/**
 * Strip lines starting with `_` (comment convention for prompt .md files)
 * and collapse any resulting consecutive blank lines.
 *
 * Lines inside fenced code blocks (``` or ~~~ delimiters per CommonMark)
 * are never stripped, so code examples with `_`-prefixed identifiers are preserved.
 */
export function stripCommentLines(content: string): string {
  const normalized = content.replace(/\r\n/g, "\n");
  let openFenceChar: string | null = null;
  const filtered = normalized.split("\n").filter((line) => {
    const fenceMatch = line.match(/^ {0,3}(`{3,}|~{3,})/);
    if (fenceMatch) {
      const char = fenceMatch[1][0];
      if (!openFenceChar) {
        openFenceChar = char;
      } else if (char === openFenceChar) {
        openFenceChar = null;
      }
    }
    if (openFenceChar) {
      return true;
    }
    return !line.trimStart().startsWith("_");
  });
  return filtered
    .join("\n")
    .replace(/\n{3,}/g, "\n\n")
    .trim();
}