/**
 * Unique search/replace (Grok-shaped). No Bare imports.
 */

function countOccurrences(hay, needle) {
  if (!needle) return 0;
  const h = String(hay || '');
  const n = String(needle);
  let count = 0;
  let i = 0;
  while (i < h.length) {
    const at = h.indexOf(n, i);
    if (at < 0) break;
    count += 1;
    i = at + Math.max(1, n.length);
  }
  return count;
}

function applySearchReplace(cur, oldString, newString, replaceAll) {
  const old = oldString == null ? '' : String(oldString);
  const neu = newString == null ? '' : String(newString);
  const text = cur == null ? '' : String(cur);
  if (!old) {
    if (text.trim()) {
      throw new Error(
        'old_string is empty but the file is not empty; refuse overwrite. Use write_file to replace the whole file, or pass a unique old_string.'
      );
    }
    return { text: neu, created: true, replacements: 1 };
  }
  const n = countOccurrences(text, old);
  if (n === 0) throw new Error('old_string not found');
  if (n > 1 && !replaceAll) {
    throw new Error(
      'old_string matched ' + n + ' times; add surrounding lines to make it unique, or set replace_all to true.'
    );
  }
  const next = replaceAll ? text.split(old).join(neu) : text.replace(old, neu);
  return { text: next, created: false, replacements: replaceAll ? n : 1 };
}

function contextSnippet(text, needle, radius) {
  const lines = String(text || '').split('\n');
  const r = radius == null ? 3 : radius;
  const want = String(needle || '');
  let idx = -1;
  if (want) {
    for (let i = 0; i < lines.length; i++) {
      if (lines[i].indexOf(want) >= 0) {
        idx = i;
        break;
      }
    }
  }
  if (idx < 0) idx = 0;
  const start = Math.max(0, idx - r);
  const end = Math.min(lines.length, idx + r + 1);
  return lines
    .slice(start, end)
    .map((l, i) => String(start + i + 1).padStart(6) + '| ' + l)
    .join('\n');
}

module.exports = { countOccurrences, applySearchReplace, contextSnippet };