/* $Id$ */

/*
 * This file is part of OpenTTD.
 * OpenTTD 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, version 2.
 * OpenTTD 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 OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file queue.cpp Implementation of the Queue/Hash. */

#include "../../stdafx.h"
#include "../../core/alloc_func.hpp"
#include "queue.h"


/*
 * Insertion Sorter
 */

static void InsSort_Clear(Queue *q, bool free_values)
{
	InsSortNode *node = q->data.inssort.first;
	InsSortNode *prev;

	while (node != NULL) {
		if (free_values) free(node->item);
		prev = node;
		node = node->next;
		free(prev);
	}
	q->data.inssort.first = NULL;
}

static void InsSort_Free(Queue *q, bool free_values)
{
	q->clear(q, free_values);
}

static bool InsSort_Push(Queue *q, void *item, int priority)
{
	InsSortNode *newnode = MallocT<InsSortNode>(1);

	newnode->item = item;
	newnode->priority = priority;
	if (q->data.inssort.first == NULL ||
			q->data.inssort.first->priority >= priority) {
		newnode->next = q->data.inssort.first;
		q->data.inssort.first = newnode;
	} else {
		InsSortNode *node = q->data.inssort.first;
		while (node != NULL) {
			if (node->next == NULL || node->next->priority >= priority) {
				newnode->next = node->next;
				node->next = newnode;
				break;
			}
			node = node->next;
		}
	}
	return true;
}

static void *InsSort_Pop(Queue *q)
{
	InsSortNode *node = q->data.inssort.first;
	void *result;

	if (node == NULL) return NULL;
	result = node->item;
	q->data.inssort.first = q->data.inssort.first->next;
	assert(q->data.inssort.first == NULL || q->data.inssort.first->priority >= node->priority);
	free(node);
	return result;
}

static bool InsSort_Delete(Queue *q, void *item, int priority)
{
	return false;
}

void init_InsSort(Queue *q)
{
	q->push = InsSort_Push;
	q->pop = InsSort_Pop;
	q->del = InsSort_Delete;
	q->clear = InsSort_Clear;
	q->free = InsSort_Free;
	q->data.inssort.first = NULL;
}


/*
 * Binary Heap
 * For information, see: http://www.policyalmanac.org/games/binaryHeaps.htm
 */

#define BINARY_HEAP_BLOCKSIZE (1 << BINARY_HEAP_BLOCKSIZE_BITS)
#define BINARY_HEAP_BLOCKSIZE_MASK (BINARY_HEAP_BLOCKSIZE - 1)

/* To make our life easy, we make the next define
 *  Because Binary Heaps works with array from 1 to n,
 *  and C with array from 0 to n-1, and we don't like typing
 *  q->data.binaryheap.elements[i - 1] every time, we use this define. */
#define BIN_HEAP_ARR(i) q->data.binaryheap.elements[((i) - 1) >> BINARY_HEAP_BLOCKSIZE_BITS][((i) - 1) & BINARY_HEAP_BLOCKSIZE_MASK]

static void BinaryHeap_Clear(Queue *q, bool free_values)
{
	/* Free all items if needed and free all but the first blocks of memory */
	uint i;
	uint j;

	for (i = 0; i < q->data.binaryheap.blocks; i++) {
		if (q->data.binaryheap.elements[i] == NULL) {
			/* No more allocated blocks */
			break;
		}
		/* For every allocated block */
		if (free_values) {
			for (j = 0; j < (1 << BINARY_HEAP_BLOCKSIZE_BITS); j++) {
				/* For every element in the block */
				if ((q->data.binaryheap.size >> BINARY_HEAP_BLOCKSIZE_BITS) == i &&
						(q->data.binaryheap.size & BINARY_HEAP_BLOCKSIZE_MASK) == j) {
					break; // We're past the last element
				}
				free(q->data.binaryheap.elements[i][j].item);
			}
		}
		if (i != 0) {
			/* Leave the first block of memory alone */
			free(q->data.binaryheap.elements[i]);
			q->data.binaryheap.elements[i] = NULL;
		}
	}
	q->data.binaryheap.size = 0;
	q->data.binaryheap.blocks = 1;
}

static void BinaryHeap_Free(Queue *q, bool free_values)
{
	uint i;

	q->clear(q, free_values);
	for (i = 0; i < q->data.binaryheap.blocks; i++) {
		if (q->data.binaryheap.elements[i] == NULL) break;
		free(q->data.binaryheap.elements[i]);
	}
	free(q->data.binaryheap.elements);
}

