/* Copyright (c) 2008, 2009
 *      Juergen Weigert (jnweiger@immd4.informatik.uni-erlangen.de)
 *      Michael Schroeder (mlschroe@immd4.informatik.uni-erlangen.de)
 *      Micah Cowan (micah@cowan.name)
 *      Sadrul Habib Chowdhury (sadrul@users.sourceforge.net)
 * Copyright (c) 1993-2002, 2003, 2005, 2006, 2007
 *      Juergen Weigert (jnweiger@immd4.informatik.uni-erlangen.de)
 *      Michael Schroeder (mlschroe@immd4.informatik.uni-erlangen.de)
 * Copyright (c) 1987 Oliver Laumann
 *
 * 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, 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 (see the file COPYING); if not, see
 * http://www.gnu.org/licenses/, or contact Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA  02111-1301  USA
 *
 ****************************************************************
 */

#include <sys/types.h>		/* dev_t, ino_t, off_t, ... */
#include <sys/stat.h>		/* struct stat */
#include <fcntl.h>		/* O_WRONLY for logfile_reopen */


#include "config.h"
#include "screen.h"
#include "extern.h"
#include "logfile.h"

static void changed_logfile __P((struct logfile *));
static struct logfile *lookup_logfile __P((char *));
static int stolen_logfile __P((struct logfile *));

static struct logfile *logroot = NULL;

static void
changed_logfile(l)
struct logfile *l;
{
  struct stat o, *s = l->st;

  if (fstat(fileno(l->fp), &o) < 0)		/* get trouble later */
    return;
  if (o.st_size > s->st_size)		/* aha, appended text */
    {
      s->st_size = o.st_size;		/* this should have changed */
      s->st_mtime = o.st_mtime;		/* only size and mtime */
    }
}

/*
 * Requires fd to be open and need_fd to be closed.
 * If possible, need_fd will be open afterwards and refer to 
 * the object originally reffered by fd. fd will be closed then.
 * Works just like ``fcntl(fd, DUPFD, need_fd); close(fd);''
 * 
 * need_fd is returned on success, else -1 is returned.
 */
int
lf_move_fd(fd, need_fd)
int need_fd, fd;
{
  int r = -1;
  
  if (fd == need_fd)
    return fd;
  if (fd >=0 && fd < need_fd)
    r = lf_move_fd(dup(fd), need_fd);
  close(fd);
  return r;
}

static int
logfile_reopen(name, wantfd, l)
char *name;
int wantfd;
struct logfile *l;
{
  int got_fd;

  close(wantfd);
  if (((got_fd = open(name, O_WRONLY | O_CREAT | O_APPEND, 0666)) < 0) ||
      lf_move_fd(got_fd, wantfd) < 0)
    {
      logfclose(l);
      debug1("logfile_reopen: failed for %s\n", name);
      return -1;
    }
  changed_logfile(l);
  debug2("logfile_reopen: %d = %s\n", wantfd, name);
  return 0;
}

static int (* lf_reopen_fn)() = logfile_reopen;

/* 
 * Whenever logfwrite discoveres that it is required to close and
 * reopen the logfile, the function registered here is called.
 * If you do not register anything here, the above logfile_reopen()
 * will be used instead.
 * Your function should perform the same steps as logfile_reopen():
 * a) close the original filedescriptor without flushing any output
 * b) open a new logfile for future output on the same filedescriptor number.
 * c) zero out st_dev, st_ino to tell the stolen_logfile() indcator to 
 *    reinitialise itself.
 * d) return 0 on success.
 */
void
logreopen_register(fn)
int (*fn) __P((char *, int, struct logfile *));
{
  lf_reopen_fn = fn ? fn : logfile_reopen;
}

