/**
 * server.js — SoundGame 用户系统 + 静态文件服务器（Node 零依赖，仅内置模块）。
 *
 * P0-B 无感用户系统（research/platform/01-identity.md 方案 B + 03-data-sync.md §3）：
 *
 * 1. 静态托管 web/ 根目录（正确 MIME，简化版 Range 供音频拖动）。
 *    web/server/ 目录（含 data/ 的 token 与 PIN 哈希）一律 404，不对外提供。
 *
 * 2. JSON API：
 *    - POST /api/device   {token?}            匿名自动建档 → {profileId, token, name}（自动名
 *                                            「玩家一/二/…」）；带有效 token 时为重附着（幂等）
 *    - GET  /api/profile                      当前档案信息（Bearer）
 *    - PUT  /api/profile  {name}              改名（Bearer）
 *    - POST /api/claim    {name?, pin?}       认领：给当前档案命名和/或设 PIN（scrypt 哈希）。
 *                                            若名字+PIN 已有档案 → 验 PIN 后把当前匿名档案的
 *                                            进度按桶 LWW 合并进目标档案并改绑 token（换设备登录）
 *    - POST /api/login    {username, pin}     旧客户端兼容（v1 用户迁移后仍可登录）
 *    - POST /api/register {username, pin}     旧客户端兼容（等价于直接建已认领档案，建议改用 claim）
 *    - POST /api/logout                       吊销当前 token（Bearer）
 *    - GET  /api/progress?game=xxx            读单桶，保持 {game, data} 形状（radio 等游戏兼容）
 *    - GET  /api/progress                     读全部桶 {games: {...}}（大厅一次拉回，修 03 §1.2）
 *    - PUT  /api/progress {game, data, baseUpdatedAt?}
 *                                            写桶。baseUpdatedAt 与服务器桶不符 → 409 + 服务器桶
 *                                            （LWW 冲突，客户端择优重试）；缺省视为 legacy 放行
 *                                            （console 警告——各游戏存量 PUT 不带此字段）。
 *
 * 3. 数据落盘（data/ 目录自动创建；env SG_DATA_DIR 可覆盖，供测试）：
 *    data/profiles.json          { seq, profiles: { <pid>: {name, pinHash, createdAt} } }
 *    data/tokens.json            { <token>: {profileId, createdAt, lastSeen, expiresAt} }
 *    data/profiles/<pid>.json    { id, games: { <game>: {updatedAt, rev, data} } }（桶级包装）
 *    v1 兼容迁移（启动时单向，原文件保留不动）：
 *      users.json   {username: pin明文}      → profiles.json（PIN 立即 scrypt 哈希，pid=旧用户名）
 *      sessions.json {token: username}       → tokens.json（补 180 天滑动过期）
 *      <username>.json {game: data}          → profiles/<username>.json（每桶补 updatedAt/rev）
 *
 * 安全水位（家庭局域网）：PIN scrypt 哈希（N=16384, r=8）、token 180 天滑动过期 +
 * 登出吊销 + 惰性清扫、/api/device per-IP 频控（默认 10 个/天，env SG_DEVICE_LIMIT）。
 * HTTP 明文传输不变——请勿暴露公网，详见 web/server/README.md。
 */

const http = require('node:http');
const fs = require('node:fs');
const fsp = require('node:fs/promises');
const path = require('node:path');
const crypto = require('node:crypto');

const PORT = Number(process.env.PORT) || 8000;
const ROOT = path.resolve(__dirname, '..'); // web/
const DATA_DIR = process.env.SG_DATA_DIR
  ? path.resolve(process.env.SG_DATA_DIR)
  : path.join(__dirname, 'data'); // web/server/data/
const PROFILES_DIR = path.join(DATA_DIR, 'profiles');
const PROFILES_FILE = path.join(DATA_DIR, 'profiles.json');
const TOKENS_FILE = path.join(DATA_DIR, 'tokens.json');
const USERS_FILE = path.join(DATA_DIR, 'users.json'); // v1 兼容
const SESSIONS_FILE = path.join(DATA_DIR, 'sessions.json'); // v1 兼容

