/* GNU mailutils - a suite of utilities for electronic mail
   Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Library Public License as published by
   the Free Software Foundation; either version 2, 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 Library General Public License for more details.

   You should have received a copy of the GNU Library General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <sys/types.h>
#include <stdio.h>
#include <pwd.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <netdb.h>

#include <mailutils/stream.h>
#include <mailutils/address.h>
#include <mailer0.h>
#include <registrar0.h>

static struct _record _smtp_record =
{
  MU_SMTP_SCHEME,
  _url_smtp_init,      /* url init.  */
  NULL,                /* Mailbox init.  */
  &_mailer_smtp_init,  /* Mailer init.  */
  NULL, /* Folder init.  */
  NULL, /* No need for a back pointer.  */
  NULL, /* _is_scheme method.  */
  NULL, /* _get_url method.  */
  NULL, /* _get_mailbox method.  */
  NULL, /* _get_mailer method.  */
  NULL  /* _get_folder method.  */
};
/* We export : url parsing and the initialisation of
   the mailbox, via the register entry/record.  */
record_t smtp_record = &_smtp_record;

struct _smtp
{
  mailer_t mailer;
  char *mailhost;
  char *localhost;

  /* Buffered the IO.  */
  char *ptr;
  char *nl;
  char *buffer;
  size_t buflen;

  enum smtp_state
  {
    SMTP_NO_STATE, SMTP_OPEN, SMTP_GREETINGS, SMTP_EHLO, SMTP_EHLO_ACK,
    SMTP_HELO, SMTP_HELO_ACK, SMTP_QUIT, SMTP_QUIT_ACK, SMTP_ENV_FROM,
    SMTP_ENV_RCPT, SMTP_MAIL_FROM, SMTP_MAIL_FROM_ACK, SMTP_RCPT_TO,
    SMTP_RCPT_TO_ACK, SMTP_DATA, SMTP_DATA_ACK, SMTP_SEND, SMTP_SEND_ACK,
    SMTP_SEND_DOT
  } state;

  int extended;

  address_t mail_from;
  address_t rcpt_to;
  size_t rcpt_index;

  off_t offset;
  int dsn;
  message_t message;
};

typedef struct _smtp * smtp_t;

/* Usefull little Macros, since these are very repetitive.  */
#define CLEAR_STATE(smtp) \
 smtp->state = SMTP_NO_STATE

/* Clear the state and close the stream.  */
#define CHECK_ERROR_CLOSE(mailer, smtp, status) \
do \
  { \
     if (status != 0) \
       { \
          stream_close (mailer->stream); \
          CLEAR_STATE (smtp); \
          return status; \
       } \
  } \
while (0)

/* Clear the state.  */
#define CHECK_ERROR(smtp, status) \
do \
  { \
     if (status != 0) \
       { \
          CLEAR_STATE (smtp); \
          return status; \
       } \
  } \
while (0)

/* Clear the state for non recoverable error.  */
#define CHECK_EAGAIN(smtp, status) \
do \
  { \
    if (status != 0) \
      { \
         if (status != EAGAIN && status != EINPROGRESS && status != EINTR) \
           { \
             CLEAR_STATE (smtp); \
           } \
         return status; \
      } \
   }  \
while (0)

static void smtp_destroy (mailer_t);
static int smtp_open (mailer_t, int);
static int smtp_close (mailer_t);
static int smtp_send_message (mailer_t, message_t);
static int smtp_writeline (smtp_t smtp, const char *format, ...);
static int smtp_readline (smtp_t);
static int smtp_read_ack (smtp_t);
static int smtp_write (smtp_t);

static int get_rcpt (message_t , address_t *);
static int get_from (message_t , char *, address_t *);

int
_mailer_smtp_init (mailer_t mailer)
{
  smtp_t smtp;

  /* Allocate memory specific to smtp mailer.  */
  smtp = mailer->data = calloc (1, sizeof (*smtp));
  if (mailer->data == NULL)
    return ENOMEM;

  smtp->mailer = mailer; /* Back pointer.  */
  smtp->state = SMTP_NO_STATE;

  mailer->_destroy = smtp_destroy;
  mailer->_open = smtp_open;
  mailer->_close = smtp_close;
  mailer->_send_message = smtp_send_message;

