/*
 * Copyright (C) 1996-2002,2010,2013 Michael R. Elkins <me@mutt.org>
 *
 *     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 2 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, write to the Free Software
 *     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

/* This file contains code to parse ``mbox'' and ``mmdf'' style mailboxes */

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include "mutt.h"
#include "mailbox.h"
#include "mx.h"
#include "sort.h"
#include "copy.h"
#include "mutt_curses.h"

#include <sys/stat.h>
#include <dirent.h>
#include <string.h>
#include <utime.h>
#include <sys/file.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>

/* struct used by mutt_sync_mailbox() to store new offsets */
struct m_update_t
{
  short valid;
  LOFF_T hdr;
  LOFF_T body;
  long lines;
  LOFF_T length;
};

/* parameters:
 * ctx - context to lock
 * excl - exclusive lock?
 * retry - should retry if unable to lock?
 */
int mbox_lock_mailbox (CONTEXT *ctx, int excl, int retry)
{
  int r;

  if ((r = mx_lock_file (ctx->path, fileno (ctx->fp), excl, 1, retry)) == 0)
    ctx->locked = 1;
  else if (retry && !excl)
  {
    ctx->readonly = 1;
    return 0;
  }

  return (r);
}

void mbox_unlock_mailbox (CONTEXT *ctx)
{
  if (ctx->locked)
  {
    fflush (ctx->fp);

    mx_unlock_file (ctx->path, fileno (ctx->fp), 1);
    ctx->locked = 0;
  }
}

int mmdf_parse_mailbox (CONTEXT *ctx)
{
  char buf[HUGE_STRING];
  char return_path[LONG_STRING];
  int count = 0, oldmsgcount = ctx->msgcount;
  int lines;
  time_t t;
  LOFF_T loc, tmploc;
  HEADER *hdr;
  struct stat sb;
#ifdef NFS_ATTRIBUTE_HACK
#ifdef HAVE_UTIMENSAT
  struct timespec ts[2];
#endif /* HAVE_UTIMENSAT */
  struct utimbuf newtime;
#endif
  progress_t progress;
  char msgbuf[STRING];

  if (stat (ctx->path, &sb) == -1)
  {
    mutt_perror (ctx->path);
    return (-1);
  }
  mutt_get_stat_timespec (&ctx->atime, &sb, MUTT_STAT_ATIME);
  mutt_get_stat_timespec (&ctx->mtime, &sb, MUTT_STAT_MTIME);
  ctx->size = sb.st_size;

#ifdef NFS_ATTRIBUTE_HACK
  if (sb.st_mtime > sb.st_atime)
  {
#ifdef HAVE_UTIMENSAT
    ts[0].tv_sec = 0;
    ts[0].tv_nsec = UTIME_NOW;
    ts[1].tv_sec = 0;
    ts[1].tv_nsec = UTIME_OMIT;
    utimensat (AT_FDCWD, ctx->path, ts, 0);
#else
    newtime.actime = time (NULL);
    newtime.modtime = sb.st_mtime;
    utime (ctx->path, &newtime);
#endif /* HAVE_UTIMENSAT */
  }
#endif

  buf[sizeof (buf) - 1] = 0;

  if (!ctx->quiet)
  {
    snprintf (msgbuf, sizeof (msgbuf), _("Reading %s..."), ctx->path);
    mutt_progress_init (&progress, msgbuf, MUTT_PROGRESS_MSG, ReadInc, 0);
  }

  FOREVER
  {
    if (fgets (buf, sizeof (buf) - 1, ctx->fp) == NULL)
      break;

    if (mutt_strcmp (buf, MMDF_SEP) == 0)
    {
      loc = ftello (ctx->fp);

      count++;
      if (!ctx->quiet)
	mutt_progress_update (&progress, count,
			      (int) (loc / (ctx->size / 100 + 1)));

      if (ctx->msgcount == ctx->hdrmax)
	mx_alloc_memory (ctx);
      ctx->hdrs[ctx->msgcount] = hdr = mutt_new_header ();
      hdr->offset = loc;
      hdr->index = ctx->msgcount;

      if (fgets (buf, sizeof (buf) - 1, ctx->fp) == NULL)
      {
	/* TODO: memory leak??? */
	dprint (1, (debugfile, "mmdf_parse_mailbox: unexpected EOF\n"));
	break;
      }

      return_path[0] = 0;

      if (!is_from (buf, return_path, sizeof (return_path), &t))
      {
	if (fseeko (ctx->fp, loc, SEEK_SET) != 0)
	{
	  dprint (1, (debugfile, "mmdf_parse_mailbox: fseek() failed\n"));
	  mutt_error _("Mailbox is corrupt!");
	  return (-1);
	}
      }
      else
	hdr->received = t - mutt_local_tz (t);

      hdr->env = mutt_read_rfc822_header (ctx->fp, hdr, 0, 0);

      loc = ftello (ctx->fp);

      if (hdr->content->length > 0 && hdr->lines > 0)
      {
	tmploc = loc + hdr->content->length;

	if (0 < tmploc && tmploc < ctx->size)
	{
	  if (fseeko (ctx->fp, tmploc, SEEK_SET) != 0 ||
	      fgets (buf, sizeof (buf) - 1, ctx->fp) == NULL ||
	      mutt_strcmp (MMDF_SEP, buf) != 0)
	  {
	    if (fseeko (ctx->fp, loc, SEEK_SET) != 0)
	      dprint (1, (debugfile, "mmdf_parse_mailbox: fseek() failed\n"));
	    hdr->content->length = -1;
	  }
	}
	else
	  hdr->content->length = -1;
      }
      else
	hdr->content->length = -1;

