# net_snapshot.ludic — N1: whole-world snapshot to a memory buffer
# (NETWORKING-DESIGN §5, §13 N1). The rollback/replication substrate.
#
# save()/load() snapshot the entire ECS world to a file; world_size/world_save/
# world_load generalize the identical layout to a caller-owned memory buffer:
#   world_size()          -> exact snapshot byte count
#   world_save(buf)       -> bytes written (entities, components, vars)
#   world_load(buf, len)  -> restore the world from those bytes
# That is all rollback needs (save → predict → on misprediction restore and
# re-sim) and all state replication needs (snapshot → ship → apply). This program
# spawns a Unit (hp 50), snapshots the world, mutates hp to 7, then restores — hp
# reads back 50. Prints 50 / 7 / 50, driven entirely from Ludic (no C host).
program NetSnapshot {
  property Health { hp: int = 0, max: int = 0 }
  model Unit { Health }

  entry {
    unsafe {                                 # raw buffers on purpose: built with --unsafe (L7)
      spawn Unit { Health { hp: 50, max: 100 } }
      let buf = bytes(world_size())
      for (Health) in query [Health, {Unit}] {
        print(Health.hp)                    # 50
        let n = world_save(buf)             # snapshot the whole world
        Health.hp = 7
        print(Health.hp)                    # 7
        world_load(buf, n)                  # roll the world back
        print(Health.hp)                    # 50 — restored from bytes
      }
    }
  }
}