import { effect, h, signal } from '@ui-arch/frame';
import type { Signal } from '@ui-arch/frame';
import { bindOutside, pushOverlay } from './overlay.js';
import { flip, trackShift } from './position.js';
import type { MultiSelectProps } from './types.js';

/*** 多选下拉：标签式回显 + 可搜索弹层，value 数组信号双向绑定，到 max 未选项自动禁用 ***/ 
export function multiSelect(props: MultiSelectProps): HTMLElement {
  // —— 状态集中声明 ——
  const value: Signal<string[]> = props.value ?? signal<string[]>([]); // 选中值
  const open = signal(false);      // 弹层开合
  const query = signal('');        // 搜索词
  const active = signal(-1);       // 键盘高亮下标
  const place = signal<'top' | 'bottom'>('bottom'); // 实际方位
  const searchable = props.searchable !== false;    // 缺省可搜索
  let releaseEsc: (() => void) | null = null;       // Esc 栈注销函数

  /*** 按搜索词过滤候选：禁用项仍展示（便于解释为何点不了） ***/
  const visible = () => {
    const q = query().trim().toLowerCase();
    return q ? props.options.filter((o) => o.label.toLowerCase().includes(q)) : props.options;
  };

  /*** 提交变更：写信号 + 回调（上限由弹层禁用项兜住，这里不再拒绝） ***/
  const update = (next: string[]): void => {
    value(next);
    props.onChange?.([...next]);
  };

  /*** 单项切换：已选则移除，未选且未到上限则加入 ***/
  const toggle = (v: string): void => {
    const cur = new Set(value());
    if (cur.has(v)) cur.delete(v);
    else if (props.max == null || cur.size < props.max) cur.add(v);
    update([...cur]);
  };

  /*** 全选 / 反选：只作用于当前过滤后的候选，上限时按顺序补到 max 为止 ***/
  const toggleAll = (): void => {
    const opts = visible().filter((o) => !o.disabled);
    const cur = new Set(value());
    const allOn = opts.length > 0 && opts.every((o) => cur.has(o.value));
    if (allOn) opts.forEach((o) => cur.delete(o.value)); // 全选态再点即清空这批
    else for (const o of opts) {
      if (props.max != null && cur.size >= props.max) break; // 到上限就停，不静默超选
      cur.add(o.value);
    }
    update([...cur]);
  };

  const tagWrap = h('span', { class: 'ua-multiselect-tags' }) as HTMLElement; // 标签区：每次重绘只换这里
  const box = h('div', { class: 'ua-multiselect-box' }) as HTMLElement;      // 标签 + 输入框容器
  const input = h('input', {
    type: 'text',
    class: 'ua-multiselect-input',
    placeholder: '',
    'aria-label': props.placeholder ?? '多选下拉',
    role: 'combobox',
    'aria-expanded': () => String(open()),
    disabled: props.disabled,
    oninput: (e: Event) => {
      query((e.target as HTMLInputElement).value);
      active(-1);
      open(true); // 输入即展开，便于边打边选
    },
  }) as HTMLInputElement;
  box.append(tagWrap, input); // 标签区在前、输入框在后，横向排布
  const list = h('ul', { class: 'ua-multiselect-list', role: 'listbox', 'aria-multiselectable': 'true' }) as HTMLElement;
  const pop = h('div', { class: () => `ua-multiselect-pop${open() ? ' ua-open' : ''}${place() === 'top' ? ' is-flip' : ''}` }, list) as HTMLElement;
  const clearBtn = h('button', { type: 'button', class: 'ua-select-clear', 'aria-label': '清空所选', hidden: true, onClick: (e: Event) => { e.stopPropagation(); update([]); input.focus(); } }, '×') as HTMLElement; // 复用 select 清空钮样式；阻止冒泡免得清完又展开
  const root = h('div', { class: () => `ua-multiselect${open() ? ' ua-open' : ''}` }, box, props.clearable ? clearBtn : null, pop) as HTMLElement;
  effect(() => { clearBtn.hidden = !value().length; }); // 有值才显示（clearable 未开时按钮根本不挂载）

