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

/*** 树形：递归渲染节点，箭头展开/收起，点击标签选中；键盘 Enter 选中、→ 展开、← 收起，被禁用的节点不响应 ***/
export function tree(props: TreeProps): HTMLElement {
  // —— 状态集中声明 ——
  const expanded = props.expanded ?? signal<string[]>([]); // 展开的 key 集合，外部不传则内部维护
  const selected = props.selected ?? signal(''); // 当前选中 key
  const rows = new Map<string, HTMLElement>(); // key → 行元素，供响应式同步
  const toggles = new Map<string, HTMLElement>(); // key → 展开箭头，供响应式同步

  /*** 展开/收起一个节点（写回信号后由 effect 统一刷新 DOM） ***/
  const toggle = (key: string) => {
    const cur = expanded();
    expanded(cur.includes(key) ? cur.filter((k) => k !== key) : [...cur, key]);
  };

  /*** 选中节点：写信号并回调 ***/
  const pick = (node: TreeNode) => {
    selected(node.key);
    props.onSelect?.(node);
  };

  /*** 递归构建节点行：父行 + 子容器（子容器缩进一级） ***/
  const build = (node: TreeNode, depth: number): HTMLElement => {
    const on = expanded().includes(node.key);
    const caret = h('span', { class: 'ua-tree-caret', 'aria-hidden': 'true' }, '›');
    const row = h(
      'div',
      {
        class: 'ua-tree-row',
        role: 'treeitem',
        'aria-level': String(depth + 1),
        'aria-expanded': String(on),
        tabindex: '0',
        onClick: (e: Event) => {
          if (node.disabled) return; // 卫语句：禁用节点不响应
          if ((e.target as HTMLElement) === caret) toggle(node.key); // 点箭头只展开/收起
          else pick(node);
        },
      },
      caret,
      h('span', { class: 'ua-tree-label' }, node.label),
    );
    rows.set(node.key, row);
    toggles.set(node.key, caret);
    if (!node.children?.length) caret.classList.add('ua-tree-caret-leaf'); // 叶子节点箭头置空位占位
    const box = h('div', { class: 'ua-tree-children', role: 'group' }, ...(node.children ?? []).map((c) => build(c, depth + 1)));
    return h('div', { class: 'ua-tree-node' }, row, box);
  };

  const root = h('div', { class: 'ua-tree', role: 'tree' }, ...props.nodes.map((n) => build(n, 0))) as HTMLElement;
  if (props.defaultExpandAll) {
    const all: string[] = [];
    const walk = (list: TreeNode[]) => list.forEach((n) => { if (n.children?.length) { all.push(n.key); walk(n.children); } });
    walk(props.nodes);
    if (!expanded().length) expanded(all); // 仅在外部未给初值时展开全部
  }

  effect(() => {
    const open = expanded();
    const sel = selected();
    for (const [key, row] of rows) {
      const on = open.includes(key);
      row.classList.toggle('ua-tree-open', on);
      row.classList.toggle('ua-tree-selected', key === sel);
      row.setAttribute('aria-selected', String(key === sel));
      row.setAttribute('aria-expanded', String(on));
      toggles.get(key)?.classList.toggle('ua-tree-caret-open', on); // 箭头随展开态旋转
      const box = row.nextElementSibling as HTMLElement | null;
      if (box) box.hidden = !on; // 收起即隐藏子容器
    }
  });

  root.addEventListener('keydown', (e: KeyboardEvent) => {
    const row = (e.target as HTMLElement).closest('.ua-tree-row') as HTMLElement | null;
    if (!row) return; // 卫语句：焦点不在节点行
    const key = [...rows.entries()].find(([, el]) => el === row)?.[0];
    if (!key) return; // 卫语句：找不到对应节点
    const node = findNode(props.nodes, key);
    if (!node || node.disabled) return; // 卫语句：禁用节点不接管键盘
    if (e.key === 'Enter' || e.key === ' ') { e.preventDefault(); pick(node); return; }
    if (e.key === 'ArrowRight' && !expanded().includes(key)) { e.preventDefault(); toggle(key); return; } // → 展开
    if (e.key === 'ArrowLeft' && expanded().includes(key)) { e.preventDefault(); toggle(key); } // ← 收起
  });

  return root;
}

/*** 按 key 深度查找节点（键盘操作需要拿到原始节点对象） ***/
function findNode(nodes: TreeNode[], key: string): TreeNode | null {
  for (const n of nodes) {
    if (n.key === key) return n;
    const hit = n.children ? findNode(n.children, key) : null;
    if (hit) return hit;
  }
  return null;
}