/**
 * 机器人智慧服务系统 · 状态服务 Alpha (status-service)
 * 端口: 3020
 * 职责: 设备状态上报接收、最新状态缓存、历史状态查询、SSE 实时订阅
 * 数据: services/status/data/status.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 app = express();
const PORT = 3020;
const DATA_FILE = path.join(__dirname, 'data', 'status.json');
const MAX_HISTORY_PER_DEVICE = 500; // 每设备历史条数上限（超出丢弃最旧）

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

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

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

// ─── SSE 订阅者 ───────────────────────────────────────────
const subscribers = new Set(); // res 集合

function broadcast(payload) {
  const msg = `data: ${JSON.stringify(payload)}\n\n`;
  for (const res of subscribers) {
    try { res.write(msg); } catch { subscribers.delete(res); }
  }
}

// ─── 路由：上报 ───────────────────────────────────────────
// POST /api/status/report  状态上报（设备 -> 平台）
// body: { deviceId, position?, battery?, mode?, speed?, sensors?, alarms?, timestamp? }
app.post('/api/status/report', (req, res) => {
  const {
    deviceId, position, battery, mode, speed, sensors, alarms, timestamp, meta = {},
  } = req.body || {};
  if (!deviceId) {
    return res.status(400).json({ code: 40001, msg: 'deviceId 为必填项' });
  }

  const now = new Date().toISOString();
  const record = {
    deviceId,
    position: position || null,          // {x,y,z,yaw}
    battery: battery ?? null,            // 0~100 整数百分比
    mode: mode || null,                  // idle/patrol/charging/working/emergency
    speed: speed ?? null,                // m/s
    sensors: sensors || {},              // 传感器键值
    alarms: alarms || [],                // 告警编码列表
    meta,
    ts: timestamp || now,                // 设备侧时间（ISO）
    receivedAt: now,                     // 平台接收时间（ISO）
  };

  const data = readData();
  data.latest[deviceId] = record;
  const history = data.history[deviceId] || (data.history[deviceId] = []);
  history.push(record);
  if (history.length > MAX_HISTORY_PER_DEVICE) history.splice(0, history.length - MAX_HISTORY_PER_DEVICE);
  writeData(data);

  // 实时广播给订阅者
  broadcast({ type: 'status', deviceId, record });

  res.json({ code: 0, msg: '状态已接收', data: { deviceId, receivedAt: now } });
});

// ─── 路由：查询 ───────────────────────────────────────────
// GET /api/status/summary  全设备最新状态汇总
app.get('/api/status/summary', (req, res) => {
  const data = readData();
  res.json({ code: 0, data: Object.values(data.latest) });
});

// GET /api/status/:deviceId/latest  指定设备最新状态
app.get('/api/status/:deviceId/latest', (req, res) => {
  const data = readData();
  const record = data.latest[req.params.deviceId];
  if (!record) return res.status(404).json({ code: 40401, msg: '该设备暂无状态上报' });
  res.json({ code: 0, data: record });
});

// GET /api/status/history/:deviceId?from=&to=&limit=  历史状态
app.get('/api/status/history/:deviceId', (req, res) => {
  const data = readData();
  const history = data.history[req.params.deviceId] || [];
  const { from, to, limit } = req.query;
  let list = history;
  if (from) list = list.filter((r) => r.ts >= from);
  if (to) list = list.filter((r) => r.ts <= to);
  const n = Math.min(parseInt(limit, 10) || 100, 500);
  res.json({ code: 0, data: list.slice(-n) });
});

// GET /api/status/subscribe  SSE 实时订阅
app.get('/api/status/subscribe', (req, res) => {
  res.setHeader('Content-Type', 'text/event-stream');
  res.setHeader('Cache-Control', 'no-cache');
  res.setHeader('Connection', 'keep-alive');
  res.write(`data: ${JSON.stringify({ type: 'connected', msg: '订阅成功' })}\n\n`);
  subscribers.add(res);
  req.on('close', () => subscribers.delete(res));
});

app.listen(PORT, () => {
  console.log(`✅ 状态服务 Alpha 已启动 → http://localhost:${PORT}`);
  console.log(`   API 示例: POST /api/status/report  {deviceId, position, battery, mode}`);
  console.log(`            GET  /api/status/:deviceId/latest`);
  console.log(`            GET  /api/status/subscribe  (SSE)`);
});