#ifndef PACK_OBJECTS_H
#define PACK_OBJECTS_H

#include "object-store.h"

#define DEFAULT_DELTA_CACHE_SIZE (256 * 1024 * 1024)

#define OE_DFS_STATE_BITS       2
#define OE_DEPTH_BITS           12
#define OE_IN_PACK_BITS         10
#define OE_Z_DELTA_BITS         20
/*
 * Note that oe_set_size() becomes expensive when the given size is
 * above this limit. Don't lower it too much.
 */
#define OE_SIZE_BITS            31
#define OE_DELTA_SIZE_BITS      20

/*
 * State flags for depth-first search used for analyzing delta cycles.
 *
 * The depth is measured in delta-links to the base (so if A is a delta
 * against B, then A has a depth of 1, and B a depth of 0).
 */
enum dfs_state {
        DFS_NONE = 0,
        DFS_ACTIVE,
        DFS_DONE,
        DFS_NUM_STATES
};

/*
 * The size of struct nearly determines pack-objects's memory
 * consumption. This struct is packed tight for that reason. When you
 * add or reorder something in this struct, think a bit about this.
 *
 * basic object info
 * -----------------
 * idx.oid is filled up before delta searching starts. idx.crc32 is
 * only valid after the object is written out and will be used for
 * generating the index. idx.offset will be both gradually set and
 * used in writing phase (base objects get offset first, then deltas
 * refer to them)
 *
 * "size" is the uncompressed object size. Compressed size of the raw
 * data for an object in a pack is not stored anywhere but is computed
 * and made available when reverse .idx is made. Note that when a
 * delta is reused, "size" is the uncompressed _delta_ size, not the
 * canonical one after the delta has been applied.
 *
 * "hash" contains a path name hash which is used for sorting the
 * delta list and also during delta searching. Once prepare_pack()
 * returns it's no longer needed.
 *
 * source pack info
 * ----------------
 * The (in_pack, in_pack_offset) tuple contains the location of the
 * object in the source pack. in_pack_header_size allows quickly
 * skipping the header and going straight to the zlib stream.
 *
 * "type" and "in_pack_type" both describe object type. in_pack_type
 * may contain a delta type, while type is always the canonical type.
 *
 * deltas
 * ------
 * Delta links (delta, delta_child and delta_sibling) are created to
 * reflect that delta graph from the source pack then updated or added
 * during delta searching phase when we find better deltas.
 *
 * delta_child and delta_sibling are last needed in
 * compute_write_order(). "delta" and "delta_size" must remain valid
 * at object writing phase in case the delta is not cached.
 *
 * If a delta is cached in memory and is compressed, delta_data points
 * to the data and z_delta_size contains the compressed size. If it's
 * uncompressed [1], z_delta_size must be zero. delta_size is always
 * the uncompressed size and must be valid even if the delta is not
 * cached.
 *
 * [1] during try_delta phase we don't bother with compressing because
 * the delta could be quickly replaced with a better one.
 */
struct object_entry {
        struct pack_idx_entry idx;
        void *delta_data;       /* cached delta (uncompressed) */
        off_t in_pack_offset;
        uint32_t hash;                  /* name hint hash */
        unsigned size_:OE_SIZE_BITS;
        unsigned size_valid:1;
        uint32_t delta_idx;     /* delta base object */
        uint32_t delta_child_idx; /* deltified objects who bases me */
        uint32_t delta_sibling_idx; /* other deltified objects who
                                     * uses the same base as me
                                     */
        unsigned delta_size_:OE_DELTA_SIZE_BITS; /* delta data size (uncompressed) */
        unsigned delta_size_valid:1;
        unsigned in_pack_idx:OE_IN_PACK_BITS;   /* already in pack */
        unsigned z_delta_size:OE_Z_DELTA_BITS;
        unsigned type_valid:1;
        unsigned type_:TYPE_BITS;
        unsigned no_try_delta:1;
        unsigned in_pack_type:TYPE_BITS; /* could be delta */
        unsigned preferred_base:1; /*
                                    * we do not pack this, but is available
                                    * to be used as the base object to delta
                                    * objects against.
                                    */
        unsigned tagged:1; /* near the very tip of refs */
        unsigned filled:1; /* assigned write-order */
        unsigned dfs_state:OE_DFS_STATE_BITS;
        unsigned char in_pack_header_size;
        unsigned depth:OE_DEPTH_BITS;

        /*
         * pahole results on 64-bit linux (gcc and clang)
         *
         *   size: 80, bit_padding: 20 bits, holes: 8 bits
         *
         * and on 32-bit (gcc)
         *
         *   size: 76, bit_padding: 20 bits, holes: 8 bits
         */
};

struct packing_data {
        struct object_entry *objects;
        uint32_t nr_objects, nr_alloc;

        int32_t *index;
        uint32_t index_size;

        unsigned int *in_pack_pos;

        /*
         * Only one of these can be non-NULL and they have different
         * sizes. if in_pack_by_idx is allocated, oe_in_pack() returns
         * the pack of an object using in_pack_idx field. If not,
         * in_pack[] array is used the same way as in_pack_pos[]
         */
        struct packed_git **in_pack_by_idx;
        struct packed_git **in_pack;

        uintmax_t oe_size_limit;
};

