#ifndef MT_SHADOW_H
#define MT_SHADOW_H

#include <librr/types.h>
#include <shadow-tag.h>

typedef struct MtShadowRegistry MtShadowRegistry;
typedef struct MtShadow MtShadow;
typedef struct MtShadowPool MtShadowPool;
typedef struct MtShadowLookupTree MtShadowLookupTree;

/// @brief: An MtShadow contains the actual information which is used
///  each time when an entity is modified. It contains the tags and
///  other meta-information as well as data required for optimization.
struct MtShadow
{
    void *context;
    MtShadowTag *tag_chain_start;
    u32_t identifier;

    MtShadowPool *pool;
    MtShadow *pool_next;
};

struct MtShadowPool
{
    usz_t capacity;
    MtShadow *shadows;
    MtShadow *first_free;
    MtShadowPool *continuation;
};

typedef struct MtShadowLookupLevel3
{
    MtShadow *next[256];
} MtShadowLookupLevel3;

typedef struct MtShadowLookupLevel2
{
    MtShadowLookupLevel3 *next[256];
} MtShadowLookupLevel2;

typedef struct MtShadowLookup1
{
    MtShadowLookupLevel2 *next[256];
} MtShadowLookupLevel1;

struct MtShadowLookupTree
{
    MtShadowLookupLevel1 *next[256];
};

struct MtShadowRegistry
{
    // TODO: The IDs must be assigned using a singly linked list of indices
    // to the next free entry, the index representing the ID's value and having
    // stored the next free entry's index. Conceptually similar to the internals
    // of the old File Allocation Table filesystems (FAT12, FAT16, FAT32).
    u32_t id_counter;
    MtShadowPool root_pool;
    MtShadowLookupTree lookup_tree;
    void *context_ptr;
};

MtShadowRegistry mt_create_shadow_registry(void *context_ptr);
void mt_cleanup_shadow_registry(MtShadowRegistry *registry);

MtShadow * mt_create_shadow(MtShadowRegistry *registry);
MtShadow * mt_lookup_shadow(MtShadowRegistry *registry, u32_t identifier);
void mt_delete_shadow(MtShadowRegistry *registry, MtShadow *shadow);

void mt_cleanup_shadow_pool(MtShadowPool *pool);
void mt_free_shadow_pool(MtShadowPool *pool);
MtShadowLookupTree mt_create_shadow_lookup_tree();

void mt_init_shadow_pool(MtShadowPool *pool, usz_t capacity);
MtShadowPool * mt_new_shadow_pool(usz_t capacity);
MtShadow * mt_pool_shadow(MtShadowPool *pool);
void mt_unpool_shadow(MtShadow *shadow);

#endif // MT_SHADOW_H