import { effect, h, signal } from '@ui-arch/frame';
import type { 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、点标签选中；multi 时带勾选框且父子级联，键盘 Enter/空格选中或勾选 ***/ 
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 checked: Signal<string[]> = props.checked ?? signal<string[]>([]); // 勾选 key 集合（multi 生效）
  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
  const boxes = new Map<string, HTMLInputElement>(); // key → 勾选框
  const selfOf = new Map<string, TreeNode>();        // key → 节点对象
  const parentOf = new Map<string, string | null>(); // key → 父 key（根为 null）
  let tabStop: string | null = null;                 // roving tabindex：整棵树只保留一个 Tab 停点
  const keyword = signal('');                        // 搜索词：非空时按标签过滤，命中节点保留父链
  const nodeEls = new Map<string, HTMLElement>();    // key → 节点根（行 + 子容器），整枝显隐用

  /*** 切换 Tab 停点：只有当前行 tabindex=0，其余 -1，Tab 进出树只停一次 ***/
  const syncTabStop = (key: string | null): void => {
    tabStop = key;
    for (const [k, row] of rows) row.tabIndex = k === key ? 0 : -1;
  };

  /*** 行元素 → key（键盘导航与焦点同步共用） ***/
  const keyOf = (row: HTMLElement): string | null => [...rows.entries()].find(([, el]) => el === row)?.[0] ?? null;

  /*** 子孙 key 列表（含被禁用项，勾选时再按禁用过滤） ***/
  const descOf = (node: TreeNode): string[] => (node.children ?? []).flatMap((c) => [c.key, ...descOf(c)]);

  /*** 展开/收起一个节点（写回信号后由 effect 统一刷新 DOM） ***/
  const toggle = (key: string): void => {
    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): void => {
    selected(node.key);
    props.onSelect?.(node);
  };

  /*** 勾选级联：向下整套写入，向上回算父级（子全选才勾上父） ***/
  const setCheck = (node: TreeNode, on: boolean): void => {
    const next = new Set(checked());
    for (const key of [node.key, ...descOf(node)]) {
      if (selfOf.get(key)?.disabled) continue; // 禁用项不参与级联
      on ? next.add(key) : next.delete(key);
    }
    let up = parentOf.get(node.key) ?? null;
    while (up) {
      const kids = (selfOf.get(up)?.children ?? []).filter((c) => !c.disabled);
      if (on && kids.length && kids.every((c) => next.has(c.key))) next.add(up); // 子全选才上勾
      else if (!on) next.delete(up); // 子有未选：父必取消
      up = parentOf.get(up) ?? null;
    }
    checked([...next]);
    props.onCheck?.([...next]);
  };

  /*** 递归构建节点行：父行 + 子容器（子容器缩进一级），multi 时行首插入勾选框 ***/
  const build = (node: TreeNode, depth: number, parent: string | null): HTMLElement => {
    const on = expanded().includes(node.key);
    const caret = h('span', { class: 'ua-tree-caret', 'aria-hidden': 'true' }, '›');
    const box = props.multi
      ? (h('input', { type: 'checkbox', class: 'ua-checkbox ua-tree-box', 'aria-label': node.label, disabled: node.disabled }) as HTMLInputElement)
      : null;
    if (box) {
      box.addEventListener('click', (e) => { e.stopPropagation(); setCheck(node, box.checked); }); // 勾选不触发选中
      boxes.set(node.key, box);
    }
    const row = h(
      'div',
      { class: 'ua-tree-row', role: 'treeitem', 'aria-level': String(depth + 1), 'aria-expanded': String(on), tabindex: '-1' }, // 由 roving tabStop 决定谁可 Tab
      box,
      caret,
      h('span', { class: 'ua-tree-label' }, node.label),
    );
    row.addEventListener('click', (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);
    });
    rows.set(node.key, row);
    toggles.set(node.key, caret);
    selfOf.set(node.key, node);
    parentOf.set(node.key, parent);
    if (!node.children?.length) caret.classList.add('ua-tree-caret-leaf'); // 叶子箭头置空位占位
    const kids = h('div', { class: 'ua-tree-children', role: 'group' }, ...(node.children ?? []).map((c) => build(c, depth + 1, node.key)));
    const nodeEl = h('div', { class: 'ua-tree-node' }, row, kids) as HTMLElement;
    nodeEls.set(node.key, nodeEl);
    return nodeEl;
  };