      if (hdr->content->length < 0)
      {
	lines = -1;
	do
        {
	  loc = ftello (ctx->fp);
	  if (fgets (buf, sizeof (buf) - 1, ctx->fp) == NULL)
	    break;
	  lines++;
	} while (mutt_strcmp (buf, MMDF_SEP) != 0);

	hdr->lines = lines;
	hdr->content->length = loc - hdr->content->offset;
      }

      if (!hdr->env->return_path && return_path[0])
	hdr->env->return_path = rfc822_parse_adrlist (hdr->env->return_path, return_path);

      if (!hdr->env->from)
	hdr->env->from = rfc822_cpy_adr (hdr->env->return_path, 0);

      ctx->msgcount++;
    }
    else
    {
      dprint (1, (debugfile, "mmdf_parse_mailbox: corrupt mailbox!\n"));
      mutt_error _("Mailbox is corrupt!");
      return (-1);
    }
  }

  if (ctx->msgcount > oldmsgcount)
    mx_update_context (ctx, ctx->msgcount - oldmsgcount);

  return (0);
}

/* Note that this function is also called when new mail is appended to the
 * currently open folder, and NOT just when the mailbox is initially read.
 *
 * NOTE: it is assumed that the mailbox being read has been locked before
 * this routine gets called.  Strange things could happen if it's not!
 */
int mbox_parse_mailbox (CONTEXT *ctx)
{
  struct stat sb;
  char buf[HUGE_STRING], return_path[STRING];
  HEADER *curhdr;
  time_t t;
  int count = 0, lines = 0;
  LOFF_T loc;
#ifdef NFS_ATTRIBUTE_HACK
#ifdef HAVE_UTIMENSAT
  struct timespec ts[2];
#endif /* HAVE_UTIMENSAT */
  struct utimbuf newtime;
#endif
  progress_t progress;
  char msgbuf[STRING];

  /* Save information about the folder at the time we opened it. */
  if (stat (ctx->path, &sb) == -1)
  {
    mutt_perror (ctx->path);
    return (-1);
  }

  ctx->size = sb.st_size;
  mutt_get_stat_timespec (&ctx->mtime, &sb, MUTT_STAT_MTIME);
  mutt_get_stat_timespec (&ctx->atime, &sb, MUTT_STAT_ATIME);

#ifdef NFS_ATTRIBUTE_HACK
  if (sb.st_mtime > sb.st_atime)
  {
#ifdef HAVE_UTIMENSAT
    ts[0].tv_sec = 0;
    ts[0].tv_nsec = UTIME_NOW;
    ts[1].tv_sec = 0;
    ts[1].tv_nsec = UTIME_OMIT;
    utimensat (AT_FDCWD, ctx->path, ts, 0);
#else
    newtime.actime = time (NULL);
    newtime.modtime = sb.st_mtime;
    utime (ctx->path, &newtime);
#endif /* HAVE_UTIMENSAT */
  }
#endif

  if (!ctx->readonly)
    ctx->readonly = access (ctx->path, W_OK) ? 1 : 0;

  if (!ctx->quiet)
  {
    snprintf (msgbuf, sizeof (msgbuf), _("Reading %s..."), ctx->path);
    mutt_progress_init (&progress, msgbuf, MUTT_PROGRESS_MSG, ReadInc, 0);
  }

  loc = ftello (ctx->fp);
  while (fgets (buf, sizeof (buf), ctx->fp) != NULL)
  {
    if (is_from (buf, return_path, sizeof (return_path), &t))
    {
      /* Save the Content-Length of the previous message */
      if (count > 0)
      {
#define PREV ctx->hdrs[ctx->msgcount-1]

	if (PREV->content->length < 0)
	{
	  PREV->content->length = loc - PREV->content->offset - 1;
	  if (PREV->content->length < 0)
	    PREV->content->length = 0;
	}
	if (!PREV->lines)
	  PREV->lines = lines ? lines - 1 : 0;
      }

      count++;

      if (!ctx->quiet)
	mutt_progress_update (&progress, count,
			      (int)(ftello (ctx->fp) / (ctx->size / 100 + 1)));

      if (ctx->msgcount == ctx->hdrmax)
	mx_alloc_memory (ctx);

      curhdr = ctx->hdrs[ctx->msgcount] = mutt_new_header ();
      curhdr->received = t - mutt_local_tz (t);
      curhdr->offset = loc;
      curhdr->index = ctx->msgcount;

      curhdr->env = mutt_read_rfc822_header (ctx->fp, curhdr, 0, 0);

      /* if we know how long this message is, either just skip over the body,
       * or if we don't know how many lines there are, count them now (this will
       * save time by not having to search for the next message marker).
       */
      if (curhdr->content->length > 0)
      {
	LOFF_T tmploc;

	loc = ftello (ctx->fp);

