#ifndef _LSUP_TRIPLE_H
#define _LSUP_TRIPLE_H

#include "term.h"

typedef struct LSUP_Triple {
    LSUP_Term *s;
    LSUP_Term *p;
    LSUP_Term *o;
} LSUP_Triple;

typedef enum {
    TRP_POS_S = 0,
    TRP_POS_P = 1,
    TRP_POS_O = 2,
} LSUP_TriplePos;


LSUP_Triple *
LSUP_triple_new(LSUP_Term *s, LSUP_Term *p, LSUP_Term *o);

#define TRP_DUMMY LSUP_triple_new (NULL, NULL, NULL)


LSUP_Triple *
LSUP_triple_new_from_btriple (const LSUP_BufferTriple *sspo);


LSUP_BufferTriple *
LSUP_btriple_new_from_triple (const LSUP_Triple *spo);


/** @brief Initialize internal term pointers in a heap-allocated triple.
 *
 * NOTE: the term structures are not copied. If the triple is freed with
 * #LSUP_triple_free(), the originally provided terms are freed too.
 *
 * @param spo[in] Triple pointer to initialize.
 */
LSUP_rc
LSUP_triple_init (LSUP_Triple *spo, LSUP_Term *s, LSUP_Term *p, LSUP_Term *o);


/** @brief Free the internal pointers of a triple.
 *
 * @param spo[in] Triple to be freed.
 */
void
LSUP_triple_done (LSUP_Triple *spo);


/** @brief Free a triple and all its internal pointers.
 *
 * NOTE: If the term pointers are not to be freed (e.g. they are owned by a
 * back end), use a simple free(spo) instead of this.
 *
 * @param spo[in] Triple to be freed.
 */
void
LSUP_triple_free (LSUP_Triple *spo);


#define _FN_BODY \
    if (n == TRP_POS_S) return trp->s; \
    if (n == TRP_POS_P) return trp->p; \
    if (n == TRP_POS_O) return trp->o; \
    return NULL;


/** @brief Get triple by term position.
 *
 * Useful for looping over all terms.
 *
 * @param trp[in] Triple pointer.
 *
 * @param n[in] A number between 0÷2.
 *
 * @return Corresponding triple term or NULL if n is out of range.
 */
inline LSUP_Term *
LSUP_triple_pos (const LSUP_Triple *trp, LSUP_TriplePos n)
{ _FN_BODY }


/** @brief Get serialized triple by term position.
 *
 * Useful for looping over all terms.
 *
 * @param trp[in] Serialized triple pointer.
 *
 * @param n[in] A number between 0÷2.
 *
 * @return Corresponding serialized term or NULL if n is out of range.
 */
inline LSUP_Buffer *
LSUP_btriple_pos (const LSUP_BufferTriple *trp, LSUP_TriplePos n)
{ _FN_BODY }
#undef _FN_BODY


/** @brief Hash a triple.
 *
 * TODO This doesn't handle blank nodes correctly.
 */
inline LSUP_Key
LSUP_triple_hash (const LSUP_Triple *trp)
{
    LSUP_BufferTriple *strp = LSUP_btriple_new_from_triple (trp);
    LSUP_Key hash = LSUP_btriple_hash (strp);
    LSUP_btriple_free (strp);

    return hash;
}

#endif