server.js

"use strict";

var restify = require("restify")
var request = require("request")
var CoinAPI = require("./lib/CoinAPI")
var self = null

module.exports = class Server {
  constructor(address, port, trackingID) {
    self = this
    self.address = address
    self.port = port
    self.trackingID = trackingID
    this.api = new CoinAPI()
    self.metrics = {
      "startTime": 0,
      "lastSuccessfulRefresh": 0,
      "coins": 0
    }
    self.app = restify.createServer({
      "name": "CoinmarketCap API Server"
    })
    /* Register quit events so the server quits when it's supposed to */
    var events = ["SIGHUP", "SIGINT", "SIGQUIT", "SIGILL", "SIGTRAP", "SIGABRT",
      "SIGBUS", "SIGFPE", "SIGUSR1", "SIGSEGV", "SIGUSR2", "SIGTERM"
    ]
    events.forEach(function (event) {
      process.on(event, function() {
        self.stop(event)
      })
    })
    /* Rate limiting */
    self.app.use(restify.throttle({
      burst: 100,
      rate: 50, // requests/second
      ip: true
    }))
    /* Serve index file */
    self.app.get("/", function (req, res, next) {
      next()
    },
    restify.serveStatic({
      directory: __dirname,
      file: "index.html"
    }))
    /* Serve API */
    this.app.get(/\/api\/*/, self.handleAPIRequest)
    /* Metrics */
    self.app.get("/metrics", self.handleMetricsRequest)
    /* Schedule API refresh */
    self.APIRefreshHandler = setInterval(self.handleAPIRefresh, 300000)
    /* Initial refresh */
    self.handleAPIRefresh()
  }
  start() {
    self.app.listen(self.port, self.address, function() {
      // Server started
      self.metrics.startTime = Date(Date.now())
      self.log("Server started.")
    })
  }
  trackEvent(category, action, value) {
    if (!self.trackingID) return
    // https://developers.google.com/analytics/devguides/collection/protocol/v1/parameters
    request.post("https://www.google-analytics.com/collect").form({
      v: 1,
      t: "event", 
      tid: self.trackingID,
      uid: "server",
      ec: category,
      ea: action,
      ev: value
    })
  }
  log(msg, isSevere) {
    console.log("%s: %s", Date(Date.now()), msg)
  }
  handleAPIRequest(req, res, next) {
    var coin = null
    var property = null
    var result = null
    res.setHeader("Content-Type", "application/json")
    res.header("Access-Control-Allow-Origin", "*")
    res.header("Access-Control-Allow-Headers", "X-Requested-With")
    var query = req.path().substring(5).toLowerCase()
    self.trackEvent("Request", query)
    if (query == "") {
      res.send({"error": "This isn't an endpoint!"})
      return
    }
    if (query == "all") {
      res.send(self.api.coins)
      return
    }
    var slashLocation = query.indexOf("/")
    var queryContainsProperty = (slashLocation > -1) // i.e. /api/btc/market_cap
    if (queryContainsProperty) {
      property = query.substring(slashLocation + 1)
      coin = query.substring(0, slashLocation)
    }
    else {
      coin = query
    }
    coin = self.api.getCoin(coin)
    if (coin) {
      if (property) {
        if (coin[property]) {
          result = coin[property]
        }
        else {
          result = {"error": "Invalid property requested"}
        }
      }
      else {
        result = coin
      }
    }
    else {
      result = {"error": "Requested coin does not exist or has not been updated yet."}
    }
    res.send(result)
  }
  handleAPIRefresh() {
    self.api.refresh(function (numCoinsUpdated) {
      var success = (numCoinsUpdated == 100)
      var isSevere = !success
      self.log("Updated " + numCoinsUpdated + " coins. Success: " + success, isSevere)
      self.trackEvent("Update", success ? "Success" : "Failure", numCoinsUpdated)
      if (success) {
        self.metrics.lastSuccessfulRefresh = Date(Date.now())
        self.metrics.coins = numCoinsUpdated
      }
    }, function(error, statusCode) {
      console.log("Error while refreshing API", error, "with status code", statusCode)
      self.trackEvent("Update", "Error", statusCode)
    })
  }
  handleMetricsRequest(req, res, next) {
    res.setHeader("Content-Type", "application/json")
    res.header("Access-Control-Allow-Origin", "*")
    res.header("Access-Control-Allow-Headers", "X-Requested-With")
    res.send(self.metrics)
    next()
  }
  stop(event) {
    // Server stopped
    clearInterval(self.APIRefreshHandler)
    self.log("Server stopped with event: " + event + ". Last metrics: " + JSON.stringify(this.metrics))
    process.exit(1)
  }
}