/*
 * Libitree: an interval tree library in C
 *
 * Copyright (C) 2018 Alessandro Vullo
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include "interval_list.h"

#include <stdlib.h>
#include <stdio.h>

#ifndef HEIGHT_LIMIT
#define HEIGHT_LIMIT 64
#endif

/* Note: doesn't own the interval, comes from the tree
   which is responsible for deallocating the interval. */
typedef struct ilistnode
{
  const interval_t *interval;
  struct ilistnode *next;
} ilistnode_t;

struct ilist
{
  ilistnode_t *head, *tail; /* Dummy nodes */
  size_t size;
};

struct ilisttrav
{
  ilist_t *list;   /* Paired list */
  ilistnode_t *it; /* Current node */
};

static ilistnode_t *ilistnode_new(const interval_t *i, ilistnode_t *next)
{
  ilistnode_t *node = (ilistnode_t *)malloc(sizeof *node);
  if (node != NULL)
  {
    node->interval = i; /* NOTE: doesn't own the interval, pointer aliasing */
    node->next = next;
  }

  return node;
}

/*
   Destroy a single node, assuming it's been unlinked.
   Returns the next node specified by the link.
*/
ilistnode_t *ilistnode_delete(ilistnode_t *node)
{
  ilistnode_t *next = NULL;
  if (node != NULL)
  {
    /* Save a reference to the next node
       since we're about to destroy this one */
    next = node->next;
    free(node);
  }

  return next;
}

ilist_t *ilist_new()
{
  ilist_t *list = (ilist_t *)malloc(sizeof *list);
  if (list != NULL)
  {
    ilistnode_t *tail = ilistnode_new(NULL, NULL);
    if (tail == NULL)
    {
      free(list);
      list = NULL;
    }
    else
    {
      list->tail = tail;
      list->head = ilistnode_new(NULL, list->tail);

      if (list->head == NULL)
      {
        free(list);
        list = NULL;
      }
      list->size = 0;
    }
  }

  return list;
}

void ilist_delete(ilist_t *list)
{
  if (list == NULL)
  {
    return;
  }

  ilistnode_t *it = list->head;
  while (it != list->tail)
  {
    it = ilistnode_delete(it);
  }

  ilistnode_delete(it); /* Delete tail */
  free(list);
}

size_t ilist_size(ilist_t *list)
{
  return list->size;
}

static ilistnode_t *insert_before(ilist_t *, ilistnode_t *, interval_t *);
static ilistnode_t *insert_after(ilist_t *list, ilistnode_t *pos, interval_t *i)
{
  ilistnode_t *node = NULL;
  if (list != NULL && pos != NULL)
  {
    if (pos != list->tail)
    {
      node = ilistnode_new(i, pos->next);
      if (node != NULL)
      {
        pos->next = node;
        ++list->size;
      }
    }
    else
    {
      node = insert_before(list, pos, i);
    }
  }

  return node;
}

static ilistnode_t *insert_before(ilist_t *list, ilistnode_t *pos, interval_t *i)
{
  ilistnode_t *node = NULL;
  if (list != NULL && pos != NULL)
  {
    if (pos != list->head)
    {
      /* Find the previous node */
      ilistnode_t *it = list->head;
      while (it->next != pos)
      {
        it = it->next;
      }

      /* Create a new node and set the new link */
      node = ilistnode_new(i, it->next);
      if (node != NULL)
      {
        it->next = node;
        ++list->size;
      }
    }
    else
    {
      node = insert_after(list, pos, i);
    }
  }

  return node;
}

int ilist_append(ilist_t *list, interval_t *i)
{

  ilistnode_t *node = insert_before(list, list->tail, i);
  if (node != NULL)
  {
    return 1;
  }

  return 0;
}

ilisttrav_t *ilisttrav_new(ilist_t *list)
{
  if (list == NULL)
  {
    return NULL;
  }

  ilisttrav_t *trav = (ilisttrav_t *)malloc(sizeof(ilisttrav_t));
  if (trav != NULL)
  {
    trav->list = list;
  }

  return trav;
}

void ilisttrav_delete(ilisttrav_t *trav)
{
  free(trav);
}

const interval_t *ilisttrav_first(ilisttrav_t *trav)
{
  if (trav->list == NULL)
  {
    return NULL;
  }

  trav->it = trav->list->head->next;

  return trav->it == NULL || trav->it == trav->list->tail ? NULL : trav->it->interval;
}

const interval_t *ilisttrav_last(ilisttrav_t *trav)
{
  if (trav->list == NULL)
  {
    return NULL;
  }

  trav->it = trav->list->head;
  while (trav->it->next != trav->list->tail)
  {
    trav->it = trav->it->next;
  }

  return trav->it == trav->list->head || trav->it == NULL ? NULL : trav->it->interval;
}

const interval_t *ilisttrav_next(ilisttrav_t *trav)
{
  if (trav == NULL)
  {
    return NULL;
  }

  trav->it = trav->it->next;
  return trav->it == NULL || trav->it == trav->list->tail ? NULL : trav->it->interval;
}

/* Very inefficient, need a doubly linked list to properly support this */
const interval_t *ilisttrav_prev(ilisttrav_t *trav)
{
  if (trav == NULL)
  {
    return NULL;
  }

  ilistnode_t *it = trav->list->head;
  while (it->next != trav->it)
  {
    it = it->next;
  }

  trav->it = it;
  return trav->it == trav->list->head || trav->it == NULL ? NULL : trav->it->interval;
}