	/* The test below avoids a potential integer overflow if the
	 * content-length is huge (thus necessarily invalid).
	 */
	tmploc = curhdr->content->length < ctx->size ? loc + curhdr->content->length + 1 : -1;

	if (0 < tmploc && tmploc < ctx->size)
	{
	  /*
	   * check to see if the content-length looks valid.  we expect to
	   * to see a valid message separator at this point in the stream
	   */
	  if (fseeko (ctx->fp, tmploc, SEEK_SET) != 0 ||
	      fgets (buf, sizeof (buf), ctx->fp) == NULL ||
	      mutt_strncmp ("From ", buf, 5) != 0)
	  {
	    dprint (1, (debugfile, "mbox_parse_mailbox: bad content-length in message %d (cl=" OFF_T_FMT ")\n", curhdr->index, curhdr->content->length));
	    dprint (1, (debugfile, "\tLINE: %s", buf));
	    if (fseeko (ctx->fp, loc, SEEK_SET) != 0) /* nope, return the previous position */
	    {
	      dprint (1, (debugfile, "mbox_parse_mailbox: fseek() failed\n"));
	    }
	    curhdr->content->length = -1;
	  }
	}
	else if (tmploc != ctx->size)
	{
	  /* content-length would put us past the end of the file, so it
	   * must be wrong
	   */
	  curhdr->content->length = -1;
	}

	if (curhdr->content->length != -1)
	{
	  /* good content-length.  check to see if we know how many lines
	   * are in this message.
	   */
	  if (curhdr->lines == 0)
	  {
	    int cl = curhdr->content->length;

	    /* count the number of lines in this message */
	    if (fseeko (ctx->fp, loc, SEEK_SET) != 0)
	      dprint (1, (debugfile, "mbox_parse_mailbox: fseek() failed\n"));
	    while (cl-- > 0)
	    {
	      if (fgetc (ctx->fp) == '\n')
		curhdr->lines++;
	    }
	  }

	  /* return to the offset of the next message separator */
	  if (fseeko (ctx->fp, tmploc, SEEK_SET) != 0)
	    dprint (1, (debugfile, "mbox_parse_mailbox: fseek() failed\n"));
	}
      }

      ctx->msgcount++;

      if (!curhdr->env->return_path && return_path[0])
	curhdr->env->return_path = rfc822_parse_adrlist (curhdr->env->return_path, return_path);

      if (!curhdr->env->from)
	curhdr->env->from = rfc822_cpy_adr (curhdr->env->return_path, 0);

      lines = 0;
    }
    else
      lines++;

    loc = ftello (ctx->fp);
  }

  /*
   * Only set the content-length of the previous message if we have read more
   * than one message during _this_ invocation.  If this routine is called
   * when new mail is received, we need to make sure not to clobber what
   * previously was the last message since the headers may be sorted.
   */
  if (count > 0)
  {
    if (PREV->content->length < 0)
    {
      PREV->content->length = ftello (ctx->fp) - PREV->content->offset - 1;
      if (PREV->content->length < 0)
	PREV->content->length = 0;
    }

    if (!PREV->lines)
      PREV->lines = lines ? lines - 1 : 0;

    mx_update_context (ctx, count);
  }

  return (0);
}

#undef PREV

/* open a mbox or mmdf style mailbox */
static int mbox_open_mailbox (CONTEXT *ctx)
{
  int rc;

  if ((ctx->fp = fopen (ctx->path, "r")) == NULL)
  {
    mutt_perror (ctx->path);
    return (-1);
  }
  mutt_block_signals ();
  if (mbox_lock_mailbox (ctx, 0, 1) == -1)
  {
    mutt_unblock_signals ();
    return (-1);
  }

  if (ctx->magic == MUTT_MBOX)
    rc = mbox_parse_mailbox (ctx);
  else if (ctx->magic == MUTT_MMDF)
    rc = mmdf_parse_mailbox (ctx);
  else
    rc = -1;
  mutt_touch_atime (fileno (ctx->fp));

  mbox_unlock_mailbox (ctx);
  mutt_unblock_signals ();
  return (rc);
}

static int mbox_open_mailbox_append (CONTEXT *ctx, int flags)
{
  ctx->fp = safe_fopen (ctx->path, flags & MUTT_NEWFOLDER ? "w" : "a");
  if (!ctx->fp)
  {
    mutt_perror (ctx->path);
    return -1;
  }

  mutt_block_signals ();
  if (mbox_lock_mailbox (ctx, 1, 1) != 0)
  {
    mutt_error (_("Couldn't lock %s\n"), ctx->path);
    mutt_unblock_signals ();
    safe_fclose (&ctx->fp);
    return -1;
  }

  fseek (ctx->fp, 0, 2);

  return 0;
}

static int mbox_close_mailbox (CONTEXT *ctx)
{
  if (ctx->append && ctx->fp)
  {
    mx_unlock_file (ctx->path, fileno (ctx->fp), 1);
    mutt_unblock_signals ();
  }

  safe_fclose (&ctx->fp);

  return 0;
}

static int mbox_open_message (CONTEXT *ctx,  MESSAGE *msg, int msgno)
{
  msg->fp = ctx->fp;

  return 0;
}

static int mbox_close_message (CONTEXT *ctx, MESSAGE *msg)
{
  msg->fp = NULL;

  return 0;
}

static int mbox_commit_message (CONTEXT *ctx, MESSAGE *msg)
{
  if (fputc ('\n', msg->fp) == EOF)
    return -1;

  if ((fflush (msg->fp) == EOF) ||
      (fsync (fileno (msg->fp)) == -1))
  {
    mutt_perror _("Can't write message");
    return -1;
  }

  return 0;
}

static int mmdf_commit_message (CONTEXT *ctx, MESSAGE *msg)
{
  if (fputs (MMDF_SEP, msg->fp) == EOF)
    return -1;

  if ((fflush (msg->fp) == EOF) ||
      (fsync (fileno (msg->fp)) == -1))
  {
    mutt_perror _("Can't write message");
    return -1;
  }

  return 0;
}

static int mbox_open_new_message (MESSAGE *msg, CONTEXT *dest, HEADER *hdr)
{
  msg->fp = dest->fp;
  return 0;
}

