/*
  Copyright 2010 Nathan Phillip Brink, Ethan Zonca

  This file is a part of DistRen.

  DistRen is free software: you can redistribute it and/or modify
  it under the terms of the GNU Affero General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  DistRen is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU Affero General Public License for more details.

  You should have received a copy of the GNU Affero General Public License
  along with DistRen.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef _DISTREN_REMOTEIO_H
#define _DISTREN_REMOTEIO_H

#include <stdlib.h>

/**
 * @file RemoteIO provides an abstraction to the method of talking to a remote distrend. It is a layer on top of execio that should provide an equivalent interface.
 *
 * RemoteIO works on top of multiio, so for it to work you write your
 * program in an event-oriented fashion and call multiio_poll().
 */

struct remoteio_opts;
struct remoteio;

/**
 * asynchronous read handler signature.
 *
 * This is the signature of the callback that is called when data is
 * available for reading. The handler may process as much of the
 * available data as it wants. When it has processed a chunk of data,
 * it must return the length of the data that it processed. If the
 * handler returns 0, the handler is essentially signalling ``I can't
 * figure out what this means until I see more''.
 *
 * If you need to close a socket after reading certain data from it,
 * you may call remoteio_close() from inside of this function.
 *
 * @param rem the associated remoteio handle
 * @param generic_data a pointer that is stored in remoteio's struct remoteio_opts which isn't client-specific
 * @param buf a pointer to the buffer containing data waiting to be processed
 * @param len the size of buf that may be accessed
 * @param data the pointer passed to remoteio_open(). _NOT_ the data just received on the socket.
 * @return the number of bytes that the function accepted and thus should be removed from the rem handle.
 */
typedef size_t(*remoteio_read_handle_func_t)(struct remoteio *rem, void *generic_data, void *buf, size_t len, void *data);

/**
 * asynchronous close handler which is called whenever remoteio_close() is called.
 *
 * As reading is now event-oriented and as libremoteio may itself call
 * remoteio_close(), you need a way to be informed that a socket is
 * being closed. This is particularly important if you have to clean
 * up your read_handler_data.
 *
 * @param generic_data a pointer set by a call to remoteio_generic_data_set().
 * @param data the same pointer passed to remoteio_open().
 */
typedef void (*remoteio_close_handle_func_t)(void *generic_data, void *data);

/**
 * Determines the value of generic_data which is passed to
 * remoteio_read_handle_func_t
 *
 * @param opts the remoteio runtime options
 */
int remoteio_generic_data_set(struct remoteio_opts *opts, void *generic_data);

/**
   Opens connection with to a remote distrend. Returns 1 on error.

   @todo should this be asynchronous? YES! but optionally, perhaps
   @param opts the configuration settings for remoteio gotten from options_init().
   @param read_handler the function to call when data has been read from the server.
   @param read_handler_data the data to pass to the read_handler function.
   @param servername the name of the configuration file entry for the server.
   From this, information about how to make the outgoing connection is derived.
 */
int remoteio_open_server(struct remoteio **rem,
			 struct remoteio_opts *opts,
			 remoteio_read_handle_func_t read_handler,
			 void *read_handler_data,
			 remoteio_close_handle_func_t close_handler,
			 const char *servername);

/**
 * Initializes a remoteio instance for a socket that's already been floating
 * around for a while. I.e., this socket probably came from accept().
 *
 * @param rem a pointer to where the poiner to the newly allocated struct remoteio should be stored.
 * @param opts remoteio's options
 * @param read_handler the function to call when data has been read from the server.
 * @param read_handler_data the data to pass to the read_handler function.
 * @param opts self explanatory.
 */
int remoteio_open_socket(struct remoteio **rem,
			 struct remoteio_opts *opts,
			 remoteio_read_handle_func_t read_handler,
			 void *read_handler_data,
			 remoteio_close_handle_func_t close_handler,
			 int fd);

/**
 * Queue bytes to be written to the remote host.
 *
 * @param rem the remoteio handle
 * @param buf a buffer to be queued for writing. We will copy this, so the caller has to handle its memory (and free() it if necessary).
 * @param len number of bytes to grab from buf
 * @return 0 on success, 1 on failure
 */
int remoteio_write(struct remoteio *rem, const void *buf, size_t len);

/**
 * Closes a remoteio session.
 *
 * It is safe to call this function from within
 * remoteio_read_handle_func_t.
 *
 * @return nonzero on error
*/
int remoteio_close(struct remoteio *rem);

/**
 * Returns the number of unfulfilled remoteio_write() calls pending on
 * a remoteio handle.
 */
size_t remoteio_sendq_len(const struct remoteio *rem);

#endif