import { effect, h, signal } from '@ui-arch/frame';
import type { MenuItem, MenuProps } from './types.js';

/*** 下拉菜单：触发器 + 自绘弹层，项支持禁用 / 危险 / 分隔线；点项 / 点外部 / Esc 关闭，↑↓ 环形导航 ***/
export function menu(props: MenuProps): HTMLElement {
  // —— 状态集中声明 ——
  const open = signal(false);              // 弹层开合
  const focusables: HTMLButtonElement[] = []; // 可聚焦项（跳过分隔线与禁用项），供键盘导航

  const pick = (item: MenuItem): void => {
    open(false);                           // 选中即收起
    props.onSelect?.(item.value);
  };

  // —— 菜单项：分隔线走独立分支，其余为原生 button 保证键盘可达 ——
  const rows = props.items.map((item) => {
    if (item.divider) return h('div', { class: 'ua-menu-divider', role: 'separator' });
    const btn = h(
      'button',
      {
        type: 'button',
        class: `ua-menu-item${item.danger ? ' is-danger' : ''}`,
        role: 'menuitem',
        disabled: item.disabled ? true : undefined,
        onClick: () => pick(item),
      },
      item.label,
    ) as HTMLButtonElement;
    if (!item.disabled) focusables.push(btn); // 禁用项不参与导航
    return btn;
  });

  const trigger = h(
    'button',
    {
      type: 'button',
      class: `ua-btn ua-btn-${props.variant ?? 'ghost'} ua-menu-trigger`,
      'aria-haspopup': 'menu',
      'aria-expanded': () => String(open()),
      onClick: () => open(!open()),
    },
    props.label,
    h('span', { class: 'ua-menu-caret' }, '▾'),
  );

  const pop = h(
    'div',
    {
      class: () => `ua-menu-pop${open() ? ' ua-open' : ''}${props.align === 'end' ? ' is-end' : ''}`,
      role: 'menu',
    },
    ...rows,
  );

  const root = h('div', { class: () => `ua-menu${open() ? ' ua-open' : ''}` }, trigger, pop);

  root.addEventListener('keydown', (e: KeyboardEvent) => {
    if (e.key === 'Escape') {
      open(false);
      trigger.focus();                     // 收起后焦点回到触发器，键盘流不断
      return;
    }
    if (e.key !== 'ArrowDown' && e.key !== 'ArrowUp') return; // 卫语句：只接管上下键
    e.preventDefault();
    if (!open()) {
      open(true);
      focusables[0]?.focus();              // 首次按下即展开并进首项
      return;
    }
    const at = focusables.indexOf(document.activeElement as HTMLButtonElement);
    const step = e.key === 'ArrowDown' ? 1 : -1;
    focusables[(at + step + focusables.length) % focusables.length]?.focus(); // 环形移动
  });

  document.addEventListener('click', (e) => {
    if (root.contains(e.target as Node)) return; // 卫语句：组件内点击不处理
    open(false);                                 // 点外部收起
  });

  effect(() => open()); // 建立依赖，保证开合信号生效
  return root;
}