static bool BinaryHeap_Push(Queue *q, void *item, int priority)
{
#ifdef QUEUE_DEBUG
	printf("[BinaryHeap] Pushing an element. There are %d elements left\n", q->data.binaryheap.size);
#endif

	if (q->data.binaryheap.size == q->data.binaryheap.max_size) return false;
	assert(q->data.binaryheap.size < q->data.binaryheap.max_size);

	if (q->data.binaryheap.elements[q->data.binaryheap.size >> BINARY_HEAP_BLOCKSIZE_BITS] == NULL) {
		/* The currently allocated blocks are full, allocate a new one */
		assert((q->data.binaryheap.size & BINARY_HEAP_BLOCKSIZE_MASK) == 0);
		q->data.binaryheap.elements[q->data.binaryheap.size >> BINARY_HEAP_BLOCKSIZE_BITS] = MallocT<BinaryHeapNode>(BINARY_HEAP_BLOCKSIZE);
		q->data.binaryheap.blocks++;
#ifdef QUEUE_DEBUG
		printf("[BinaryHeap] Increasing size of elements to %d nodes\n", q->data.binaryheap.blocks *  BINARY_HEAP_BLOCKSIZE);
#endif
	}

	/* Add the item at the end of the array */
	BIN_HEAP_ARR(q->data.binaryheap.size + 1).priority = priority;
	BIN_HEAP_ARR(q->data.binaryheap.size + 1).item = item;
	q->data.binaryheap.size++;

	/* Now we are going to check where it belongs. As long as the parent is
	 * bigger, we switch with the parent */
	{
		BinaryHeapNode temp;
		int i;
		int j;

		i = q->data.binaryheap.size;
		while (i > 1) {
			/* Get the parent of this object (divide by 2) */
			j = i / 2;
			/* Is the parent bigger then the current, switch them */
			if (BIN_HEAP_ARR(i).priority <= BIN_HEAP_ARR(j).priority) {
				temp = BIN_HEAP_ARR(j);
				BIN_HEAP_ARR(j) = BIN_HEAP_ARR(i);
				BIN_HEAP_ARR(i) = temp;
				i = j;
			} else {
				/* It is not, we're done! */
				break;
			}
		}
	}

	return true;
}

static bool BinaryHeap_Delete(Queue *q, void *item, int priority)
{
	uint i = 0;

#ifdef QUEUE_DEBUG
	printf("[BinaryHeap] Deleting an element. There are %d elements left\n", q->data.binaryheap.size);
#endif

	/* First, we try to find the item.. */
	do {
		if (BIN_HEAP_ARR(i + 1).item == item) break;
		i++;
	} while (i < q->data.binaryheap.size);
	/* We did not find the item, so we return false */
	if (i == q->data.binaryheap.size) return false;

	/* Now we put the last item over the current item while decreasing the size of the elements */
	q->data.binaryheap.size--;
	BIN_HEAP_ARR(i + 1) = BIN_HEAP_ARR(q->data.binaryheap.size + 1);

	/* Now the only thing we have to do, is resort it..
	 * On place i there is the item to be sorted.. let's start there */
	{
		uint j;
		BinaryHeapNode temp;
		/* Because of the fact that Binary Heap uses array from 1 to n, we need to
		 * increase i by 1
		 */
		i++;

		for (;;) {
			j = i;
			/* Check if we have 2 childs */
			if (2 * j + 1 <= q->data.binaryheap.size) {
				/* Is this child smaller than the parent? */
				if (BIN_HEAP_ARR(j).priority >= BIN_HEAP_ARR(2 * j).priority) i = 2 * j;
				/* Yes, we _need_ to use i here, not j, because we want to have the smallest child
				 *  This way we get that straight away! */
				if (BIN_HEAP_ARR(i).priority >= BIN_HEAP_ARR(2 * j + 1).priority) i = 2 * j + 1;
			/* Do we have one child? */
			} else if (2 * j <= q->data.binaryheap.size) {
				if (BIN_HEAP_ARR(j).priority >= BIN_HEAP_ARR(2 * j).priority) i = 2 * j;
			}

			/* One of our childs is smaller than we are, switch */
			if (i != j) {
				temp = BIN_HEAP_ARR(j);
				BIN_HEAP_ARR(j) = BIN_HEAP_ARR(i);
				BIN_HEAP_ARR(i) = temp;
			} else {
				/* None of our childs is smaller, so we stay here.. stop :) */
				break;
			}
		}
	}

	return true;
}

static void *BinaryHeap_Pop(Queue *q)
{
	void *result;

#ifdef QUEUE_DEBUG
	printf("[BinaryHeap] Popping an element. There are %d elements left\n", q->data.binaryheap.size);
#endif

	if (q->data.binaryheap.size == 0) return NULL;