const DEVICE_LIMIT = Number(process.env.SG_DEVICE_LIMIT) || 10; // per-IP 每日匿名建档上限
const TOKEN_TTL_MS = 180 * 24 * 3600 * 1000; // 180 天滑动
const TOKEN_TOUCH_MS = 6 * 3600 * 1000; // 滑动续期节流（6h 内不重复落盘）

const MIME = {
  '.html': 'text/html; charset=utf-8',
  '.js': 'text/javascript; charset=utf-8',
  '.mjs': 'text/javascript; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.json': 'application/json; charset=utf-8',
  '.png': 'image/png',
  '.jpg': 'image/jpeg',
  '.jpeg': 'image/jpeg',
  '.gif': 'image/gif',
  '.svg': 'image/svg+xml',
  '.ico': 'image/x-icon',
  '.ogg': 'audio/ogg',
  '.m4a': 'audio/mp4',
  '.mp3': 'audio/mpeg',
  '.wav': 'audio/wav',
  '.mp4': 'video/mp4',
  '.txt': 'text/plain; charset=utf-8',
  '.md': 'text/markdown; charset=utf-8',
};

const USERNAME_RE = /^[A-Za-z0-9_\-一-龥]{1,24}$/;
const PIN_RE = /^\d{4,6}$/;
const TOKEN_RE = /^[0-9a-f]{16,128}$/i;

// ---------------- 状态 ----------------

/** @type {{ seq: number, profiles: Record<string, {name: string, pinHash: string|null, createdAt: string}> }} */
let profileIndex = { seq: 0, profiles: {} };
/** @type {Record<string, {profileId: string, createdAt: string, lastSeen: string, expiresAt: string}>} */
let tokens = {};

/** 按文件串行的写入队列：file -> Promise 链尾 */
const writeQueues = new Map();

function enqueueWrite(file, fn) {
  const tail = writeQueues.get(file) || Promise.resolve();
  const next = tail.then(fn, fn); // 前序失败不阻塞后续
  writeQueues.set(file, next.catch(() => {}));
  return next;
}

async function readJson(file, fallback) {
  try {
    return JSON.parse(await fsp.readFile(file, 'utf8'));
  } catch (_) {
    return fallback;
  }
}

/** 队列化原子写（tmp + rename）。 */
function writeJson(file, obj) {
  return enqueueWrite(file, async () => {
    const tmp = file + '.tmp';
    await fsp.writeFile(tmp, JSON.stringify(obj, null, 2));
    await fsp.rename(tmp, file);
  });
}

// ---------------- PIN：scrypt 哈希（node:crypto 内置，零依赖） ----------------

const SCRYPT = { N: 16384, r: 8, p: 1, keylen: 64 };

function hashPin(pin) {
  const salt = crypto.randomBytes(16);
  const hash = crypto.scryptSync(pin, salt, SCRYPT.keylen, SCRYPT);
  return `scrypt$${SCRYPT.N}$${SCRYPT.r}$${SCRYPT.p}$${salt.toString('hex')}$${hash.toString('hex')}`;
}

/** 恒时比较；v1 明文 PIN（不以 scrypt$ 开头）直接比对（调用方负责透明升级为哈希）。 */
function verifyPin(pin, stored) {
  if (typeof stored !== 'string' || !stored || typeof pin !== 'string') return false;
  if (!stored.startsWith('scrypt$')) return stored === pin;
  const parts = stored.split('$');
  if (parts.length !== 6) return false;
  try {
    const [, N, r, p, saltHex, hashHex] = parts;
    const expected = Buffer.from(hashHex, 'hex');
    const actual = crypto.scryptSync(pin, Buffer.from(saltHex, 'hex'), expected.length, {
      N: Number(N), r: Number(r), p: Number(p),
    });
    return expected.length === actual.length && crypto.timingSafeEqual(expected, actual);
  } catch (_) {
    return false;
  }
}