  /* Set our properties.  */
  mailer->properties = calloc (1, sizeof (*(mailer->properties)));
  if (mailer->properties == NULL)
    return ENOMEM;
  mailer->properties_count = 1;
  mailer->properties[0].key = strdup ("SMTP");
  mailer->properties[0].value = 1;

  return 0;
}

static void
smtp_destroy(mailer_t mailer)
{
  smtp_t smtp = mailer->data;
  smtp_close (mailer);
  if (smtp->mailhost)
    free (smtp->mailhost);
  if (smtp->localhost)
    free (smtp->localhost);
  if (smtp->buffer)
    free (smtp->buffer);
  if (smtp->mail_from)
    address_destroy (&(smtp->mail_from));
  if (smtp->rcpt_to)
    address_destroy (&(smtp->rcpt_to));
  free (smtp);
  mailer->data = NULL;
}

static int
smtp_open (mailer_t mailer, int flags)
{
  smtp_t smtp = mailer->data;
  int status;
  long port;
  size_t buf_len = 0;

  /* Sanity checks.  */
  if (smtp == NULL)
    return EINVAL;

  mailer->flags = flags;

  /* Fetch the mailer server name and the port in the url_t.  */
  if ((status = url_get_host (mailer->url, NULL, 0, &buf_len)) != 0
      || buf_len == 0 || (status = url_get_port (mailer->url, &port)) != 0)
    return status;

  switch (smtp->state)
    {
    case SMTP_NO_STATE:
      /* Get the mailhost.  */
      if (smtp->mailhost)
	{
	  free (smtp->mailhost);
	  smtp->mailhost = NULL;
	}
      smtp->mailhost = calloc (buf_len + 1, sizeof (char));
      if (smtp->mailhost == NULL)
	return ENOMEM;
      url_get_host (mailer->url, smtp->mailhost, buf_len + 1, NULL);

      if (smtp->localhost)
	{
	  free (smtp->localhost);
	  smtp->localhost = NULL;
	}
      /* Fetch our localhost name.  */
      buf_len = 64;
      do
	{
	  char *tmp;
	  errno = 0;
	  buf_len *= 2;    /* Initial guess */
	  tmp = realloc (smtp->localhost, buf_len);
	  if (tmp == NULL)
	    {
	      if (smtp->localhost)
		free (smtp->localhost);
	      smtp->localhost = NULL;
	      free (smtp->mailhost);
	      smtp->mailhost = NULL;
	      return ENOMEM;
	    }
	  smtp->localhost = tmp;
	}
      while (((status = gethostname(smtp->localhost, buf_len)) == 0
	      && !memchr (smtp->localhost, '\0', buf_len))
#ifdef ENAMETOOLONG
	     || errno == ENAMETOOLONG
#endif
	     );
      if (status != 0 && errno != 0)
	{
	  /* gethostname failed, abort.  */
	  free (smtp->localhost);
	  smtp->localhost = NULL;
	  free (smtp->mailhost);
	  smtp->mailhost = NULL;
	  return EINVAL;
	}

      /* Many SMTP servers prefer a FQDN.  */
      if (strchr (smtp->localhost, '.') == NULL)
	{
	  struct hostent *hp = gethostbyname (smtp->localhost);
	  if (hp == NULL)
	    {
	      /* Don't flag it as an error some SMTP servers can get the FQDN
		 by themselves even if the client is lying, probably
		 with getpeername().  */
	      // return EINVAL;
	    }
	  else
	    {
	      free (smtp->localhost);
	      smtp->localhost = strdup (hp->h_name);
	      if (smtp->localhost == NULL)
		{
		  free (smtp->mailhost);
		  smtp->mailhost = NULL;
		  return ENOMEM;
		}
	    }
	}

      /* allocate a working io buffer.  */
      if (smtp->buffer == NULL)
        {
          smtp->buflen = 512; /* Initial guess.  */
          smtp->buffer = malloc (smtp->buflen + 1);
          if (smtp->buffer == NULL)
            {
              CHECK_ERROR (smtp, ENOMEM);
            }
          smtp->ptr = smtp->buffer;
        }

