'use strict';

// KB Markdown 分块：与旧 bridge rag/chunker.js 保持一致的 parent/child 结构。
const MAX_CHILD_CHARS = 500;

function parseFrontmatter(text) {
  const m = String(text).match(/^---\n([\s\S]*?)\n---\n([\s\S]*)$/);
  if (!m) return { meta: {}, body: String(text) };
  const meta = {};
  const fm = m[1].split('\n');
  for (let i = 0; i < fm.length; i += 1) {
    const kv = fm[i].match(/^(\w+):\s*(.*)$/);
    if (!kv) continue;
    const key = kv[1];
    let value = kv[2].trim();
    if (value.startsWith('[')) {
      value = value.replace(/[\[\]]/g, '').split(',').map((s) => s.trim().replace(/^["']|["']$/g, '')).filter(Boolean);
    } else if (value === '') {
      const arr = [];
      while (i + 1 < fm.length && /^\s+-\s+/.test(fm[i + 1])) {
        i += 1;
        const item = fm[i].replace(/^\s+-\s+/, '').trim().replace(/^["']|["']$/g, '');
        if (item) arr.push(item);
      }
      value = arr;
    } else {
      value = value.replace(/^["']|["']$/g, '');
    }
    meta[key] = value;
  }
  return { meta, body: m[2] };
}

function splitChunks(body) {
  const chunks = [];
  let current = null;
  let section = '';
  for (const line of String(body).split('\n')) {
    const h2 = line.match(/^##\s+(.*)$/);
    if (h2) { section = h2[1].trim(); continue; }
    const q = line.match(/^###\s+Q:\s*(.*)$/);
    if (q) {
      if (current) chunks.push(current);
      current = { question: q[1].trim(), answer: '', section };
    } else if (current) {
      current.answer += line + '\n';
    }
  }
  if (current) chunks.push(current);
  return chunks.map((c) => ({ ...c, answer: c.answer.trim() }));
}

function sourceUrls(meta) {
  const raw = meta.source_urls || meta.source_url || [];
  return (Array.isArray(raw) ? raw : [raw]).map(String).filter((u) => /^https?:\/\//.test(u));
}

function createParentChildChunks(chunk, meta, sourceFile) {
  const keywords = Array.isArray(meta.keywords) ? meta.keywords : [];
  const embText = [keywords.join(' '), chunk.question, chunk.answer].filter(Boolean).join('\n');
  const parent = {
    source_file: sourceFile,
    title: meta.title || '',
    category: meta.category || '',
    section: chunk.section,
    question: chunk.question,
    answer: chunk.answer,
    keywords,
    source_urls: sourceUrls(meta),
    chunk_type: 'parent',
    embText,
  };
  if (chunk.answer.length <= MAX_CHILD_CHARS) return { parent, children: [] };
  const children = (chunk.answer.match(new RegExp(`[^\\n]{1,${MAX_CHILD_CHARS}}`, 'g')) || [chunk.answer]).map((part) => ({
    source_file: sourceFile,
    title: meta.title || '',
    category: meta.category || '',
    section: chunk.section,
    question: chunk.question,
    answer: part,
    keywords,
    source_urls: sourceUrls(meta),
    chunk_type: 'child',
    embText: [keywords.join(' '), chunk.question, part].filter(Boolean).join('\n'),
  }));
  return { parent, children };
}

module.exports = { parseFrontmatter, splitChunks, createParentChildChunks, sourceUrls, MAX_CHILD_CHARS };