// ---------------- 档案 / token ----------------

/** pid 兼容两种形态：新生 p_<hex> 与迁移档案（pid=旧用户名，已被 USERNAME_RE 限制为安全文件名字符）。 */
function profileGamesFile(pid) {
  if (typeof pid !== 'string' || !USERNAME_RE.test(pid)) throw new Error('bad pid');
  return path.join(PROFILES_DIR, `${pid}.json`);
}

async function loadGamesDoc(pid) {
  const doc = await readJson(profileGamesFile(pid), null);
  if (doc && typeof doc === 'object' && doc.games && typeof doc.games === 'object') return doc;
  return { id: pid, games: {} };
}

/** 读-改-写整体进队列（fn 收到当前 doc，返回 null 跳过落盘）。 */
function withGamesDoc(pid, fn) {
  const file = profileGamesFile(pid);
  return enqueueWrite(file, async () => {
    const doc = await loadGamesDoc(pid);
    const mutated = await fn(doc);
    if (mutated === false) return null;
    const tmp = file + '.tmp';
    await fsp.writeFile(tmp, JSON.stringify(doc, null, 2));
    await fsp.rename(tmp, file);
    return doc;
  });
}

function persistProfileIndex() {
  return writeJson(PROFILES_FILE, profileIndex);
}

function cleanupTokens() {
  const now = Date.now();
  let removed = 0;
  for (const [tok, entry] of Object.entries(tokens)) {
    if (!entry || !profileIndex.profiles[entry.profileId] || Date.parse(entry.expiresAt) < now) {
      delete tokens[tok];
      removed += 1;
    }
  }
  return removed;
}

function persistTokens() {
  const removed = cleanupTokens();
  if (removed) console.log(`[server] 清扫过期/悬空 token ${removed} 条`);
  return writeJson(TOKENS_FILE, tokens);
}

function issueToken(profileId) {
  const token = crypto.randomBytes(24).toString('hex');
  const now = new Date().toISOString();
  tokens[token] = {
    profileId,
    createdAt: now,
    lastSeen: now,
    expiresAt: new Date(Date.now() + TOKEN_TTL_MS).toISOString(),
  };
  persistTokens();
  return token;
}

/** Bearer 鉴权 + 滑动续期（节流落盘）。返回 {token, profileId, profile} 或 null。 */
function authProfile(req) {
  const h = req.headers.authorization || '';
  const m = h.match(/^Bearer\s+([0-9a-f]+)$/i);
  if (!m) return null;
  const token = m[1].toLowerCase();
  return authByToken(token);
}

function authByToken(token) {
  const entry = tokens[token];
  if (!entry || !profileIndex.profiles[entry.profileId]) return null;
  if (Date.parse(entry.expiresAt) < Date.now()) {
    delete tokens[token];
    persistTokens();
    return null;
  }
  if (Date.now() - Date.parse(entry.lastSeen) > TOKEN_TOUCH_MS) {
    entry.lastSeen = new Date().toISOString();
    entry.expiresAt = new Date(Date.now() + TOKEN_TTL_MS).toISOString();
    persistTokens();
  }
  return { token, profileId: entry.profileId, profile: profileIndex.profiles[entry.profileId] };
}

function newProfileId() {
  for (;;) {
    const pid = 'p_' + crypto.randomBytes(6).toString('hex');
    if (!profileIndex.profiles[pid]) return pid;
  }
}

/** 桶级 LWW 裁决（03 §3.4）：updatedAt 新者胜，同值比 rev。 */
function newerBucket(a, b) {
  if (!a) return b;
  if (!b) return a;
  if (a.updatedAt !== b.updatedAt) return a.updatedAt > b.updatedAt ? a : b;
  return (a.rev || 0) >= (b.rev || 0) ? a : b;
}

function findClaimedByName(name) {
  for (const [pid, p] of Object.entries(profileIndex.profiles)) {
    if (p.pinHash && p.name === name) return pid;
  }
  return null;
}

/** 自动名：玩家一、玩家二 … 玩家九十九（预生成语音词表覆盖一~九，见 01 §4.2）。 */
function cnNum(n) {
  const d = ['零', '一', '二', '三', '四', '五', '六', '七', '八', '九'];
  if (!Number.isInteger(n) || n <= 0 || n > 99) return String(n);
  if (n < 10) return d[n];
  const t = Math.floor(n / 10);
  const u = n % 10;
  return (t > 1 ? d[t] : '') + '十' + (u ? d[u] : '');
}

