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

/*** 标签页：active 信号双向绑定 + 滑动指示条 + 方向键环形导航；内容由调用方按 active 派生 ***/
export function tabs(props: TabsProps): HTMLElement {
  // —— 状态集中声明 ——
  const buttons: HTMLButtonElement[] = []; // 页签按钮，顺序与 tabs 一致
  const indicator = h('span', { class: 'ua-tabs-indicator' });
  const head = h('div', { class: 'ua-tabs-head', role: 'tablist' }, indicator);

  /*** 同步激活态与指示条几何位置 ***/
  const sync = () => {
    const value = props.active?.();
    for (const btn of buttons) {
      const on = btn.dataset.value === value;
      btn.classList.toggle('ua-tab-active', on);
      btn.setAttribute('aria-selected', String(on));
      btn.tabIndex = on ? 0 : -1; // 漫游 tabindex：仅激活页签可 Tab 聚焦
      if (on) {
        indicator.style.left = `${btn.offsetLeft}px`;
        indicator.style.width = `${btn.offsetWidth}px`;
      }
    }
  };

  for (const tab of props.tabs) {
    const btn = h('button', { class: 'ua-tab', role: 'tab', type: 'button' }, tab.label) as HTMLButtonElement;
    btn.dataset.value = tab.value;
    btn.disabled = tab.disabled ?? false;
    btn.addEventListener('click', () => {
      if (btn.disabled) return; // 卫语句：禁用页签不响应
      if (props.active) props.active(tab.value); // 用户切换写回信号
      props.onChange?.(tab.value);
    });
    buttons.push(btn);
    head.append(btn);
  }

  head.addEventListener('keydown', (e: KeyboardEvent) => {
    const delta = e.key === 'ArrowRight' ? 1 : e.key === 'ArrowLeft' ? -1 : 0;
    if (!delta) return; // 卫语句：非方向键放行
    const list = buttons.filter((b) => !b.disabled);
    const i = list.indexOf(document.activeElement as HTMLButtonElement);
    if (i < 0) return; // 卫语句：焦点不在页签上
    e.preventDefault();
    const next = list[(i + delta + list.length) % list.length]; // 环形移动
    next.focus();
    next.click();
  });

  effect(sync);
  requestAnimationFrame(sync); // 挂载后再量一次布局，否则指示条宽度为 0
  return h('div', { class: 'ua-tabs' }, head);
}