'use strict';

(() => {
  const monthImage = document.getElementById('month-image');
  const monthPeriod = document.getElementById('month-period');
  const decadeDay = document.getElementById('decade-day');
  const republicanDate = document.getElementById('republican-date');
  const republicanYear = document.getElementById('republican-year');
  const sextileBadge = document.getElementById('sextile-badge');
  const gregorianEquivalentValue = document.getElementById('gregorian-equivalent-value');
  const monthName = document.getElementById('month-name');
  const monthSeasonSuffix = document.getElementById('month-season-suffix');
  const monthEtymology = document.getElementById('month-etymology');
  const monthDescription = document.getElementById('month-description');

  const dateInput = document.getElementById('date-input');
  const convertForm = document.getElementById('convert-form');
  const todayButton = document.getElementById('today-button');
  const formError = document.getElementById('form-error');

  const viewHome = document.getElementById('view-home');
  const viewAbout = document.getElementById('view-about');
  const aboutTitle = document.getElementById('about-title');
  const aboutContent = document.getElementById('about-content');

  const menuToggle = document.getElementById('menu-toggle');
  const mainNav = document.getElementById('main-nav');
  const navBackdrop = document.getElementById('nav-backdrop');
  const langSwitch = document.getElementById('lang-switch');

  const ABOUT_ROUTES = {
    'about/history': 'history',
    'about/leap-years': 'leapYears',
    'about/complementary-days': 'complementaryDays',
  };

  let lastRepublicanResult = null;

  function pad(value) {
    return String(value).padStart(2, '0');
  }

  function toIsoDate({ year, month, day }) {
    return `${String(year).padStart(4, '0')}-${pad(month)}-${pad(day)}`;
  }

  function formatGregorian({ year, month, day }, weekdayKey) {
    const weekdayLabel = I18N.t(`weekdays.${weekdayKey}`, '');
    return `${weekdayLabel} ${pad(day)}/${pad(month)}/${year}`.trim();
  }

  function closeMenu() {
    mainNav.classList.remove('open');
    mainNav.setAttribute('aria-hidden', 'true');
    navBackdrop.hidden = true;
    menuToggle.setAttribute('aria-expanded', 'false');
  }

  function openMenu() {
    mainNav.classList.add('open');
    mainNav.setAttribute('aria-hidden', 'false');
    navBackdrop.hidden = false;
    menuToggle.setAttribute('aria-expanded', 'true');
  }

  function renderRepublicanResult(result) {
    lastRepublicanResult = result;
    const months = I18N.months.months || {};
    const decadeDays = I18N.months.decadeDays || {};
    const complementary = I18N.months.complementaryDays || { days: {} };

    sextileBadge.hidden = !result.isSextile;
    gregorianEquivalentValue.textContent = formatGregorian(result.gregorianDate, result.gregorianWeekdayKey);
    republicanYear.textContent = `${I18N.t('home.yearLabel')} ${result.republicanYearRoman} (${result.republicanYear})`;

    if (result.isComplementaryDay) {
      const day = complementary.days[result.complementaryDayKey] || {};
      decadeDay.textContent = complementary.title || '';
      republicanDate.textContent = day.name || '';
      monthImage.src = 'assets/months/complementary.svg';
      monthImage.alt = day.name || '';
      monthPeriod.textContent = '';
      monthName.textContent = day.name || '';
      monthSeasonSuffix.textContent = '';
      monthEtymology.textContent = '';
      monthDescription.textContent = day.description || '';
    } else {
      const month = months[result.monthKey] || {};
      const seasonSuffix = (I18N.months.seasonSuffix || {})[month.season] || '';
      decadeDay.textContent = decadeDays[result.decadeDayKey] || '';
      republicanDate.textContent = `${result.dayOfMonth} ${month.name || ''}`.trim();
      monthImage.src = `assets/months/${result.monthKey}.svg`;
      monthImage.alt = month.name || '';
      monthPeriod.textContent = month.period || '';
      monthName.textContent = month.name || '';
      monthSeasonSuffix.textContent = seasonSuffix;
      monthEtymology.textContent = month.etymology || '';
      monthDescription.textContent = month.description || '';
    }
  }