// ---------------- per-IP 频控（仅匿名建档） ----------------

const deviceCreations = new Map(); // ip -> {day, count}

function allowDeviceCreate(req) {
  const ip = String(req.socket.remoteAddress || '?').replace(/^::ffff:/, '');
  const day = new Date().toISOString().slice(0, 10);
  const rec = deviceCreations.get(ip);
  if (!rec || rec.day !== day) {
    deviceCreations.set(ip, { day, count: 1 });
    return true;
  }
  if (rec.count >= DEVICE_LIMIT) return false;
  rec.count += 1;
  return true;
}

// ---------------- HTTP 工具 ----------------

function sendJson(res, status, obj) {
  const body = JSON.stringify(obj);
  res.writeHead(status, {
    'Content-Type': 'application/json; charset=utf-8',
    'Content-Length': Buffer.byteLength(body),
    'Cache-Control': 'no-store',
  });
  res.end(body);
}

function readBody(req) {
  return new Promise((resolve, reject) => {
    const chunks = [];
    let size = 0;
    req.on('data', (c) => {
      size += c.length;
      if (size > 1024 * 1024) { // 1MB 上限
        reject(new Error('body too large'));
        req.destroy();
        return;
      }
      chunks.push(c);
    });
    req.on('end', () => resolve(Buffer.concat(chunks).toString('utf8')));
    req.on('error', reject);
  });
}

async function parseBody(req) {
  const raw = await readBody(req);
  if (!raw) return {};
  const obj = JSON.parse(raw);
  return obj && typeof obj === 'object' && !Array.isArray(obj) ? obj : {};
}

// ---------------- API ----------------

async function handleApi(req, res, url) {
  const route = `${req.method} ${url.pathname}`;

  // ---- 匿名自动建档 / 重附着 ----
  if (route === 'POST /api/device') {
    const body = await parseBody(req);
    if (body.token !== undefined) {
      if (typeof body.token !== 'string' || !TOKEN_RE.test(body.token)) {
        return sendJson(res, 400, { error: 'token 格式非法' });
      }
      const auth = authByToken(body.token.toLowerCase());
      if (auth) {
        return sendJson(res, 200, {
          ok: true, attached: true, profileId: auth.profileId, token: auth.token,
          name: auth.profile.name, claimed: !!auth.profile.pinHash,
        });
      }
      // 失效 token：视作无参，重新建档（下方统一处理）
    }
    if (!allowDeviceCreate(req)) {
      return sendJson(res, 429, { error: `本机今日匿名档案创建数已达上限（${DEVICE_LIMIT}）` });
    }
    const pid = newProfileId();
    profileIndex.seq += 1;
    const profile = {
      name: '玩家' + cnNum(profileIndex.seq),
      pinHash: null,
      createdAt: new Date().toISOString(),
    };
    profileIndex.profiles[pid] = profile;
    await persistProfileIndex();
    const token = issueToken(pid);
    return sendJson(res, 201, { ok: true, profileId: pid, token, name: profile.name, claimed: false });
  }

  // ---- 档案信息 / 改名 ----
  if (route === 'GET /api/profile') {
    const auth = authProfile(req);
    if (!auth) return sendJson(res, 401, { error: '未授权：缺少或无效 Bearer token' });
    const p = auth.profile;
    return sendJson(res, 200, {
      profileId: auth.profileId, name: p.name, claimed: !!p.pinHash, createdAt: p.createdAt,
    });
  }

  if (route === 'PUT /api/profile') {
    const auth = authProfile(req);
    if (!auth) return sendJson(res, 401, { error: '未授权：缺少或无效 Bearer token' });
    const { name } = await parseBody(req);
    if (typeof name !== 'string' || !USERNAME_RE.test(name)) {
      return sendJson(res, 400, { error: '名字需为 1~24 位字母/数字/中文/_/-' });
    }
    const holder = findClaimedByName(name);
    if (holder && holder !== auth.profileId) {
      return sendJson(res, 409, { error: '该名字已被其他已认领档案使用' });
    }
    auth.profile.name = name;
    await persistProfileIndex();
    return sendJson(res, 200, { ok: true, name });
  }

