/* Sequential list data type implemented by a hash table with a binary tree.
   Copyright (C) 2006-2007, 2009-2020 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2006.

   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 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, see <https://www.gnu.org/licenses/>.  */

/* Common code of gl_avltreehash_list.c and gl_rbtreehash_list.c.  */

/* Hash table entry representing the same value at more than one position.  */
struct gl_multiple_nodes
{
  struct gl_hash_entry h;           /* hash table entry fields; must be first */
  void *magic;                      /* used to distinguish from single node */
  gl_oset_t nodes;                  /* set of nodes, sorted by position */
};
/* A value that cannot occur at the corresponding field (->left) in
   gl_list_node_impl.  */
#define MULTIPLE_NODES_MAGIC  (void *) -1

/* Returns the position of the given node in the tree.  */
static size_t
node_position (gl_list_node_t node)
{
  size_t position = 0;

  if (node->left != NULL)
    position += node->left->branch_size;
  for (;;)
    {
      gl_list_node_t parent = node->parent;

      if (parent == NULL)
        return position;
      /* position is now relative to the subtree of node.  */
      if (parent->right == node)
        {
          position += 1;
          if (parent->left != NULL)
            position += parent->left->branch_size;
        }
      /* position is now relative to the subtree of parent.  */
      node = parent;
    }
}

/* Compares two nodes by their position in the tree.  */
static int
compare_by_position (const void *x1, const void *x2)
{
  gl_list_node_t node1 = (gl_list_node_t) x1;
  gl_list_node_t node2 = (gl_list_node_t) x2;
  size_t position1 = node_position (node1);
  size_t position2 = node_position (node2);

  return (position1 > position2 ? 1 :
          position1 < position2 ? -1 : 0);
}

/* Compares a node's position in the tree with a given threshold.  */
static bool
compare_position_threshold (const void *x, const void *threshold)
{
  gl_list_node_t node = (gl_list_node_t) x;
  size_t position = node_position (node);
  return (position >= (uintptr_t)threshold);
}

/* Returns the first element of a non-empty ordered set of nodes.  */
static gl_list_node_t
gl_oset_first (gl_oset_t set)
{
  gl_oset_iterator_t iter = gl_oset_iterator (set);
  const void *first;

  if (!gl_oset_iterator_next (&iter, &first))
    abort ();
  gl_oset_iterator_free (&iter);
  return (gl_list_node_t) first;
}

/* Adds a node to the hash table structure.
   If duplicates are allowed, this function performs in average time
   O((log n)^2): gl_oset_nx_add may need to add an element to an ordered set
   of size O(n), needing O(log n) comparison function calls.  The comparison
   function is compare_by_position, which is O(log n) worst-case.
   If duplicates are forbidden, this function is O(1).
   Return 0 upon success, -1 upon out-of-memory.  */
static int
add_to_bucket (gl_list_t list, gl_list_node_t new_node)
{
  size_t bucket = new_node->h.hashcode % list->table_size;

  /* If no duplicates are allowed, multiple nodes are not needed.  */
  if (list->base.allow_duplicates)
    {
      size_t hashcode = new_node->h.hashcode;
      const void *value = new_node->value;
      gl_listelement_equals_fn equals = list->base.equals_fn;
      gl_hash_entry_t *entryp;

      for (entryp = &list->table[bucket]; *entryp != NULL; entryp = &(*entryp)->hash_next)
        {
          gl_hash_entry_t entry = *entryp;

          if (entry->hashcode == hashcode)
            {
              if (((struct gl_multiple_nodes *) entry)->magic == MULTIPLE_NODES_MAGIC)
                {
                  /* An entry representing multiple nodes.  */
                  gl_oset_t nodes = ((struct gl_multiple_nodes *) entry)->nodes;
                  /* Only the first node is interesting.  */
                  gl_list_node_t node = gl_oset_first (nodes);
                  if (equals != NULL ? equals (value, node->value) : value == node->value)
                    {
                      /* Found already multiple nodes with the same value.
                         Add the new_node to it.  */
                      return gl_oset_nx_add (nodes, new_node);
                    }
                }
              else
                {
                  /* An entry representing a single node.  */
                  gl_list_node_t node = (struct gl_list_node_impl *) entry;
                  if (equals != NULL ? equals (value, node->value) : value == node->value)
                    {
                      /* Found already a node with the same value.  Turn it
                         into an ordered set, and add new_node to it.  */
                      gl_oset_t nodes;
                      struct gl_multiple_nodes *multi_entry;

                      nodes =
                        gl_oset_nx_create_empty (OSET_TREE_FLAVOR,
                                                 compare_by_position, NULL);
                      if (nodes == NULL)
                        return -1;

                      if (gl_oset_nx_add (nodes, node) < 0)
                        goto fail;
                      if (gl_oset_nx_add (nodes, new_node) < 0)
                        goto fail;

                      multi_entry =
                       (struct gl_multiple_nodes *) malloc (sizeof (struct gl_multiple_nodes));
                      if (multi_entry == NULL)
                        goto fail;
                      multi_entry->h.hash_next = entry->hash_next;
                      multi_entry->h.hashcode = entry->hashcode;
                      multi_entry->magic = MULTIPLE_NODES_MAGIC;
                      multi_entry->nodes = nodes;
                      *entryp = &multi_entry->h;
                      return 0;

                    fail:
                      gl_oset_free (nodes);
                      return -1;
                    }
                }
            }
        }
    }
  /* If no duplicates are allowed, multiple nodes are not needed.  */
  new_node->h.hash_next = list->table[bucket];
  list->table[bucket] = &new_node->h;
  return 0;
}
/* Tell GCC that the likely return value is 0.  */
#define add_to_bucket(list,node) \
    __builtin_expect ((add_to_bucket) (list, node), 0)