/* return 1 if address lists are strictly identical */
static int strict_addrcmp (const ADDRESS *a, const ADDRESS *b)
{
  while (a && b)
  {
    if (mutt_strcmp (a->mailbox, b->mailbox) ||
	mutt_strcmp (a->personal, b->personal))
      return (0);

    a = a->next;
    b = b->next;
  }
  if (a || b)
    return (0);

  return (1);
}

static int strict_cmp_lists (const LIST *a, const LIST *b)
{
  while (a && b)
  {
    if (mutt_strcmp (a->data, b->data))
      return (0);

    a = a->next;
    b = b->next;
  }
  if (a || b)
    return (0);

  return (1);
}

static int strict_cmp_envelopes (const ENVELOPE *e1, const ENVELOPE *e2)
{
  if (e1 && e2)
  {
    if (mutt_strcmp (e1->message_id, e2->message_id) ||
	mutt_strcmp (e1->subject, e2->subject) ||
	!strict_cmp_lists (e1->references, e2->references) ||
	!strict_addrcmp (e1->from, e2->from) ||
	!strict_addrcmp (e1->sender, e2->sender) ||
	!strict_addrcmp (e1->reply_to, e2->reply_to) ||
	!strict_addrcmp (e1->to, e2->to) ||
	!strict_addrcmp (e1->cc, e2->cc) ||
	!strict_addrcmp (e1->return_path, e2->return_path))
      return (0);
    else
      return (1);
  }
  else
  {
    if (e1 == NULL && e2 == NULL)
      return (1);
    else
      return (0);
  }
}

static int strict_cmp_parameters (const PARAMETER *p1, const PARAMETER *p2)
{
  while (p1 && p2)
  {
    if (mutt_strcmp (p1->attribute, p2->attribute) ||
	mutt_strcmp (p1->value, p2->value))
      return (0);

    p1 = p1->next;
    p2 = p2->next;
  }
  if (p1 || p2)
    return (0);

  return (1);
}

static int strict_cmp_bodies (const BODY *b1, const BODY *b2)
{
  if (b1->type != b2->type ||
      b1->encoding != b2->encoding ||
      mutt_strcmp (b1->subtype, b2->subtype) ||
      mutt_strcmp (b1->description, b2->description) ||
      !strict_cmp_parameters (b1->parameter, b2->parameter) ||
      b1->length != b2->length)
    return (0);
  return (1);
}

/* return 1 if headers are strictly identical */
int mbox_strict_cmp_headers (const HEADER *h1, const HEADER *h2)
{
  if (h1 && h2)
  {
    if (h1->received != h2->received ||
	h1->date_sent != h2->date_sent ||
	h1->content->length != h2->content->length ||
	h1->lines != h2->lines ||
	h1->zhours != h2->zhours ||
	h1->zminutes != h2->zminutes ||
	h1->zoccident != h2->zoccident ||
	h1->mime != h2->mime ||
	!strict_cmp_envelopes (h1->env, h2->env) ||
	!strict_cmp_bodies (h1->content, h2->content))
      return (0);
    else
      return (1);
  }
  else
  {
    if (h1 == NULL && h2 == NULL)
      return (1);
    else
      return (0);
  }
}

/* check to see if the mailbox has changed on disk.
 *
 * return values:
 *	MUTT_REOPENED	mailbox has been reopened
 *	MUTT_NEW_MAIL	new mail has arrived!
 *	MUTT_LOCKED	couldn't lock the file
 *	0		no change
 *	-1		error
 */
static int mbox_check_mailbox (CONTEXT *ctx, int *index_hint)
{
  struct stat st;
  char buffer[LONG_STRING];
  int unlock = 0;
  int modified = 0;

  if (stat (ctx->path, &st) == 0)
  {
    if ((mutt_stat_timespec_compare (&st, MUTT_STAT_MTIME, &ctx->mtime) == 0) &&
        st.st_size == ctx->size)
      return (0);

    if (st.st_size == ctx->size)
    {
      /* the file was touched, but it is still the same length, so just exit */
      mutt_get_stat_timespec (&ctx->mtime, &st, MUTT_STAT_MTIME);
      return (0);
    }

    if (st.st_size > ctx->size)
    {
      /* lock the file if it isn't already */
      if (!ctx->locked)
      {
	mutt_block_signals ();
	if (mbox_lock_mailbox (ctx, 0, 0) == -1)
	{
	  mutt_unblock_signals ();
	  /* we couldn't lock the mailbox, but nothing serious happened:
	   * probably the new mail arrived: no reason to wait till we can
	   * parse it: we'll get it on the next pass
	   */
	  return (MUTT_LOCKED);
	}
	unlock = 1;
      }

      /*
       * Check to make sure that the only change to the mailbox is that
       * message(s) were appended to this file.  My heuristic is that we should
       * see the message separator at *exactly* what used to be the end of the
       * folder.
       */
      if (fseeko (ctx->fp, ctx->size, SEEK_SET) != 0)
	dprint (1, (debugfile, "mbox_check_mailbox: fseek() failed\n"));
      if (fgets (buffer, sizeof (buffer), ctx->fp) != NULL)
      {
	if ((ctx->magic == MUTT_MBOX && mutt_strncmp ("From ", buffer, 5) == 0) ||
	    (ctx->magic == MUTT_MMDF && mutt_strcmp (MMDF_SEP, buffer) == 0))
	{
	  if (fseeko (ctx->fp, ctx->size, SEEK_SET) != 0)
	    dprint (1, (debugfile, "mbox_check_mailbox: fseek() failed\n"));
	  if (ctx->magic == MUTT_MBOX)
	    mbox_parse_mailbox (ctx);
	  else
	    mmdf_parse_mailbox (ctx);

