dashboard-backend/server.js

const express = require("express");
const http = require("http");
const socketIo = require("socket.io");
const cors = require("cors");
const axios = require("axios");
require("dotenv").config();

const app = express();

const server = http.createServer(app);

const io = socketIo(server, {
  cors: {
    origin: process.env.CORS_ORIGIN || "*",
    methods: ["GET", "POST"],
  },
});

// ========== (Middleware) ==========

app.use(cors());

app.use(express.json());

// ========== HTTP Route ==========

app.get("/health", (req, res) => {
  res.json({
    status: "OK",
    message: "Server is running",
    timestamp: new Date().toISOString(),
  });
});

// ========== Socket.IO Logic ==========

// 用於追蹤連接的客戶端數量
let connectedClients = 0;

// 當客戶端連接時觸發
io.on("connection", (socket) => {
  // 增加客戶端計數
  connectedClients++;

  console.log(`✅ 客戶端已連接: ${socket.id}`);
  console.log(`📊 當前連接數: ${connectedClients}`);

  // 向所有客戶端廣播當前連接數
  io.emit("clientCount", connectedClients);

  // ========== 監聽客戶端事件 ==========

  // 當客戶端要求數據時
  socket.on("requestData", async (dataType) => {
    console.log(`📤 數據請求: ${dataType}`);

    try {
      let data;

      if (dataType === "crypto") {
        // 從 CoinGecko API 獲取加密貨幣數據
        const response = await axios.get(
          "https://api.coingecko.com/api/v3/simple/price",
          {
            params: {
              // 要查詢的加密貨幣
              ids: "bitcoin,ethereum,cardano,solana,ripple",
              // 使用 USD 幣種
              vs_currencies: "usd",
              // 包含市值
              include_market_cap: true,
              // 包含24小時交易量
              include_24hr_vol: true,
              // 包含24小時漲跌幅
              include_24hr_change: true,
            },
          }
        );

        // 組織數據格式
        data = {
          type: "crypto",
          timestamp: new Date(),
          prices: response.data,
        };
      }

      // 發送數據給要求的客戶端
      socket.emit("data", data);
      console.log(`✅ 數據已發送給客戶端: ${socket.id}`);
    } catch (error) {
      console.error("❌ 獲取數據出錯:", error.message);
      // 發送錯誤信息給客戶端
      socket.emit("error", {
        message: "Failed to fetch data",
        details: error.message,
      });
    }
  });

  // ========== 定期推送數據 ==========

  // 創建定時器，每5秒推送一次數據給該客戶端
  const dataInterval = setInterval(async () => {
    try {
      // 獲取最新的加密貨幣數據
      const response = await axios.get(
        "https://api.coingecko.com/api/v3/simple/price",
        {
          params: {
            ids: "bitcoin,ethereum,cardano,solana,ripple",
            vs_currencies: "usd",
            include_market_cap: true,
            include_24hr_vol: true,
            include_24hr_change: true,
          },
        }
      );

      // 向該客戶端發送數據（實時更新）
      socket.emit("data", {
        type: "crypto",
        timestamp: new Date(),
        prices: response.data,
      });
    } catch (error) {
      console.error("❌ 定時推送出錯:", error.message);
    }
  }, 5000); // 每5000毫秒（5秒）執行一次

  // ========== 客戶端斷開連接 ==========

  // 當客戶端斷開連接時觸發
  socket.on("disconnect", () => {
    connectedClients--;
    console.log(`❌ 客戶端已斷開: ${socket.id}`);
    console.log(`📊 當前連接數: ${connectedClients}`);

    // 向所有客戶端廣播更新的連接數
    io.emit("clientCount", connectedClients);

    // 清除該客戶端的定時器
    clearInterval(dataInterval);
  });
});

// ========== 啟動服務器 ==========

// 從環境變數獲取端口，或使用默認5000
const PORT = process.env.PORT || 5000;

// 啟動伺服器
server.listen(PORT, () => {
  console.log("");
  console.log("═══════════════════════════════════════");
  console.log(`✅ 服務器運行在: http://localhost:${PORT}`);
  console.log("📡 WebSocket 已準備接收連接");
  console.log("🔗 CORS 來源:", process.env.CORS_ORIGIN || "*");
  console.log("═══════════════════════════════════════");
  console.log("");
});

// ========== 錯誤處理 ==========

// 處理未捕獲的異常
process.on("unhandledRejection", (err) => {
  console.error("❌ 未捕獲的異常:", err);
});

process.on("uncaughtException", (err) => {
  console.error("❌ 未捕獲的異常:", err);
  process.exit(1);
});