Implement version check middleware

Signed-off-by: Yukai Huang <yukaihuangtw@gmail.com>

app.js

@@ -25,6 +25,8 @@ var response = require('./lib/response')
 var models = require('./lib/models')
 var csp = require('./lib/csp')
 
+const { versionCheckMiddleware } = require('./lib/web/middleware/checkVersion')
+
 function createHttpServer () {
   if (config.useSSL) {
     const ca = (function () {
@@ -167,6 +169,10 @@ app.use(require('./lib/middleware/checkURIValid'))
 app.use(require('./lib/middleware/redirectWithoutTrailingSlashes'))
 app.use(require('./lib/middleware/codiMDVersion'))
 
+if (config.autoVersionCheck) {
+  app.use(versionCheckMiddleware)
+}
+
 // routes need sessions
 // template files
 app.set('views', config.viewPath)

lib/config/default.js

@@ -178,5 +178,6 @@ module.exports = {
   //    Generated id:   "31-good-morning-my-friend---do-you-have-5"
   //    2nd appearance: "31-good-morning-my-friend---do-you-have-5-1"
   //    3rd appearance: "31-good-morning-my-friend---do-you-have-5-2"
-  linkifyHeaderStyle: 'keep-case'
+  linkifyHeaderStyle: 'keep-case',
+  autoVersionCheck: true
 }

lib/web/middleware/checkVersion.js

@@ -0,0 +1,52 @@
+'use strict'
+
+const { promisify } = require('util')
+
+const request = require('request')
+
+const logger = require('../../logger')
+const config = require('../../config')
+
+let lastCheckAt
+let latest = true
+let versionItem = null
+
+const VERSION_CHECK_ENDPOINT = 'https://evangelion.codimd.dev/'
+const CHECK_TIMEOUT = 1000 * 60 * 60 * 24 // 1 day
+
+const rp = promisify(request)
+
+exports.versionCheckMiddleware = async function (req, res, next) {
+  if (lastCheckAt && (lastCheckAt + CHECK_TIMEOUT > Date.now())) {
+    return next()
+  }
+
+  // update lastCheckAt whether the check would fail or not
+  lastCheckAt = Date.now()
+
+  try {
+    const { statusCode, body: data } = await rp({
+      url: `${VERSION_CHECK_ENDPOINT}?v=${config.version}`,
+      method: 'GET',
+      json: true
+    })
+
+    if (statusCode !== 200 || data.status === 'error') {
+      logger.error('Version check failed.')
+      return next()
+    }
+
+    latest = data.latest
+    versionItem = latest ? null : data.versionItem
+
+    return next()
+  } catch (err) {
+    // ignore and skip version check
+    logger.error('Version check failed.')
+    logger.error(err)
+    return next()
+  }
+}
+
+exports.versionItem = versionItem
+exports.outdated = outdated