/*
 * Copyright (c) 2010, Andrea Mazzoleni. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "tommytrieinp.h"

#include <assert.h> /* for assert */

/******************************************************************************/
/* trie_inplace */

/**
 * Mask for the inner branches.
 */
#define TOMMY_TRIE_INPLACE_TREE_MASK (TOMMY_TRIE_INPLACE_TREE_MAX - 1)

/**
 * Shift for the first level of branches.
 */
#define TOMMY_TRIE_INPLACE_BUCKET_SHIFT (TOMMY_KEY_BIT - TOMMY_TRIE_INPLACE_BUCKET_BIT)

/**
 * Create a new list with a single element.
 */
tommy_inline tommy_trie_inplace_node* tommy_trie_inplace_list_insert_first(tommy_trie_inplace_node* node)
{
	/* one element "circular" prev list */
	node->prev = node;

	/* one element "0 terminated" next list */
	node->next = 0;

	return node;
}

/**
 * Add an element to an existing list.
 * \note The element is inserted at the end of the list.
 */
tommy_inline void tommy_trie_inplace_list_insert_tail_not_empty(tommy_trie_inplace_node* head, tommy_trie_inplace_node* node)
{
	/* insert in the list in the last position */

	/* insert in the "circular" prev list */
	node->prev = head->prev;
	head->prev = node;

	/* insert in the "0 terminated" next list */
	node->next = 0;
	node->prev->next = node;
}

/**
 * Remove an element from the list.
 */
tommy_inline void tommy_trie_inplace_list_remove(tommy_trie_inplace_node** let_ptr, tommy_trie_inplace_node* node)
{
	tommy_trie_inplace_node* head = *let_ptr;

	/* remove from the "circular" prev list */
	if (node->next)
		node->next->prev = node->prev;
	else
		head->prev = node->prev; /* the last */

	/* remove from the "0 terminated" next list */
	if (head == node)
		*let_ptr = node->next; /* the new first */
	else
		node->prev->next = node->next;
}

void tommy_trie_inplace_init(tommy_trie_inplace* trie_inplace)
{
	tommy_uint_t i;

	for (i = 0; i < TOMMY_TRIE_INPLACE_BUCKET_MAX; ++i)
		trie_inplace->bucket[i] = 0;

	trie_inplace->count = 0;
}

static void trie_inplace_bucket_insert(tommy_uint_t shift, tommy_trie_inplace_node** let_ptr, tommy_trie_inplace_node* insert, tommy_key_t key)
{
	tommy_trie_inplace_node* node;

	node = *let_ptr;
	while (node && node->key != key) {
		let_ptr = &node->map[(key >> shift) & TOMMY_TRIE_INPLACE_TREE_MASK];
		node = *let_ptr;
		shift -= TOMMY_TRIE_INPLACE_TREE_BIT;
	}

	/* if null, just insert the node */
	if (!node) {
		/* setup the node as a list */
		*let_ptr = tommy_trie_inplace_list_insert_first(insert);
	} else {
		/* if it's the same key, insert in the list */
		tommy_trie_inplace_list_insert_tail_not_empty(node, insert);
	}
}

void tommy_trie_inplace_insert(tommy_trie_inplace* trie_inplace, tommy_trie_inplace_node* node, void* data, tommy_key_t key)
{
	tommy_trie_inplace_node** let_ptr;
	tommy_uint_t i;

	node->data = data;
	node->key = key;
	/* clear the child pointers */
	for (i = 0; i < TOMMY_TRIE_INPLACE_TREE_MAX; ++i)
		node->map[i] = 0;

	let_ptr = &trie_inplace->bucket[key >> TOMMY_TRIE_INPLACE_BUCKET_SHIFT];

	trie_inplace_bucket_insert(TOMMY_TRIE_INPLACE_BUCKET_SHIFT, let_ptr, node, key);