	/* The best item is always on top, so give that as result */
	result = BIN_HEAP_ARR(1).item;
	/* And now we should get rid of this item... */
	BinaryHeap_Delete(q, BIN_HEAP_ARR(1).item, BIN_HEAP_ARR(1).priority);

	return result;
}

void init_BinaryHeap(Queue *q, uint max_size)
{
	assert(q != NULL);
	q->push = BinaryHeap_Push;
	q->pop = BinaryHeap_Pop;
	q->del = BinaryHeap_Delete;
	q->clear = BinaryHeap_Clear;
	q->free = BinaryHeap_Free;
	q->data.binaryheap.max_size = max_size;
	q->data.binaryheap.size = 0;
	/* We malloc memory in block of BINARY_HEAP_BLOCKSIZE
	 *   It autosizes when it runs out of memory */
	q->data.binaryheap.elements = CallocT<BinaryHeapNode*>((max_size - 1) / BINARY_HEAP_BLOCKSIZE + 1);
	q->data.binaryheap.elements[0] = MallocT<BinaryHeapNode>(BINARY_HEAP_BLOCKSIZE);
	q->data.binaryheap.blocks = 1;
#ifdef QUEUE_DEBUG
	printf("[BinaryHeap] Initial size of elements is %d nodes\n", BINARY_HEAP_BLOCKSIZE);
#endif
}

/* Because we don't want anyone else to bother with our defines */
#undef BIN_HEAP_ARR

/*
 * Hash
 */

void init_Hash(Hash *h, Hash_HashProc *hash, uint num_buckets)
{
	/* Allocate space for the Hash, the buckets and the bucket flags */
	uint i;

	assert(h != NULL);
#ifdef HASH_DEBUG
	debug("Allocated hash: %p", h);
#endif
	h->hash = hash;
	h->size = 0;
	h->num_buckets = num_buckets;
	h->buckets = (HashNode*)MallocT<byte>(num_buckets * (sizeof(*h->buckets) + sizeof(*h->buckets_in_use)));
#ifdef HASH_DEBUG
	debug("Buckets = %p", h->buckets);
#endif
	h->buckets_in_use = (bool*)(h->buckets + num_buckets);
	for (i = 0; i < num_buckets; i++) h->buckets_in_use[i] = false;
}


void delete_Hash(Hash *h, bool free_values)
{
	uint i;

	/* Iterate all buckets */
	for (i = 0; i < h->num_buckets; i++) {
		if (h->buckets_in_use[i]) {
			HashNode *node;

			/* Free the first value */
			if (free_values) free(h->buckets[i].value);
			node = h->buckets[i].next;
			while (node != NULL) {
				HashNode *prev = node;

				node = node->next;
				/* Free the value */
				if (free_values) free(prev->value);
				/* Free the node */
				free(prev);
			}
		}
	}
	free(h->buckets);
	/* No need to free buckets_in_use, it is always allocated in one
	 * malloc with buckets */
#ifdef HASH_DEBUG
	debug("Freeing Hash: %p", h);
#endif
}

#ifdef HASH_STATS
static void stat_Hash(const Hash *h)
{
	uint used_buckets = 0;
	uint max_collision = 0;
	uint max_usage = 0;
	uint usage[200];
	uint i;

	for (i = 0; i < lengthof(usage); i++) usage[i] = 0;
	for (i = 0; i < h->num_buckets; i++) {
		uint collision = 0;
		if (h->buckets_in_use[i]) {
			const HashNode *node;

			used_buckets++;
			for (node = &h->buckets[i]; node != NULL; node = node->next) collision++;
			if (collision > max_collision) max_collision = collision;
		}
		if (collision >= lengthof(usage)) collision = lengthof(usage) - 1;
		usage[collision]++;
		if (collision > 0 && usage[collision] >= max_usage) {
			max_usage = usage[collision];
		}
	}
	printf(
		"---\n"
		"Hash size: %d\n"
		"Nodes used: %d\n"
		"Non empty buckets: %d\n"
		"Max collision: %d\n",
		h->num_buckets, h->size, used_buckets, max_collision
	);
	printf("{ ");
	for (i = 0; i <= max_collision; i++) {
		if (usage[i] > 0) {
			printf("%d:%d ", i, usage[i]);
#if 0
			if (i > 0) {
				uint j;

				for (j = 0; j < usage[i] * 160 / 800; j++) putchar('#');
			}
			printf("\n");
#endif
		}
	}
	printf ("}\n");
}
#endif

void clear_Hash(Hash *h, bool free_values)
{
	uint i;

