(function () {
  'use strict';

  const form = document.getElementById('form');
  const box = document.getElementById('digits');
  const inputs = [...box.querySelectorAll('input')];
  const errorEl = document.getElementById('error');
  const submitBtn = document.getElementById('submit');
  let busy = false;

  const value = () => inputs.map((i) => i.value).join('');

  function fill(digits, from) {
    let i = from;
    for (const d of digits) {
      if (i >= inputs.length) break;
      inputs[i++].value = d;
    }
    inputs[Math.min(i, inputs.length - 1)].focus();
    if (value().length === 6) submit();
  }

  inputs.forEach((input, idx) => {
    input.addEventListener('input', () => {
      const digits = input.value.replace(/\D/g, '');
      input.value = '';
      if (digits) fill(digits, idx);
      errorEl.textContent = '';
    });
    input.addEventListener('keydown', (e) => {
      if (e.key === 'Backspace' && !input.value && idx > 0) {
        inputs[idx - 1].value = '';
        inputs[idx - 1].focus();
        e.preventDefault();
      } else if (e.key === 'ArrowLeft' && idx > 0) {
        inputs[idx - 1].focus();
      } else if (e.key === 'ArrowRight' && idx < inputs.length - 1) {
        inputs[idx + 1].focus();
      }
    });
    input.addEventListener('paste', (e) => {
      const digits = (e.clipboardData.getData('text') || '').replace(/\D/g, '');
      if (!digits) return;
      e.preventDefault();
      fill(digits, idx);
    });
    input.addEventListener('focus', () => input.select());
  });

  async function submit() {
    if (busy) return;
    const key = value();
    if (key.length !== 6) {
      errorEl.textContent = '6桁すべて入力してください。';
      return;
    }
    busy = true;
    submitBtn.disabled = true;
    try {
      await App.api('POST', '/api/auth', { key });
      const next = new URLSearchParams(location.search).get('next');
      location.replace(App.safeNext(next));
    } catch (err) {
      errorEl.textContent = err.message;
      box.classList.remove('shake');
      void box.offsetWidth;
      box.classList.add('shake');
      inputs.forEach((i) => { i.value = ''; });
      inputs[0].focus();
    } finally {
      busy = false;
      submitBtn.disabled = false;
    }
  }

  form.addEventListener('submit', (e) => {
    e.preventDefault();
    submit();
  });

  inputs[0].focus();
})();