/* $Id$ */

/*
 * 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.h Simple Queue/Hash implementations. */

#ifndef QUEUE_H
#define QUEUE_H

//#define NOFREE
//#define QUEUE_DEBUG
//#define HASH_DEBUG
//#define HASH_STATS


struct Queue;
typedef bool Queue_PushProc(Queue *q, void *item, int priority);
typedef void *Queue_PopProc(Queue *q);
typedef bool Queue_DeleteProc(Queue *q, void *item, int priority);
typedef void Queue_ClearProc(Queue *q, bool free_values);
typedef void Queue_FreeProc(Queue *q, bool free_values);

struct BinaryHeapNode {
	void *item;
	int priority;
};


struct Queue {
	/*
	 * Pushes an element into the queue, at the appropriate place for the queue.
	 * Requires the queue pointer to be of an appropriate type, of course.
	 */
	Queue_PushProc *push;
	/*
	 * Pops the first element from the queue. What exactly is the first element,
	 * is defined by the exact type of queue.
	 */
	Queue_PopProc *pop;
	/*
	 * Deletes the item from the queue. priority should be specified if
	 * known, which speeds up the deleting for some queue's. Should be -1
	 * if not known.
	 */
	Queue_DeleteProc *del;

	/* Clears the queue, by removing all values from it. Its state is
	 * effectively reset. If free_items is true, each of the items cleared
	 * in this way are free()'d.
	 */
	Queue_ClearProc *clear;
	/* Frees the queue, by reclaiming all memory allocated by it. After
	 * this it is no longer usable. If free_items is true, any remaining
	 * items are free()'d too.
	 */
	Queue_FreeProc *free;

	uint max_size;
	uint size;
	uint blocks; ///< The amount of blocks for which space is reserved in elements
	BinaryHeapNode **elements;
};


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

/* The amount of elements that will be malloc'd at a time */
#define BINARY_HEAP_BLOCKSIZE_BITS 10

/**
 * Initializes a binary heap and allocates internal memory for maximum of
 * max_size elements
 */
void init_BinaryHeap(Queue *q, uint max_size);


/*
 * Hash
 */
struct HashNode {
	uint key1;
	uint key2;
	void *value;
	HashNode *next;
};
/**
 * Generates a hash code from the given key pair. You should make sure that
 * the resulting range is clearly defined.
 */
typedef uint Hash_HashProc(uint key1, uint key2);
struct Hash {
	/* The hash function used */
	Hash_HashProc *hash;
	/* The amount of items in the hash */
	uint size;
	/* The number of buckets allocated */
	uint num_buckets;
	/* A pointer to an array of num_buckets buckets. */
	HashNode *buckets;
	/* A pointer to an array of numbuckets booleans, which will be true if
	 * there are any Nodes in the bucket */
	bool *buckets_in_use;
};

/* Call these function to manipulate a hash */

/**
 * Deletes the value with the specified key pair from the hash and returns
 * that value. Returns NULL when the value was not present. The value returned
 * is _not_ free()'d!
 */
void *Hash_Delete(Hash *h, uint key1, uint key2);
/**
 * Sets the value associated with the given key pair to the given value.
 * Returns the old value if the value was replaced, NULL when it was not yet present.
 */
void *Hash_Set(Hash *h, uint key1, uint key2, void *value);
/**
 * Gets the value associated with the given key pair, or NULL when it is not
 * present.
 */
void *Hash_Get(const Hash *h, uint key1, uint key2);

/* Call these function to create/destroy a hash */

/**
 * Builds a new hash in an existing struct. Make sure that hash() always
 * returns a hash less than num_buckets! Call delete_hash after use
 */
void init_Hash(Hash *h, Hash_HashProc *hash, uint num_buckets);
/**
 * Deletes the hash and cleans up. Only cleans up memory allocated by new_Hash
 * & friends. If free is true, it will call free() on all the values that
 * are left in the hash.
 */
void delete_Hash(Hash *h, bool free_values);
/**
 * Cleans the hash, but keeps the memory allocated
 */
void clear_Hash(Hash *h, bool free_values);
/**
 * Gets the current size of the Hash
 */
uint Hash_Size(const Hash *h);

#endif /* QUEUE_H */