import { effect, h, signal } from '@ui-arch/frame';
import { bindOutside, pushOverlay } from './overlay.js';
import { tree } from './tree.js';
import type { TreeNode, TreeSelectProps } from './types.js';

/*** 按 key 深度优先找节点，用于把选中 key 还原成显示名 ***/
function findNode(nodes: TreeNode[], key: string): TreeNode | null {
  for (const node of nodes) {
    if (node.key === key) return node; // 命中即返回
    const hit = node.children ? findNode(node.children, key) : null;
    if (hit) return hit;
  }
  return null;
}

/*** 树形选择：按钮触发弹层，内部复用 tree（搜索 / 多选 / 级联由 tree 提供）；单选选中即收起，多选保持展开 ***/
export function treeSelect(props: TreeSelectProps): HTMLElement {
  const open = signal(false); // 弹层开合
  const value = props.value ?? signal(''); // 单选 key
  const checked = props.checked ?? signal<string[]>([]); // 多选 key 集合
  let release: (() => void) | null = null; // Esc 栈注销句柄
  const labelEl = h('span', { class: 'ua-treeselect-label' });
  const trigger = h('button', {
    class: 'ua-treeselect-trigger',
    type: 'button',
    'aria-haspopup': 'tree',
    'aria-expanded': 'false',
  }, labelEl, h('span', { class: 'ua-treeselect-arrow', 'aria-hidden': 'true' }, '▾')) as HTMLButtonElement;
  const pop = h('div', { class: 'ua-treeselect-pop' });
  const inner = tree({
    nodes: props.nodes,
    searchable: props.searchable,
    multi: props.multi,
    selected: value,
    checked,
    onSelect: (node) => {
      if (!props.multi) close(); // 单选选中即收起，少一次点击
      props.onSelect?.(node);
    },
    onCheck: (keys) => {
      props.onChange?.(keys);
    },
  });
  pop.append(inner);
  const wrap = h('div', { class: 'ua-treeselect' }, trigger, pop);

  /*** 收起弹层并注销 Esc 栈 ***/
  function close(): void {
    open(false);
    release?.();
    release = null;
  }

  /*** 触发器文案：单选回显节点名，多选回显已选数量，都没选则显示占位 ***/
  const paint = (): void => {
    const keys = checked();
    if (props.multi) {
      labelEl.textContent = keys.length ? `已选 ${keys.length} 项` : (props.placeholder ?? '请选择');
    } else {
      const node = value() ? findNode(props.nodes, value()) : null;
      labelEl.textContent = node ? node.label : (props.placeholder ?? '请选择');
    }
    wrap.classList.toggle('is-empty', props.multi ? !keys.length : !value());
    trigger.disabled = Boolean(props.disabled);
  };

  trigger.addEventListener('click', () => {
    if (props.disabled) return; // 卫语句：禁用不响应
    if (open()) return close();
    open(true);
    release = pushOverlay(close); // 与其他弹层共享 Esc 栈，只关最上层
  });
  bindOutside(wrap, open, close);
  effect(() => {
    const on = open();
    wrap.classList.toggle('is-open', on);
    trigger.setAttribute('aria-expanded', String(on));
    if (on) inner.querySelector('input')?.focus(); // 展开即聚焦搜索框，键盘可直接用
  });
  effect(paint);
  return wrap;
}