#ifndef SIM_SNAPSHOT_H
#define SIM_SNAPSHOT_H

#include "sim_ent.h"
#include "sim_client.h"



/* TODO: Remove this */
struct space;






struct sim_snapshot_store {
    b32 valid;
    struct arena arena;

    /* Snapshots sorted by tick (low to high) */
    u64 first_tick;
    u64 last_tick;
    u64 num_ticks;

    struct sim_snapshot *first_free_snapshot;

    /* Tick -> snapshot lookup */
    u64 num_lookup_buckets;
    struct sim_snapshot_lookup_bucket *lookup_buckets;
};

struct sim_snapshot {
    b32 valid;
    u64 tick;
    struct sim_snapshot_store *store;
    struct sim_snapshot *next_free;
    struct sim_snapshot *next_in_bucket;
    struct sim_snapshot *prev_in_bucket;
    u64 prev_tick;
    u64 next_tick;

    struct arena arena;

    /* Real time (increases with clock assuming no lag) */
    i64 real_dt_ns;
    i64 real_time_ns;

    /* World time (affected by timescale) */
    f64 world_timescale;
    i64 world_dt_ns;
    i64 world_time_ns;

    /* When was this snapshot received */
    i64 received_at_ns;

    /* If != previous tick's continuity then don't lerp */
    u64 continuity_gen;

    /* The last physics iteration (used for tracking contact lifetime) */
    u64 phys_iteration;

    /* Which client in the client store represents the local host in the original snapshot */
    struct sim_client_handle local_client;

    /* Client lookup */
    struct sim_client_lookup_bucket *client_lookup_buckets;
    u64 num_client_lookup_buckets;

    /* Clients */
    struct arena clients_arena;
    struct sim_client *clients;
    struct sim_client_handle first_free_client;
    u64 num_clients_allocated;
    u64 num_clients_reserved;

    /* Entities */
    struct arena ents_arena;
    struct sim_ent *ents;
    struct sim_ent_handle first_free_ent;
    u64 num_ents_allocated;
    u64 num_ents_reserved;
};

/* ========================== *
 * Startup
 * ========================== */

struct sim_snapshot_startup_receipt { i32 _; };
struct sim_snapshot_startup_receipt sim_snapshot_startup(void);

/* ========================== *
 * Store
 * ========================== */

struct sim_snapshot_store *sim_snapshot_store_alloc(void);
void sim_snapshot_store_release(struct sim_snapshot_store *store);
void sim_snapshot_store_release_ticks_in_range(struct sim_snapshot_store *store, u64 start, u64 end);

/* ========================== *
 * Nil
 * ========================== */

INLINE struct sim_snapshot *sim_snapshot_nil(void)
{
    extern READONLY struct sim_snapshot **_g_sim_snapshot_nil;
    return *_g_sim_snapshot_nil;
}

INLINE struct sim_snapshot_store *sim_snapshot_store_nil(void)
{
    extern READONLY struct sim_snapshot_store **_g_sim_snapshot_store_nil;
    return *_g_sim_snapshot_store_nil;
}

/* ========================== *
 * Snapshot
 * ========================== */

struct bitbuff_writer;
struct bitbuff_reader;

/* Alloc */
struct sim_snapshot *sim_snapshot_alloc(struct sim_snapshot_store *store, struct sim_snapshot *src, u64 tick);
void sim_snapshot_release(struct sim_snapshot *sim_snapshot);

/* Lookup */
struct sim_snapshot *sim_snapshot_from_tick(struct sim_snapshot_store *store, u64 tick);

/* Lerp */
struct sim_snapshot *sim_snapshot_alloc_from_lerp(struct sim_snapshot_store *store, struct sim_snapshot *ss0, struct sim_snapshot *ss1, f64 blend);

/* Encode / decode */
void sim_snapshot_encode(struct bitbuff_writer *bw, struct sim_snapshot *ss0, struct sim_snapshot *ss1, struct sim_client *client);
void sim_snapshot_decode(struct bitbuff_reader *br, struct sim_snapshot *ss);


#endif