export function parseJsonCandidate(candidate: string | null): unknown {
  if (candidate === null) return undefined;
  for (const text of candidateJsonTexts(candidate)) {
    try {
      return JSON.parse(text) as unknown;
    } catch {
      // Try the next lossless candidate shape.
    }
  }
  return undefined;
}

export function candidateJsonTexts(candidate: string): readonly string[] {
  const trimmed = candidate.trim();
  const texts = [trimmed];
  const fenced = trimmed.match(/^```(?:json)?\s*\n(?<body>[\s\S]*?)\n```$/u)?.groups?.["body"]?.trim();
  if (fenced) texts.push(fenced);

  const objectStart = trimmed.indexOf("{");
  const objectEnd = trimmed.lastIndexOf("}");
  if (objectStart !== -1 && objectEnd > objectStart) {
    texts.push(trimmed.slice(objectStart, objectEnd + 1));
  }

  const arrayStart = trimmed.indexOf("[");
  const arrayEnd = trimmed.lastIndexOf("]");
  if (arrayStart !== -1 && arrayEnd > arrayStart) {
    texts.push(trimmed.slice(arrayStart, arrayEnd + 1));
  }

  return [...new Set(texts)];
}