#ifndef UC_HTABLE_H_
#define UC_HTABLE_H_

#include <stddef.h>

/** @file
 * Building block for hash table.
 * The hash table is stored using a chained list of buckets.
 * Nodes with different hash value can be stored in the same bucket.
 *
 *
 * The hash table manages only the hash value, not the equality
 * between nodes.
 *
 * It's up to the user to check for duplicate values
 * before adding nodes if dublicates are not desired.
 * 
 * Finding a node must be done in a user specific way, 
 * normally by iterating over all nodes with the desidred
 * hash, and deciding in some other way whether it is the desidred
 * node.
 */

/** Node the hashtable tracks.
 * Will normally be embedded inside another struct
 */
struct UHNode {
    //cached value of the hash
    size_t hash;
    //pointer to next in same bucket
    struct UHNode *next;
};

/**
 * The hash table struct
 */
struct UHTable {
    size_t cnt_elements;
    size_t cnt_buckets;
    struct UHNode **buckets;
};

/**
 * Initialize a hash table.
 * @param table hash table to initialize
 * @param buckets number of buckets
 * @return 0 on success, errno if malloc fails or buckets == 0
 */
int uc_htable_init(struct UHTable *table, size_t buckets);

/** 
 * Free resources of the hash table.
 * @param table hash table to free (does not free @table itself
 */
void uc_htable_destroy(struct UHTable *table);


/**
 * @param table 
 * @param hash find the bucket from this hash value
 * @return the bucket number for the given hash
 */
static inline size_t uc_htable_bucket(const struct UHTable *table, size_t hash)
{
    return hash % table->cnt_buckets;
}

/**
 * Get the first bucket node for the given hash.
 * The returned node might not have the same hash, since different
 * nodes can share the same bucket.
 *
 * @param table table
 * @param hash hash
 */
static inline struct UHNode *uc_htable_first_bucket(const struct UHTable *table, 
                                                    size_t hash)
{
    size_t bucket = uc_htable_bucket(table, hash);

    return table->buckets[bucket];
}

/**
 * Get the next node in the bucket. 
 * @return next node or NULL
 */
static inline struct UHNode *uc_htable_next_in_bucket(const struct UHNode *node)
{
    return node->next;
}

/**
 * Get the first node that have the given hash
 * @param table table
 * @param hash hash
 * @return first node with the given hash or NULL
 */
struct UHNode *uc_htable_first_hash(const struct UHTable *table, size_t hash);


//internal helper
struct UHNode *uc_htable_next_hash_hlp(struct UHNode *next, size_t hash);

/**
 * Get the next node with the same hash
 * @param node previous node
 * @return next node with the same hash as node or NULL
 */
static inline struct UHNode *uc_htable_next_hash(const struct UHNode *node)
{
    return uc_htable_next_hash_hlp(node->next, node->hash);
}


//internal helper
struct UHNode *uc_htable_iter_hlp(struct UHTable *table, size_t start_bucket);

/** Get the first node in the hash table
 *
 * @param table table
 * @return first node or NULL
 */
static inline struct UHNode *uc_htable_first(struct UHTable *table)
{
    return uc_htable_iter_hlp(table, 0);
}

/** Get the next node in the hash table
 *
 * @param table table
 * @param node previous node
 * @return first node or NULL
 */
struct UHNode *uc_htable_next(struct UHTable *table, struct UHNode *node);

/**
 * Swap 2 hash tables.
 *
 * @param a first table
 * @param b second table
 */
void uc_htable_swap(struct UHTable *a, struct UHTable *b);

/**
 * Iterate over all nodes in a bucket.
 * The table must not be changed while iterating.
 *
 * @param table the struct UHTable*
 * @param node_iter struct UHNode* for the current node being iterated
 * @param hash size_t hash for the bucket to iterate
 */
#define UC_HTABLE_FOREACH_BUCKET(table, node_iter, hash)\
    for ((node_iter) = uc_htable_first_bucket((table), (hash));\
         (node_iter) != NULL;\
         (node_iter) = uc_htable_next_in_bucket((node_iter)))

