public/shared.js

export function formatTime(ms) {
  // Truncate to show only seconds and hundredths (SS.hh)
  const totalMs = Math.max(0, Math.floor(ms));
  const seconds = Math.floor((totalMs / 1000) % 60);
  const hundredths = Math.floor((totalMs % 1000) / 10); // truncate, not round
  const S = seconds.toString().padStart(2, "0");
  const H = hundredths.toString().padStart(2, "0");
  return `${S}.${H}`;
}

export function createSmoothRenderer({ setText }) {
  let baseElapsedMs = 0;
  let t0 = performance.now();
  let running = false;

  function applyServerState({ running: run, elapsedMs }) {
    running = run;
    baseElapsedMs = elapsedMs;
    t0 = performance.now();
  }

  function loop() {
    const now = performance.now();
    const ms = baseElapsedMs + (running ? now - t0 : 0);
    setText(formatTime(ms));
    requestAnimationFrame(loop);
  }

  requestAnimationFrame(loop);
  return { applyServerState };
}