# world_bounds.ludic — the engine world-bounds system (#84): declare one Bounds
# config entity (rect + policy) and the engine keeps every moving Body inside the
# play area each frame — clamp / wrap / bounce / kill — instead of the game
# hand-clamping Position. Bounds/Body/Collider come from ludic.core. Driven by
# tick_fixed (Update integrates, LateUpdate applies the bounds).
#
# Deterministic; a full run prints:  184 -16 184 1 1
program WorldBounds {
  import "ludic.core/components.ludic"

  function tick_n(n: int) -> void { var i = 0;  while i < n { tick_fixed();  i += 1 } }
  function bi(b: bool) -> int { if b { return 1 };  return 0 }

  function clear_all() -> void {
    let pb = World.prop_id("Body")
    var e = World.query_next(pb, 0)
    while e >= 0 { despawn e;  e = World.query_next(pb, 0) }
    let pn = World.prop_id("Bounds")
    var c = World.query_next(pn, 0)
    while c >= 0 { despawn c;  c = World.query_next(pn, 0) }
  }

  entry {
    let PP = World.prop_id("Position")
    let fx = World.field_id(PP, "x")
    let PBody = World.prop_id("Body")
    let f_vx = World.field_id(PBody, "vx")

    # A. clamp (policy 0): a body running right is stopped at the right wall.
    spawn B0 { Bounds { x: 0, y: 0, w: 200, h: 200, policy: 0 } }
    spawn M0 { Position { x: 180, y: 50 }, Body { vx: fixed(10), policy: 1 }, Collider { w: 16, h: 16 } }
    var a = World.query_next(PBody, 0)
    tick_n(10)
    print(World.get(a, PP, fx))                      # 184 = 200 - 16 (box right edge at the wall)
    clear_all()

    # B. wrap (policy 1): past the right edge, it reappears on the left.
    spawn B1 { Bounds { x: 0, y: 0, w: 200, h: 200, policy: 1 } }
    spawn M1 { Position { x: 195, y: 50 }, Body { vx: fixed(10), policy: 1 }, Collider { w: 16, h: 16 } }
    a = World.query_next(PBody, 0)
    tick_n(1)
    print(World.get(a, PP, fx))                      # -16 = bx - w (wrapped to the far side)
    clear_all()

    # C. bounce (policy 2): clamp at the wall AND flip the velocity.
    spawn B2 { Bounds { x: 0, y: 0, w: 200, h: 200, policy: 2 } }
    spawn M2 { Position { x: 190, y: 50 }, Body { vx: fixed(10), policy: 1 }, Collider { w: 16, h: 16 } }
    a = World.query_next(PBody, 0)
    tick_n(1)
    print(World.get(a, PP, fx))                      # 184 (clamped at the wall)
    print(bi(World.get(a, PBody, f_vx) < 0))         # 1  (vx flipped negative)
    clear_all()

    # D. kill (policy 3): a body fully outside is despawned.
    spawn B3 { Bounds { x: 0, y: 0, w: 200, h: 200, policy: 3 } }
    spawn M3 { Position { x: 300, y: 50 }, Body { vx: fixed(10), policy: 1 }, Collider { w: 16, h: 16 } }
    tick_n(1)
    var live = 0
    var q = World.query_next(PBody, 0)
    while q >= 0 { live += 1;  q = World.query_next(PBody, q + 1) }
    print(live)                                      # 0 — the out-of-bounds body was killed
  }
}