(defn hijack! 
  "Hijack a nginx request and return a server channel.
   After being hijacked, the ring handler's result will be ignored.
   If ignore-nginx-filter? is true all data output to channel won't be filtered
   by any nginx HTTP header/body filters such as gzip filter, chucked filter, etc.
   We can use this function to implement long poll / Server Sent Events (SSE) easily."
  [^NginxRequest req ignore-nginx-filter?])

(defprotocol HttpServerChannel
  (close! [ch] 
    "Asynchronously close the channel. If there's remaining data to send it won't block 
     current thread  and will flush data on the background asynchronously and later close the channel safely")
  (send! [ch data flush? last?]
    "Asynchronously send data to channel without blocking current thread. 
     data can be byte[], String, or ByteBuffer
     If flush? is false it will put data into buffers chain eitherwise it will write data to network.
     If close? is true it will close channel after all data are sent.
    ")
  (send-header! [ch status headers flush? last?] 
    "Asynchronously send HTTP status & headers to channel.
     status is a integer for HTTP status code, headers is a HTTP headers map.
     If flush? is false it will put data into buffers chain eitherwise it will write data to network.
     If close? is true it will close channel after all data are sent.")
  (send-response! [ch resp]
    "Asynchronously send a complete HTTP response to channel and close channel after all data are sent.
     resp is a ring Response Map, e.g. {:status 200, headers {\"Content-Type\" \"text/html\"}, :body \"Hello, Nginx-Clojure!\" } .
     ")
  (on-close! [ch attachment listener]
    "Add a close event listener.
     attachement is a  object which will be passed to listener when close event happens
     listener is a function like (fn[attachement] ... )")
  )