
end