	  /* Only unlock the folder if it was locked inside of this routine.
	   * It may have been locked elsewhere, like in
	   * mutt_checkpoint_mailbox().
	   */

	  if (unlock)
	  {
	    mbox_unlock_mailbox (ctx);
	    mutt_unblock_signals ();
	  }

	  return (MUTT_NEW_MAIL); /* signal that new mail arrived */
	}
	else
	  modified = 1;
      }
      else
      {
	dprint (1, (debugfile, "mbox_check_mailbox: fgets returned NULL.\n"));
	modified = 1;
      }
    }
    else
      modified = 1;
  }

  if (modified)
  {
    if (mutt_reopen_mailbox (ctx, index_hint) != -1)
    {
      if (unlock)
      {
	mbox_unlock_mailbox (ctx);
	mutt_unblock_signals ();
      }
      return (MUTT_REOPENED);
    }
  }

  /* fatal error */

  mbox_unlock_mailbox (ctx);
  mx_fastclose_mailbox (ctx);
  mutt_unblock_signals ();
  mutt_error _("Mailbox was corrupted!");
  return (-1);
}

/*
 * Returns 1 if the mailbox has at least 1 new messages (not old)
 * otherwise returns 0.
 */
static int mbox_has_new(CONTEXT *ctx)
{
  int i;

  for (i = 0; i < ctx->msgcount; i++)
    if (!ctx->hdrs[i]->deleted && !ctx->hdrs[i]->read && !ctx->hdrs[i]->old)
      return 1;
  return 0;
}

/* if mailbox has at least 1 new message, sets mtime > atime of mailbox
 * so buffy check reports new mail */
void mbox_reset_atime (CONTEXT *ctx, struct stat *st)
{
  struct utimbuf utimebuf;
  struct stat _st;

  if (!st)
  {
    if (stat (ctx->path, &_st) < 0)
      return;
    st = &_st;
  }

  utimebuf.actime = st->st_atime;
  utimebuf.modtime = st->st_mtime;

  /*
   * When $mbox_check_recent is set, existing new mail is ignored, so do not
   * reset the atime to mtime-1 to signal new mail.
   */
  if (!option(OPTMAILCHECKRECENT) && utimebuf.actime >= utimebuf.modtime && mbox_has_new(ctx))
    utimebuf.actime = utimebuf.modtime - 1;

  utime (ctx->path, &utimebuf);
}

/* return values:
 *	0	success
 *	-1	failure
 */
static int mbox_sync_mailbox (CONTEXT *ctx, int *index_hint)
{
  BUFFER *tempfile = NULL;
  char buf[32];
  int i, j, save_sort = SORT_ORDER;
  int unlink_tempfile = 0;
  int rc = -1;
  int need_sort = 0; /* flag to resort mailbox if new mail arrives */
  int first = -1;	/* first message to be written */
  LOFF_T offset;	/* location in mailbox to write changed messages */
  struct stat statbuf;
  struct m_update_t *newOffset = NULL;
  struct m_update_t *oldOffset = NULL;
  FILE *fp = NULL;
  progress_t progress;
  char msgbuf[STRING];
  BUFFY *tmp = NULL;

  /* sort message by their position in the mailbox on disk */
  if (Sort != SORT_ORDER)
  {
    save_sort = Sort;
    Sort = SORT_ORDER;
    mutt_sort_headers (ctx, 0);
    Sort = save_sort;
    need_sort = 1;
  }

  /* need to open the file for writing in such a way that it does not truncate
   * the file, so use read-write mode.
   */
  if ((ctx->fp = freopen (ctx->path, "r+", ctx->fp)) == NULL)
  {
    mx_fastclose_mailbox (ctx);
    mutt_error _("Fatal error!  Could not reopen mailbox!");
    goto fatal;
  }

  mutt_block_signals ();

  if (mbox_lock_mailbox (ctx, 1, 1) == -1)
  {
    mutt_unblock_signals ();
    mutt_error _("Unable to lock mailbox!");
    goto bail;
  }

  /* Check to make sure that the file hasn't changed on disk */
  if ((i = mbox_check_mailbox (ctx, index_hint)) == MUTT_NEW_MAIL ||  i == MUTT_REOPENED)
  {
    /* new mail arrived, or mailbox reopened */
    rc = i;
    goto bail;
  }
  else if (i < 0)
    goto fatal;

  /* Create a temporary file to write the new version of the mailbox in. */
  tempfile = mutt_buffer_pool_get ();
  mutt_buffer_mktemp (tempfile);
  if ((i = open (mutt_b2s (tempfile), O_WRONLY | O_EXCL | O_CREAT, 0600)) == -1 ||
      (fp = fdopen (i, "w")) == NULL)
  {
    if (-1 != i)
    {
      close (i);
      unlink_tempfile = 1;
    }
    mutt_error _("Could not create temporary file!");
    mutt_sleep (5);
    goto bail;
  }
  unlink_tempfile = 1;

  /* find the first deleted/changed message.  we save a lot of time by only
   * rewriting the mailbox from the point where it has actually changed.
   */
  for (i = 0 ; i < ctx->msgcount && !ctx->hdrs[i]->deleted &&
               !ctx->hdrs[i]->changed && !ctx->hdrs[i]->attach_del; i++)
    ;
  if (i == ctx->msgcount)
  {
    /* this means ctx->changed or ctx->deleted was set, but no
     * messages were found to be changed or deleted.  This should
     * never happen, is we presume it is a bug in mutt.
     */
    mutt_error _("sync: mbox modified, but no modified messages! (report this bug)");
    mutt_sleep(5); /* the mutt_error /will/ get cleared! */
    dprint(1, (debugfile, "mbox_sync_mailbox(): no modified messages.\n"));
    goto bail;
  }