      /* Create a TCP stack if one is not given.  */
      if (mailer->stream == NULL)
	{
	  status = tcp_stream_create (&(mailer->stream));
	  CHECK_ERROR (smtp, status);
	  stream_setbufsiz (mailer->stream, BUFSIZ);
	}
      CHECK_ERROR (smtp, status);
      smtp->state = SMTP_OPEN;

    case SMTP_OPEN:
      MAILER_DEBUG2 (mailer, MU_DEBUG_PROT, "smtp_open (%s:%d)\n",
		     smtp->mailhost, port);
      status = stream_open (mailer->stream, smtp->mailhost, port,
			    mailer->flags);
      CHECK_EAGAIN (smtp, status);
      smtp->state = SMTP_GREETINGS;

    case SMTP_GREETINGS:
      /* Swallow the greetings.  */
      status = smtp_read_ack (smtp);
      CHECK_EAGAIN (smtp, status);
      MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
      if (smtp->buffer[0] != '2')
	{
	  stream_close (mailer->stream);
	  return EACCES;
	}
      status = smtp_writeline (smtp, "EHLO %s\r\n", smtp->localhost);
      CHECK_ERROR (smtp, status);
      MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
      smtp->state = SMTP_EHLO;

    case SMTP_EHLO:
      /* We first try Extended SMTP.  */
      status = smtp_write (smtp);
      CHECK_EAGAIN (smtp, status);
      smtp->state = SMTP_EHLO_ACK;

    case SMTP_EHLO_ACK:
      status = smtp_read_ack (smtp);
      CHECK_EAGAIN (smtp, status);
      MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
      if (smtp->buffer[0] != '2')
	{
	  smtp->extended = 0;
	  status = smtp_writeline (smtp, "HELO %s\r\n", smtp->localhost);
	  CHECK_ERROR (smtp, status);
	  smtp->state = SMTP_HELO;
	}
      else
	{
	  smtp->extended = 1;
	  break;
	}

    case SMTP_HELO:
      if (!smtp->extended)
	{
	  status = smtp_write (smtp);
	  CHECK_EAGAIN (smtp, status);
	}
      smtp->state = SMTP_HELO_ACK;

    case SMTP_HELO_ACK:
      if (!smtp->extended)
	{
	  status = smtp_read_ack (smtp);
	  CHECK_EAGAIN (smtp, status);
	  MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
	  if (smtp->buffer[0] != '2')
	    {
	      stream_close (mailer->stream);
	      CLEAR_STATE (smtp);
	      return EACCES;
	    }
	}

    default:
      break;
    }
  smtp->state = SMTP_NO_STATE;
  return 0;
}

static int
smtp_close (mailer_t mailer)
{
  smtp_t smtp = mailer->data;
  int status;
  switch (smtp->state)
    {
    case SMTP_NO_STATE:
      status = smtp_writeline (smtp, "Quit\r\n");
      CHECK_ERROR (smtp, status);
      MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
      smtp->state = SMTP_QUIT;

    case SMTP_QUIT:
      status = smtp_write (smtp);
      CHECK_EAGAIN (smtp, status);
      smtp->state = SMTP_QUIT_ACK;

    case SMTP_QUIT_ACK:
      status = smtp_read_ack (smtp);
      CHECK_EAGAIN (smtp, status);
      MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);

    default:
      break;
    }
  return stream_close (mailer->stream);
}

static int
smtp_send_message(mailer_t mailer, message_t msg)
{
  smtp_t smtp = mailer->data;
  int status;

  if (smtp == NULL || msg == NULL)
    return EINVAL;

  switch (smtp->state)
    {
    case SMTP_NO_STATE:
      smtp->state = SMTP_ENV_FROM;
      status = get_from (msg, smtp->localhost, &smtp->mail_from);
      CHECK_ERROR (smtp, status);
      status = get_rcpt (msg, &smtp->rcpt_to);
      CHECK_ERROR (smtp, status);

