(* $Id: rpc_transport.mli 2195 2015-01-01 12:23:39Z gerd $
 * ----------------------------------------------------------------------
 *
 *)

(** Low-level RPC transporters *)

open Rpc
open Rpc_packer


type 't result =
    [ `Ok of 't
    | `Error of exn
    ]

type 't result_eof =
    [ 't result
    | `End_of_file
    ]


type sockaddr =
    [ `Implied
    | `Sockaddr of Unix.sockaddr
    ]

val string_of_sockaddr : sockaddr -> string
  (** Convert to string, for debugging purposes *)


exception Error of string
  (** Passed back as [`Error]. Such errors are fatal. *)

(** Note errors on stream connections: These are normally not recoverable.
  * One should close the connection and open a new one.
 *)

type in_rule =
    [ `Deny
    | `Drop
    | `Reject
    | `Reject_with of Rpc.server_error
    | `Accept
    ]

type in_record =
    [ `Deny
    | `Drop
    | `Reject of packed_value  (* only the beginning of the message! *)
    | `Reject_with of packed_value * Rpc.server_error
    | `Accept of packed_value  (* the full message *)
    ]

class type rpc_multiplex_controller =
object
  method alive : bool
    (** If the controller is alive, the socket is not yet completely down. *)

  method event_system : Unixqueue.event_system
    (** Returns the event system *)

  method getsockname : sockaddr
    (** The address of this socket *)

  method getpeername : sockaddr
    (** The address of the peer's socket. Only available if the socket
      * is connected. (Fails otherwise.)
     *)

  method protocol : protocol
    (** The protocol encapsulation *)

  method tls_session_props : Nettls_support.tls_session_props option
    (** The TLS session properties (if TLS is enabled) *)

  method peer_user_name : string option
    (** If the transport mechanism provides a way to authenticate the
      * peer, it can return the name here.
     *)

  method file_descr : Unix.file_descr option
    (** If the transport mechanism is on top of a file descriptor, this
	is returned here. This can be useful for getting more information
	about the descriptor (e.g. credentials associated with it).
     *)

  method reading : bool
    (** True iff there is a reader *)

  method read_eof : bool
    (** Whether the EOF marker has been read *)

  method start_reading : 
    ?peek:( unit -> unit) ->
    ?before_record:( int -> sockaddr -> in_rule ) ->
    when_done:( (in_record * sockaddr) result_eof -> unit) -> unit -> unit
    (** Start reading from the connection. When a whole message has been
      * received, the [when_done] callback is invoked. The [in_record]
      * passed to [when_done] is usually [`Accept m] when [m] is the
      * undecoded message string. For other types of [in_record] see
      * the comments to [before_record] below.
      *
      * This starts one-time read job only, i.e. it is not restarted
      * after [when_done] has been invoked.
      *
      * It is an error to start reading several times at once.
      *
      * [peek]: This function is called immediately before a data chunk is
      * read from the underlying data connection.
      *
      * [before_record]: If passed, this function is called back whenever
      * a fragment of data is started. The integer is the so-far known
      * size of the
      * message in bytes. It is guaranteed that the function is
      * invoked once for every message fragment as long as the previous
      * fragments were accepted, and in total at least once
      * before [when_done]. The result of the last [before_record] call
      * determines what is returned as [in_record], e.g. a [`Deny] rule
      * causes that a [`Deny] result is passed to [when_done].
      * Also, for [`Deny] and [`Drop] no message buffer is
      * allocated (i.e. no memory consumption). For [`Reject], only
      * a very small buffer is allocated that only provides space for
      * the session identifier (xid).
      * When there is no [before_record] function, [`Accept] is passed
      * to [when_done].
      * 
     *)

  method writing : bool
   (** True iff there is a writer *)

  method start_writing :
    when_done:(unit result -> unit) -> packed_value -> sockaddr -> unit
    (** Starts writing the message. Invoked [when_done] when it is written,
      * or an error condition is reached.
      *
      * This starts one-time write job only, i.e. it is not restarted
      * after [when_done] has been invoked.
      *
      * It is an error to start writing several times at once.
     *)

  method cancel_rd_polling : unit -> unit
    (** Cancels polling for the next input message. This method must not be
      * called from the [before_record] callback function. Polling can be
      * resumed by calling [start_reading] again.
     *)

  method abort_rw : unit -> unit
    (** Aborts the current reader and/or writer forever. Note that there is no
      * clean way of resuming reading and/or writing. The readers/writers
      * are not notified about cancellation.
      *
      * This method also deallocates buffers, so far possible.
      *
      * It is allowed to go on with the shutdown, and to inactivate.
     *)

  method start_shutting_down :
    when_done:(unit result -> unit) -> unit -> unit
    (** Start shutting down the connection. After going through the shutdown
      * procedure, the [when_done] callback is invoked reporting the success
      * or failure.
      *
      * The underlying file descriptor (if any) is not closed. A shutdown
      * is only a protocol handshake. After a shutdown,[read_eof]
      * is true. Call [inactivate] to close the descriptor.
      *
      * This method also deallocates buffers, so far possible.
     *)
 
  method cancel_shutting_down : unit -> unit
    (** Cancels the shutdown procedure. After that, the state of the 
      * connection is undefined. The [when_done] callback is invoked with
      * the [`Cancelled].
      *
      * It is no error if no shutdown is in progress.
     *)

  method set_timeout : notify:(unit -> unit) -> float -> unit
    (** If there is no read or write activity for the passed number of
      * seconds, the [notify] callback is invoked.
     *)

  method inactivate : unit -> unit
    (** Inactivates the connection immediately, and releases any resources
      * the controller is responsible for (e.g. closes file descriptors). 
      * Note that this is more than
      * cancelling all pending operations and shutting the connection down.
      * However, the details of this method are implementation-defined.
      * Callbacks are not invoked.
     *)

end


val stream_rpc_multiplex_controller :
       ?close_inactive_descr:bool ->
       ?preclose:(unit -> unit) ->
       ?tls:((module Netsys_crypto_types.TLS_CONFIG) * string option) ->
       role:[`Client|`Server] ->
       Unix.file_descr -> Unixqueue.event_system ->
         rpc_multiplex_controller
  (** The multiplex controller for stream encapsulation

      - [close_inactive_descr]: If true, the descriptor is closed when
        inactivated
      - [preclose]: This function is called just before the descriptor
        is closed.
      - [tls]: Enables TLS support for the passed config and the passed DNS
        peer name
   *)


val datagram_rpc_multiplex_controller :
       ?close_inactive_descr:bool ->
       ?preclose:(unit -> unit) ->
       role:[`Client|`Server] ->
       Unix.file_descr -> Unixqueue.event_system ->
         rpc_multiplex_controller
  (** The multiplex controller for datagrams ((D)TLS not yet supported) *)


(** {1 Debugging} *)

module Debug : sig
  val enable : bool ref
    (** Enables {!Netlog}-style debugging *)

end
