// v1.10.5: XML-tag tool-call fallback. Some models emit
// <tool_call><function=foo><parameter=key>value</parameter></function></tool_call>
// in plain content instead of using the OpenAI tool_calls JSON channel.
// The streaming loop in inference.ts extracts these blocks via these helpers.

export const XML_TOOL_OPEN = '<tool_call>';
export const XML_TOOL_CLOSE = '</tool_call>';

export function parseXmlToolCall(
  block: string,
): { name: string; args: Record<string, unknown> } | null {
  const nameMatch = block.match(/<function=([^>]+)>/);
  if (!nameMatch || !nameMatch[1]) return null;
  const name = nameMatch[1].trim();
  if (!name) return null;
  const args: Record<string, unknown> = {};
  // Non-greedy body so each <parameter=…>…</parameter> pair is matched
  // independently even when multiple appear in the same block.
  const paramRe = /<parameter=([^>]+)>([\s\S]*?)<\/parameter>/g;
  for (const m of block.matchAll(paramRe)) {
    const key = (m[1] ?? '').trim();
    if (!key) continue;
    const raw = (m[2] ?? '').trim();
    try {
      args[key] = JSON.parse(raw);
    } catch {
      args[key] = raw;
    }
  }
  return { name, args };
}

// Locate the first character that begins (or completely contains) an
// unfinished <tool_call> opener in `s`. Returns -1 when `s` can be flushed
// to the client in full without risking a partial tag leak.
//   Case 1: a full `<tool_call>` opener with no matching closer — caller
//           must keep everything from that index forward until the next
//           chunk arrives with the closer.
//   Case 2: `s` ends with a strict prefix of `<tool_call>` (e.g. `<tool_c`).
//           Caller must keep just that suffix in the buffer.
// Note: case 1 assumes the calling loop already extracted every complete
// <tool_call>…</tool_call> pair before reaching this check.
export function partialXmlOpenerStart(s: string): number {
  const fullOpener = s.indexOf(XML_TOOL_OPEN);
  if (fullOpener !== -1) return fullOpener;
  const lastLt = s.lastIndexOf('<');
  if (lastLt === -1) return -1;
  const suffix = s.slice(lastLt);
  if (XML_TOOL_OPEN.startsWith(suffix) && suffix.length < XML_TOOL_OPEN.length) {
    return lastLt;
  }
  return -1;
}