	++trie_inplace->count;
}

static tommy_trie_inplace_node* trie_inplace_bucket_remove(tommy_uint_t shift, tommy_trie_inplace_node** let_ptr, tommy_trie_inplace_node* remove, tommy_key_t key)
{
	tommy_trie_inplace_node* node;
	int i;
	tommy_trie_inplace_node** leaf_let_ptr;
	tommy_trie_inplace_node* leaf;

	node = *let_ptr;
	while (node && node->key != key) {
		let_ptr = &node->map[(key >> shift) & TOMMY_TRIE_INPLACE_TREE_MASK];
		node = *let_ptr;
		shift -= TOMMY_TRIE_INPLACE_TREE_BIT;
	}

	if (!node)
		return 0;

	/* if the node to remove is not specified */
	if (!remove)
		remove = node; /* remove the first */

	tommy_trie_inplace_list_remove(let_ptr, remove);

	/* if not change in the node, nothing more to do */
	if (*let_ptr == node)
		return remove;

	/* if we have a substitute */
	if (*let_ptr != 0) {
		/* copy the child pointers to the new one */
		node = *let_ptr;
		for (i = 0; i < TOMMY_TRIE_INPLACE_TREE_MAX; ++i)
			node->map[i] = remove->map[i];

		return remove;
	}

	/* find a leaf */
	leaf_let_ptr = 0;
	leaf = remove;

	/* search backward, statistically we have more zeros than ones */
	i = TOMMY_TRIE_INPLACE_TREE_MAX - 1;
	while (i >= 0) {
		if (leaf->map[i]) {
			leaf_let_ptr = &leaf->map[i];
			leaf = *leaf_let_ptr;
			i = TOMMY_TRIE_INPLACE_TREE_MAX - 1;
			continue;
		}
		--i;
	}

	/* if it's itself a leaf */
	if (!leaf_let_ptr)
		return remove;

	/* remove the leaf */
	*leaf_let_ptr = 0;

	/* copy the child pointers */
	for (i = 0; i < TOMMY_TRIE_INPLACE_TREE_MAX; ++i)
		leaf->map[i] = remove->map[i];

	/* put it in place */
	*let_ptr = leaf;

	return remove;
}

void* tommy_trie_inplace_remove(tommy_trie_inplace* trie_inplace, tommy_key_t key)
{
	tommy_trie_inplace_node* ret;
	tommy_trie_inplace_node** let_ptr;

	let_ptr = &trie_inplace->bucket[key >> TOMMY_TRIE_INPLACE_BUCKET_SHIFT];

	ret = trie_inplace_bucket_remove(TOMMY_TRIE_INPLACE_BUCKET_SHIFT, let_ptr, 0, key);

	if (!ret)
		return 0;

	--trie_inplace->count;

	return ret->data;
}

void* tommy_trie_inplace_remove_existing(tommy_trie_inplace* trie_inplace, tommy_trie_inplace_node* node)
{
	tommy_trie_inplace_node* ret;
	tommy_key_t key = node->key;
	tommy_trie_inplace_node** let_ptr;

	let_ptr = &trie_inplace->bucket[key >> TOMMY_TRIE_INPLACE_BUCKET_SHIFT];

	ret = trie_inplace_bucket_remove(TOMMY_TRIE_INPLACE_BUCKET_SHIFT, let_ptr, node, key);

	/* the element removed must match the one passed */
	assert(ret == node);

	--trie_inplace->count;

	return ret->data;
}

tommy_trie_inplace_node* tommy_trie_inplace_bucket(tommy_trie_inplace* trie_inplace, tommy_key_t key)
{
	tommy_trie_inplace_node* node;
	tommy_uint_t shift;

	node = trie_inplace->bucket[key >> TOMMY_TRIE_INPLACE_BUCKET_SHIFT];
	shift = TOMMY_TRIE_INPLACE_BUCKET_SHIFT;

	while (node && node->key != key) {
		node = node->map[(key >> shift) & TOMMY_TRIE_INPLACE_TREE_MASK];
		shift -= TOMMY_TRIE_INPLACE_TREE_BIT;
	}

	return node;
}

tommy_size_t tommy_trie_inplace_memory_usage(tommy_trie_inplace* trie_inplace)
{
	return tommy_trie_inplace_count(trie_inplace) * (tommy_size_t)sizeof(tommy_trie_inplace_node);
}