export type Heading = { id: string; text: string; level: number; line: number };
export function headingsFor(content: string): Heading[] {
  let fenced = false;
  const counts = new Map<string, number>();
  return content.split("\n").flatMap((line, index) => {
    if (/^\s*(```|~~~)/.test(line)) {
      fenced = !fenced;
      return [];
    }
    const match = !fenced && line.match(/^(#{2,3})\s+(.+?)\s*#*$/);
    if (!match) return [];
    const text = match[2].replace(/[`*_]/g, "");
    const base =
      text
        .toLowerCase()
        .replace(/[^\p{L}\p{N}\s-]/gu, "")
        .trim()
        .replace(/\s+/g, "-") || "section";
    const count = counts.get(base) ?? 0;
    counts.set(base, count + 1);
    return [
      {
        id: count ? `${base}-${count}` : base,
        text,
        level: match[1].length,
        line: index + 1,
      },
    ];
  });
}