    case SMTP_ENV_FROM:
      {
	size_t len = 0;
	char *from;
	address_get_email (smtp->mail_from, 1, NULL, 0, &len);
	if (len == 0)
	  CHECK_ERROR (smtp, EINVAL);
	from = calloc (len + 1, sizeof (char));
	if (from == NULL)
	  CHECK_ERROR (smtp, ENOMEM);
	address_get_email (smtp->mail_from, 1, from, len + 1, NULL);
	status = smtp_writeline (smtp, "MAIL FROM: %s\r\n", from);
	free (from);
	address_destroy (&smtp->mail_from);
	CHECK_ERROR (smtp, status);
	MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
	smtp->state = SMTP_MAIL_FROM;
      }

    case SMTP_MAIL_FROM:
      status = smtp_write (smtp);
      CHECK_EAGAIN (smtp, status);
      smtp->state = SMTP_MAIL_FROM_ACK;

    case SMTP_MAIL_FROM_ACK:
      status = smtp_read_ack (smtp);
      CHECK_EAGAIN (smtp, status);
      MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
      if (smtp->buffer[0] != '2')
	{
	  stream_close (mailer->stream);
	  CLEAR_STATE (smtp);
	  return EACCES;
	}

      /* We use a goto, since we may have multiple recipients,
	 we come back here and doit all over again ... Not pretty.  */
    case SMTP_ENV_RCPT:
    RCPT_TO:
      {
	size_t i = 0;
	smtp->rcpt_index++;
	address_get_count (smtp->rcpt_to, &i);
	if (smtp->rcpt_index <= i)
	  {
	    size_t len = 0;
	    char *to;
	    address_get_email (smtp->rcpt_to, smtp->rcpt_index, NULL, 0, &len);
	    if (len == 0)
	      CHECK_ERROR (smtp, EINVAL);
	    to = calloc (len + 1, sizeof (char));
	    if (to == NULL)
	      CHECK_ERROR (smtp, ENOMEM);
	    address_get_email (smtp->rcpt_to, smtp->rcpt_index, to, len + 1, NULL);
	    status = smtp_writeline (smtp, "RCPT TO: %s\r\n", to);
	    free (to);
	    CHECK_ERROR (smtp, status);
	    MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
	    smtp->state = SMTP_RCPT_TO;
	  }
	else
	  {
	    address_destroy (&(smtp->rcpt_to));
	    smtp->rcpt_index = 0;
	    smtp->state = SMTP_DATA;
	  }
      }

    case SMTP_RCPT_TO:
      if (smtp->rcpt_to)
	{
	  status = smtp_write (smtp);
	  CHECK_EAGAIN (smtp, status);
	  smtp->state = SMTP_RCPT_TO_ACK;
	}

    case SMTP_RCPT_TO_ACK:
      if (smtp->rcpt_to)
	{
	  status = smtp_read_ack (smtp);
	  CHECK_EAGAIN (smtp, status);
	  MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
	  if (smtp->buffer[0] != '2')
	    {
	      stream_close (mailer->stream);
	      CLEAR_STATE (smtp);
	      return EACCES;
	    }
	  goto RCPT_TO;
	}
      /* We are done with the rcpt.  */
      status = smtp_writeline (smtp, "DATA\r\n");
      CHECK_ERROR (smtp, status);
      MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
      smtp->state = SMTP_DATA;

    case SMTP_DATA:
      status = smtp_write (smtp);
      CHECK_EAGAIN (smtp, status);
      smtp->state = SMTP_DATA_ACK;

    case SMTP_DATA_ACK:
      status = smtp_read_ack (smtp);
      CHECK_EAGAIN (smtp, status);
      MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
      if (smtp->buffer[0] != '3')
	{
	  stream_close (mailer->stream);
	  CLEAR_STATE (smtp);
	  return EACCES;
	}
      smtp->offset = 0;
      smtp->state = SMTP_SEND;

    case SMTP_SEND:
      {
	stream_t stream;
	size_t n = 0;
	char data[256] = "";
	/* We may be here after an EAGAIN so check if we have something
	   in the buffer and flush it.  */
	status = smtp_write (smtp);
	CHECK_EAGAIN (smtp, status);
	message_get_stream (msg, &stream);
	while ((status = stream_readline (stream, data, sizeof (data) - 1,
					  smtp->offset, &n)) == 0 && n > 0)
	  {
	    if (data [n - 1] == '\n')
	      data [n -1] = '\0';
	    if (data[0] == '.')
	      {
		status = smtp_writeline (smtp, ".%s\r\n", data);
		CHECK_ERROR (smtp, status);
	      }
	    else
	      {
		status = smtp_writeline (smtp, "%s\r\n", data);
		CHECK_ERROR (smtp, status);
	      }
	    smtp->offset += n;
	    MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
		status = smtp_write (smtp);
	    CHECK_EAGAIN (smtp, status);
	  }
	smtp->offset = 0;
	status = smtp_writeline (smtp, ".\r\n");
	CHECK_ERROR (smtp, status);
	smtp->state = SMTP_SEND_DOT;
      }