  // ---- 认领：命名 / 设 PIN / 名字+PIN 登录（合并） ----
  if (route === 'POST /api/claim') {
    const body = await parseBody(req);
    const auth = authProfile(req) || (typeof body.token === 'string' && TOKEN_RE.test(body.token)
      ? authByToken(body.token.toLowerCase())
      : null);
    if (!auth) return sendJson(res, 401, { error: '未授权：缺少或无效 Bearer token' });
    const { name, pin } = body;
    if (pin !== undefined && pin !== null && (typeof pin !== 'string' || !PIN_RE.test(pin))) {
      return sendJson(res, 400, { error: 'PIN 需为 4~6 位数字' });
    }
    const profile = auth.profile;

    // 只设 PIN（不改名）：当前档案升级为可跨设备登录
    if (name === undefined || name === null || name === '') {
      if (!pin) return sendJson(res, 400, { error: '缺少 name 或 pin' });
      profile.pinHash = hashPin(pin);
      await persistProfileIndex();
      return sendJson(res, 200, { ok: true, profileId: auth.profileId, name: profile.name, claimed: true });
    }

    if (typeof name !== 'string' || !USERNAME_RE.test(name)) {
      return sendJson(res, 400, { error: '名字需为 1~24 位字母/数字/中文/_/-' });
    }
    const targetPid = findClaimedByName(name);

    // 目标不存在（或就是自己）：原地命名 + 设 PIN，进度零迁移
    if (!targetPid || targetPid === auth.profileId) {
      profile.name = name;
      if (pin) profile.pinHash = hashPin(pin);
      await persistProfileIndex();
      return sendJson(res, 200, { ok: true, profileId: auth.profileId, name, claimed: !!profile.pinHash });
    }

    // 目标已存在：验 PIN → 当前匿名档案按桶 LWW 合并进目标 → token 改绑
    if (profile.pinHash) {
      return sendJson(res, 409, { error: '当前档案已设 PIN；请先用「新玩家」建匿名档案再登录' });
    }
    if (!pin) return sendJson(res, 401, { error: `「${name}」已设 PIN，请输入 PIN 登录` });
    const target = profileIndex.profiles[targetPid];
    if (!verifyPin(pin, target.pinHash)) {
      return sendJson(res, 401, { error: 'PIN 不正确' });
    }
    if (!target.pinHash.startsWith('scrypt$')) {
      target.pinHash = hashPin(pin); // v1 明文透明升级（迁移漏网兜底）
    }
    const srcPid = auth.profileId;
    let mergedGames = 0;
    await withGamesDoc(targetPid, (dst) => {
      // 源/目标两文件各自串行；合并按桶 LWW（newerBucket），重复执行幂等
      return loadGamesDoc(srcPid).then((src) => {
        for (const [game, bucket] of Object.entries(src.games)) {
          const cur = dst.games[game];
          if (!cur || newerBucket(cur, bucket) !== cur) {
            dst.games[game] = bucket;
            mergedGames += 1;
          }
        }
      });
    });
    tokens[auth.token].profileId = targetPid; // token 改绑目标档案
    await persistTokens();
    delete profileIndex.profiles[srcPid]; // 匿名源档案出索引（其 games 文件成孤儿，惰性清理见下）
    await persistProfileIndex();
    enqueueWrite(profileGamesFile(srcPid), async () => {
      await fsp.unlink(profileGamesFile(srcPid)).catch(() => {});
    });
    console.log(`[server] claim 合并: ${srcPid} → ${targetPid}（${mergedGames} 桶更新）`);
    return sendJson(res, 200, {
      ok: true, merged: true, mergedGames, profileId: targetPid, name: target.name, claimed: true,
    });
  }

  // ---- 旧客户端兼容：登录（v1 用户名+PIN，映射到档案） ----
  if (route === 'POST /api/login') {
    const { username, pin } = await parseBody(req);
    const pid = typeof username === 'string' ? findClaimedByName(username) : null;
    if (!pid || typeof pin !== 'string' || !verifyPin(pin, profileIndex.profiles[pid].pinHash)) {
      return sendJson(res, 401, { error: '用户名或 PIN 错误' });
    }
    const profile = profileIndex.profiles[pid];
    if (!profile.pinHash.startsWith('scrypt$')) {
      profile.pinHash = hashPin(pin); // 明文透明升级
      await persistProfileIndex();
    }
    const token = issueToken(pid);
    return sendJson(res, 200, { ok: true, token, username: profile.name, profileId: pid, name: profile.name });
  }

