ludic/examples/networking/net_roles.ludic

# net_roles.ludic — N5: handler roles + the drivable sim (NETWORKING-DESIGN §6.2,
# §5, §13 N5).
#
# A handler's network role is a declarative annotation, never a runtime branch in
# ordinary code:
#   (unmarked)  runs on every peer — the shared, deterministic simulation
#   @Server     runs only on the authority (clients get the result via @Sync)
#   @Predicted  runs on the owning client and the server (auto-reconciled)
# The runtime sets the peer's role register (set_role); offline it defaults to
# server, so guards collapse to "run here" and a non-networked build is unchanged.
#
# The per-frame phases are also exposed as callables — tick_fixed() runs the sim
# phases — so this game owns its own loop via `entry` (for prediction/rollback,
# replay, headless tests). Acting as a client then the server: 1, then 102.
program NetRoles {
  property Score { n: int = 0 }
  model Board { Score }

  handler Both phase Update { for (Score) in query [Score] { Score.n = Score.n + 1 } }        # runs everywhere
  @Server handler ServerOnly phase Update { for (Score) in query [Score] { Score.n = Score.n + 100 } }   # authority only

  entry {
    spawn Board { Score { n: 0 } }

    set_role(0)                                  # act as a client
    tick_fixed()                                 # Both(+1); ServerOnly skipped
    for (Score) in query [Score] { print(Score.n) }   # 1

    set_role(1)                                  # act as the server
    tick_fixed()                                 # Both(+1) + ServerOnly(+100)
    for (Score) in query [Score] { print(Score.n) }   # 102
  }
}