/**
 * 机器人智慧服务系统 · 设备接入服务 Alpha (device-access-service)
 * 端口: 3010
 * 职责: 设备注册/注销、心跳保活、在线状态管理、连接凭证签发
 * 数据: services/device-access/data/devices.json（本地文件替代数据库）
 * 文档: 详见 docs/DOC-08-设备数据字典-V1.0草案.md
 */
const express = require('express');
const cors = require('cors');
const fs = require('fs');
const path = require('path');
const { v4: uuidv4 } = require('uuid');

const app = express();
const PORT = 3010;
const DATA_FILE = path.join(__dirname, 'data', 'devices.json');
const HEARTBEAT_TIMEOUT_MS = 60 * 1000;   // 心跳超时阈值（60s 未上报判定离线）
const SCAN_INTERVAL_MS = 30 * 1000;       // 离线扫描周期（30s）
const ONLINE_TTL_MS = 30 * 1000;          // 上报后在线有效期（30s，期内视为在线）

// 设备类型定义（与 DOC-08 一致）
const DEVICE_TYPES = ['inspection_robot', 'drone', 'charging_pile', 'gateway', 'sensor'];

app.use(cors());
app.use(express.json());

// ─── 文件读写 ─────────────────────────────────────────────
function readDevices() {
  try {
    const raw = fs.readFileSync(DATA_FILE, 'utf-8');
    return JSON.parse(raw);
  } catch {
    return [];
  }
}

function writeDevices(devices) {
  fs.writeFileSync(DATA_FILE, JSON.stringify(devices, null, 2), 'utf-8');
}

// 内存索引（latest heartbeat 不落盘，重启后按 lastHeartbeat 重新判定）
const onlineCache = new Map(); // deviceId -> lastSeenAt

// ─── 工具函数 ─────────────────────────────────────────────
function toPublic(dev) {
  const lastSeen = onlineCache.get(dev.deviceId);
  const online = !!lastSeen && (Date.now() - lastSeen) < ONLINE_TTL_MS;
  return {
    ...dev,
    online,
    lastHeartbeat: lastSeen ? new Date(lastSeen).toISOString() : dev.lastHeartbeat || null,
  };
}

// ─── 路由：注册 ───────────────────────────────────────────
// POST /api/devices/register  注册设备
app.post('/api/devices/register', (req, res) => {
  const { deviceId, type, name, secret, capabilities = [], location, meta = {} } = req.body || {};
  if (!deviceId || !type) {
    return res.status(400).json({ code: 40001, msg: 'deviceId 与 type 为必填项' });
  }
  if (!DEVICE_TYPES.includes(type)) {
    return res.status(400).json({ code: 40002, msg: `type 非法，允许值: ${DEVICE_TYPES.join(', ')}` });
  }
  const devices = readDevices();
  if (devices.some((d) => d.deviceId === deviceId)) {
    return res.status(409).json({ code: 40901, msg: `设备 ${deviceId} 已注册` });
  }
  const dev = {
    deviceId,
    type,
    name: name || deviceId,
    secret: secret || uuidv4().replace(/-/g, '').slice(0, 16),
    capabilities,
    location: location || null,
    meta,
    status: 'inactive', // inactive | online | offline
    registeredAt: new Date().toISOString(),
    lastHeartbeat: null,
  };
  devices.push(dev);
  writeDevices(devices);
  onlineCache.set(deviceId, Date.now());
  res.json({ code: 0, msg: '注册成功', data: toPublic(dev) });
});

// ─── 路由：查询 ───────────────────────────────────────────
// GET /api/devices?type=&online=&keyword=  设备列表
app.get('/api/devices', (req, res) => {
  const { type, online, keyword } = req.query;
  let list = readDevices().map(toPublic);
  if (type) list = list.filter((d) => d.type === type);
  if (online === 'true') list = list.filter((d) => d.online);
  if (online === 'false') list = list.filter((d) => !d.online);
  if (keyword) list = list.filter((d) => d.deviceId.includes(keyword) || (d.name || '').includes(keyword));
  res.json({ code: 0, data: list });
});

// GET /api/devices/:id  设备详情
app.get('/api/devices/:id', (req, res) => {
  const dev = readDevices().find((d) => d.deviceId === req.params.id);
  if (!dev) return res.status(404).json({ code: 40401, msg: '设备不存在' });
  res.json({ code: 0, data: toPublic(dev) });
});

// GET /api/devices/:id/online  在线状态查询
app.get('/api/devices/:id/online', (req, res) => {
  const dev = readDevices().find((d) => d.deviceId === req.params.id);
  if (!dev) return res.status(404).json({ code: 40401, msg: '设备不存在' });
  res.json({ code: 0, data: { deviceId: dev.deviceId, online: toPublic(dev).online } });
});

// ─── 路由：生命周期 ───────────────────────────────────────
// POST /api/devices/:id/heartbeat  心跳上报（保活）
app.post('/api/devices/:id/heartbeat', (req, res) => {
  const devices = readDevices();
  const dev = devices.find((d) => d.deviceId === req.params.id);
  if (!dev) return res.status(404).json({ code: 40401, msg: '设备不存在' });
  const now = Date.now();
  onlineCache.set(dev.deviceId, now);
  dev.status = 'online';
  dev.lastHeartbeat = new Date(now).toISOString();
  if (req.body && typeof req.body.meta === 'object') {
    dev.meta = { ...(dev.meta || {}), ...req.body.meta };
  }
  writeDevices(devices);
  res.json({ code: 0, msg: '心跳已记录', data: toPublic(dev) });
});

// POST /api/devices/:id/offline  主动下线
app.post('/api/devices/:id/offline', (req, res) => {
  const devices = readDevices();
  const dev = devices.find((d) => d.deviceId === req.params.id);
  if (!dev) return res.status(404).json({ code: 40401, msg: '设备不存在' });
  onlineCache.delete(dev.deviceId);
  dev.status = 'offline';
  writeDevices(devices);
  res.json({ code: 0, msg: '设备已下线', data: toPublic(dev) });
});

// DELETE /api/devices/:id  注销设备
app.delete('/api/devices/:id', (req, res) => {
  const devices = readDevices();
  const idx = devices.findIndex((d) => d.deviceId === req.params.id);
  if (idx === -1) return res.status(404).json({ code: 40401, msg: '设备不存在' });
  const [removed] = devices.splice(idx, 1);
  writeDevices(devices);
  onlineCache.delete(removed.deviceId);
  res.json({ code: 0, msg: '设备已注销', data: { deviceId: removed.deviceId } });
});

// ─── 离线扫描（心跳超时判定）─────────────────────────────
setInterval(() => {
  const now = Date.now();
  const devices = readDevices();
  let changed = false;
  for (const dev of devices) {
    const lastSeen = onlineCache.get(dev.deviceId);
    if (lastSeen && now - lastSeen > HEARTBEAT_TIMEOUT_MS) {
      onlineCache.delete(dev.deviceId);
      if (dev.status === 'online') {
        dev.status = 'offline';
        changed = true;
        console.log(`[heartbeat-timeout] 设备 ${dev.deviceId} 心跳超时，判定离线`);
      }
    }
  }
  if (changed) writeDevices(devices);
}, SCAN_INTERVAL_MS);

app.listen(PORT, () => {
  console.log(`✅ 设备接入服务 Alpha 已启动 → http://localhost:${PORT}`);
  console.log(`   API 示例: GET  /api/devices`);
  console.log(`            POST /api/devices/register  {deviceId, type, name, capabilities}`);
  console.log(`            POST /api/devices/:id/heartbeat`);
});