import Link from 'next/link';
import { fmtInt } from '@/lib/format';
import { pageInfo, pageWindow } from '@/lib/pagination';

/**
 * Server-side pager (URL state, §295). Renders "Showing a–b of N", previous/next links with
 * rel=prev/next, and a compact page window. Pure links: works without JavaScript and is crawlable.
 */
export function Pager({
  total,
  pageSize,
  page,
  hrefFor,
  label = 'Pagination',
  noun,
  className = '',
}: {
  total: number;
  pageSize: number;
  page: number;
  /** URL for a given page (1-based). Page 1 should drop the param so canonical URLs stay clean. */
  hrefFor: (page: number) => string;
  /** aria-label for the <nav>; use a distinct label when a page has several pagers. */
  label?: string;
  /** Row noun for the summary, e.g. "evidence items". */
  noun?: string;
  className?: string;
}) {
  const info = pageInfo(page, pageSize, total);
  if (total <= 0) return null;
  const linkCls = 'ci-pager-link';
  const disabledCls = 'ci-pager-link is-disabled';
  return (
    <nav aria-label={label} className={`ci-pager mt-3 flex flex-wrap items-center justify-between gap-2 text-[13px] text-ink-2 ${className}`}>
      <p className="m-0">
        Showing <span className="ci-num">{fmtInt(info.from)}</span>–<span className="ci-num">{fmtInt(info.to)}</span> of <span className="ci-num">{fmtInt(total)}</span>
        {noun ? ` ${noun}` : ''}
      </p>
      {info.pageCount > 1 ? (
        <ul className="m-0 flex list-none items-center gap-1 p-0">
          <li>
            {info.hasPrev ? (
              <Link className={linkCls} href={hrefFor(info.page - 1)} rel="prev" aria-label={`Previous page (${info.page - 1})`}>
                ← Previous
              </Link>
            ) : (
              <span className={disabledCls} aria-disabled="true">
                ← Previous
              </span>
            )}
          </li>
          {pageWindow(info.page, info.pageCount).map((p, i) =>
            p == null ? (
              <li key={`gap-${i}`} aria-hidden className="px-1 text-ink-4">
                …
              </li>
            ) : (
              <li key={p}>
                {p === info.page ? (
                  <span className="ci-pager-link is-current ci-num" aria-current="page" aria-label={`Page ${p}, current page`}>
                    {p}
                  </span>
                ) : (
                  <Link className={`${linkCls} ci-num`} href={hrefFor(p)} aria-label={`Page ${p}`}>
                    {p}
                  </Link>
                )}
              </li>
            ),
          )}
          <li>
            {info.hasNext ? (
              <Link className={linkCls} href={hrefFor(info.page + 1)} rel="next" aria-label={`Next page (${info.page + 1})`}>
                Next →
              </Link>
            ) : (
              <span className={disabledCls} aria-disabled="true">
                Next →
              </span>
            )}
          </li>
        </ul>
      ) : null}
    </nav>
  );
}