breadcrumb-the-shire/web/js/components/app-theme-toggle.js

/**
 * Theme switcher — light/dark toggle and menu with server-side persistence.
 */
import { optionalEl, warnOnce } from '../core/app-dom.js';

const setTheme = (theme) => {
  document.documentElement.dataset.theme = theme;
};

const isDarkTheme = (theme) => theme && theme.startsWith('dark');

const setIcon = (iconEl, theme) => {
  if (!iconEl) {return;}
  iconEl.classList.remove('bi-sun-fill', 'bi-moon-stars-fill');
  iconEl.classList.add(isDarkTheme(theme) ? 'bi-moon-stars-fill' : 'bi-sun-fill');
};

const updateTheme = async (menu, theme) => {
  const url = menu.dataset.themeUrl;
  const csrfKey = menu.dataset.csrfKey;
  const csrfToken = menu.dataset.csrfToken;
  if (!url || !csrfKey || !csrfToken) {
    return true;
  }
  const body = new URLSearchParams({ theme, [csrfKey]: csrfToken });
  const response = await fetch(url, {
    method: 'POST',
    headers: {
      'Content-Type': 'application/x-www-form-urlencoded',
      'Accept': 'application/json',
      'X-Requested-With': 'fetch'
    },
    body
  });
  return response.ok;
};

const initThemeMenu = () => {
  const menu = optionalEl('[data-theme-menu]');
  if (!menu) {return;}
  const icon = menu.querySelector('[data-theme-icon]');
  const options = Array.from(menu.querySelectorAll('[data-theme-option]'));
  if (!options.length) {
    warnOnce('UI_EL_MISSING', 'Missing theme options', { module: 'theme-toggle' });
    return;
  }

  let pending = false;
  const getCurrent = () => document.documentElement.dataset.theme || '';
  const setActive = (theme) => {
    options.forEach((option) => {
      const isActive = option.dataset.themeValue === theme;
      option.classList.toggle('active', isActive);
      if (isActive) {
        option.setAttribute('aria-current', 'true');
      } else {
        option.removeAttribute('aria-current');
      }
    });
  };

  setIcon(icon, getCurrent());
  setActive(getCurrent());

  options.forEach((option) => {
    option.addEventListener('click', async (event) => {
      event.preventDefault();
      if (pending) {return;}
      const next = option.dataset.themeValue || '';
      if (!next) {return;}
      const current = getCurrent();
      if (next === current) {return;}
      pending = true;
      setTheme(next);
      setIcon(icon, next);
      setActive(next);
      const ok = await updateTheme(menu, next);
      if (!ok) {
        setTheme(current);
        setIcon(icon, current);
        setActive(current);
      }
      pending = false;
    });
  });
};

const initThemeToggle = () => {
  const button = optionalEl('[data-theme-toggle]');
  if (!button) {return;}
  const icon = button.querySelector('i');
  let pending = false;
  const getCurrent = () => document.documentElement.dataset.theme || '';
  setIcon(icon, getCurrent());

  button.addEventListener('click', async () => {
    if (pending) {return;}
    const current = getCurrent();
    const next = isDarkTheme(current) ? 'light' : 'dark';
    pending = true;
    setTheme(next);
    setIcon(icon, next);
    const ok = await updateTheme(button, next);
    if (!ok) {
      setTheme(current);
      setIcon(icon, current);
    }
    pending = false;
  });
};

if (document.readyState === 'loading') {
  document.addEventListener('DOMContentLoaded', () => {
    initThemeMenu();
    initThemeToggle();
  });
} else {
  initThemeMenu();
  initThemeToggle();
}