/*
 * If the logfile has been removed, truncated, unlinked or the like,
 * return nonzero.
 * The l->st structure initialised by logfopen is updated
 * on every call.
 */
static int
stolen_logfile(l)
struct logfile *l;
{
  struct stat o, *s = l->st;

  o = *s;
  if (fstat(fileno(l->fp), s) < 0)		/* remember that stat failed */
    s->st_ino = s->st_dev = 0;
  ASSERT(s == l->st);
  if (!o.st_dev && !o.st_ino)			/* nothing to compare with */
    return 0;

  if ((!s->st_dev && !s->st_ino) ||	/* stat failed, that's new! */
      !s->st_nlink ||			/* red alert: file unlinked */
      (s->st_size < o.st_size) ||		/*           file truncated */
      (s->st_mtime != o.st_mtime) ||		/*            file modified */
      ((s->st_ctime != o.st_ctime) &&   	/*     file changed (moved) */
       !(s->st_mtime == s->st_ctime && 		/*  and it was not a change */
         o.st_ctime < s->st_ctime)))		/* due to delayed nfs write */
    {
      debug1("stolen_logfile: %s stolen!\n", l->name);
      debug3("st_dev %d, st_ino %d, st_nlink %d\n", 
             (int)s->st_dev, (int)s->st_ino, (int)s->st_nlink);
      debug2("s->st_size %d, o.st_size %d\n", (int)s->st_size, (int)o.st_size);
      debug2("s->st_mtime %d, o.st_mtime %d\n", 
             (int)s->st_mtime, (int)o.st_mtime);
      debug2("s->st_ctime %d, o.st_ctime %d\n", 
             (int)s->st_ctime, (int)o.st_ctime);
      return -1;
    }

  debug1("stolen_logfile: %s o.k.\n", l->name);
  return 0;
}

static struct logfile *
lookup_logfile(name)
char *name;
{
  struct logfile *l;

  for (l = logroot; l; l = l->next)
    if (!strcmp(name, l->name))
      return l;
  return NULL;
}

struct logfile *
logfopen(name, fp)
char *name;
FILE *fp;
{
  struct logfile *l;

  if (!fp)
    {
      if (!(l = lookup_logfile(name)))
        return NULL;
      l->opencount++;
      return l;
    }

  if (!(l = (struct logfile *)malloc(sizeof(struct logfile))))
    return NULL;
  if (!(l->st = (struct stat *)malloc(sizeof(struct stat))))
    {
      free((char *)l);
      return NULL;
    }

  if (!(l->name = SaveStr(name)))
    {
      free((char *)l->st);
      free((char *)l);
      return NULL;
    }
  l->fp = fp;
  l->opencount = 1;
  l->writecount = 0;
  l->flushcount = 0;
  changed_logfile(l);

  l->next = logroot;
  logroot = l;
  return l;
}

int
islogfile(name)
char *name;
{
  if (!name)
    return logroot ? 1 : 0;
  return lookup_logfile(name) ? 1 : 0;
}

int
logfclose(l)
struct logfile *l;
{
  struct logfile **lp;

  for (lp = &logroot; *lp; lp = &(*lp)->next)
    if (*lp == l)
      break;

  if (!*lp)
    return -1;

  if ((--l->opencount) > 0)
    return 0;
  if (l->opencount < 0)
    abort();

  *lp = l->next;
  fclose(l->fp);
  free(l->name);
  free((char *)l);
  return 0;
}

/* 
 * XXX
 * write and flush both *should* check the file's stat, if it disappeared
 * or changed, re-open it.
 */
int
logfwrite(l, buf, n)
struct logfile *l;
char *buf;
int n;
{
  int r;

  if (stolen_logfile(l) && lf_reopen_fn(l->name, fileno(l->fp), l))
    return -1;
  r = fwrite(buf, n, 1, l->fp);
  l->writecount += l->flushcount + 1;
  l->flushcount = 0;
  changed_logfile(l); 
  return r;
}

int
logfflush(l)
struct logfile *l;
{
  int r = 0;

  if (!l)
    for (l = logroot; l; l = l->next)
      {
	if (stolen_logfile(l) && lf_reopen_fn(l->name, fileno(l->fp), l))
	  return -1;
	r |= fflush(l->fp);
	l->flushcount++;
	changed_logfile(l); 
      }
  else
    {
      if (stolen_logfile(l) && lf_reopen_fn(l->name, fileno(l->fp), l))
	return -1;
      r = fflush(l->fp);
      l->flushcount++;
      changed_logfile(l); 
    }
  return r;
}