/** @file store.htable.h
 *
 * @brief Simple in-memory triple store back end based on hash tables.
 *
 * This is the simplest choice to do in-memory manipulation of RDF graphs and
 * it has some limitations: most notably, it only supports triples without
 * context (one graph per store) and it is not indexed. This means that it is
 * optimized for fast writes and sequential lookups (iteration). Lookups on
 * arbitrary terms are supported but require iterating over all the triples.
 * This implementation is most convenient for graphs where retrieval is done
 * via iteration.
 *
 * Also, as it may be obvious, this store is not persistent.
 *
 * For faster random lookups and persistence, the MDB backend is preferred. If
 * persistence is not required (e.g. ingesting and manipulating a very large
 * graph and outputting some results on a file) an ad-hoc MDB store located in
 * RAM disk can be used, which is much faster.
 */
#ifndef _LSUP_STORE_HTABLE_H
#define _LSUP_STORE_HTABLE_H

#include "triple.h"
#include "htable.h"


typedef struct HTStore LSUP_HTStore;
typedef struct HTIterator LSUP_HTIterator;

LSUP_HTStore *
LSUP_htstore_new(size_t capacity);


/** @brief Boolean operation on hash table triples.
 *
 * The resulting store is compacted to the minimum size necessary to hold all
 * results.
 *
 * @param op[in] Operation type. See #LSUP_bool_op
 *
 * @param s1[in] First store.
 *
 * @param s2[in] Second store.
 *
 * @return New store resulting from the operation. It must be freed with
 * #LSUP_htstore_free after use.
 */
LSUP_HTStore *
LSUP_htstore_bool_op(
        const LSUP_bool_op op, const LSUP_HTStore *s1, const LSUP_HTStore *s2);

void
LSUP_htstore_free(LSUP_HTStore *ht);

LSUP_rc
LSUP_htstore_resize(LSUP_HTStore *ht, htsize_t size);

LSUP_rc
LSUP_htstore_add(LSUP_HTStore *store, const LSUP_SerTriple *sspo);

LSUP_rc
LSUP_htstore_remove(
        LSUP_HTStore *store, const LSUP_SerTriple *sspo, size_t *ct);

LSUP_HTIterator *
LSUP_htstore_lookup(
        LSUP_HTStore *store, const LSUP_SerTriple *sspo, size_t *ct);

htsize_t
LSUP_htstore_size(LSUP_HTStore *ht);

htsize_t
LSUP_htstore_capacity(const LSUP_HTStore *ht);

LSUP_rc
LSUP_htiter_next(LSUP_HTIterator *it, LSUP_SerTriple *sspo);

void
LSUP_htiter_free(LSUP_HTIterator *it);

#endif  // _LSUP_STORE_HTABLE_H