#ifdef HASH_STATS
	if (h->size > 2000) stat_Hash(h);
#endif

	/* Iterate all buckets */
	for (i = 0; i < h->num_buckets; i++) {
		if (h->buckets_in_use[i]) {
			HashNode *node;

			h->buckets_in_use[i] = false;
			/* Free the first value */
			if (free_values) free(h->buckets[i].value);
			node = h->buckets[i].next;
			while (node != NULL) {
				HashNode *prev = node;

				node = node->next;
				if (free_values) free(prev->value);
				free(prev);
			}
		}
	}
	h->size = 0;
}

/** Finds the node that that saves this key pair. If it is not
 * found, returns NULL. If it is found, *prev is set to the
 * node before the one found, or if the node found was the first in the bucket
 * to NULL. If it is not found, *prev is set to the last HashNode in the
 * bucket, or NULL if it is empty. prev can also be NULL, in which case it is
 * not used for output.
 */
static HashNode *Hash_FindNode(const Hash *h, uint key1, uint key2, HashNode** prev_out)
{
	uint hash = h->hash(key1, key2);
	HashNode *result = NULL;

#ifdef HASH_DEBUG
	debug("Looking for %u, %u", key1, key2);
#endif
	/* Check if the bucket is empty */
	if (!h->buckets_in_use[hash]) {
		if (prev_out != NULL) *prev_out = NULL;
		result = NULL;
	/* Check the first node specially */
	} else if (h->buckets[hash].key1 == key1 && h->buckets[hash].key2 == key2) {
		/* Save the value */
		result = h->buckets + hash;
		if (prev_out != NULL) *prev_out = NULL;
#ifdef HASH_DEBUG
		debug("Found in first node: %p", result);
#endif
	/* Check all other nodes */
	} else {
		HashNode *prev = h->buckets + hash;
		HashNode *node;

		for (node = prev->next; node != NULL; node = node->next) {
			if (node->key1 == key1 && node->key2 == key2) {
				/* Found it */
				result = node;
#ifdef HASH_DEBUG
				debug("Found in other node: %p", result);
#endif
				break;
			}
			prev = node;
		}
		if (prev_out != NULL) *prev_out = prev;
	}
#ifdef HASH_DEBUG
	if (result == NULL) debug("Not found");
#endif
	return result;
}

void *Hash_Delete(Hash *h, uint key1, uint key2)
{
	void *result;
	HashNode *prev; // Used as output var for below function call
	HashNode *node = Hash_FindNode(h, key1, key2, &prev);

	if (node == NULL) {
		/* not found */
		result = NULL;
	} else if (prev == NULL) {
		/* It is in the first node, we can't free that one, so we free
		 * the next one instead (if there is any)*/
		/* Save the value */
		result = node->value;
		if (node->next != NULL) {
			HashNode *next = node->next;
			/* Copy the second to the first */
			*node = *next;
			/* Free the second */
#ifndef NOFREE
			free(next);
#endif
		} else {
			/* This was the last in this bucket
			 * Mark it as empty */
			uint hash = h->hash(key1, key2);
			h->buckets_in_use[hash] = false;
		}
	} else {
		/* It is in another node
		 * Save the value */
		result = node->value;
		/* Link previous and next nodes */
		prev->next = node->next;
		/* Free the node */
#ifndef NOFREE
		free(node);
#endif
	}
	if (result != NULL) h->size--;
	return result;
}


void *Hash_Set(Hash *h, uint key1, uint key2, void *value)
{
	HashNode *prev;
	HashNode *node = Hash_FindNode(h, key1, key2, &prev);

	if (node != NULL) {
		/* Found it */
		void *result = node->value;

		node->value = value;
		return result;
	}
	/* It is not yet present, let's add it */
	if (prev == NULL) {
		/* The bucket is still empty */
		uint hash = h->hash(key1, key2);
		h->buckets_in_use[hash] = true;
		node = h->buckets + hash;
	} else {
		/* Add it after prev */
		node = MallocT<HashNode>(1);
		prev->next = node;
	}
	node->next = NULL;
	node->key1 = key1;
	node->key2 = key2;
	node->value = value;
	h->size++;
	return NULL;
}

void *Hash_Get(const Hash *h, uint key1, uint key2)
{
	HashNode *node = Hash_FindNode(h, key1, key2, NULL);

#ifdef HASH_DEBUG
	debug("Found node: %p", node);
#endif
	return (node != NULL) ? node->value : NULL;
}

uint Hash_Size(const Hash *h)
{
	return h->size;
}