import { h, renderList, signal } from '@ui-arch/frame';
import type { PaginationProps } from './types.js';
import { select } from './select.js';

/*** 页码序列：≤7 页全展开；否则保留首尾与当前页 ±1 窗口，缺口折叠为省略号（null 占位） ***/
function pageSequence(page: number, totalPages: number): (number | null)[] {
  if (totalPages <= 7) return Array.from({ length: totalPages }, (_, i) => i + 1);
  const marks = [1, 2, page - 1, page, page + 1, totalPages - 1, totalPages].filter((p) => p >= 1 && p <= totalPages);
  const seq: (number | null)[] = [];
  let prev = 0;
  for (const p of [...new Set(marks)].sort((a, b) => a - b)) {
    if (p - prev > 1) seq.push(null); // 缺口 → 省略号
    seq.push(p);
    prev = p;
  }
  return seq;
}

/*** 独立分页器：受控组件，page 为双向绑定信号；页码过多折叠省略号，首末页禁用翻页，jumpable 可跳页，pageSizes 可切每页条数 ***/

export function pagination(props: PaginationProps): HTMLElement {
  // —— 状态集中声明 ——
  const size = signal(props.pageSize); // 每页条数：可从 switcher 改动，故用信号持有
  const totalPages = () => Math.max(1, Math.ceil(props.total / size())); // 总页数随时可重算
  const pages = h('div', { class: 'ua-pagination-pages' }); // 页码区，随页码重绘
  const tail = h('div', { class: 'ua-pagination-tail' });   // 附加区（条数切换 + 跳页），只创建一次
  const go = (p: number) => {
    const next = Math.min(totalPages(), Math.max(1, p)); // 钳制到有效页码范围
    props.page(next);
    props.onChange?.(next);
  };

  // —— 每页条数切换器：传了候选才渲染，切换即回第 1 页 ——
  if ((props.pageSizes ?? []).length > 1) {
    const sizeValue = signal(String(size()));
    tail.append(
      select({
        options: props.pageSizes!.map((n) => ({ value: String(n), label: `${n} 条/页` })),
        value: sizeValue,
        onChange: (v) => {
          size(Number(v));
          props.onPageSizeChange?.(Number(v));
          go(1); // 条数变了旧页码无意义，统一回首页
        },
      }),
    );
  }

  // —— 跳页输入：jumpable 且多页时渲染，回车跳转 ——
  if (props.jumpable) {
    const jump = h('input', { class: 'ua-page-jump', inputmode: 'numeric', 'aria-label': '跳转到指定页' }) as HTMLInputElement;
    jump.addEventListener('change', () => {
      const n = parseInt(jump.value, 10);
      jump.value = ''; // 跳转后清空输入，避免残留旧页码
      if (!Number.isNaN(n)) go(n); // 非数字忽略，由 go 钳制范围
    });
    tail.append(h('span', { class: 'ua-page-jump-wrap' }, jump, h('span', { class: 'ua-page-total' }, () => `/ ${totalPages()} 页`)));
  }

  const nav = h('nav', { class: 'ua-pagination', 'aria-label': '分页' }, pages, tail);
  renderList(pages, () => {
    const totalNow = totalPages();
    const page = Math.min(totalNow, Math.max(1, props.page()));
    const items: HTMLElement[] = [h('button', { class: 'ua-page-btn', disabled: page <= 1, 'aria-label': '上一页', onClick: () => go(page - 1) }, '‹')];
    for (const it of pageSequence(page, totalNow)) {
      items.push(
        it == null
          ? h('span', { class: 'ua-page-gap', 'aria-hidden': 'true' }, '…')
          : h('button', { class: `ua-page-btn${it === page ? ' ua-active' : ''}`, disabled: it === page, 'aria-current': it === page ? 'page' : null, 'aria-label': `第 ${it} 页`, onClick: () => go(it) }, String(it)),
      );
    }
    items.push(h('button', { class: 'ua-page-btn', disabled: page >= totalNow, 'aria-label': '下一页', onClick: () => go(page + 1) }, '›'));
    return items;
  });
  return nav;
}