18. Tester prędkości pisania

function useTypingTest(targetText) {
  const [input, setInput] = useState('');
  const [startTime, setStartTime] = useState(null);
  const [finished, setFinished] = useState(false);

  function handleInput(e) {
    const value = e.target.value;
    if (!startTime && value.length === 1) setStartTime(Date.now());
    setInput(value);
    if (value === targetText) setFinished(true);
  }

  const wpm = useMemo(() => {
    if (!startTime || !finished) return 0;
    const minutes = (Date.now() - startTime) / 60000;
    const words = targetText.split(' ').length;
    return Math.round(words / minutes);
  }, [finished, startTime, targetText]);

  const accuracy = useMemo(() => {
    if (!input.length) return 100;
    let correct = 0;
    for (let i = 0; i < input.length; i++) {
      if (input[i] === targetText[i]) correct++;
    }
    return Math.round((correct / input.length) * 100);
  }, [input, targetText]);

  return { input, handleInput, wpm, accuracy, finished };
}