#ifndef SIM_STEP_H
#define SIM_STEP_H

struct space;
struct sim_snapshot;
struct sim_snapshot_list;
struct sim_lookup;

/* ========================== *
 * Sim lookup
 * ========================== */

 /* Structure used to accelerate up entity lookup (rebuilt every step) */
 /* TODO: Remove this and do something better. Just a hack to de-couple old sim ctx from step. */

struct sim_lookup_key {
    u64 hash;
};

struct sim_lookup_entry {
    struct sim_lookup_key key;
    struct sim_ent_handle ent;
    struct sim_lookup_entry *next;
    struct sim_lookup_entry *prev;
};

struct sim_lookup_bucket {
    struct sim_lookup_entry *first;
    struct sim_lookup_entry *last;
};

struct sim_lookup {
    struct arena arena;
    struct sim_lookup_bucket *buckets;
    u64 num_buckets;
    struct sim_lookup_entry *first_free_entry;
};

struct sim_lookup sim_lookup_alloc(u64 num_buckets);
void sim_lookup_release(struct sim_lookup *l);
void sim_lookup_reset(struct sim_lookup *l);

struct sim_lookup_entry *sim_lookup_get(struct sim_lookup *l, struct sim_lookup_key key);
void sim_lookup_set(struct sim_lookup *l, struct sim_lookup_key key, struct sim_ent_handle handle);
void sim_lookup_remove(struct sim_lookup *l, struct sim_lookup_entry *entry);


struct sim_lookup_key sim_lookup_key_from_two_handles(struct sim_ent_handle h0, struct sim_ent_handle h1);

/* ========================== *
 * Sim accel
 * ========================== */

 /* Structure used to accelerate up entity lookup (rebuilt every step) */
 /* TODO: Remove this and do something better. Just a hack to de-couple old sim ctx from step. */

struct sim_accel {
    struct space *space;
    struct sim_lookup contact_lookup;
#if COLLIDER_DEBUG
    struct sim_lookup collision_debug_lookup;
#endif
};

struct sim_accel sim_accel_alloc(void);
void sim_accel_release(struct sim_accel *accel);
void sim_accel_rebuild(struct sim_snapshot *ss, struct sim_accel *accel);

/* ========================== *
 * Sim step
 * ========================== */

struct sim_step_ctx {
    b32 is_master;
    struct sim_accel *accel;
    struct sim_snapshot *world;
    i64 sim_dt_ns;
};

void sim_step(struct sim_step_ctx *ctx);

#endif