// ask-lib.js — 共享检索库（浏览器 + Node 通用，UMD）。
// 与 src/asr.py 的 _ask_tokens / _ask_retrieve 严格对应（同一套分词与打分），
// 供 web/ask.html（客户端降级检索）与 api/ask.js（服务端 RAG 检索）复用，避免两份实现走样。
// 改这里就要同步改 asr.py，并跑 scripts/check_ask_parity.py 验一致。
(function (root, factory) {
  if (typeof module === "object" && module.exports) module.exports = factory();
  else root.AskLib = factory();
})(typeof self !== "undefined" ? self : this, function () {
  "use strict";

  // 与 asr._ASK_STOP 一致（中文单字停用词只过滤单字 token，不影响二元组）。
  var STOP = new Set([
    "the","a","an","of","to","in","on","at","for","and","or","is","are","be","do","does","did",
    "what","whats","how","when","where","which","who","can","could","would","i","me","my","you","your",
    "请问","一下","什么","怎么","怎样","如何","吗","呢","的","了","有","我","要","去","想","最近","一个","可以"
  ]);

  // 类别优先级（与 asr._CAT_PRIO 一致）。
  var CAT_PRIO = {
    "handbook":3,"appliances":3,"manual":3,"estate-rules":3,"facilities-howto":2,"booking-rules":2,
    "bus":2,"facilities":2,"faq":2,"news":1
  };

  // ASCII 词（≥2、去停用词）+ 中文单字 + 相邻二元组。须与 asr._ask_tokens 一致。
  function askTokens(text) {
    if (!text) return [];
    var s = String(text).toLowerCase();
    var toks = [];
    var m, re1 = /[a-z0-9]+/g;
    while ((m = re1.exec(s)) !== null) {
      var w = m[0];
      if (w.length >= 2 && !STOP.has(w)) toks.push(w);
    }
    var re2 = /[一-鿿]+/g;
    while ((m = re2.exec(s)) !== null) {
      var run = m[0];
      for (var i = 0; i < run.length; i++) {
        var c = run[i];
        if (!STOP.has(c)) toks.push(c);
        if (i + 1 < run.length) toks.push(c + run[i + 1]);
      }
    }
    return toks;
  }

  function setOf(arr) { return new Set(arr); }
  function inter(a, b) { var n = 0, out = []; b.forEach(function (t) { if (a.has(t)) out.push(t); }); return out; }

  function chunkSets(c) {
    var ti = setOf(askTokens(c.title || ""));
    var tx = setOf(askTokens(c.text || ""));
    var kw = new Set();
    (c.keywords || []).forEach(function (k) { askTokens(k).forEach(function (t) { kw.add(t); }); });
    return { ti: ti, tx: tx, kw: kw };
  }

  // idf 加权词重叠检索；返回 top-k chunk。与 asr._ask_retrieve 一致。
  function askRetrieve(index, question, k) {
    k = k || 5;
    var chunks = (index && index.chunks) || [];
    var df = Object.create(null), docs = [];
    chunks.forEach(function (c) {
      var s = chunkSets(c);
      docs.push({ c: c, s: s });
      var all = new Set();
      s.ti.forEach(function (t) { all.add(t); });
      s.tx.forEach(function (t) { all.add(t); });
      s.kw.forEach(function (t) { all.add(t); });
      all.forEach(function (t) { df[t] = (df[t] || 0) + 1; });
    });
    var N = Math.max(1, docs.length);
    function idf(t) { return Math.log((N + 1) / ((df[t] || 0) + 1)) + 1.0; }
    var q = setOf(askTokens(question));
    if (q.size === 0) return [];
    var scored = [];
    docs.forEach(function (d) {
      var s = 0;
      inter(d.s.tx, q).forEach(function (t) { s += idf(t); });
      inter(d.s.kw, q).forEach(function (t) { s += 2.0 * idf(t); });
      inter(d.s.ti, q).forEach(function (t) { s += 1.5 * idf(t); });
      if (s > 0) {
        s *= 1.0 + 0.04 * (CAT_PRIO[d.c.category] || 1);
        scored.push({ s: s, c: d.c });
      }
    });
    scored.sort(function (a, b) { return b.s - a.s; });
    return scored.slice(0, k).map(function (x) { return x.c; });
  }

  return { askTokens: askTokens, askRetrieve: askRetrieve, STOP: STOP, CAT_PRIO: CAT_PRIO };
});