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

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

static inline uint32_t pack_name_hash(const char *name)
{
        uint32_t c, hash = 0;

        if (!name)
                return 0;

        /*
         * This effectively just creates a sortable number from the
         * last sixteen non-whitespace characters. Last characters
         * count "most", so things that end in ".c" sort together.
         */
        while ((c = *name++) != 0) {
                if (isspace(c))
                        continue;
                hash = (hash >> 2) + (c << 24);
        }
        return hash;
}

static inline enum object_type oe_type(const struct object_entry *e)
{
        return e->type_valid ? e->type_ : OBJ_BAD;
}

static inline void oe_set_type(struct object_entry *e,
                               enum object_type type)
{
        if (type >= OBJ_ANY)
                BUG("OBJ_ANY cannot be set in pack-objects code");

        e->type_valid = type >= OBJ_NONE;
        e->type_ = (unsigned)type;
}

static inline unsigned int oe_in_pack_pos(const struct packing_data *pack,
                                          const struct object_entry *e)
{
        return pack->in_pack_pos[e - pack->objects];
}

static inline void oe_set_in_pack_pos(const struct packing_data *pack,
                                      const struct object_entry *e,
                                      unsigned int pos)
{
        pack->in_pack_pos[e - pack->objects] = pos;
}

static inline struct packed_git *oe_in_pack(const struct packing_data *pack,
                                            const struct object_entry *e)
{
        if (pack->in_pack_by_idx)
                return pack->in_pack_by_idx[e->in_pack_idx];
        else
                return pack->in_pack[e - pack->objects];
}

void oe_map_new_pack(struct packing_data *pack,
                     struct packed_git *p);
static inline void oe_set_in_pack(struct packing_data *pack,
                                  struct object_entry *e,
                                  struct packed_git *p)
{
        if (!p->index)
                oe_map_new_pack(pack, p);
        if (pack->in_pack_by_idx)
                e->in_pack_idx = p->index;
        else
                pack->in_pack[e - pack->objects] = p;
}

static inline struct object_entry *oe_delta(
                const struct packing_data *pack,
                const struct object_entry *e)
{
        if (e->delta_idx)
                return &pack->objects[e->delta_idx - 1];
        return NULL;
}

static inline void oe_set_delta(struct packing_data *pack,
                                struct object_entry *e,
                                struct object_entry *delta)
{
        if (delta)
                e->delta_idx = (delta - pack->objects) + 1;
        else
                e->delta_idx = 0;
}

static inline struct object_entry *oe_delta_child(
                const struct packing_data *pack,
                const struct object_entry *e)
{
        if (e->delta_child_idx)
                return &pack->objects[e->delta_child_idx - 1];
        return NULL;
}

static inline void oe_set_delta_child(struct packing_data *pack,
                                      struct object_entry *e,
                                      struct object_entry *delta)
{
        if (delta)
                e->delta_child_idx = (delta - pack->objects) + 1;
        else
                e->delta_child_idx = 0;
}

static inline struct object_entry *oe_delta_sibling(
                const struct packing_data *pack,
                const struct object_entry *e)
{
        if (e->delta_sibling_idx)
                return &pack->objects[e->delta_sibling_idx - 1];
        return NULL;
}

static inline void oe_set_delta_sibling(struct packing_data *pack,
                                        struct object_entry *e,
                                        struct object_entry *delta)
{
        if (delta)
                e->delta_sibling_idx = (delta - pack->objects) + 1;
        else
                e->delta_sibling_idx = 0;
}

unsigned long oe_get_size_slow(struct packing_data *pack,
                               const struct object_entry *e);
static inline unsigned long oe_size(struct packing_data *pack,
                                    const struct object_entry *e)
{
        if (e->size_valid)
                return e->size_;

        return oe_get_size_slow(pack, e);
}

static inline int oe_size_less_than(struct packing_data *pack,
                                    const struct object_entry *lhs,
                                    unsigned long rhs)
{
        if (lhs->size_valid)
                return lhs->size_ < rhs;
        if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
                return 0;
        return oe_get_size_slow(pack, lhs) < rhs;
}

static inline int oe_size_greater_than(struct packing_data *pack,
                                       const struct object_entry *lhs,
                                       unsigned long rhs)
{
        if (lhs->size_valid)
                return lhs->size_ > rhs;
        if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
                return 1;
        return oe_get_size_slow(pack, lhs) > rhs;
}

static inline void oe_set_size(struct packing_data *pack,
                               struct object_entry *e,
                               unsigned long size)
{
        if (size < pack->oe_size_limit) {
                e->size_ = size;
                e->size_valid = 1;
        } else {
                e->size_valid = 0;
                if (oe_get_size_slow(pack, e) != size)
                        BUG("'size' is supposed to be the object size!");
        }
}

static inline unsigned long oe_delta_size(struct packing_data *pack,
                                          const struct object_entry *e)
{
        if (e->delta_size_valid)
                return e->delta_size_;
        return oe_size(pack, e);
}

static inline void oe_set_delta_size(struct packing_data *pack,
                                     struct object_entry *e,
                                     unsigned long size)
{
        e->delta_size_ = size;
        e->delta_size_valid = e->delta_size_ == size;
        if (!e->delta_size_valid && size != oe_size(pack, e))
                BUG("this can only happen in check_object() "
                    "where delta size is the same as entry size");
}

#endif