// 원본 품셈 보기 자료(System\BookData — civil·archit·machine·electric·culture·forest·woods) 읽기.
// DBISAM 4 암호 표: 키 = MD5(원본 세션 암호), Blowfish-CBC(IV 0) — .dat 머리 0x200 은 평문, 필드 설명은 한 사슬,
// 레코드는 레코드마다·.blb 512 바이트 블록은 블록마다 사슬을 새로 시작. 필드 pkid·upperid·orderno·chapter·title·keywords·content(BLOB).
// 본문 BLOB = zlib 압축 RTF(WPTools) → 글자(문단 줄바꿈, 표 칸 탭). Node 가 Blowfish 를 빼서 직접 구현(상수는 π 16진 자리).
// 설치 폴더는 EST_BOOK_DIR 로 바꿀 수 있다. 읽기 전용.
const fs = require("fs");
const path = require("path");
const zlib = require("zlib");
const crypto = require("crypto");

const DIR = process.env.EST_BOOK_DIR || "C:/Dasansoft/Est Plus 2/System/BookData";
const PASSWORD = 'LW`bdGD"4[';

// π 소수부 16진 자리 → Blowfish P(18)·S(4×256) 초기값
function piWords(count) {
  const digits = count * 8 + 8,
    scale = 1n << BigInt(digits * 4 + 64);
  const atan = (x) => {
    const xx = x * x;
    let term = scale / x,
      sum = term,
      k = 1n;
    for (let sign = -1n; term; sign = -sign, k += 2n) {
      term /= xx;
      sum += (sign * term) / (k + 2n);
    }
    return sum;
  };
  const pi = 16n * atan(5n) - 4n * atan(239n);
  const frac = (pi - 3n * scale) >> 64n;
  const hex = frac.toString(16).padStart(digits, "0");
  return Array.from({ length: count }, (_, i) => parseInt(hex.slice(i * 8, i * 8 + 8), 16) >>> 0);
}

function blowfish(key) {
  const init = piWords(18 + 1024),
    P = init.slice(0, 18),
    S = [0, 1, 2, 3].map((i) => init.slice(18 + i * 256, 18 + (i + 1) * 256));
  const F = (x) =>
    ((((S[0][x >>> 24] + S[1][(x >>> 16) & 255]) >>> 0) ^ S[2][(x >>> 8) & 255]) +
      S[3][x & 255]) >>>
    0;
  function encrypt(l, r) {
    for (let i = 0; i < 16; i++) {
      l = (l ^ P[i]) >>> 0;
      r = (r ^ F(l)) >>> 0;
      [l, r] = [r, l];
    }
    [l, r] = [r, l];
    r = (r ^ P[16]) >>> 0;
    l = (l ^ P[17]) >>> 0;
    return [l, r];
  }
  function decrypt(l, r) {
    for (let i = 17; i > 1; i--) {
      l = (l ^ P[i]) >>> 0;
      r = (r ^ F(l)) >>> 0;
      [l, r] = [r, l];
    }
    [l, r] = [r, l];
    r = (r ^ P[1]) >>> 0;
    l = (l ^ P[0]) >>> 0;
    return [l, r];
  }
  for (let i = 0, k = 0; i < 18; i++) {
    let w = 0;
    for (let j = 0; j < 4; j++, k++) w = ((w << 8) | key[k % key.length]) >>> 0;
    P[i] = (P[i] ^ w) >>> 0;
  }
  let l = 0,
    r = 0;
  for (let i = 0; i < 18; i += 2) {
    [l, r] = encrypt(l, r);
    P[i] = l;
    P[i + 1] = r;
  }
  for (const box of S)
    for (let i = 0; i < 256; i += 2) {
      [l, r] = encrypt(l, r);
      box[i] = l;
      box[i + 1] = r;
    }
  // CBC 풀기(IV 0), 8 바이트 미만 꼬리는 그대로
  return function cbc(buf) {
    const out = Buffer.from(buf),
      n = buf.length - (buf.length % 8);
    let pl = 0,
      pr = 0;
    for (let o = 0; o < n; o += 8) {
      const cl = buf.readUInt32BE(o),
        cr = buf.readUInt32BE(o + 4),
        [dl, dr] = decrypt(cl, cr);
      out.writeUInt32BE((dl ^ pl) >>> 0, o);
      out.writeUInt32BE((dr ^ pr) >>> 0, o + 4);
      pl = cl;
      pr = cr;
    }
    return out;
  };
}

let cbc = null;
const dec = (buf) =>
  (cbc ||= blowfish(crypto.createHash("md5").update(PASSWORD, "latin1").digest()))(buf);
const cp949 = new TextDecoder("euc-kr");
const books = new Map();

function load(name) {
  if (books.has(name)) return books.get(name);
  if (!/^[a-z]+$/.test(name)) throw Error("품셈 이름이 올바르지 않습니다.");
  const d = fs.readFileSync(path.join(DIR, `${name}.dat`));
  const size = d.readUInt16LE(0x2d),
    nf = d[0x2f],
    descEnd = d.indexOf(0, 0x48),
    desc = cp949.decode(d.subarray(0x48, Math.min(descEnd < 0 ? 0x68 : descEnd, 0x68)));
  const fd = dec(d.subarray(0x200, 0x200 + nf * 0x300));
  const fields = [];
  for (let i = 0; i < nf; i++) {
    const b = fd.subarray(i * 0x300, (i + 1) * 0x300);
    fields.push([b.subarray(3, 3 + b[2]).toString("latin1"), b[0xa4], b.readUInt16LE(0xac)]);
  }
  const rows = [];
  for (let o = 0x200 + nf * 0x300; o + size <= d.length; o += size) {
    const r = dec(d.subarray(o, o + size)),
      row = {};
    for (const [fn, t, off] of fields) {
      if (!r[off]) row[fn] = null;
      else if (t === 6) row[fn] = r.readInt32LE(off + 1);
      else if (t === 1) {
        const end = r.indexOf(0, off + 1);
        row[fn] = cp949.decode(r.subarray(off + 1, end < 0 ? off + 302 : Math.min(end, off + 302)));
      } else row[fn] = r.readUInt32LE(off + 1);
    }
    if (row.pkid != null) rows.push(row);
  }
  const book = { name, desc, rows, byId: new Map(rows.map((r) => [r.pkid, r])), texts: new Map() };
  books.set(name, book);
  return book;
}

