Modelling Formula One qualifying as a state machine

f1-qualifying-state-machine.js

const S1Time = Symbol('S1Time');

function DriverTime() {
  function* NoTime() {
    yield on('sector1Set', SectorTime, id('Sector1'));
    yield on('sector2Set', SectorTime, id('Sector2'));
    yield on('sector3Set', SectorTime, id('Sector3'));
  }
  
  function* SectorTime() {
    const previousBest = yield read('bestTime');
    const newTime = yield read('duration');
    const runIndex = yield read('runIndex');
    yield cond(previousBest == null, set('bestTime', newTime));
    yield cond(newTime < previousBest, set('bestTime', newTime));
    // Or:
    yield new Map([
      [previousBest == null, set('bestTime', newTime)],
      [newTime < previousBest, set('bestTime', newTime)],
    ]);
  }
  
  return NoTime;
}