  /*** 重绘标签区与候选：标签带删除钮，候选带勾选态与禁用态 ***/
  const render = (): void => {
    const cur = value();
    const full = props.max != null && cur.length >= props.max; // 是否已达上限
    const cut = props.maxTagCount != null && cur.length > props.maxTagCount ? cur.slice(0, props.maxTagCount) : cur; // 折叠后仍显示的标签
    const labelOf = (v: string): string => props.options.find((o) => o.value === v)?.label ?? v;
    const tags = cut.map((v) => {
      const label = labelOf(v);
      const del = h('button', { type: 'button', class: 'ua-multiselect-x', 'aria-label': `移除 ${label}`, onClick: () => toggle(v) }, '×');
      return h('span', { class: 'ua-multiselect-tag' }, h('span', {}, label), del);
    });
    if (cut.length < cur.length) { // 溢出项折成一枚 +N，悬停给全量、点击展开弹层
      const rest = cur.slice(cut.length).map(labelOf).join('、');
      tags.push(h('span', { class: 'ua-multiselect-tag is-more', title: rest, 'aria-label': `另有 ${cur.length - cut.length} 项：${rest}`, onClick: () => open(true) }, `+${cur.length - cut.length}`));
    }
    tagWrap.replaceChildren(...tags); // 只换标签，输入框保持挂载（重建会丢焦点与输入内容）
    input.placeholder = cur.length ? '' : props.placeholder ?? '请选择'; // 有标签时不挤占占位文案
    const rows: HTMLElement[] = []; // 候选行：分组小标题与选项混排（小标题不可聚焦，不占 active 下标）
    if (props.selectAll) { // 全选行：占 active 下标 -1，键盘 ↑↓ 能走到，不用鼠标也能全选
      const opts = visible();
      const picked = opts.filter((o) => cur.includes(o.value)).length;
      const allOn = opts.length > 0 && picked === opts.length;
      rows.push(h(
        'li',
        {
          class: () => `ua-multiselect-opt ua-multiselect-all${open() && active() === -1 ? ' is-active' : ''}${opts.length ? '' : ' is-disabled'}`,
          role: 'option',
          'aria-selected': String(allOn),
          onmousedown: (e: Event) => { e.preventDefault(); if (opts.length) toggleAll(); }, // 阻止默认：保住输入焦点
        },
        h('span', { class: 'ua-multiselect-check', 'aria-hidden': 'true' }, allOn ? '✓' : picked ? '–' : ''), // – 为半选：部分可选
        h('span', {}, opts.length ? `全选（${picked}/${opts.length}）` : '全选'),
      ));
    }
    let prevGroup = ''; // 上一个候选的分组名，只在组首插一次标题
    visible().forEach((o, i) => {
      if (o.group && o.group !== prevGroup) rows.push(h('li', { class: 'ua-multiselect-group', role: 'presentation' }, o.group));
      prevGroup = o.group ?? ''; // 无分组的候选打断连续段，后续同名组会重新起标题
      const on = cur.includes(o.value);
      const dead = o.disabled === true || (full && !on); // 到上限：未选项不可再点
      rows.push(h(
        'li',
        {
          class: () => `ua-multiselect-opt${on ? ' is-selected' : ''}${active() === i ? ' is-active' : ''}${dead ? ' is-disabled' : ''}`,
          role: 'option',
          'aria-selected': String(on),
          onmousedown: (e: Event) => { e.preventDefault(); if (!dead) toggle(o.value); }, // 阻止默认：保住输入焦点，弹层不收起
        },
        h('span', { class: 'ua-multiselect-check', 'aria-hidden': 'true' }, on ? '✓' : ''),
        h('span', {}, o.label),
      ));
    });
    if (!rows.length) rows.push(h('li', { class: 'ua-multiselect-empty' }, '无匹配项'));
    list.replaceChildren(...rows);
  };

  box.addEventListener('click', () => { if (!(props.disabled === true)) { open(true); input.focus(); } }); // 点空白处展开并聚焦输入
  root.addEventListener('keydown', (e: KeyboardEvent) => {
    const opts = visible();
    const base = props.selectAll ? -1 : 0; // 全选行占 -1 号位：环形导航的起点随之左移一格
    const slots = opts.length + (props.selectAll ? 1 : 0); // 可停留的位置总数（含全选行）
    if (e.key === 'ArrowDown' || e.key === 'ArrowUp') {
      e.preventDefault();
      if (!open()) { open(true); active(base); return; }
      if (!slots) return; // 无候选也没全选行：不动
      const dir = e.key === 'ArrowDown' ? 1 : -1;
      active(base + (((active() - base) + dir + slots) % slots)); // 环形移动，越界回绕
      return;
    }
    if (e.key === 'Enter' && open() && slots && active() >= base) {
      e.preventDefault();
      if (active() === -1) toggleAll(); // 全选行
      else toggle(opts[active()].value);
      return;
    }
    if (e.key === 'Backspace' && !input.value && value().length) { update(value().slice(0, -1)); return; } // 空输入时退格删末个标签
    if (e.key === 'Escape') { open(false); return; }
  });

  bindOutside(root, open, () => open(false)); // 点外部收起：仅展开期间挂监听，收起即摘
  effect(render);
  effect(() => {
    if (open()) releaseEsc ??= pushOverlay(() => { open(false); input.focus(); }); // 入栈逐层关闭
    else { releaseEsc?.(); releaseEsc = null; }
  });
  let releaseShift: (() => void) | null = null; // 展开期间的位移跟随释放函数（滚动 / 缩放重算翻转）
  effect(() => {
    if (!open()) { // 收起即摘监听：弹层不在，重算方位没有意义
      releaseShift?.();
      releaseShift = null;
      return;
    }
    place(flip(box, pop, 'bottom')); // 打开先算一次：空间不足自动翻转
    releaseShift ??= trackShift(() => place(flip(box, pop, 'bottom'))); // 展开期间跟着滚动重算：视口空间会变
  });
  return root;
}