#include "uthash.h"

#include "namespace.h"
#include "store_htable.h"


/**
 * Callback type for key comparison.
 */
typedef bool (*LSUP_key_eq_fn_t)(
        const LSUP_Key spok[], const LSUP_Key luk[]);


typedef struct triple_entry_t {
    LSUP_TripleKey      key;
    UT_hash_handle      hh;
} TripleEntry;

typedef struct idx_entry_t {
    LSUP_Key            key;
    LSUP_Buffer *       sterm;
    UT_hash_handle      hh;
} IndexEntry;

typedef struct ht_store_t {
    TripleEntry *       keys;       // Triple keys (set).
    IndexEntry *        idx;        // Dictionary of keys to serialized terms.
} HTStore;

typedef struct ht_iterator_t {
    HTStore *           store;      // Store being iterated.
    size_t              i;          // Number of records found at any point of
                                    // a lookup iteration, or number of records
                                    // added at any point of an add loop.
    LSUP_Key            luk[3];     // 0÷3 lookup keys.
    LSUP_key_eq_fn_t    eq_fn;      // Equality function to test triples.
    int                 rc;         // Return code for *next* result.
    TripleEntry *       entry;     // Retrieved SPO key.
} HTIterator;


/**
 * Identity hashing function.
 *
 * Since the key is already a strong hash, reuse it for entry allocation.
 */
//#define HASH_FUNCTION (s,len,hashv) (hashv) = (unsigned)(s)

/* * * CALLBACKS * * */

/**
 * Dummy callback for queries with all parameters unbound. Returns true.
*/
static bool lookup_none_eq_fn(
        const LSUP_Key spok[], const LSUP_Key luk[])
{ return true; }

/**
 * Keyset lookup for S key.
 */
static bool lookup_sk_eq_fn(
        const LSUP_Key spok[], const LSUP_Key luk[])
{ return spok[0] == luk[0]; }

/**
 * Keyset lookup for P key.
 */
static bool lookup_pk_eq_fn(
        const LSUP_Key spok[], const LSUP_Key luk[])
{ return spok[1] == luk[0]; }

/**
 * Keyset lookup for O key.
 */
static bool lookup_ok_eq_fn(
        const LSUP_Key spok[], const LSUP_Key luk[])
{ return spok[2] == luk[0]; }

/**
 * Keyset lookup for S and P keys.
 */
static bool lookup_spk_eq_fn(
        const LSUP_Key spok[], const LSUP_Key luk[])
{ return spok[0] == luk[0] && spok[1] == luk[1]; }

/**
 * Keyset lookup for S and O keys.
 */
static bool lookup_sok_eq_fn(
        const LSUP_Key spok[], const LSUP_Key luk[])
{ return spok[0] == luk[0] && spok[2] == luk[1]; }

/**
 * Keyset lookup for P and O keys.
 */
static bool lookup_pok_eq_fn(
        const LSUP_Key spok[], const LSUP_Key luk[])
{ return spok[1] == luk[0] && spok[2] == luk[1]; }

/**
 * Keyset lookup for S, P and O keys.
 */
static bool lookup_spok_eq_fn(
        const LSUP_Key spok[], const LSUP_Key luk[])
{ return spok[0] == luk[0] && spok[1] == luk[1] && spok[2] == luk[2]; }


/* * * Other prototypes. * * */

static inline LSUP_rc tkey_to_strp (
        const HTStore *store, const LSUP_Key spok[], LSUP_SerTriple *sspo);


/* * * API * * */

HTStore *
LSUP_htstore_new (void)
{
    HTStore *ht;
    MALLOC_GUARD (ht, NULL);

    ht->keys = NULL;
    ht->idx = NULL;

    return ht;
}


HTStore *
LSUP_htstore_copy (const HTStore *src)
{
    HTStore *dest = LSUP_htstore_new();
    if (UNLIKELY (!dest)) return NULL;

    if (LSUP_htstore_copy_contents (dest, src) < 0) {
        LSUP_htstore_free (dest);
        return NULL;
    }

    return dest;
}


LSUP_rc
LSUP_htstore_copy_contents (HTStore *dest, const HTStore *src)
{
    TripleEntry *dest_trp = malloc (
            HASH_COUNT (src->keys) * sizeof (*dest_trp));
    if (UNLIKELY (!dest_trp)) return LSUP_MEM_ERR;

    IndexEntry *dest_idx = malloc (
            HASH_COUNT (src->idx) * sizeof (*dest_idx));
    if (UNLIKELY (!dest_idx)) {
        free (dest_trp);
        return LSUP_MEM_ERR;
    }

    TripleEntry *src_trp;
    IndexEntry *src_idx;
    unsigned i;

    // Copy triple data.
    for (
        src_trp = src->keys, i = 0; src_trp != NULL;
        src_trp = src->keys->hh.next
    ) {
        memcpy (dest_trp + i, src_trp, sizeof (*dest_trp));
        HASH_ADD (hh, dest->keys, key, TRP_KLEN, dest_trp + i);
        i++;
    }

