export interface BibEntry {
  type: string;
  key: string;
  fields: Record<string, string>;
}

/** Minimal BibTeX parser (enough for key extraction and field checks). */
export function parseBib(text: string): BibEntry[] {
  const entries: BibEntry[] = [];
  const re = /@(\w+)\s*\{\s*([^,\s]+)\s*,/g;
  for (const m of text.matchAll(re)) {
    const type = (m[1] ?? "").toLowerCase();
    if (type === "comment" || type === "preamble" || type === "string") continue;
    const start = (m.index ?? 0) + m[0].length;
    let depth = 1;
    let i = start;
    while (i < text.length && depth > 0) {
      if (text[i] === "{") depth++;
      else if (text[i] === "}") depth--;
      i++;
    }
    const body = text.slice(start, i - 1);
    const fields: Record<string, string> = {};
    const fre = /(\w+)\s*=\s*(\{((?:[^{}]|\{[^{}]*\})*)\}|"([^"]*)"|([^,\n]+))/g;
    for (const f of body.matchAll(fre))
      fields[(f[1] ?? "").toLowerCase()] = (f[3] ?? f[4] ?? f[5] ?? "").trim();
    entries.push({ type, key: m[2] ?? "", fields });
  }
  return entries;
}

export function citeKeysInTex(tex: string): string[] {
  const keys = new Set<string>();
  const re =
    /\\(?:cite|citep|citet|citeauthor|citeyear|parencite|textcite|autocite|citealp|citealt|nocite)\*?(?:\[[^\]]*\]){0,2}\{([^}]+)\}/g;
  for (const m of tex.matchAll(re))
    for (const k of (m[1] ?? "").split(",")) if (k.trim() && k.trim() !== "*") keys.add(k.trim());
  return [...keys];
}