class Addressable::URI

def merge(hash)
  if !hash.respond_to?(:to_hash)
    raise TypeError, "Can't convert #{hash.class} into Hash."
  end
  hash = hash.to_hash
  if hash.has_key?(:authority)
    if (hash.keys & [:userinfo, :user, :password, :host, :port]).any?
      raise ArgumentError,
        "Cannot specify both an authority and any of the components " +
        "within the authority."
    end
  end
  if hash.has_key?(:userinfo)
    if (hash.keys & [:user, :password]).any?
      raise ArgumentError,
        "Cannot specify both a userinfo and either the user or password."
    end
  end
  uri = self.class.new
  uri.defer_validation do
    # Bunch of crazy logic required because of the composite components
    # like userinfo and authority.
    uri.scheme =
      hash.has_key?(:scheme) ? hash[:scheme] : self.scheme
    if hash.has_key?(:authority)
      uri.authority =
        hash.has_key?(:authority) ? hash[:authority] : self.authority
    end
    if hash.has_key?(:userinfo)
      uri.userinfo =
        hash.has_key?(:userinfo) ? hash[:userinfo] : self.userinfo
    end
    if !hash.has_key?(:userinfo) && !hash.has_key?(:authority)
      uri.user =
        hash.has_key?(:user) ? hash[:user] : self.user
      uri.password =
        hash.has_key?(:password) ? hash[:password] : self.password
    end
    if !hash.has_key?(:authority)
      uri.host =
        hash.has_key?(:host) ? hash[:host] : self.host
      uri.port =
        hash.has_key?(:port) ? hash[:port] : self.port
    end
    uri.path =
      hash.has_key?(:path) ? hash[:path] : self.path
    uri.query =
      hash.has_key?(:query) ? hash[:query] : self.query
    uri.fragment =
      hash.has_key?(:fragment) ? hash[:fragment] : self.fragment
  end
  return uri
end