    case SMTP_SEND_DOT:
      status = smtp_write (smtp);
      CHECK_EAGAIN (smtp, status);
      smtp->state = SMTP_SEND_ACK;

    case SMTP_SEND_ACK:
      status = smtp_read_ack (smtp);
      CHECK_EAGAIN (smtp, status);
      MAILER_DEBUG0 (mailer, MU_DEBUG_PROT, smtp->buffer);
      observable_notify (mailer->observable, MU_EVT_MAILER_MESSAGE_SENT);
      if (smtp->buffer[0] != '2')
	{
	  stream_close (mailer->stream);
	  CLEAR_STATE (smtp);
	  return EACCES;
	}

    default:
      break;
    }
  CLEAR_STATE (smtp);
  return 0;
}

static int
get_from (message_t msg, char *localhost, address_t *pmail_from)
{
  int status;
  size_t size = 0;
  char *from;
  header_t header = NULL;

  message_get_header (msg, &header);
  status = header_get_value (header, MU_HEADER_FROM, NULL, 0, &size);
  /* If it's not in the header create one form the passwd.  */
  if (status != 0 || size == 0)
    {
      struct passwd *pwd = getpwuid (getuid ());
      /* Not in the passwd ???? We have a problem.  */
      if (pwd == 0 || pwd->pw_name == NULL)
	{
	  size = 10 + strlen (localhost) + 1;
	  from = calloc (size, sizeof (char));
	  if (from == NULL)
	    return ENOMEM;
	  snprintf (from, size, "%d@%s", getuid(), localhost);
	}
      else
	{
	  from  = calloc (strlen (pwd->pw_name) + 1
			  + strlen (localhost) + 1, sizeof (char));
	  if (from == NULL)
	    return ENOMEM;
	  sprintf(from, "%s@%s", pwd->pw_name, localhost);
	}
    }
  else
    {
      from = calloc (size + 1, sizeof (char));
      if (from == NULL)
	return ENOMEM;
      header_get_value (header, MU_HEADER_FROM, from, size + 1, NULL);
    }
  /* Check if a Fully Qualified Name, some smtp servers
     notably sendmail insists on it, for good reasons.  */
  if (strchr (from, '@') == NULL)
    {
      char *tmp;
      tmp = malloc (strlen (from) + 1 +strlen (localhost) + 1);
      if (tmp == NULL)
	{
	  free (from);
	  return ENOMEM;
	}
      sprintf (tmp, "%s@%s", from, localhost);
      free (from);
      from = tmp;
    }
  status = address_create (pmail_from, from);
  free (from);
  return status;
}

static int
get_rcpt (message_t msg, address_t *prcpt_to)
{
  char *rcpt;
  int status;
  size_t size = 0;
  header_t header = NULL;

  message_get_header (msg, &header);
  status = header_get_value (header, MU_HEADER_TO, NULL, 0, &size);
  if (status == 0 && size != 0)
    {
      char *tmp;
      size_t len;
      rcpt = calloc (size + 1, sizeof (char));
      if (rcpt == NULL)
	return ENOMEM;
      header_get_value (header, MU_HEADER_TO, rcpt, size + 1, NULL);

      size = 0;
      status = header_get_value (header, MU_HEADER_CC, NULL, 0, &size);
      if (status == 0 && size != 0)
	{
	  len = strlen (rcpt);
	  tmp = realloc (rcpt, (len + 1 + size + 1) * sizeof (char));
	  if (tmp == NULL)
	    {
	      free (rcpt);
	      return ENOMEM;
	    }
	  else
	    rcpt = tmp;
	  rcpt[len] = ',';
	  header_get_value (header, MU_HEADER_CC, rcpt + len + 1,
			    size + 1, NULL);