    // Copy index data.
    for (
        src_idx = src->idx, i = 0; src_idx != NULL;
        src_idx = src->idx->hh.next
    ) {
        memcpy (dest_idx + i, src_idx, sizeof (*dest_idx));
        HASH_ADD (hh, dest->idx, key, KLEN, dest_idx + i);
        i++;
    }

    return LSUP_OK;
}


HTStore *
LSUP_htstore_bool_op(
        const LSUP_bool_op op, const HTStore *s1, const HTStore *s2)
{
    HTStore *dest;
    TripleEntry *trp_cur;

    dest = LSUP_htstore_new();

    if (UNLIKELY (
            op != LSUP_BOOL_UNION
            && op != LSUP_BOOL_SUBTRACTION
            && op != LSUP_BOOL_INTERSECTION
            && op != LSUP_BOOL_XOR)) {
        fprintf (stderr, "Operation not supported.\n");
        goto fail;
    }

    if (op == LSUP_BOOL_UNION) {
        dest = LSUP_htstore_copy (s1);
        if (UNLIKELY (!dest) || LSUP_htstore_copy_contents (dest, s2) < 0)
            goto fail;

        return dest;
    }

    LSUP_SerTriple *sspo = STRP_DUMMY;

    LSUP_HTIterator *it = LSUP_htstore_add_init(dest);

    if (op == LSUP_BOOL_XOR) {
        // Add triples from s2 if not found in s1.
        for (
            trp_cur = s2->keys; trp_cur != NULL;
            trp_cur = s2->keys->hh.next
        ) {
            TripleEntry *ins = NULL;
            HASH_FIND (hh, s1->keys, trp_cur->key, TRP_KLEN, ins);

            if (!ins) {
                tkey_to_strp (s2, trp_cur->key, sspo);
                LSUP_htstore_add_iter (it, sspo);
            }
        }
    }

    for (
        trp_cur = s1->keys; trp_cur != NULL;
        trp_cur = s1->keys->hh.next
    ) {
        TripleEntry *ins = NULL;
        HASH_FIND (hh, s2->keys, trp_cur->key, TRP_KLEN, ins);

        // For XOR and subtraction, add if not found.
        // For intersection, add if found.
        if ((op == LSUP_BOOL_INTERSECTION) ^ (ins == NULL)) {
            tkey_to_strp (s1, trp_cur->key, sspo);
            LSUP_htstore_add_iter (it, sspo);
        }
    }
    LSUP_striple_free (sspo);
    LSUP_htstore_add_done (it);

    return dest;

fail:
    LSUP_htstore_free (dest);
    return NULL;
}


void
LSUP_htstore_free (HTStore *ht)
{
    IndexEntry *idx_entry, *idx_tmp;
    size_t ct = 0;
    HASH_ITER (hh, ht->idx, idx_entry, idx_tmp) {
        HASH_DEL (ht->idx, idx_entry);
        LSUP_buffer_free (idx_entry->sterm);
        free (idx_entry);
        ct++;
    }

    TripleEntry *trp_entry, *trp_tmp;
    HASH_ITER (hh, ht->keys, trp_entry, trp_tmp) {
        HASH_DEL (ht->keys, trp_entry);
        free (trp_entry);
    }

    free (ht);
}


size_t
LSUP_htstore_size (LSUP_HTStore *ht)
{ return HASH_COUNT (ht->keys); }


LSUP_HTIterator *
LSUP_htstore_add_init (HTStore *store)
{
    HTIterator *it;
    MALLOC_GUARD (it, NULL);

    it->store = store;
    it->i = 0;

    return it;
}


LSUP_rc
LSUP_htstore_add_iter (HTIterator *it, const LSUP_SerTriple *sspo)
{
    LSUP_TripleKey spok = {
        LSUP_buffer_hash (sspo->s),
        LSUP_buffer_hash (sspo->p),
        LSUP_buffer_hash (sspo->o),
    };

    // Add triple.
    TRACE ("Inserting spok: {%lx, %lx, %lx}", spok[0], spok[1], spok[2]);

    TripleEntry *k_ins = NULL;
    HASH_FIND (hh, it->store->keys, spok, TRP_KLEN, k_ins);
    if (k_ins == NULL) {
        TRACE (STR, "Triple not found, inserting.");
        MALLOC_GUARD (k_ins, LSUP_MEM_ERR);

        memcpy (k_ins->key, spok, TRP_KLEN);
        HASH_ADD (hh, it->store->keys, key, TRP_KLEN, k_ins);

        it->i++;
    } else {
        TRACE (STR, "Triple found. Skipping.");
        return LSUP_NOACTION;
    }

    // Add terms to index.
    for (int i = 0; i < 3; i++) {
        spok[i] = LSUP_buffer_hash (LSUP_striple_pos (sspo, i));
        //TRACE ("Indexing term key %lx\n", spok[i]);