  function showFormError(messageKey) {
    formError.textContent = I18N.t(messageKey);
    formError.hidden = false;
  }

  function hideFormError() {
    formError.hidden = true;
    formError.textContent = '';
  }

  async function fetchAndRender(url) {
    hideFormError();
    const response = await fetch(url);
    const payload = await response.json();
    if (!payload.ok) {
      if (payload.error === 'BEFORE_EPOCH') {
        showFormError('form.errorBeforeEpoch');
      } else if (payload.error === 'INVALID_DATE') {
        showFormError('form.errorInvalid');
      } else {
        showFormError('form.errorGeneric');
      }
      return;
    }
    renderRepublicanResult(payload.republicanDate);
    dateInput.value = toIsoDate(payload.republicanDate.gregorianDate);
  }

  async function loadToday() {
    try {
      await fetchAndRender('/api/today');
    } catch (error) {
      showFormError('form.errorGeneric');
    }
  }

  async function handleConvertSubmit(event) {
    event.preventDefault();
    const value = dateInput.value; // yyyy-mm-dd from <input type="date">
    if (!value) return;
    const [year, month, day] = value.split('-').map((part) => Number.parseInt(part, 10));
    try {
      await fetchAndRender(`/api/convert?year=${year}&month=${month}&day=${day}`);
    } catch (error) {
      showFormError('form.errorGeneric');
    }
  }

  function renderAboutView(sectionKey) {
    const section = I18N.about[sectionKey];
    if (!section) return;
    aboutTitle.textContent = section.title;
    aboutContent.innerHTML = '';
    (section.sections || []).forEach((block) => {
      const heading = document.createElement('h2');
      heading.textContent = block.heading;
      aboutContent.appendChild(heading);
      (block.paragraphs || []).forEach((paragraph) => {
        const p = document.createElement('p');
        p.textContent = paragraph;
        aboutContent.appendChild(p);
      });
    });
  }

  function route() {
    const hash = window.location.hash.replace(/^#\/?/, '');
    closeMenu();

    document.querySelectorAll('.nav-link').forEach((link) => link.classList.remove('active'));

    if (hash in ABOUT_ROUTES) {
      viewHome.hidden = true;
      viewAbout.hidden = false;
      renderAboutView(ABOUT_ROUTES[hash]);
      const activeLink = document.querySelector(`.nav-link[href="#/${hash}"]`);
      if (activeLink) activeLink.classList.add('active');
    } else {
      viewHome.hidden = false;
      viewAbout.hidden = true;
      const activeLink = document.querySelector('.nav-link[href="#/"]');
      if (activeLink) activeLink.classList.add('active');
    }
  }

  function bindEvents() {
    menuToggle.addEventListener('click', () => {
      if (mainNav.classList.contains('open')) {
        closeMenu();
      } else {
        openMenu();
      }
    });
    navBackdrop.addEventListener('click', closeMenu);
    window.addEventListener('hashchange', route);

    convertForm.addEventListener('submit', handleConvertSubmit);
    todayButton.addEventListener('click', () => {
      loadToday();
    });

    langSwitch.addEventListener('click', async () => {
      const nextLang = I18N.currentLang === 'fr' ? 'en' : 'fr';
      await I18N.setLang(nextLang);
    });

    I18N.onChange((lang) => {
      langSwitch.textContent = lang.toUpperCase();
      if (lastRepublicanResult) {
        renderRepublicanResult(lastRepublicanResult);
      }
      if (!viewAbout.hidden) {
        const hash = window.location.hash.replace(/^#\/?/, '');
        if (hash in ABOUT_ROUTES) renderAboutView(ABOUT_ROUTES[hash]);
      }
    });
  }

  async function init() {
    bindEvents();
    const initialLang = I18N.detectInitialLang();
    await I18N.load(initialLang);
    langSwitch.textContent = initialLang.toUpperCase();
    route();
    await loadToday();
  }

  init();
})();