function blob(name, first) {
  const b = fs.readFileSync(path.join(DIR, `${name}.blb`));
  const parts = [];
  let block = first,
    total = null,
    got = 0;
  const seen = new Set();
  while (block && !seen.has(block)) {
    seen.add(block);
    const x = dec(b.subarray(block * 512, (block + 1) * 512)),
      next = x.readUInt32LE(4),
      length = x.readUInt16LE(8);
    if (total == null) total = x.readUInt32LE(14);
    parts.push(x.subarray(18, 18 + length));
    got += length;
    block = next;
    if (got >= total) break;
  }
  return zlib.inflateSync(Buffer.concat(parts));
}

const SKIP = /^\{\\(\*|fonttbl|colortbl|stylesheet|info|pict|listtable|listoverridetable|object)/;
function rtfText(raw) {
  const s = raw.toString("latin1"),
    out = [],
    pend = [];
  let i = 0,
    depth = 0,
    skip = null,
    uc = 1;
  const flush = () => {
    if (pend.length) out.push(cp949.decode(Buffer.from(pend.splice(0))));
  };
  while (i < s.length) {
    const c = s[i];
    if (c === "{") {
      depth++;
      if (skip == null && SKIP.test(s.slice(i, i + 24))) skip = depth;
      i++;
    } else if (c === "}") {
      if (skip === depth) skip = null;
      depth--;
      i++;
    } else if (c === "\\") {
      const hx = /^\\'([0-9a-fA-F]{2})/.exec(s.slice(i, i + 4));
      if (hx) {
        if (skip == null) pend.push(parseInt(hx[1], 16));
        i += 4;
        continue;
      }
      const cw = /^\\([a-zA-Z]+)(-?\d+)? ?/.exec(s.slice(i, i + 40));
      if (cw) {
        const [whole, w, a] = cw;
        i += whole.length;
        if (skip != null) continue;
        if (w === "u" && a) {
          flush();
          out.push(String.fromCharCode(Number(a) & 0xffff));
          i += uc;
        } else if (w === "uc" && a) uc = Number(a);
        else if (["par", "line", "row"].includes(w)) {
          flush();
          out.push("\n");
        } else if (["cell", "tab"].includes(w)) {
          flush();
          out.push("\t");
        }
        continue;
      }
      if (skip == null && "\\{}".includes(s[i + 1] ?? "")) pend.push(s.charCodeAt(i + 1));
      i += 2;
    } else if (c === "\r" || c === "\n") i++;
    else {
      if (skip == null) pend.push(s.charCodeAt(i) & 0xff);
      i++;
    }
  }
  flush();
  return out.join("");
}

function list() {
  const names = fs
    .readFileSync(path.join(DIR, "filelist.ini"), "latin1")
    .split(/\s+/)
    .filter(Boolean);
  return names.map((name) => {
    const b = load(name);
    return { name, desc: b.desc, nodes: b.rows.length };
  });
}
function tree(name) {
  const b = load(name);
  return b.rows.map(({ pkid, upperid, orderno, chapter, title, content }) => ({
    pkid,
    parent: b.byId.has(upperid) ? upperid : null,
    order: orderno,
    chapter: chapter ?? "",
    title: title ?? "",
    content: Boolean(content),
  }));
}
function text(name, pkid) {
  const b = load(name),
    r = b.byId.get(Number(pkid));
  if (!r) throw Error("품셈 항목이 없습니다.");
  if (!r.content) return { pkid: r.pkid, chapter: r.chapter, title: r.title, text: "" };
  if (!b.texts.has(r.pkid)) b.texts.set(r.pkid, rtfText(blob(name, r.content)));
  return {
    pkid: r.pkid,
    chapter: r.chapter ?? "",
    title: r.title ?? "",
    text: b.texts.get(r.pkid),
  };
}
// 원본 전체검색(actFullSearch 0xdf8514): 검색어의 빈칸·'|' 를 지우고 제목(또는 제목+본문)에 들어 있으면.
// 키워드검색(actKeywordSearch): keywords 칸에 들어 있으면.
function search(name, word, mode = "title") {
  const b = load(name),
    kw = String(word ?? "").replace(/[\s|]/g, "");
  if (!kw) throw Error("검색어를 입력하세요.");
  return b.rows
    .filter((r) => {
      if (mode === "keyword") return String(r.keywords ?? "").includes(kw);
      if (String(r.title ?? "").includes(kw)) return true;
      return mode === "body" && r.content && text(name, r.pkid).text.includes(kw);
    })
    .map((r) => ({ pkid: r.pkid, chapter: r.chapter ?? "", title: r.title ?? "" }));
}

module.exports = { list, tree, text, search, piWords, blowfish, rtfText };