/**
 * Theme switcher — light/dark toggle and menu with server-side persistence.
 */
import { warnOnce, resolveHost } 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 (source, theme) => {
  const url = source.dataset.themeUrl;
  const csrfKey = source.dataset.csrfKey;
  const csrfToken = source.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;
};

export function initThemeControls(root = document, options = {}) {
  const host = resolveHost(root);
  const menuSelector = String(options.menuSelector || '[data-theme-menu]').trim() || '[data-theme-menu]';
  const toggleSelector = String(options.toggleSelector || '[data-theme-toggle]').trim() || '[data-theme-toggle]';

  const cleanupFns = [];
  const menu = host.matches?.(menuSelector) ? host : host.querySelector(menuSelector);
  if (menu instanceof HTMLElement) {
    const icon = menu.querySelector('[data-theme-icon]');
    const optionsEls = Array.from(menu.querySelectorAll('[data-theme-option]'));
    if (!optionsEls.length) {
      warnOnce('UI_EL_MISSING', 'Missing theme options', { module: 'theme-toggle' });
    } else {
      let pending = false;
      const getCurrent = () => document.documentElement.dataset.theme || '';
      const setActive = (theme) => {
        optionsEls.forEach((optionEl) => {
          const isActive = optionEl.dataset.themeValue === theme;
          optionEl.classList.toggle('active', isActive);
          if (isActive) {
            optionEl.setAttribute('aria-current', 'true');
          } else {
            optionEl.removeAttribute('aria-current');
          }
        });
      };

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

      optionsEls.forEach((optionEl) => {
        const onOptionClick = async (event) => {
          event.preventDefault();
          if (pending) {
            return;
          }
          const next = optionEl.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;
        };
        optionEl.addEventListener('click', onOptionClick);
        cleanupFns.push(() => optionEl.removeEventListener('click', onOptionClick));
      });
    }
  }

  const button = host.matches?.(toggleSelector) ? host : host.querySelector(toggleSelector);
  if (button instanceof HTMLButtonElement) {
    const icon = button.querySelector('i');
    let pending = false;
    const getCurrent = () => document.documentElement.dataset.theme || '';
    setIcon(icon, getCurrent());

    const onButtonClick = 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;
    };
    button.addEventListener('click', onButtonClick);
    cleanupFns.push(() => button.removeEventListener('click', onButtonClick));
  }

  const destroy = () => {
    cleanupFns.forEach((cleanup) => cleanup());
  };

  return { destroy };
}

export const initThemeToggle = initThemeControls;