  /*** 命中集合：自身标签含关键词或子孙含关键词（父链整条保留，避免结果断在中间） ***/
  const hitting = (): Set<string> => {
    const q = keyword().trim().toLowerCase();
    const set = new Set<string>();
    if (!q) return set; // 卫语句：无关键词不过滤
    const walk = (node: TreeNode): boolean => {
      let hit = node.label.toLowerCase().includes(q);
      for (const c of node.children ?? []) if (walk(c)) hit = true; // 子孙命中同样保留本节点
      if (hit) set.add(node.key);
      return hit;
    };
    props.nodes.forEach(walk);
    return set;
  };

  const root = h('div', { class: 'ua-tree', role: 'tree' }, ...props.nodes.map((n) => build(n, 0, null))) as HTMLElement;
  syncTabStop(props.nodes.find((n) => !n.disabled)?.key ?? null); // 初始停点：首个可用根节点
  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();
    const picked = checked();
    const hits = hitting(); // 搜索命中集合；空集合表示未过滤
    const filtering = keyword().trim().length > 0;
    for (const [key, row] of rows) {
      const on = open.includes(key);
      const shown = !filtering || hits.has(key);
      const nodeEl = nodeEls.get(key);
      if (nodeEl) nodeEl.hidden = !shown; // 不命中整枝隐藏，连带子节点退出键盘遍历
      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 kids = row.nextElementSibling as HTMLElement | null;
      if (kids) kids.hidden = filtering ? !shown : !on; // 搜索时命中枝强制展开，否则跟随展开态
      const box = boxes.get(key);
      if (!box) continue; // 卫语句：非多选模式没有勾选框
      const self = selfOf.get(key);
      const hit = picked.includes(key);
      box.checked = hit;
      box.indeterminate = !hit && !!self && descOf(self).some((k) => picked.includes(k)); // 半选：子级部分勾选
    }
  });

  /*** 当前可见的节点行（收起分支的子节点不参与 ↑↓ 遍历） ***/
  const visibleRows = (): HTMLElement[] =>
    Array.from(root.querySelectorAll<HTMLElement>('.ua-tree-row')).filter((el) => !el.closest('[hidden]')); // 收起或搜索隐藏的枝都不参与 ↑↓ 遍历

  root.addEventListener('focusin', (e: FocusEvent) => {
    const row = (e.target as HTMLElement).closest('.ua-tree-row') as HTMLElement | null;
    const key = row ? keyOf(row) : null;
    if (key && key !== tabStop) syncTabStop(key); // 焦点跟随：下次 Tab 直接回到这行
  });

  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
    if (e.key === 'ArrowDown' || e.key === 'ArrowUp' || e.key === 'Home' || e.key === 'End') {
      const list = visibleRows();
      const at = list.indexOf(row);
      if (at < 0) return; // 卫语句：行已不在可见集
      e.preventDefault();
      const next = e.key === 'Home' ? list[0] : e.key === 'End' ? list[list.length - 1] : list[at + (e.key === 'ArrowDown' ? 1 : -1)];
      next?.focus(); // 行间移动只改焦点，不改变选中
      return;
    }
    const key = keyOf(row);
    const node = key ? selfOf.get(key) : null;
    if (!node || node.disabled || !key) return; // 卫语句：找不到或禁用节点
    if (e.key === 'Enter' || e.key === ' ') {
      e.preventDefault();
      if (props.multi) setCheck(node, !checked().includes(key)); // 多选：回车/空格切换勾选
      else 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
  });

  if (!props.searchable) return root;
  const search = h('input', {
    type: 'search',
    class: 'ua-tree-search',
    placeholder: '搜索节点…',
    'aria-label': '搜索节点',
    oninput: (e: Event) => keyword((e.target as HTMLInputElement).value),
  }) as HTMLInputElement;
  return h('div', { class: 'ua-tree-box' }, search, root); // 搜索框放在 role=tree 之外，语义不混
}