/*
  filedescriptor.c  -  file handling

  Copyright (C)         Lumiera.org
    2008,               Christian Thaeter <ct@pipapo.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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "lib/mutex.h"
#include "lib/safeclib.h"
#include "lib/cuckoo.h"

#include "backend/filedescriptor.h"

#include <sys/types.h>
#include <fcntl.h>
#include <limits.h>
#include <unistd.h>


NOBUG_DEFINE_FLAG (filedescriptor);

static Cuckoo registry = NULL;
static lumiera_mutex registry_mutex = {PTHREAD_MUTEX_INITIALIZER};


static size_t
h1 (const void* item, const uint32_t r)
{
  const LumieraFiledescriptor i = (const LumieraFiledescriptor) item;
  return i->stat.st_dev^i->stat.st_ino^i->flags^((i->stat.st_dev^i->stat.st_ino^i->flags)>>7)^r;
}

static size_t
h2 (const void* item, const uint32_t r)
{
  const LumieraFiledescriptor i = (const LumieraFiledescriptor) item;
  return i->stat.st_dev^i->stat.st_ino^i->flags^((i->stat.st_dev^i->stat.st_ino^i->flags)>>5)^r;
}

static size_t
h3 (const void* item, const uint32_t r)
{
  const LumieraFiledescriptor i = (const LumieraFiledescriptor) item;
  return i->stat.st_dev^i->stat.st_ino^i->flags^((i->stat.st_dev^i->stat.st_ino^i->flags)>>3)^r;
}


static int
cmp (const void* keya, const void* keyb)
{
  const LumieraFiledescriptor a = (const LumieraFiledescriptor) keya;
  const LumieraFiledescriptor b = (const LumieraFiledescriptor) keyb;
  return a->stat.st_dev == b->stat.st_dev && a->stat.st_ino == b->stat.st_ino && a->flags == b->flags;
}


static Cuckoo
lumiera_filedescriptor_registry_new (void)
{
  NOBUG_INIT_FLAG (filedescriptor);

  Cuckoo registry = cuckoo_new (h1, h2, h3, cmp,
                                sizeof (struct lumiera_reference_struct),
                                3);
  if (!registry)
    LUMIERA_DIE (NO_MEMORY);

  return registry;
}

/**
 * Find existing filedescriptor or create one
 * @param descriptor strong reference to be initialized with the filedescriptor,
 *        a filedescriptor will be deleted when its last string reference gets deleted.
 * @param name name of the file
 * @param flags opening flags for the filedescriptor
 * @return descriptor on success or NULL on error
 */
LumieraReference
lumiera_filedescriptor_acquire (LumieraReference descriptor, const char* name, int flags)
{
  UNCHECKED;
  lumiera_mutexacquirer registry_lock;
  lumiera_mutexacquirer_init_mutex (&registry_lock, &registry_mutex, LUMIERA_LOCKED);

  if (!registry)
    registry = lumiera_filedescriptor_registry_new ();

  struct lumiera_filedescriptor_struct findme;
  findme.flags = flags;

  for (int retry = 0; !retry; ++retry)
    {
      if (stat (name, &findme.stat) == 0)
        break;
      else
        {
          if (errno == ENOENT && flags&O_CREAT)
            {
              TRACE (filedescriptor, "try creating file: %s", name);
              char* slash = lumiera_tmpbuf_strndup (name, PATH_MAX);

              while ((slash = strchr (slash+1, '/')))
                {
                  *slash = '\0';
                  if (mkdir (name, 0777) == -1)
                    {
                      LUMIERA_ERROR_SET (filedescriptor, ERRNO);
                      goto efile;
                    }
                  *slash = '/';
                }

              int fd;
              fd = creat (name, 0777);
              if (fd == -1)
                {
                  LUMIERA_ERROR_SET (filedescriptor, ERRNO);
                  goto efile;
                }
              close (fd);
              /* will now retry the fstat once */
            }
          else
            {
              LUMIERA_ERROR_SET (filedescriptor, ERRNO);
              goto efile;
            }
        }
    }

  /* lookup/create descriptor */
  LumieraReference elem = cuckoo_find (registry, &findme);

  if (!elem)
    {
      TRACE (filedescriptor, "Descriptor not found");

      lumiera_reference_strong_init_once (descriptor,
                                          lumiera_filedescriptor_new (&findme),
                                          (void(*)(void*))lumiera_filedescriptor_delete);

      if (!lumiera_reference_get (descriptor))
        goto ecreate;

      lumiera_reference weak_descriptor;
      lumiera_reference_weak_init (&weak_descriptor, descriptor);
      cuckoo_insert (registry, &weak_descriptor);
    }
  else
    {
      lumiera_reference_strong_init (descriptor, elem);
    }
  lumiera_mutexacquirer_unlock (&registry_lock);

  return descriptor;

 efile:
 ecreate:
  lumiera_mutexacquirer_unlock (&registry_lock);
  return NULL;
}


/**
 * Allocate a new filedescriptor cloned from a template
 * @param template the source filedescriptor
 * @return the constrccted filedescriptor
 */
LumieraFiledescriptor
lumiera_filedescriptor_new (LumieraFiledescriptor template)
{
  UNIMPLEMENTED("");
  return NULL;
}

/**
 * delete a filedescriptor and free its resources
 * @param descriptor filedescriptor to be freed
 */
void
lumiera_filedescriptor_delete (LumieraFiledescriptor descriptor)
{
  UNIMPLEMENTED("");
}