  /* save the index of the first changed/deleted message */
  first = i;
  /* where to start overwriting */
  offset = ctx->hdrs[i]->offset;

  /* the offset stored in the header does not include the MMDF_SEP, so make
   * sure we seek to the correct location
   */
  if (ctx->magic == MUTT_MMDF)
    offset -= (sizeof MMDF_SEP - 1);

  /* allocate space for the new offsets */
  newOffset = safe_calloc (ctx->msgcount - first, sizeof (struct m_update_t));
  oldOffset = safe_calloc (ctx->msgcount - first, sizeof (struct m_update_t));

  if (!ctx->quiet)
  {
    snprintf (msgbuf, sizeof (msgbuf), _("Writing %s..."), ctx->path);
    mutt_progress_init (&progress, msgbuf, MUTT_PROGRESS_MSG, WriteInc, ctx->msgcount);
  }

  for (i = first, j = 0; i < ctx->msgcount; i++)
  {
    if (!ctx->quiet)
      mutt_progress_update (&progress, i, (int)(ftello (ctx->fp) / (ctx->size / 100 + 1)));
    /*
     * back up some information which is needed to restore offsets when
     * something fails.
     */

    oldOffset[i-first].valid  = 1;
    oldOffset[i-first].hdr    = ctx->hdrs[i]->offset;
    oldOffset[i-first].body   = ctx->hdrs[i]->content->offset;
    oldOffset[i-first].lines  = ctx->hdrs[i]->lines;
    oldOffset[i-first].length = ctx->hdrs[i]->content->length;

    if (! ctx->hdrs[i]->deleted)
    {
      j++;

      if (ctx->magic == MUTT_MMDF)
      {
	if (fputs (MMDF_SEP, fp) == EOF)
	{
	  mutt_perror (mutt_b2s (tempfile));
	  mutt_sleep (5);
	  goto bail;
	}

      }

      /* save the new offset for this message.  we add `offset' because the
       * temporary file only contains saved message which are located after
       * `offset' in the real mailbox
       */
      newOffset[i - first].hdr = ftello (fp) + offset;

      if (mutt_copy_message (fp, ctx, ctx->hdrs[i], MUTT_CM_UPDATE,
                             CH_FROM | CH_UPDATE | CH_UPDATE_LEN) != 0)
      {
	mutt_perror (mutt_b2s (tempfile));
	mutt_sleep (5);
	goto bail;
      }

      /* Since messages could have been deleted, the offsets stored in memory
       * will be wrong, so update what we can, which is the offset of this
       * message, and the offset of the body.  If this is a multipart message,
       * we just flush the in memory cache so that the message will be reparsed
       * if the user accesses it later.
       */
      newOffset[i - first].body = ftello (fp) - ctx->hdrs[i]->content->length + offset;
      mutt_free_body (&ctx->hdrs[i]->content->parts);

      switch (ctx->magic)
      {
	case MUTT_MMDF:
	  if (fputs(MMDF_SEP, fp) == EOF)
	  {
	    mutt_perror (mutt_b2s (tempfile));
	    mutt_sleep (5);
	    goto bail;
	  }
	  break;
	default:
	  if (fputs("\n", fp) == EOF)
	  {
	    mutt_perror (mutt_b2s (tempfile));
	    mutt_sleep (5);
	    goto bail;
	  }
      }
    }
  }

  if (fclose (fp) != 0)
  {
    fp = NULL;
    dprint(1, (debugfile, "mbox_sync_mailbox: safe_fclose (&) returned non-zero.\n"));
    mutt_perror (mutt_b2s (tempfile));
    mutt_sleep (5);
    goto bail;
  }
  fp = NULL;

  /* Save the state of this folder. */
  if (stat (ctx->path, &statbuf) == -1)
  {
    mutt_perror (ctx->path);
    mutt_sleep (5);
    goto bail;
  }

  unlink_tempfile = 0;

  if ((fp = fopen (mutt_b2s (tempfile), "r")) == NULL)
  {
    mutt_unblock_signals ();
    mx_fastclose_mailbox (ctx);
    dprint (1, (debugfile, "mbox_sync_mailbox: unable to reopen temp copy of mailbox!\n"));
    mutt_perror (mutt_b2s (tempfile));
    mutt_sleep (5);
    goto fatal;
  }

  if (fseeko (ctx->fp, offset, SEEK_SET) != 0 ||  /* seek the append location */
      /* do a sanity check to make sure the mailbox looks ok */
      fgets (buf, sizeof (buf), ctx->fp) == NULL ||
      (ctx->magic == MUTT_MBOX && mutt_strncmp ("From ", buf, 5) != 0) ||
      (ctx->magic == MUTT_MMDF && mutt_strcmp (MMDF_SEP, buf) != 0))
  {
    dprint (1, (debugfile, "mbox_sync_mailbox: message not in expected position."));
    dprint (1, (debugfile, "\tLINE: %s\n", buf));
    i = -1;
  }
  else
  {
    if (fseeko (ctx->fp, offset, SEEK_SET) != 0) /* return to proper offset */
    {
      i = -1;
      dprint (1, (debugfile, "mbox_sync_mailbox: fseek() failed\n"));
    }
    else
    {
      /* copy the temp mailbox back into place starting at the first
       * change/deleted message
       */
      if (!ctx->quiet)
	mutt_message _("Committing changes...");
      i = mutt_copy_stream (fp, ctx->fp);

