Made of little things.

// Runs the PIT bot until a successful PIT, then plays the replay loop twice and checks that
// no car appears or disappears partway through. Run with: bun tools/replay-check.ts
import { Recorder } from '../src/game/replay.ts';
import { Sim, forwardSpeed, wrapAngle, type Input } from '../src/game/sim.ts';

function bot(sim: Sim): Input {
  const p = sim.player, t = sim.suspect, gap = t.s - p.s, side = p.x <= t.x ? -1 : 1;
  const tx = gap < 7 && gap > 1 ? t.x + side * 1.2 : gap < 25 ? t.x + side * 2.2 : t.x;
  const wantYaw = Math.max(-0.25, Math.min(0.25, (tx - p.x) * 0.12 - p.vx * 0.05));
  const closing = forwardSpeed(p) - forwardSpeed(t);
  return { throttle: gap > 20 ? 1 : closing > (gap - 3) * 0.8 ? -0.4 : 1, steer: Math.max(-1, Math.min(1, (wantYaw - wrapAngle(p.yaw)) * 6)) };
}

for (let attempt = 0; attempt < 10; attempt++) {
  const sim = new Sim(1);
  const rec = new Recorder();
  let pitAt = -1;
  while (sim.time < 240) {
    sim.step(1 / 120, pitAt < 0 ? bot(sim) : { throttle: 0, steer: 0 });
    rec.record(sim);
    sim.events.length = 0;
    if (pitAt < 0 && sim.outcome === 'pit') pitAt = sim.time;
    if (pitAt >= 0 && sim.time > pitAt + 2.5) break;
    if (pitAt < 0 && sim.outcome !== 'running') break;
  }
  if (pitAt < 0) continue;
  const replay = rec.replay(sim.lastRearHit);
  let ids: string | null = null, frames = 0, changes = 0, loops = 0;
  while (loops < 2 && frames < 5000) {
    replay.advance(1 / 60);
    if (replay.camera().snap && frames > 0) loops++;
    const now = replay.state().cars.map((c) => c.id).sort((a, b) => a - b).join(',');
    if (ids !== null && now !== ids) changes++;
    ids = now;
    frames++;
  }
  console.log(`PIT at ${pitAt.toFixed(1)}s; ${frames} replay frames over ${loops} loops; ${ids!.split(',').length} cars; car set changed ${changes} times`);
  process.exit(changes ? 1 : 0);
}
console.log('no PIT in 10 attempts');