import Link from 'next/link';
import { cn } from '@/lib/cn';
import { fmtInt } from '@/lib/format';

/** URL-driven pagination (server component). `makeHref(offset)` builds the link preserving current filters. */
export function Pagination({ total, limit, offset, makeHref, className }: { total: number; limit: number; offset: number; makeHref: (offset: number) => string; className?: string }) {
  const pages = Math.max(1, Math.ceil(total / limit));
  const page = Math.floor(offset / limit) + 1;
  if (pages <= 1) return <p className={cn('tnum text-xs text-ink-3', className)}>{fmtInt(total)} results</p>;
  const from = offset + 1;
  const to = Math.min(total, offset + limit);
  const btn = 'inline-flex h-10 min-w-10 items-center justify-center border border-rule px-3 text-sm text-ink-2 hover:bg-surface-2 hover:text-ink';
  return (
    <nav className={cn('flex flex-wrap items-center justify-between gap-3', className)} aria-label="Pagination">
      <p className="tnum text-xs text-ink-3">
        {fmtInt(from)}–{fmtInt(to)} of {fmtInt(total)}
      </p>
      <div className="flex items-center gap-1.5">
        {page > 1 ? (
          <Link href={makeHref(Math.max(0, offset - limit))} className={btn} rel="prev">
            ‹ Prev
          </Link>
        ) : (
          <span className={cn(btn, 'opacity-40')}>‹ Prev</span>
        )}
        <span className="mono px-2 text-xs text-ink-3">
          {page} / {fmtInt(pages)}
        </span>
        {page < pages ? (
          <Link href={makeHref(offset + limit)} className={btn} rel="next">
            Next ›
          </Link>
        ) : (
          <span className={cn(btn, 'opacity-40')}>Next ›</span>
        )}
      </div>
    </nav>
  );
}

/** Build a query-string href preserving existing params. */
export function withParams(base: string, current: Record<string, string | undefined>, patch: Record<string, string | number | undefined | null>): string {
  const p = new URLSearchParams();
  for (const [k, v] of Object.entries(current)) if (v !== undefined && v !== '') p.set(k, v);
  for (const [k, v] of Object.entries(patch)) {
    if (v === undefined || v === null || v === '' || v === 0 || v === '0') p.delete(k);
    else p.set(k, String(v));
  }
  const s = p.toString();
  return s ? `${base}?${s}` : base;
}