Linux update notifications

Fixes #257

main/auto-updater.js

@@ -3,9 +3,11 @@ module.exports = {
 }
 
 var electron = require('electron')
+var get = require('simple-get')
 
 var config = require('../config')
 var log = require('./log')
+var windows = require('./windows')
 
 var autoUpdater = electron.autoUpdater
 
@@ -20,7 +22,7 @@ function init () {
    * We always check for updates on app startup. To keep app startup fast, we delay this
    * first check so it happens when there is less going on.
    */
-  setTimeout(() => autoUpdater.checkForUpdates(), config.AUTO_UPDATE_CHECK_STARTUP_DELAY)
+  setTimeout(checkForUpdates, config.AUTO_UPDATE_CHECK_STARTUP_DELAY)
 
   autoUpdater.on('checking-for-update', () => log('Checking for app update'))
   autoUpdater.on('update-available', () => log('App update available'))
@@ -29,3 +31,22 @@ function init () {
     log('App update downloaded: ', releaseName, updateURL)
   })
 }
+
+function checkForUpdates () {
+  // Electron's built-in auto updater only supports Mac and Windows, for now
+  if (process.platform !== 'linux') {
+    return autoUpdater.checkForUpdates()
+  }
+
+  // If we're on Linux, we have to do it ourselves
+  get.concat(config.AUTO_UPDATE_URL, function (err, res, data) {
+    if (err) return log('Error checking for app update: ' + err.message)
+    if (![200, 204].includes(res.statusCode)) return log('Error checking for app update, got HTTP ' + res.statusCode)
+    if (res.statusCode !== 200) return
+
+    var obj = JSON.parse(data)
+    // TODO: version should be included in the response object, we shouldn'v have to parse obj.name
+    var version = obj.name.slice(obj.name.lastIndexOf('v') + 1)
+    windows.main.send('dispatch', 'updateAvailable', version)
+  })
+}