#include "cache.h"
#include "object.h"
#include "pack.h"
#include "pack-objects.h"
#include "packfile.h"
#include "config.h"

static uint32_t locate_object_entry_hash(struct packing_data *pdata,
                                         const unsigned char *sha1,
                                         int *found)
{
        uint32_t i, mask = (pdata->index_size - 1);

        i = sha1hash(sha1) & mask;

        while (pdata->index[i] > 0) {
                uint32_t pos = pdata->index[i] - 1;

                if (!hashcmp(sha1, pdata->objects[pos].idx.oid.hash)) {
                        *found = 1;
                        return i;
                }

                i = (i + 1) & mask;
        }

        *found = 0;
        return i;
}

static inline uint32_t closest_pow2(uint32_t v)
{
        v = v - 1;
        v |= v >> 1;
        v |= v >> 2;
        v |= v >> 4;
        v |= v >> 8;
        v |= v >> 16;
        return v + 1;
}

static void rehash_objects(struct packing_data *pdata)
{
        uint32_t i;
        struct object_entry *entry;

        pdata->index_size = closest_pow2(pdata->nr_objects * 3);
        if (pdata->index_size < 1024)
                pdata->index_size = 1024;

        free(pdata->index);
        pdata->index = xcalloc(pdata->index_size, sizeof(*pdata->index));

        entry = pdata->objects;

        for (i = 0; i < pdata->nr_objects; i++) {
                int found;
                uint32_t ix = locate_object_entry_hash(pdata,
                                                       entry->idx.oid.hash,
                                                       &found);

                if (found)
                        BUG("Duplicate object in hash");

                pdata->index[ix] = i + 1;
                entry++;
        }
}

struct object_entry *packlist_find(struct packing_data *pdata,
                                   const unsigned char *sha1,
                                   uint32_t *index_pos)
{
        uint32_t i;
        int found;

        if (!pdata->index_size)
                return NULL;

        i = locate_object_entry_hash(pdata, sha1, &found);

        if (index_pos)
                *index_pos = i;

        if (!found)
                return NULL;

        return &pdata->objects[pdata->index[i] - 1];
}

static void prepare_in_pack_by_idx(struct packing_data *pdata)
{
        struct packed_git **mapping, *p;
        int cnt = 0, nr = 1U << OE_IN_PACK_BITS;

        ALLOC_ARRAY(mapping, nr);
        /*
         * oe_in_pack() on an all-zero'd object_entry
         * (i.e. in_pack_idx also zero) should return NULL.
         */
        mapping[cnt++] = NULL;
        for (p = get_packed_git(the_repository); p; p = p->next, cnt++) {
                if (cnt == nr) {
                        free(mapping);
                        return;
                }
                p->index = cnt;
                mapping[cnt] = p;
        }
        pdata->in_pack_by_idx = mapping;
}

/*
 * A new pack appears after prepare_in_pack_by_idx() has been
 * run. This is likely a race.
 *
 * We could map this new pack to in_pack_by_idx[] array, but then we
 * have to deal with full array anyway. And since it's hard to test
 * this fall back code, just stay simple and fall back to using
 * in_pack[] array.
 */
void oe_map_new_pack(struct packing_data *pack,
                     struct packed_git *p)
{
        uint32_t i;

        REALLOC_ARRAY(pack->in_pack, pack->nr_alloc);

        for (i = 0; i < pack->nr_objects; i++)
                pack->in_pack[i] = oe_in_pack(pack, pack->objects + i);

        FREE_AND_NULL(pack->in_pack_by_idx);
}

/* assume pdata is already zero'd by caller */
void prepare_packing_data(struct packing_data *pdata)
{
        if (git_env_bool("GIT_TEST_FULL_IN_PACK_ARRAY", 0)) {
                /*
                 * do not initialize in_pack_by_idx[] to force the
                 * slow path in oe_in_pack()
                 */
        } else {
                prepare_in_pack_by_idx(pdata);
        }

        pdata->oe_size_limit = git_env_ulong("GIT_TEST_OE_SIZE",
                                             1U << OE_SIZE_BITS);
        pdata->oe_delta_size_limit = git_env_ulong("GIT_TEST_OE_DELTA_SIZE",
                                                   1UL << OE_DELTA_SIZE_BITS);
}

struct object_entry *packlist_alloc(struct packing_data *pdata,
                                    const unsigned char *sha1,
                                    uint32_t index_pos)
{
        struct object_entry *new_entry;

        if (pdata->nr_objects >= pdata->nr_alloc) {
                pdata->nr_alloc = (pdata->nr_alloc  + 1024) * 3 / 2;
                REALLOC_ARRAY(pdata->objects, pdata->nr_alloc);

                if (!pdata->in_pack_by_idx)
                        REALLOC_ARRAY(pdata->in_pack, pdata->nr_alloc);
                if (pdata->delta_size)
                        REALLOC_ARRAY(pdata->delta_size, pdata->nr_alloc);
        }

        new_entry = pdata->objects + pdata->nr_objects++;

        memset(new_entry, 0, sizeof(*new_entry));
        hashcpy(new_entry->idx.oid.hash, sha1);

        if (pdata->index_size * 3 <= pdata->nr_objects * 4)
                rehash_objects(pdata);
        else
                pdata->index[index_pos] = pdata->nr_objects;

        if (pdata->in_pack)
                pdata->in_pack[pdata->nr_objects - 1] = NULL;

        return new_entry;
}