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

/*** 抽屉：open 信号驱动侧滑面板，点遮罩 / × / Esc 关闭；Tab 焦点陷阱 + 关闭归还焦点，与 modal 的分工是不打断主视图、可从侧边保留上下文 ***/
export function drawer(props: DrawerProps, ...children: unknown[]): HTMLElement {
  const close = (): void => {
    if (!props.open()) return; // 卫语句：已关闭不重复触发回调
    props.open(false);
    props.onClose?.();
  };
  const overlay = h('div', {
    class: () => `ua-drawer-overlay${props.open() ? ' ua-open' : ''}`,
    onClick: (e: Event) => {
      if (e.target === overlay) close(); // 卫语句：仅点遮罩本身关闭
    },
  });
  const panel = h(
    'aside',
    {
      class: `ua-drawer ua-drawer-${props.placement ?? 'right'}`,
      style: `width:${props.width ?? 320}px`,
      role: 'dialog',
      'aria-hidden': () => String(!props.open()),
    },
    h('div', { class: 'ua-drawer-head' }, h('h3', { class: 'ua-drawer-title' }, props.title), h('button', { class: 'ua-drawer-close', 'aria-label': '关闭抽屉', onClick: close }, '×')),
    h('div', { class: 'ua-drawer-body' }, ...children),
    props.footer ? h('div', { class: 'ua-drawer-foot' }, props.footer) : null,
  );
  overlay.append(panel);

  let lastFocus: HTMLElement | null = null; // 打开前焦点宿主，关闭时归还
  const focusables = (): HTMLElement[] =>
    Array.from(panel.querySelectorAll<HTMLElement>('button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'))
      .filter((el) => !el.hasAttribute('disabled')); // 面板内可聚焦元素（排除禁用）
  effect(() => {
    if (props.open()) {
      lastFocus = document.activeElement as HTMLElement | null; // 记录打开前焦点
      (panel.querySelector('button, input, textarea') as HTMLElement | null)?.focus(); // 打开时聚焦首个可交互元素
    } else if (lastFocus) {
      lastFocus.focus(); // 关闭时归还焦点
      lastFocus = null;
    }
  });
  overlay.addEventListener('keydown', (e: KeyboardEvent) => {
    if (e.key !== 'Tab' || !props.open()) return; // 仅处理打开中的 Tab
    const els = focusables();
    if (els.length === 0) { e.preventDefault(); return; } // 无可聚焦元素：拦截 Tab 防焦点逃逸
    const first = els[0];
    const last = els[els.length - 1];
    if (e.shiftKey && (document.activeElement === first || !panel.contains(document.activeElement))) {
      e.preventDefault(); last.focus(); // Shift+Tab 到首位时回绕到末尾
    } else if (!e.shiftKey && (document.activeElement === last || !panel.contains(document.activeElement))) {
      e.preventDefault(); first.focus(); // Tab 到末位时回绕到开头
    }
  });
  document.addEventListener('keydown', (e: KeyboardEvent) => {
    if (e.key === 'Escape' && props.open()) close();
  });
  return overlay;
}