let activeDropdown = null;

function normalizeItems(items) {
  const value = typeof items === 'function' ? items() : items;
  return Array.isArray(value) ? value.filter(Boolean) : [];
}

function resolvePlacement({ placement, align }) {
  if (placement === 'bottom-start' || placement === 'top-start') return 'left';
  if (placement === 'bottom-end' || placement === 'top-end') return 'right';
  return align === 'left' ? 'left' : 'right';
}

export function createDropdownMenu({
  anchorEl,
  items = [],
  renderContent = null,
  className = '',
  minWidth = 210,
  offset = 7,
  placement = 'bottom-end',
  align = null,
  leftShift = 0,
  transparent = false,
  dimBackground = true,
  keepAnchorPressed = true,
  onOpen = null,
  onClose = null,
} = {}) {
  let portal = null;
  let menuEl = null;
  let destroyed = false;

  const setAnchorOpen = (isOpen) => {
    if (!anchorEl) return;
    anchorEl.setAttribute('aria-haspopup', 'menu');
    anchorEl.setAttribute('aria-expanded', isOpen ? 'true' : 'false');
    if (keepAnchorPressed && isOpen) anchorEl.dataset.open = 'true';
    else delete anchorEl.dataset.open;
  };

  const close = ({ focusAnchor = false } = {}) => {
    if (!portal) return;
    portal.remove();
    portal = null;
    menuEl = null;
    if (activeDropdown === api) activeDropdown = null;
    setAnchorOpen(false);
    onClose?.();
    if (focusAnchor) anchorEl?.focus?.();
  };

  const position = () => {
    if (!portal || !menuEl || !anchorEl) return;
    const rect = anchorEl.getBoundingClientRect();
    const margin = 10;
    const menuWidth = menuEl.offsetWidth || minWidth;
    const side = resolvePlacement({ placement, align });
    const baseLeft = side === 'left' ? rect.left : rect.right - menuWidth;
    const desiredLeft = baseLeft - Number(leftShift || 0);
    const left = Math.max(margin, Math.min(window.innerWidth - menuWidth - margin, desiredLeft));

    const menuHeight = menuEl.offsetHeight || 180;
    const prefersTop = String(placement || '').startsWith('top-');
    let top = prefersTop ? rect.top - menuHeight - offset : rect.bottom + offset;
    if (!prefersTop && top + menuHeight > window.innerHeight - margin) {
      top = Math.max(margin, rect.top - menuHeight - offset);
    } else if (prefersTop && top < margin) {
      top = Math.min(window.innerHeight - menuHeight - margin, rect.bottom + offset);
    }

    menuEl.style.left = `${Math.round(left)}px`;
    menuEl.style.top = `${Math.round(top)}px`;
  };

  const appendItems = () => {
    normalizeItems(items).forEach((item) => {
      if (item.divider) {
        const divider = document.createElement('div');
        divider.className = 'dropdown-menu__divider';
        divider.setAttribute('role', 'separator');
        menuEl.append(divider);
        return;
      }

      const button = document.createElement('button');
      button.type = 'button';
      button.className = `dropdown-menu__item${item.selected ? ' is-selected' : ''}${item.danger ? ' is-danger' : ''}${item.className ? ` ${item.className}` : ''}`;
      button.setAttribute('role', 'menuitem');
      button.disabled = Boolean(item.disabled);

      if (item.iconHtml) {
        const icon = document.createElement('span');
        icon.className = 'dropdown-menu__icon';
        icon.innerHTML = item.iconHtml;
        button.append(icon);
      } else if (item.iconSrc) {
        const icon = document.createElement('img');
        icon.className = 'dropdown-menu__icon';
        icon.src = item.iconSrc;
        icon.alt = '';
        icon.setAttribute('aria-hidden', 'true');
        button.append(icon);
      }

      const label = document.createElement('span');
      label.textContent = String(item.label || '');
      button.append(label);
      button.addEventListener('click', async (event) => {
        event.preventDefault();
        event.stopPropagation();
        if (button.disabled) return;
        close();
        await item.action?.();
      });
      menuEl.append(button);
    });
  };

  const open = () => {
    if (destroyed || !anchorEl || portal) return;
    if (activeDropdown && activeDropdown !== api) activeDropdown.close();

    portal = document.createElement('div');
    portal.className = `dropdown-portal${dimBackground ? ' dropdown-portal--dim' : ''}`;

    if (dimBackground) {
      const backdrop = document.createElement('div');
      backdrop.className = 'dropdown-backdrop';
      backdrop.setAttribute('aria-hidden', 'true');
      backdrop.addEventListener('pointerdown', (event) => {
        if (event.target === backdrop) close();
      });
      portal.append(backdrop);
    }

    menuEl = document.createElement('div');
    menuEl.className = `dropdown-menu${transparent ? ' dropdown-menu--transparent' : ''}${className ? ` ${className}` : ''}`;
    menuEl.setAttribute('role', 'menu');
    menuEl.style.minWidth = `${minWidth}px`;

    if (typeof renderContent === 'function') {
      const content = renderContent({ close, menuEl });
      if (content instanceof Node) menuEl.append(content);
    } else {
      appendItems();
    }

    menuEl.addEventListener('pointerdown', (event) => event.stopPropagation());
    menuEl.addEventListener('click', (event) => event.stopPropagation());
    portal.append(menuEl);
    document.body.append(portal);
    activeDropdown = api;
    setAnchorOpen(true);
    onOpen?.();
    position();
  };

  const toggle = () => {
    if (portal) close();
    else open();
  };

  const onAnchorClick = (event) => {
    event.preventDefault();
    event.stopPropagation();
    toggle();
  };
  const onOutsidePointerDown = (event) => {
    if (!portal) return;
    if (menuEl?.contains(event.target) || anchorEl?.contains(event.target)) return;
    close();
  };
  const onKeydown = (event) => {
    if (event.key !== 'Escape' || !portal) return;
    close({ focusAnchor: true });
  };
  const onNavigation = () => close();
  const onViewportChange = () => position();

  setAnchorOpen(false);
  anchorEl?.addEventListener('click', onAnchorClick);
  document.addEventListener('pointerdown', onOutsidePointerDown, true);
  document.addEventListener('keydown', onKeydown);
  window.addEventListener('popstate', onNavigation);
  window.addEventListener('hashchange', onNavigation);
  window.addEventListener('resize', onViewportChange, { passive: true });
  window.addEventListener('scroll', onViewportChange, { passive: true, capture: true });

  const api = {
    open,
    close,
    toggle,
    position,
    get isOpen() {
      return Boolean(portal);
    },
    destroy() {
      if (destroyed) return;
      destroyed = true;
      close();
      anchorEl?.removeEventListener('click', onAnchorClick);
      document.removeEventListener('pointerdown', onOutsidePointerDown, true);
      document.removeEventListener('keydown', onKeydown);
      window.removeEventListener('popstate', onNavigation);
      window.removeEventListener('hashchange', onNavigation);
      window.removeEventListener('resize', onViewportChange);
      window.removeEventListener('scroll', onViewportChange, true);
      setAnchorOpen(false);
    },
  };

  return api;
}