Function redactFindingSpans

lib/redact-engine.ts:452–480

(input: string, opts: ScanOptions = {})

 * structure-preserving path.)
 */
export function redactFindingSpans(input: string, opts: ScanOptions = {}): string | null {
  const { findings } = scan(input, opts);
  if (findings.some((f) => MARKER_ONLY_PATTERN_IDS.has(f.id))) return null;
  const targets = findings.map((f) => ({ f, ...locateSpan(input, f) }));
  if (targets.some((t) => t.start < 0)) return null;

  // Coalesce overlapping/touching ranges — splicing two intersecting spans
  // independently applies a stale end offset to already-modified text and
  // can leave trailing secret bytes in place.
  targets.sort((a, b) => a.start - b.start);
  const merged: Array<{ start: number; end: number; ids: string[] }> = [];
  for (const t of targets) {
    const last = merged[merged.length - 1];
    if (last && t.start <= last.end) {
      last.end = Math.max(last.end, t.end);
      if (!last.ids.includes(t.f.id)) last.ids.push(t.f.id);
    } else {
      merged.push({ start: t.start, end: t.end, ids: [t.f.id] });
    }
  }

  // Right-to-left so earlier offsets remain valid after splicing.
  let body = input;
  for (let i = merged.length - 1; i >= 0; i--) {
    const m = merged[i];
    body = body.slice(0, m.start) + `<REDACTED-${m.ids.join("+")}>` + body.slice(m.end);
  }
  return body;
}

function locateSpan(input: string, f: Finding): { start: number; end: number } {
  // Re-derive the offset from line/col on the original text.