/* Removes a node from the hash table structure.
   If duplicates are allowed, this function performs in average time
   O((log n)^2): gl_oset_remove may need to remove an element from an ordered
   set of size O(n), needing O(log n) comparison function calls.  The
   comparison function is compare_by_position, which is O(log n) worst-case.
   If duplicates are forbidden, this function is O(1) on average.  */
static void
remove_from_bucket (gl_list_t list, gl_list_node_t old_node)
{
  size_t bucket = old_node->h.hashcode % list->table_size;

  if (list->base.allow_duplicates)
    {
      size_t hashcode = old_node->h.hashcode;
      const void *value = old_node->value;
      gl_listelement_equals_fn equals = list->base.equals_fn;
      gl_hash_entry_t *entryp;

      for (entryp = &list->table[bucket]; ; entryp = &(*entryp)->hash_next)
        {
          gl_hash_entry_t entry = *entryp;

          if (entry == &old_node->h)
            {
              /* Found old_node as a single node in the bucket.  Remove it.  */
              *entryp = old_node->h.hash_next;
              break;
            }
          if (entry == NULL)
            /* node is not in the right bucket.  Did the hash codes
               change inadvertently?  */
            abort ();
          if (((struct gl_multiple_nodes *) entry)->magic == MULTIPLE_NODES_MAGIC
              && entry->hashcode == hashcode)
            {
              /* An entry representing multiple nodes.  */
              gl_oset_t nodes = ((struct gl_multiple_nodes *) entry)->nodes;
              /* Only the first node is interesting.  */
              gl_list_node_t node = gl_oset_first (nodes);
              if (equals != NULL ? equals (value, node->value) : value == node->value)
                {
                  /* Found multiple nodes with the same value.
                     old_node must be one of them.  Remove it.  */
                  if (!gl_oset_remove (nodes, old_node))
                    abort ();
                  if (gl_oset_size (nodes) == 1)
                    {
                      /* Replace a one-element set with a single node.  */
                      node = gl_oset_first (nodes);
                      node->h.hash_next = entry->hash_next;
                      *entryp = &node->h;
                      gl_oset_free (nodes);
                      free (entry);
                    }
                  break;
                }
            }
        }
    }
  else
    {
      /* If no duplicates are allowed, multiple nodes are not needed.  */
      gl_hash_entry_t *entryp;

      for (entryp = &list->table[bucket]; ; entryp = &(*entryp)->hash_next)
        {
          if (*entryp == &old_node->h)
            {
              *entryp = old_node->h.hash_next;
              break;
            }
          if (*entryp == NULL)
            /* node is not in the right bucket.  Did the hash codes
               change inadvertently?  */
            abort ();
        }
    }
}

/* Builds up the hash table during initialization: Stores all the nodes of
   list->root in the hash table.
   Returns 0 upon success, -1 upon out-of-memory.  */
static int
add_nodes_to_buckets (gl_list_t list)
{
  /* Iterate across all nodes.  */
  gl_list_node_t node = list->root;
  iterstack_t stack;
  iterstack_item_t *stack_ptr = &stack[0];

  for (;;)
    {
      /* Descend on left branch.  */
      for (;;)
        {
          if (node == NULL)
            break;
          stack_ptr->node = node;
          stack_ptr->rightp = false;
          node = node->left;
          stack_ptr++;
        }
      /* Climb up again.  */
      for (;;)
        {
          if (stack_ptr == &stack[0])
            goto done;
          stack_ptr--;
          if (!stack_ptr->rightp)
            break;
        }
      node = stack_ptr->node;
      /* Add the current node to the hash table.  */
      node->h.hashcode =
        (list->base.hashcode_fn != NULL
         ? list->base.hashcode_fn (node->value)
         : (size_t)(uintptr_t) node->value);
      if (add_to_bucket (list, node) < 0)
        goto fail;
      /* Descend on right branch.  */
      stack_ptr->rightp = true;
      node = node->right;
      stack_ptr++;
    }
 done:
  return 0;

 fail:
  /* Undo everything.  */
  for (;;)
    {
      /* Descend on left branch.  */
      stack_ptr->rightp = false;
      node = node->left;
      stack_ptr++;
      /* Descend on right branch.  */
      for (;;)
        {
          if (node == NULL)
            break;
          stack_ptr->node = node;
          stack_ptr->rightp = true;
          node = node->right;
          stack_ptr++;
        }
      /* Climb up again.  */
      for (;;)
        {
          if (stack_ptr == &stack[0])
            goto fail_done;
          stack_ptr--;
          if (stack_ptr->rightp)
            break;
        }
      node = stack_ptr->node;
      /* Remove the current node from the hash table.  */
      remove_from_bucket (list, node);
    }
 fail_done:
  return -1;
}
/* Tell GCC that the likely return value is 0.  */
#if __GNUC__ >= 3
# define add_nodes_to_buckets(list) \
    __builtin_expect ((add_nodes_to_buckets) (list), 0)
#endif