ludic/examples/networking/net_demo.ludic

# net_demo.ludic — N6: a networked game end to end, in pure Ludic, no C at all
# (NETWORKING-DESIGN §13 N6). It exercises the whole stack the earlier phases
# built: an RPC carries client input to the authority (N4), the authority mutates
# authoritative state (N5 roles), and the blessed runtime replicates that state
# back to a peer that had diverged (N2 @Sync + N3 @Owned + net_rt.ludic).
#
# One process, one loopback transport, so the round-trips are observable. The
# sequence a real client/server splits across machines is played here in order:
#
#   1. client emits Move(dx:5)   — an @ToServer RPC → serialized onto the wire
#   2. net_pump()                — the authority drains it, @On(Move) applies +5
#   3. rt_replicate(ship)        — the authority ships the ship's synced state
#   4. Pos.x = 999               — the client diverges (mispredicts)
#   5. rt_receive()              — the client reconciles to the authoritative x=5
#
# Prints 5 / 999 / 5. Build & run with the Ludic toolchain only:
#   bin/x app examples/networking/net_demo.ludic --headless && ./build/net_demo_headless
import "net_rt.ludic"

program NetDemo {
  @Sync property Pos { x: int = 0, y: int = 0 }
  @Owned model Ship { @Sync Pos }

  @ToServer event Move { dx: int = 0 }                        # client → server RPC
  @On(Move) handler DoMove {                                  # the authority applies input
    for (Pos) in query [Pos, {Ship}] { Pos.x = Pos.x + dx }
  }

  entry {
    spawn Ship { Pos { x: 0, y: 0 } }

    emit Move(dx: 5)                                          # 1. client input → wire
    net_pump()                                               # 2. authority applies it

    for (Pos) in query [Pos, {Ship}] {
      print(Pos.x)                                            # 5  — server state advanced
      rt_replicate(self())                                    # 3. authority replicates
      Pos.x = 999                                             # 4. client diverges
      print(Pos.x)                                            # 999
    }

    rt_receive()                                             # 5. client reconciles
    for (Pos) in query [Pos, {Ship}] { print(Pos.x) }        # 5  — back to authoritative
  }
}