const CJK_QUERY_STOP_WORDS = new Set([
  '之前', '什么', '哪个', '多少', '记得', '记住', '有没有', '是否', '我的', '你是',
  '我们', '一下', '可以', '这个', '那个', '请问', '告诉', '说过', '提到', '聊过',
]);

function extractQueryTokens(query) {
  const q = String(query ?? '').trim();
  if (!q) return [];
  const tokens = new Set();
  for (const part of q.replace(/[^\p{L}\p{N}]+/gu, ' ').split(/\s+/)) {
    const token = part.trim();
    if (token.length >= 2 && !CJK_QUERY_STOP_WORDS.has(token)) tokens.add(token);
  }
  for (const run of q.match(/[\p{Script=Han}]{2,}/gu) ?? []) {
    if (run.length <= 6 && !CJK_QUERY_STOP_WORDS.has(run)) tokens.add(run);
    for (let i = 0; i < run.length - 1; i += 1) {
      const bigram = run.slice(i, i + 2);
      if (!CJK_QUERY_STOP_WORDS.has(bigram)) tokens.add(bigram);
    }
  }
  return [...tokens];
}

function scoreMemoryForRecall(text, tokens) {
  let score = 0;
  for (const token of tokens) {
    if (text.includes(token)) score += 1;
  }
  if (/别名.{0,8}是/u.test(text)) score += 5;
  if (/[？?]\s*$/.test(text)) score -= 3;
  if (/^用户记住/u.test(text)) score -= 2;
  return score;
}

export function filterMemoriesByQuery(memories, query) {
  const items = Array.isArray(memories) ? memories : [];
  const tokens = extractQueryTokens(query);
  if (!tokens.length || !items.length) return items.slice(0, Math.min(items.length, 5));
  const matched = items
    .map((item) => {
      const text = String(item?.text ?? item?.memory_text ?? '').trim();
      return { item, text, score: scoreMemoryForRecall(text, tokens) };
    })
    .filter(({ text, score }) => text && score > 0)
    .sort((a, b) => b.score - a.score)
    .map(({ item }) => item);
  return matched.length ? matched.slice(0, 5) : items.slice(0, 5);
}

export async function resolveMemoriesWithLegacyFallback({
  memoryV2 = null,
  conversationMemoryService = null,
  userId,
  sessionId = null,
  query = null,
  limit = 20,
  recallQuestion = false,
} = {}) {
  if (!userId || limit <= 0) return [];
  if (recallQuestion && conversationMemoryService?.listMemories) {
    const legacy = await conversationMemoryService.listMemories(userId, { limit }).catch(() => []);
    const filtered = filterMemoriesByQuery(legacy, query);
    if (filtered.length) return filtered;
  }
  if (memoryV2?.resolve) {
    const resolved = await memoryV2.resolve({
      userId,
      sessionId,
      query,
      limit,
    }).catch(() => null);
    const memories = Array.isArray(resolved?.memories) ? resolved.memories : [];
    if (memories.length) return memories;
  }
  if (!conversationMemoryService?.listMemories) return [];
  const legacy = await conversationMemoryService.listMemories(userId, { limit }).catch(() => []);
  return filterMemoriesByQuery(legacy, query);
}