  // ---- 旧客户端兼容：注册（直接建已认领档案；新客户端请用 /api/device + /api/claim） ----
  if (route === 'POST /api/register') {
    const { username, pin } = await parseBody(req);
    if (typeof username !== 'string' || !USERNAME_RE.test(username)) {
      return sendJson(res, 400, { error: '用户名需为 1~24 位字母/数字/中文/_/-' });
    }
    if (typeof pin !== 'string' || !PIN_RE.test(pin)) {
      return sendJson(res, 400, { error: 'PIN 需为 4~6 位数字' });
    }
    if (findClaimedByName(username)) {
      return sendJson(res, 409, { error: '用户名已被注册' });
    }
    const pid = newProfileId();
    profileIndex.profiles[pid] = { name: username, pinHash: hashPin(pin), createdAt: new Date().toISOString() };
    profileIndex.seq += 1;
    await persistProfileIndex();
    const token = issueToken(pid);
    return sendJson(res, 201, { ok: true, username, profileId: pid, token });
  }

  // ---- 登出（吊销当前 token） ----
  if (route === 'POST /api/logout') {
    const auth = authProfile(req);
    if (!auth) return sendJson(res, 401, { error: '未授权：缺少或无效 Bearer token' });
    delete tokens[auth.token];
    await persistTokens();
    return sendJson(res, 200, { ok: true });
  }

  // ---- 进度：读单桶 / 读全桶 ----
  if (route === 'GET /api/progress') {
    const auth = authProfile(req);
    if (!auth) return sendJson(res, 401, { error: '未授权：缺少或无效 Bearer token' });
    const game = url.searchParams.get('game');
    const doc = await loadGamesDoc(auth.profileId);
    if (!game) {
      // 全桶一次拉回（大厅用；03 §3.3——替代旧的 8 次串行 GET）
      const games = {};
      for (const [g, bucket] of Object.entries(doc.games)) {
        games[g] = { updatedAt: bucket.updatedAt, rev: bucket.rev, data: bucket.data };
      }
      return sendJson(res, 200, { profileId: auth.profileId, name: auth.profile.name, games });
    }
    if (!/^[A-Za-z0-9_\-]{1,32}$/.test(game)) {
      return sendJson(res, 400, { error: 'game 需为 1~32 位字母/数字/_/-' });
    }
    const bucket = doc.games[game];
    // 形状兼容旧客户端：{game, data}（radio 直接读 j.data）
    return sendJson(res, 200, {
      game,
      data: bucket ? bucket.data : null,
      updatedAt: bucket ? bucket.updatedAt : null,
      rev: bucket ? bucket.rev : 0,
    });
  }

  // ---- 进度：写桶（baseUpdatedAt LWW 守卫） ----
  if (route === 'PUT /api/progress') {
    const auth = authProfile(req);
    if (!auth) return sendJson(res, 401, { error: '未授权：缺少或无效 Bearer token' });
    const { game, data, baseUpdatedAt } = await parseBody(req);
    if (typeof game !== 'string' || !/^[A-Za-z0-9_\-]{1,32}$/.test(game)) {
      return sendJson(res, 400, { error: 'game 需为 1~32 位字母/数字/_/-' });
    }
    if (data === undefined) {
      return sendJson(res, 400, { error: '缺少 data 字段' });
    }
    if (baseUpdatedAt !== undefined && typeof baseUpdatedAt !== 'string') {
      return sendJson(res, 400, { error: 'baseUpdatedAt 需为字符串（上次已知服务器桶 updatedAt）' });
    }
    const pid = auth.profileId;
    let conflict = null;
    let written = null;
    await withGamesDoc(pid, (doc) => {
      const bucket = doc.games[game];
      if (baseUpdatedAt !== undefined && bucket && bucket.updatedAt !== baseUpdatedAt) {
        conflict = bucket; // 409 在队列外返回（响应不能在队列回调里写两次）
        return false;
      }
      if (baseUpdatedAt === undefined) {
        console.warn(`[server] legacy PUT（缺 baseUpdatedAt，放行）: pid=${pid} game=${game}`);
      }
      const now = new Date().toISOString(); // 服务器时钟裁决（03 §3.1）
      doc.games[game] = { updatedAt: now, rev: (bucket ? bucket.rev || 0 : 0) + 1, data };
      written = doc.games[game];
    });
    if (conflict) {
      return sendJson(res, 409, {
        error: '进度已被其他设备更新（LWW 冲突），请择优后重试',
        game,
        server: { updatedAt: conflict.updatedAt, rev: conflict.rev, data: conflict.data },
      });
    }
    return sendJson(res, 200, { ok: true, game, updatedAt: written.updatedAt, rev: written.rev });
  }