/**
 * Iterate over all nodes that has the given hash.
 * The table must not be changed while iterating.
 * Normally the user would check in a user specific way
 * if the node_iter is equal to the node one wants to find.
 *
 * @param table the struct UHTable*
 * @param node_iter struct UHNode* for the current node being iterated
 * @param hash size_t hash for the node(s) to iterate over
 */
#define UC_HTABLE_FOREACH_HASH(table, node_iter, hash)\
    for ((node_iter) = uc_htable_first_hash((table), (hash));\
         (node_iter) != NULL;\
         (node_iter) = uc_htable_next_hash((node_iter)))

/**
 * "Safe" variant of UC_HTABLE_FOREACH_HASH, the iterated node
 * (or any previously iterated nodes) can be freed while iterating
 *
 * @param table the struct UHTable*
 * @param node_iter struct UHNode* for the current node being iterated
 * @param next_iter struct UHNode* for the next node, required by the
 *                  iteration, next_iter must not be altered while iterating.
 * @param hash size_t hash for the node(s) to iterate over
 */
#define UC_HTABLE_FOREACH_HASH_SAFE(table, node_iter, next_iter, hash)\
    for ((node_iter) = uc_htable_first_hash((table), (hash));\
         (node_iter) != NULL && (((next_iter) = (node_iter->next)), 1);\
         (node_iter) = (next))

/**
 * Iterate over all nodes in a table
 * The table must not be changed while iterating.
 *
 * @param table the struct UHTable*
 * @param node_iter struct UHNode* for the current node being iterated
 */
#define UC_HTABLE_FOREACH(table, node_iter)\
    for ((node_iter) = uc_htable_first((table));\
         (node_iter) != NULL;\
         (node_iter) = uc_htable_next((table), (node_iter)))

/**
 * "Safe" variant of UC_HTABLE_FOREACH, the iterated node
 * (or any previously iterated nodes) can be freed while iterating
 *
 * @param table the struct UHTable*
 * @param node_iter struct UHNode* for the current node being iterated
 * @param next_iter struct UHNode* for the next node, required by the
 *                  iteration, next_iter must not be altered while iterating.
*/
#define UC_HTABLE_FOREACH_SAFE(table, node_iter, next_iter)\
    for ((node_iter) = uc_htable_first((table));\
         (node_iter) != NULL &&\
         ((next_iter) = uc_htable_next((table), (node_iter)), 1);\
         (node_iter) = (next))


/**
 * Check if the given node pointer exists in the hash table
 *
 * @param table table
 * @param node node to check for
 * @return 0 if the node does not exist in table non-0 if it does
 */
int uc_htable_has_node(struct UHTable *table, struct UHNode *node);


/**
 *
 * @return 0 if table is empty non-0 if it contains any nodes
 */
static inline int uc_htable_isempty(const struct UHTable *table)
{
    return table->cnt_elements == 0;
}

/**
 * Get number of elements in the hash table.
 *
 * @rparam table table
 * @return number of elements
 */
static inline size_t uc_htable_count(const struct UHTable *table)
{
    return table->cnt_elements;
}

/** Clears all nodes from the hash table, making it empty.
 * No memory is released.
 * @param table table to clear
 */
void uc_htable_clear(struct UHTable *table);

/** Insert a new node.
 * The new node pointer must exist as long as it is part of the 
 * hash table. The hash table does not check for duplicates in any way.
 *
 * @param table table to insert into
 * @param node new node to insert.
 * @param hash hash value of the new node
 */
void uc_htable_insert(struct UHTable *table, struct UHNode *node, size_t hash);

/** Remove a node.
 *  If the node pointer is not part of the table,
 *  no action is taken
 *
 * @param table table to remove from.
 * @param node node to remove.
 */
void uc_htable_remove(struct UHTable *table, struct UHNode *node);

/** Resize the hash table. This changes the number of buckets, and re-inserts
 * all nodes.
 *
 * @param table table to resize
 * @param buckets new number of buckets, must be > 0
 * @return 0 on success, errno if malloc fails or buckets == 0
 */
int uc_htable_resize(struct UHTable *table, size_t buckets);


#endif