      if (ferror (ctx->fp))
        i = -1;
    }
    if (i == 0)
    {
      ctx->size = ftello (ctx->fp); /* update the size of the mailbox */
      if (ftruncate (fileno (ctx->fp), ctx->size) != 0)
      {
        i = -1;
        dprint (1, (debugfile, "mbox_sync_mailbox: ftruncate() failed\n"));
      }
    }
  }

  safe_fclose (&fp);
  fp = NULL;
  mbox_unlock_mailbox (ctx);

  if (safe_fclose (&ctx->fp) != 0 || i == -1)
  {
    BUFFER *savefile;
    /* error occurred while writing the mailbox back, so keep the temp copy
     * around
     */
    savefile = mutt_buffer_pool_get ();
    mutt_buffer_printf (savefile, "%s/mutt.%s-%s-%u",
	      NONULL (Tempdir), NONULL(Username), NONULL(Hostname), (unsigned int)getpid ());
    rename (mutt_b2s (tempfile), mutt_b2s (savefile));
    mutt_unblock_signals ();
    mx_fastclose_mailbox (ctx);
    mutt_buffer_pretty_mailbox (savefile);
    mutt_error (_("Write failed!  Saved partial mailbox to %s"), mutt_b2s (savefile));
    mutt_buffer_pool_release (&savefile);

    mutt_sleep (5);
    goto fatal;
  }

  /* Restore the previous access/modification times */
  mbox_reset_atime (ctx, &statbuf);

  /* reopen the mailbox in read-only mode */
  if ((ctx->fp = fopen (ctx->path, "r")) == NULL)
  {
    unlink (mutt_b2s (tempfile));
    mutt_unblock_signals ();
    mx_fastclose_mailbox (ctx);
    mutt_error _("Fatal error!  Could not reopen mailbox!");
    goto fatal;
  }

  /* update the offsets of the rewritten messages */
  for (i = first, j = first; i < ctx->msgcount; i++)
  {
    if (!ctx->hdrs[i]->deleted)
    {
      ctx->hdrs[i]->offset = newOffset[i - first].hdr;
      ctx->hdrs[i]->content->hdr_offset = newOffset[i - first].hdr;
      ctx->hdrs[i]->content->offset = newOffset[i - first].body;
      ctx->hdrs[i]->index = j++;
    }
  }
  FREE (&newOffset);
  FREE (&oldOffset);
  unlink (mutt_b2s (tempfile)); /* remove partial copy of the mailbox */
  mutt_buffer_pool_release (&tempfile);
  mutt_unblock_signals ();

  if (option(OPTCHECKMBOXSIZE))
  {
    tmp = mutt_find_mailbox (ctx->path);
    if (tmp && tmp->new == 0)
      mutt_update_mailbox (tmp);
  }

  return (0); /* signal success */

bail:  /* Come here in case of disaster */

  safe_fclose (&fp);

  if (tempfile && unlink_tempfile)
    unlink (mutt_b2s (tempfile));

  /* restore offsets, as far as they are valid */
  if (first >= 0 && oldOffset)
  {
    for (i = first; i < ctx->msgcount && oldOffset[i-first].valid; i++)
    {
      ctx->hdrs[i]->offset = oldOffset[i-first].hdr;
      ctx->hdrs[i]->content->hdr_offset = oldOffset[i-first].hdr;
      ctx->hdrs[i]->content->offset = oldOffset[i-first].body;
      ctx->hdrs[i]->lines = oldOffset[i-first].lines;
      ctx->hdrs[i]->content->length = oldOffset[i-first].length;
    }
  }

  /* this is ok to call even if we haven't locked anything */
  mbox_unlock_mailbox (ctx);

  mutt_unblock_signals ();
  FREE (&newOffset);
  FREE (&oldOffset);

  if ((ctx->fp = freopen (ctx->path, "r", ctx->fp)) == NULL)
  {
    mutt_error _("Could not reopen mailbox!");
    mx_fastclose_mailbox (ctx);
    goto fatal;
  }

  if (need_sort)
    /* if the mailbox was reopened, the thread tree will be invalid so make
     * sure to start threading from scratch.  */
    mutt_sort_headers (ctx, (need_sort == MUTT_REOPENED));

fatal:
  mutt_buffer_pool_release (&tempfile);
  return rc;
}

int mutt_reopen_mailbox (CONTEXT *ctx, int *index_hint)
{
  int (*cmp_headers) (const HEADER *, const HEADER *) = NULL;
  HEADER **old_hdrs;
  int old_msgcount;
  int msg_mod = 0;
  int index_hint_set;
  int i, j;
  int rc = -1;

  /* silent operations */
  ctx->quiet = 1;

  if (!ctx->quiet)
    mutt_message _("Reopening mailbox...");

  /* our heuristics require the old mailbox to be unsorted */
  if (Sort != SORT_ORDER)
  {
    short old_sort;

    old_sort = Sort;
    Sort = SORT_ORDER;
    mutt_sort_headers (ctx, 1);
    Sort = old_sort;
  }

  old_hdrs = NULL;
  old_msgcount = 0;