  return sendJson(res, 404, { error: '未知 API 端点' });
}

// ---------------- 静态文件 ----------------

async function serveStatic(req, res, url) {
  let pathname;
  try {
    pathname = decodeURIComponent(url.pathname);
  } catch (_) {
    return sendJson(res, 400, { error: '非法 URL' });
  }
  let filePath = path.normalize(path.join(ROOT, pathname));
  if (!filePath.startsWith(ROOT + path.sep) && filePath !== ROOT) {
    res.writeHead(403).end('Forbidden');
    return;
  }
  // web/server/（token / PIN 哈希 / 进度数据）一律不对外提供（规范化后判定，防穿越变体）
  const serverDir = path.join(ROOT, 'server') + path.sep;
  if (filePath.startsWith(serverDir)) {
    res.writeHead(404).end('Not Found');
    return;
  }

  let stat;
  try {
    stat = await fsp.stat(filePath);
    if (stat.isDirectory()) {
      filePath = path.join(filePath, 'index.html');
      stat = await fsp.stat(filePath);
    }
  } catch (_) {
    res.writeHead(404).end('Not Found');
    return;
  }

  const mime = MIME[path.extname(filePath).toLowerCase()] || 'application/octet-stream';
  const headers = {
    'Content-Type': mime,
    'Accept-Ranges': 'bytes',
    'Cache-Control': 'no-cache',
  };

  // 简化版 Range：仅支持单个 bytes=start-end / start- / -suffix
  const range = req.headers.range;
  if (range) {
    const m = range.match(/^bytes=(\d*)-(\d*)$/);
    if (m && (m[1] !== '' || m[2] !== '')) {
      let start, end;
      if (m[1] === '') { // 后缀范围：最后 N 字节
        const n = Number(m[2]);
        start = Math.max(stat.size - n, 0);
        end = stat.size - 1;
      } else {
        start = Number(m[1]);
        end = m[2] === '' ? stat.size - 1 : Math.min(Number(m[2]), stat.size - 1);
      }
      if (start > end || start >= stat.size) {
        res.writeHead(416, { 'Content-Range': `bytes */${stat.size}` }).end();
        return;
      }
      res.writeHead(206, {
        ...headers,
        'Content-Range': `bytes ${start}-${end}/${stat.size}`,
        'Content-Length': end - start + 1,
      });
      if (req.method === 'HEAD') return res.end();
      fs.createReadStream(filePath, { start, end }).pipe(res);
      return;
    }
  }

  res.writeHead(200, { ...headers, 'Content-Length': stat.size });
  if (req.method === 'HEAD') return res.end();
  fs.createReadStream(filePath).pipe(res);
}

// ---------------- v1 → v2 迁移（启动时，单向，原文件保留） ----------------

async function migrate() {
  await fsp.mkdir(PROFILES_DIR, { recursive: true });
  const now = new Date().toISOString();

