module HTTP::Chainable

def via(*proxy)
  proxy_hash = {}
  proxy_hash[:proxy_address]  = proxy[0] if proxy[0].is_a?(String)
  proxy_hash[:proxy_port]     = proxy[1] if proxy[1].is_a?(Integer)
  proxy_hash[:proxy_username] = proxy[2] if proxy[2].is_a?(String)
  proxy_hash[:proxy_password] = proxy[3] if proxy[3].is_a?(String)
  if [2, 4].include?(proxy_hash.keys.size)
    branch default_options.with_proxy(proxy_hash)
  else
    fail(RequestError, "invalid HTTP proxy: #{proxy_hash}")
  end
end