import type { ReactNode } from "react";

// Must match the backend's search::HL_PRE / HL_POST sentinel characters
// (U+0002 / U+0003). Written as escapes so they survive copy-paste.
const PRE = "\x02";
const POST = "\x03";

/** Renders a sentinel-marked snippet: matched spans become <mark>, the rest is text.
 *  Pure string handling — no HTML is injected, so this is XSS-safe. */
export function Highlight({ text }: { text: string }) {
  const nodes: ReactNode[] = [];
  let rest = text;
  let key = 0;

  while (rest.length > 0) {
    const start = rest.indexOf(PRE);

    if (start === -1) {
      nodes.push(rest);
      break;
    }

    if (start > 0) nodes.push(rest.slice(0, start));

    const end = rest.indexOf(POST, start + PRE.length);

    if (end === -1) {
      // Malformed: no closing marker. Emit the remainder verbatim, minus the marker.
      nodes.push(rest.slice(start + PRE.length));
      break;
    }

    nodes.push(
      <mark key={key++} className="bg-yellow-200">
        {rest.slice(start + PRE.length, end)}
      </mark>,
    );
    rest = rest.slice(end + POST.length);
  }

  return <>{nodes}</>;
}