	  size = 0;
	  status = header_get_value (header, MU_HEADER_BCC, NULL, 0, &size);
	  if (status == 0 && size != 0)
	    {
	      len = strlen (rcpt);
	      tmp = realloc (rcpt, (len + 1 + size + 1) * sizeof (char));
	      if (tmp == NULL)
		{
		  free (rcpt);
		  return ENOMEM;
		}
	      else
		rcpt = tmp;
	      rcpt[len] = ',';
	      header_get_value (header, MU_HEADER_BCC, rcpt + len + 1,
				size + 1, NULL);
	    }
	}
      status = address_create (prcpt_to, rcpt);
      free (rcpt);
      return status;
    }
  return EINVAL;
}

/* C99 says that a conforming implementations of snprintf ()
   should return the number of char that would have been call
   but many GNU/Linux && BSD implementations return -1 on error.
   Worse QNX/Neutrino actually does not put the terminal
   null char.  So let's try to cope.  */
static int
smtp_writeline (smtp_t smtp, const char *format, ...)
{
  int len;
  va_list ap;
  int done = 1;

  va_start(ap, format);
  do
    {
      len = vsnprintf (smtp->buffer, smtp->buflen - 1, format, ap);
      if (len < 0 || (len >= (int)smtp->buflen)
	  || !memchr (smtp->buffer, '\0', len + 1))
        {
          smtp->buflen *= 2;
          smtp->buffer = realloc (smtp->buffer, smtp->buflen);
          if (smtp->buffer == NULL)
            return ENOMEM;
	  done = 0;
        }
      else
	done = 1;
    }
  while (!done);
  va_end(ap);
  smtp->ptr = smtp->buffer + len;
  return 0;
}

static int
smtp_write (smtp_t smtp)
{
  int status = 0;
  size_t len;
  if (smtp->ptr > smtp->buffer)
    {
      len = smtp->ptr - smtp->buffer;
      status = stream_write (smtp->mailer->stream, smtp->buffer, len,
			     0, &len);
      if (status == 0)
        {
          memmove (smtp->buffer, smtp->buffer + len, len);
          smtp->ptr -= len;
        }
    }
  else
    {
      smtp->ptr = smtp->buffer;
      len = 0;
    }
  return status;
}

static int
smtp_read_ack (smtp_t smtp)
{
  int status;
  int multi;

  do
    {
      multi = 0;
      status = smtp_readline (smtp);
      if ((smtp->ptr - smtp->buffer) > 4
	  && smtp->buffer[3] == '-')
	multi = 1;
      if (status == 0)
	smtp->ptr = smtp->buffer;
    }
  while (multi && status == 0);

  if (status == 0)
    smtp->ptr = smtp->buffer;
  return status;
}

/* Read a complete line form the pop server. Transform CRLF to LF,
   put a null in the buffer when done.  */
static int
smtp_readline (smtp_t smtp)
{
  size_t n = 0;
  size_t total = smtp->ptr - smtp->buffer;
  int status;

  /* Must get a full line before bailing out.  */
  do
    {
      status = stream_readline (smtp->mailer->stream, smtp->buffer + total,
				smtp->buflen - total, 0, &n);
      if (status != 0)
        return status;

      /* Server went away, consider this like an error.  */
      if (n == 0)
	return EIO;

      total += n;
      smtp->nl = memchr (smtp->buffer, '\n', total);
      if (smtp->nl == NULL)  /* Do we have a full line.  */
        {
          /* Allocate a bigger buffer ?  */
          if (total >= smtp->buflen -1)
            {
              smtp->buflen *= 2;
              smtp->buffer = realloc (smtp->buffer, smtp->buflen + 1);
              if (smtp->buffer == NULL)
                return ENOMEM;
            }
        }
      smtp->ptr = smtp->buffer + total;
    }
  while (smtp->nl == NULL);

  /* \r\n --> \n\0  */
  if (smtp->nl > smtp->buffer)
    {
      *(smtp->nl - 1) = '\n';
      *(smtp->nl) = '\0';
      smtp->ptr = smtp->nl;
    }
  return 0;
}