/**
 * Head+tail truncation with a recovery marker. No Bare imports.
 */

const CHAR_PER_TOKEN = 4;

function estimateTokens(s) {
  return Math.ceil(String(s || '').length / CHAR_PER_TOKEN);
}

function truncateWithMarker(text, maxChars) {
  const s = text == null ? '' : typeof text === 'string' ? text : JSON.stringify(text);
  const max = maxChars > 0 ? maxChars : 12000;
  if (s.length <= max) return s;
  const keep = Math.max(80, Math.floor((max - 80) / 2));
  const omitted = s.length - keep * 2;
  return (
    s.slice(0, keep) +
    '\n\n[truncated ' +
    omitted +
    ' chars; use offset/limit or a narrower path to read the middle]\n\n' +
    s.slice(-keep)
  );
}

function renderToolResult(out, maxChars) {
  let payload = out;
  if (out && typeof out === 'object' && !Array.isArray(out) && Array.isArray(out.images)) {
    payload = Object.assign({}, out);
    delete payload.images;
  }
  const raw = typeof payload === 'string' ? payload : JSON.stringify(payload);
  return truncateWithMarker(raw, maxChars != null ? maxChars : 12000);
}

module.exports = { CHAR_PER_TOKEN, estimateTokens, truncateWithMarker, renderToolResult };