        IndexEntry *ins = NULL;
        HASH_FIND (hh, it->store->idx, spok + i, KLEN, ins);
        if (ins == NULL) {
            MALLOC_GUARD (ins, LSUP_MEM_ERR);
            ins->key = spok[i];
            ins->sterm = LSUP_buffer_new (
                    (LSUP_striple_pos (sspo, i))->size,
                    (LSUP_striple_pos (sspo, i))->addr);
            HASH_ADD (hh, it->store->idx, key, KLEN, ins);
        }
    }

    return LSUP_OK;
}


void
LSUP_htstore_add_done (HTIterator *it)
{ LSUP_htiter_free (it); }


LSUP_rc
LSUP_htstore_remove(
        LSUP_HTStore *store, const LSUP_SerTriple *sspo, size_t *ct)
{
    LSUP_HTIterator *it = LSUP_htstore_lookup (store, sspo);
    if (UNLIKELY (!it)) return LSUP_DB_ERR;

    *ct = 0;

    TripleEntry *tmp = malloc (sizeof (*tmp));
    HASH_ITER (hh, store->keys, it->entry, tmp) {
        if (it->eq_fn (it->entry->key, it->luk)) {
            HASH_DEL (store->keys, it->entry);
            free (it->entry);

            (*ct)++;
        }
    }

    // TODO clean up orphan indices in separate (async, scheduled) function.

    return LSUP_OK;
}


HTIterator *
LSUP_htstore_lookup (HTStore *store, const LSUP_SerTriple *sspo)
{
    HTIterator *it;
    MALLOC_GUARD (it, NULL);

    it->store = store;
    //it->cur = 0;
    it->rc = LSUP_END;

    if (HASH_COUNT (store->keys) == 0) return it;

    LSUP_TripleKey spok = {
        LSUP_buffer_hash (sspo->s),
        LSUP_buffer_hash (sspo->p),
        LSUP_buffer_hash (sspo->o),
    };

    // s p o
    if (spok[0] != NULL_KEY && spok[1] != NULL_KEY && spok[2] != NULL_KEY) {
        memcpy (it->luk, spok, sizeof (LSUP_TripleKey));
        it->eq_fn = lookup_spok_eq_fn;

    } else if (spok[0] != NULL_KEY) {
        it->luk[0] = spok[0];

        // s p ?
        if (spok[1] != NULL_KEY) {
            it->luk[1] = spok[1];
            it->eq_fn = lookup_spk_eq_fn;

        // s ? o
        } else if (spok[2] != NULL_KEY) {
            it->luk[1] = spok[2];
            it->eq_fn = lookup_sok_eq_fn;

        // s ? ?
        } else {
            it->eq_fn = lookup_sk_eq_fn;
        }
    //it->cur = 0;

    } else if (spok[1] != NULL_KEY) {
        it->luk[0] = spok[1];

        // ? p o
        if (spok[2] != NULL_KEY) {
            it->luk[1] = spok[2];
            it->eq_fn = lookup_pok_eq_fn;

        // ? p ?
        } else it->eq_fn = lookup_pk_eq_fn;

    // ? ? o
    } else if (spok[2] != NULL_KEY) {
        it->luk[0] = spok[2];
        it->eq_fn = lookup_ok_eq_fn;

    // ? ? ?
    } else it->eq_fn = lookup_none_eq_fn;

    it->entry = it->store->keys; // First record in hash table.
    it->rc = it->entry == NULL ? LSUP_END : LSUP_OK;
    it->i = 0;

    return it;
}


void
LSUP_htiter_free (LSUP_HTIterator *it)
{ free (it); }


size_t
LSUP_htiter_cur (LSUP_HTIterator *it)
{ return it->i; }


LSUP_rc
LSUP_htiter_next (HTIterator *it, LSUP_SerTriple *sspo)
{
    // If the previous iteration hit the end, return.
    if (it->rc != LSUP_OK) return it->rc;

    it->rc = LSUP_NORESULT;

    while (it->rc == LSUP_NORESULT) {
        if (!it->entry) it->rc = LSUP_END;

        else {
            if (it->eq_fn (it->entry->key, it->luk)) {
                tkey_to_strp (it->store, it->entry->key, sspo);
                if (!sspo->s || !sspo->p || !sspo->o) return LSUP_DB_ERR;

                TRACE (
                    "Found spok: {%lx, %lx, %lx}",
                    it->entry->key[0], it->entry->key[1], it->entry->key[2]
                );

                it->rc = LSUP_OK;
                it->i++;
            }

            it->entry = it->entry->hh.next;
        }
    }
    return it->rc;
}


/* * * Statics * * */

inline static LSUP_rc
tkey_to_strp (
        const HTStore *store, const LSUP_Key spok[], LSUP_SerTriple *sspo)
{
    // owned by the store.
    IndexEntry *tmp = NULL;

    HASH_FIND (hh, store->idx, spok + 0, KLEN, tmp);
    sspo->s = tmp->sterm;
    sspo->s->size = tmp->sterm->size;

    HASH_FIND (hh, store->idx, spok + 1, KLEN, tmp);
    sspo->p = tmp->sterm;
    sspo->s->size = tmp->sterm->size;

    HASH_FIND (hh, store->idx, spok + 2, KLEN, tmp);
    if (UNLIKELY (!tmp)) return LSUP_ERROR;
    sspo->o = tmp->sterm;

    return LSUP_OK;
}