Robots signaling each other

# Robots signaling each other: three robots, each a real fiber (a real OS
# thread under the hood, or a real WASI-threads Worker when compiled to
# wasm32-wasip1-threads), navigate toward waypoints on a small grid. When a
# robot reaches a waypoint it calls emit("signal", ...) -- a `when signal`
# handler registered on the MAIN thread fires and prints the announcement,
# demonstrating that events now cross real thread boundaries (see the
# EVENT_HANDLERS fix: it used to be thread_local, so a fiber's emit() was a
# silent no-op; now it's a shared, Mutex-protected registry visible from
# any thread this runtime spawns).
#
# Movement steps are yielded one at a time (fiber_yield) and printed by
# whichever thread calls fiber_resume -- the main thread in this program,
# driving all three robots round-robin -- so the full step-by-step path is
# always captured in program order regardless of execution target.

when signal do
  print("SIGNAL " + event_data)
end

make a function called robot takes info returns done
  let id = info[0]
  let mut x = info[1]
  let mut y = info[2]
  let waypoints = info[3]
  let mut wi = 0
  let wp_count = to_num(list_len(waypoints))
  while wi < wp_count do
    let wp = list_get(waypoints, wi)
    let tx = wp[0]
    let ty = wp[1]
    while (x != tx) or (y != ty) do
      if x < tx then
        x = x + 1
      else
        if x > tx then
          x = x - 1
        end
      end
      if y < ty then
        y = y + 1
      else
        if y > ty then
          y = y - 1
        end
      end
      fiber_yield(id + "," + x + "," + y)
    end
    emit("signal", id + " reached (" + x + "," + y + ")")
    wi = wi + 1
  end
  return id + ",DONE"
end

let r0 = fiber_new("robot")
let r1 = fiber_new("robot")
let r2 = fiber_new("robot")

let v0 = fiber_resume(r0, ["R0", 0, 0, [[5, 2], [9, 5]]])
print(v0)
let v1 = fiber_resume(r1, ["R1", 9, 0, [[4, 3], [0, 5]]])
print(v1)
let v2 = fiber_resume(r2, ["R2", 0, 5, [[7, 4], [9, 0]]])
print(v2)

let mut done0 = false
let mut done1 = false
let mut done2 = false
while not (done0 and done1 and done2) do
  if not done0 then
    let v0 = fiber_resume(r0, 0)
    print(v0)
    if v0 == "R0,DONE" then
      done0 = true
    end
  end
  if not done1 then
    let v1 = fiber_resume(r1, 0)
    print(v1)
    if v1 == "R1,DONE" then
      done1 = true
    end
  end
  if not done2 then
    let v2 = fiber_resume(r2, 0)
    print(v2)
    if v2 == "R2,DONE" then
      done2 = true
    end
  end
end
print("all robots done")