  /* simulate a close */
  if (ctx->id_hash)
    hash_destroy (&ctx->id_hash, NULL);
  if (ctx->subj_hash)
    hash_destroy (&ctx->subj_hash, NULL);
  hash_destroy (&ctx->label_hash, NULL);
  mutt_clear_threads (ctx);
  FREE (&ctx->v2r);
  if (ctx->readonly)
  {
    for (i = 0; i < ctx->msgcount; i++)
      mutt_free_header (&(ctx->hdrs[i])); /* nothing to do! */
    FREE (&ctx->hdrs);
  }
  else
  {
    /* save the old headers */
    old_msgcount = ctx->msgcount;
    old_hdrs = ctx->hdrs;
    ctx->hdrs = NULL;
  }

  ctx->hdrmax = 0;	/* force allocation of new headers */
  ctx->msgcount = 0;
  ctx->vcount = 0;
  ctx->vsize = 0;
  ctx->tagged = 0;
  ctx->deleted = 0;
  ctx->new = 0;
  ctx->unread = 0;
  ctx->flagged = 0;
  ctx->changed = 0;
  ctx->id_hash = NULL;
  ctx->subj_hash = NULL;
  mutt_make_label_hash (ctx);

  switch (ctx->magic)
  {
    case MUTT_MBOX:
    case MUTT_MMDF:
      cmp_headers = mbox_strict_cmp_headers;
      safe_fclose (&ctx->fp);
      if (!(ctx->fp = safe_fopen (ctx->path, "r")))
	rc = -1;
      else
	rc = (ctx->magic == MUTT_MBOX) ? mbox_parse_mailbox (ctx) :
          mmdf_parse_mailbox (ctx);
      break;

    default:
      rc = -1;
      break;
  }

  if (rc == -1)
  {
    /* free the old headers */
    for (j = 0; j < old_msgcount; j++)
      mutt_free_header (&(old_hdrs[j]));
    FREE (&old_hdrs);

    ctx->quiet = 0;
    return (-1);
  }

  mutt_touch_atime (fileno (ctx->fp));

  /* now try to recover the old flags */

  index_hint_set = (index_hint == NULL);

  if (!ctx->readonly)
  {
    for (i = 0; i < ctx->msgcount; i++)
    {
      int found = 0;

      /* some messages have been deleted, and new  messages have been
       * appended at the end; the heuristic is that old messages have then
       * "advanced" towards the beginning of the folder, so we begin the
       * search at index "i"
       */
      for (j = i; j < old_msgcount; j++)
      {
	if (old_hdrs[j] == NULL)
	  continue;
	if (cmp_headers (ctx->hdrs[i], old_hdrs[j]))
	{
	  found = 1;
	  break;
	}
      }
      if (!found)
      {
	for (j = 0; j < i && j < old_msgcount; j++)
	{
	  if (old_hdrs[j] == NULL)
	    continue;
	  if (cmp_headers (ctx->hdrs[i], old_hdrs[j]))
	  {
	    found = 1;
	    break;
	  }
	}
      }

      if (found)
      {
	/* this is best done here */
	if (!index_hint_set && *index_hint == j)
	  *index_hint = i;

	if (old_hdrs[j]->changed)
	{
	  /* Only update the flags if the old header was changed;
	   * otherwise, the header may have been modified externally,
	   * and we don't want to lose _those_ changes
	   */
	  mutt_set_flag (ctx, ctx->hdrs[i], MUTT_FLAG, old_hdrs[j]->flagged);
	  mutt_set_flag (ctx, ctx->hdrs[i], MUTT_REPLIED, old_hdrs[j]->replied);
	  mutt_set_flag (ctx, ctx->hdrs[i], MUTT_OLD, old_hdrs[j]->old);
	  mutt_set_flag (ctx, ctx->hdrs[i], MUTT_READ, old_hdrs[j]->read);
	}
	mutt_set_flag (ctx, ctx->hdrs[i], MUTT_DELETE, old_hdrs[j]->deleted);
	mutt_set_flag (ctx, ctx->hdrs[i], MUTT_PURGE, old_hdrs[j]->purge);
	mutt_set_flag (ctx, ctx->hdrs[i], MUTT_TAG, old_hdrs[j]->tagged);

	/* we don't need this header any more */
	mutt_free_header (&(old_hdrs[j]));
      }
    }

    /* free the remaining old headers */
    for (j = 0; j < old_msgcount; j++)
    {
      if (old_hdrs[j])
      {
	mutt_free_header (&(old_hdrs[j]));
	msg_mod = 1;
      }
    }
    FREE (&old_hdrs);
  }

  ctx->quiet = 0;

  return ((ctx->changed || msg_mod) ? MUTT_REOPENED : MUTT_NEW_MAIL);
}

/*
 * Returns:
 * 1 if the mailbox is not empty
 * 0 if the mailbox is empty
 * -1 on error
 */
int mbox_check_empty (const char *path)
{
  struct stat st;

  if (stat (path, &st) == -1)
    return -1;

  return ((st.st_size == 0));
}

static int mbox_msg_padding_size (CONTEXT *ctx)
{
  return 1;
}

static int mmdf_msg_padding_size (CONTEXT *ctx)
{
  return 10;
}

struct mx_ops mx_mbox_ops = {
  .open = mbox_open_mailbox,
  .open_append = mbox_open_mailbox_append,
  .close = mbox_close_mailbox,
  .open_msg = mbox_open_message,
  .close_msg = mbox_close_message,
  .commit_msg = mbox_commit_message,
  .open_new_msg = mbox_open_new_message,
  .check = mbox_check_mailbox,
  .sync = mbox_sync_mailbox,
  .msg_padding_size = mbox_msg_padding_size,
  .save_to_header_cache = NULL,
};

struct mx_ops mx_mmdf_ops = {
  .open = mbox_open_mailbox,
  .open_append = mbox_open_mailbox_append,
  .close = mbox_close_mailbox,
  .open_msg = mbox_open_message,
  .close_msg = mbox_close_message,
  .commit_msg = mmdf_commit_message,
  .open_new_msg = mbox_open_new_message,
  .check = mbox_check_mailbox,
  .sync = mbox_sync_mailbox,
  .msg_padding_size = mmdf_msg_padding_size,
  .save_to_header_cache = NULL,
};