  // users.json（v1 {username: pin明文}）→ profiles.json（pid=旧用户名，PIN 立即哈希）
  if (!fs.existsSync(PROFILES_FILE)) {
    const idx = { seq: 0, profiles: {} };
    const oldUsers = await readJson(USERS_FILE, null);
    let migrated = 0;
    if (oldUsers && typeof oldUsers === 'object') {
      for (const [name, pin] of Object.entries(oldUsers)) {
        if (typeof name !== 'string' || !USERNAME_RE.test(name)) continue;
        idx.profiles[name] = {
          name,
          pinHash: typeof pin === 'string' && pin.startsWith('scrypt$') ? pin : hashPin(String(pin)),
          createdAt: now,
        };
        idx.seq += 1;
        // 旧进度文件 <username>.json（扁平 {game: data}）→ profiles/<username>.json 桶包装
        const oldProg = await readJson(path.join(DATA_DIR, `${name}.json`), null);
        const games = {};
        if (oldProg && typeof oldProg === 'object') {
          for (const [g, d] of Object.entries(oldProg)) {
            if (typeof g === 'string' && /^[A-Za-z0-9_\-]{1,32}$/.test(g)) {
              games[g] = { updatedAt: now, rev: 1, data: d };
            }
          }
        }
        await writeJson(profileGamesFile(name), { id: name, games });
        migrated += 1;
      }
    }
    await writeJson(PROFILES_FILE, idx);
    if (migrated > 0) {
      console.log(`[server] v1 迁移: users.json → profiles.json（${migrated} 个档案，PIN 已 scrypt 哈希；原文件保留不动）`);
    }
  }
  profileIndex = await readJson(PROFILES_FILE, { seq: 0, profiles: {} });
  if (!profileIndex || typeof profileIndex !== 'object' || !profileIndex.profiles) {
    profileIndex = { seq: 0, profiles: {} };
  }
  profileIndex.seq = Number(profileIndex.seq) || 0;

  // sessions.json（v1 {token: username}）→ tokens.json（补 180 天滑动过期）
  if (!fs.existsSync(TOKENS_FILE)) {
    const migratedTokens = {};
    const oldSessions = await readJson(SESSIONS_FILE, null);
    let n = 0;
    if (oldSessions && typeof oldSessions === 'object') {
      for (const [tok, user] of Object.entries(oldSessions)) {
        if (typeof tok === 'string' && TOKEN_RE.test(tok) && profileIndex.profiles[user]) {
          migratedTokens[tok.toLowerCase()] = {
            profileId: user, createdAt: now, lastSeen: now,
            expiresAt: new Date(Date.now() + TOKEN_TTL_MS).toISOString(),
          };
          n += 1;
        }
      }
    }
    await writeJson(TOKENS_FILE, migratedTokens);
    if (n > 0) console.log(`[server] v1 迁移: sessions.json → tokens.json（${n} 条 token 补 180 天过期；原文件保留不动）`);
  }
  tokens = await readJson(TOKENS_FILE, {});
}

// ---------------- 启动 ----------------

async function main() {
  await fsp.mkdir(DATA_DIR, { recursive: true });
  await migrate();
  const removed = cleanupTokens();
  if (removed) {
    console.log(`[server] 清扫过期/悬空 token ${removed} 条`);
    await persistTokens();
  }

  const server = http.createServer(async (req, res) => {
    try {
      const url = new URL(req.url, `http://${req.headers.host || 'localhost'}`);
      if (url.pathname.startsWith('/api/')) {
        return await handleApi(req, res, url);
      }
      if (req.method !== 'GET' && req.method !== 'HEAD') {
        res.writeHead(405).end('Method Not Allowed');
        return;
      }
      return await serveStatic(req, res, url);
    } catch (e) {
      if (e instanceof SyntaxError) {
        return sendJson(res, 400, { error: '请求体不是合法 JSON' });
      }
      console.error('[server] 未处理异常:', e);
      if (!res.headersSent) sendJson(res, 500, { error: '服务器内部错误' });
      else res.end();
    }
  });

  server.listen(PORT, () => {
    console.log(`[server] SoundGame 服务器已启动: http://localhost:${PORT}/`);
    console.log(`[server] 静态根目录: ${ROOT}`);
    console.log(`[server] 数据目录:   ${DATA_DIR}`);
    console.log(`[server] 档案数: ${Object.keys(profileIndex.profiles).length}，token 数: ${Object.keys(tokens).length}`);
  });
}

main().catch((e) => {
  console.error('[server] 启动失败:', e);
  process.exit(1);
});