/**
 * coopgammad -- Cooperative gamma server
 * Copyright (C) 2016  Mattias Andrée (maandree@kth.se)
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include "communication.h"
#include "state.h"
#include "coopgamma-server/server.h"

#include <sys/socket.h>
#include <errno.h>
#include <string.h>



/**
 * Send a message
 * 
 * @param   conn  The index of the connection
 * @param   buf   The data to send
 * @param   n     The size of `buf`
 * @return        Zero on success, -1 on error, 1 if disconncted
 *                EINTR, EAGAIN, EWOULDBLOCK, and ECONNRESET count
 *                as success (ECONNRESET cause 1 to be returned),
 *                and are handled appropriately.
 */
int send_message(size_t conn, char* restrict buf, size_t n)
{
  struct ring* restrict ring = outbound + conn;
  int fd = connections[conn];
  int saved_errno;
  size_t ptr = 0;
  ssize_t sent;
  size_t chunksize = n;
  size_t sendsize;
  size_t old_n;
  char* old_buf;
    
  while ((old_buf = ring_peek(ring, &old_n)))
    {
      size_t old_ptr = 0;
      while (old_ptr < n)
	{
	  sendsize = old_n - old_ptr < chunksize ? old_n - old_ptr : chunksize;
	  sent = send(fd, old_buf + old_ptr, sendsize, 0);
	  if (sent < 0)
	    {
	      if (errno != EMSGSIZE)
		goto fail;
	      chunksize >>= 1;
	      if (chunksize == 0)
		goto fail;
	      continue;
	    }
	  old_ptr += (size_t)sent;
	  ring_pop(ring, (size_t)sent);
	}
    }
  
  while (ptr < n)
    {
      sendsize = n - ptr < chunksize ? n - ptr : chunksize;
      sent = send(fd, buf + ptr, sendsize, 0);
      if (sent < 0)
	{
	  if (errno != EMSGSIZE)
	    goto fail;
	  chunksize >>= 1;
	  if (chunksize == 0)
	    goto fail;
	  continue;
	}
      ptr += (size_t)sent;
    }
  
  free(buf);
  return 0;
  
 fail:
  switch (errno)
    {
    case EINTR:
    case EAGAIN:
#if EAGAIN != EWOULDBLOCK
    case EWOULDBLOCK:
#endif
      if (ring_push(ring, buf + ptr, n - ptr) < 0)
	goto proper_fail;
      free(buf);
      return 0;
    case ECONNRESET:
      free(buf);
      if (connection_closed(fd) < 0)
	return -1;
      return 1;
    default:
      break;
    }
 proper_fail:
  saved_errno = errno;
  free(buf);
  errno = saved_errno;
  return -1;
}


/**
 * Send a custom error without an error number
 * 
 * @param   conn        The index of the connection
 * @param   message_id  The ID of the message to which this message is a response
 * @param   desc        The error description to send
 * @return              1: Client disconnected
 *                      0: Success (possibily delayed)
 *                      -1: An error occurred
 */
int (send_error)(size_t conn, const char* restrict message_id, const char* restrict desc)
{
  char* restrict buf;
  size_t n;
  
  MAKE_MESSAGE(&buf, &n, 0,
	       "Command: error\n"
	       "In response to: %s\n"
	       "Error: custom\n"
	       "Length: %zu\n"
	       "\n"
	       "%s\n",
	       message_id, strlen(desc) + 1, desc);
  
  return send_message(conn, buf, n);
}


/**
 * Send a standard error
 * 
 * @param   conn        The index of the connection
 * @param   message_id  The ID of the message to which this message is a response
 * @param   number      The value of `errno`, 0 to indicate success
 * @return              1: Client disconnected
 *                      0: Success (possibily delayed)
 *                      -1: An error occurred
 */
int (send_errno)(size_t conn, const char* restrict message_id, int number)
{
  char* restrict buf;
  size_t n;
  
  MAKE_MESSAGE(&buf, &n, 0,
	       "Command: error\n"
	       "In response to: %s\n"
	       "Error: %i\n"
	       "\n",
	       message_id, number);
  
  return send_message(conn, buf, n);
}