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

/*** 下拉选择：自绘弹层替代原生 select，value 信号双向绑定；支持 ↑↓/Home/End 键盘导航，点选项 / 点外部 / Esc 关闭 ***/
export function select(props: SelectProps): HTMLElement {
  // —— 状态集中声明 ——
  const open = signal(false);              // 弹层开合
  const value = props.value ?? signal(''); // 选中值；未传信号则内部持有

  const labelOf = (v: string) => props.options.find((o) => o.value === v)?.label ?? '';
  const current = () => labelOf(value()); // 触发器显示文案（响应式）

  const pick = (v: string) => {
    value(v);
    open(false);
    props.onChange?.(v);
  };

  // —— 触发器 ——
  const trigger = h(
    'button',
    {
      type: 'button',
      class: 'ua-select-trigger',
      'aria-haspopup': 'listbox',
      'aria-expanded': () => String(open()),
      disabled: props.disabled,             // 布尔或信号禁用，h() 直接透传（原生 button 拦截点击）
      onClick: () => open(!open()),
    },
    h('span', { class: () => `ua-select-value${value() ? '' : ' is-empty'}` }, () => current() || props.placeholder || ''),
    h('span', { class: 'ua-select-arrow' }, '▾'),
  );

  // —— 选项弹层 ——
  const options = props.options.map((opt) =>
    h(
      'button',
      {
        type: 'button',
        class: () => `ua-option${opt.value === value() ? ' ua-option-selected' : ''}`,
        role: 'option',
        'aria-selected': () => String(opt.value === value()),
        onClick: () => pick(opt.value),
      },
      opt.label,
    ),
  );
  const pop = h('div', { class: () => `ua-select-pop${open() ? ' ua-open' : ''}`, role: 'listbox' }, ...options);

  const root = h('div', { class: () => `ua-select${open() ? ' ua-open' : ''}` }, trigger, pop); // 根带开合类，供箭头旋转

  root.addEventListener('keydown', (e: KeyboardEvent) => {
    if (e.key === 'Escape') { open(false); trigger.focus(); return; } // Esc 关闭并回焦触发器
    if (e.key === 'ArrowDown' || e.key === 'ArrowUp') {
      e.preventDefault(); // 阻止页面滚动
      if (!open()) { open(true); options[0]?.focus(); return; } // 未展开：展开并聚焦首个选项
      const idx = options.indexOf(document.activeElement as HTMLElement); // 展开中：在选项间环形移动
      const dir = e.key === 'ArrowDown' ? 1 : -1;
      const next = (idx + dir + options.length) % options.length;
      options[next]?.focus();
      return;
    }
    if (e.key === 'Home' && open()) { e.preventDefault(); options[0]?.focus(); return; } // Home 跳首项
    if (e.key === 'End' && open()) { e.preventDefault(); options[options.length - 1]?.focus(); } // End 跳末项
  });
  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); // 点外部关闭
  });
  effect(() => open()); // 建立依赖，保证开合信号生效
  return root;
}