/****************************************************************************
 * fs/inode/fs_inodereserve.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <assert.h>
#include <errno.h>

#include <nuttx/kmalloc.h>
#include <nuttx/fs/fs.h>

#include "inode/inode.h"

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: inode_namelen
 ****************************************************************************/

static int inode_namelen(FAR const char *name)
{
  const char *tmp = name;
  while (*tmp && *tmp != '/')
    {
      tmp++;
    }

  return tmp - name;
}

/****************************************************************************
 * Name: inode_namecpy
 ****************************************************************************/

static void inode_namecpy(char *dest, const char *src)
{
  while (*src && *src != '/')
    {
      *dest++ = *src++;
    }

  *dest = '\0';
}

/****************************************************************************
 * Name: inode_alloc
 ****************************************************************************/

static FAR struct inode *inode_alloc(FAR const char *name)
{
  FAR struct inode *node;
  int namelen;

  namelen = inode_namelen(name);
  node    = (FAR struct inode *)kmm_zalloc(FSNODE_SIZE(namelen));
  if (node)
    {
      inode_namecpy(node->i_name, name);
    }

  return node;
}

/****************************************************************************
 * Name: inode_insert
 ****************************************************************************/

static void inode_insert(FAR struct inode *node,
                         FAR struct inode *peer,
                         FAR struct inode *parent)
{
  /* If peer is non-null, then new node simply goes to the right
   * of that peer node.
   */

  if (peer)
    {
      node->i_peer   = peer->i_peer;
      node->i_parent = parent;
      peer->i_peer   = node;
    }

  /* Then it must go at the head of parent's list of children. */

  else
    {
      DEBUGASSERT(parent != NULL);
      node->i_peer    = parent->i_child;
      node->i_parent  = parent;
      parent->i_child = node;
    }
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: inode_root_reserve
 *
 * Description:
 *   Reserve the root inode for the pseudo file system.
 *
 ****************************************************************************/

void inode_root_reserve(void)
{
  g_root_inode = inode_alloc("");
}

/****************************************************************************
 * Name: inode_reserve
 *
 * Description:
 *   Reserve an (initialized) inode the pseudo file system.  The initial
 *   reference count on the new inode is zero.
 *
 * Input Parameters:
 *   path - The path to the inode to create
 *   inode - The location to return the inode pointer
 *
 * Returned Value:
 *   Zero on success (with the inode point in 'inode'); A negated errno
 *   value is returned on failure:
 *
 *   EINVAL - 'path' is invalid for this operation
 *   EEXIST - An inode already exists at 'path'
 *   ENOMEM - Failed to allocate in-memory resources for the operation
 *
 * Assumptions:
 *   Caller must hold the inode semaphore
 *
 ****************************************************************************/

int inode_reserve(FAR const char *path, FAR struct inode **inode)
{
  struct inode_search_s desc;
  FAR struct inode *left;
  FAR struct inode *parent;
  FAR const char *name;
  int ret;

  /* Assume failure */

  DEBUGASSERT(path != NULL && inode != NULL);
  *inode = NULL;

  if (path[0] == '\0')
    {
      return -EINVAL;
    }

  /* Find the location to insert the new subtree */

  SETUP_SEARCH(&desc, path, false);

  ret = inode_search(&desc);
  if (ret >= 0)
    {
      /* It is an error if the node already exists in the tree (or if it
       * lies within a mountpoint, we don't distinguish here).
       */

      ret = -EEXIST;
      goto errout_with_search;
    }

  /* Now we now where to insert the subtree */

  name   = desc.path;
  left   = desc.peer;
  parent = desc.parent;

  for (; ; )
    {
      FAR struct inode *node;

      /* Create a new node -- we need to know if this is the
       * the leaf node or some intermediary.  We can find this
       * by looking at the next name.
       */

      FAR const char *nextname = inode_nextname(name);
      if (*nextname != '\0')
        {
          /* Insert an operationless node */

          node = inode_alloc(name);
          if (node != NULL)
            {
              inode_insert(node, left, parent);

              /* Set up for the next time through the loop */

              name   = nextname;
              left   = NULL;
              parent = node;
              continue;
            }
        }
      else
        {
          node = inode_alloc(name);
          if (node != NULL)
            {
              inode_insert(node, left, parent);
              *inode = node;
              ret = OK;
              break;
            }
        }

      /* We get here on failures to allocate node memory */

      ret = -ENOMEM;
      break;
    }

errout_with_search:
  RELEASE_SEARCH(&desc);
  return ret;
}