Refactored maintenance app to be a class with DI

refs #12568

- DI pattern through constructor allows for very clear separation of concerns and makes it easy to extract the class into a separate module

core/server/index.js

@@ -93,10 +93,6 @@ const initExpressApps = async () => {
     return parentApp;
 };
 
-const initMaintenanceApp = () => {
-    return require('./web/maintenance')();
-};
-
 /**
  * - initialise models
  * - initialise i18n
@@ -142,7 +138,7 @@ const minimalRequiredSetupToStartGhost = async (dbState) => {
         config.set('maintenance:enabled', true);
         logging.info('Blog is in maintenance mode.');
 
-        ghostServer.rootApp = initMaintenanceApp();
+        ghostServer.rootApp = require('./web/maintenance');
 
         try {
             migrator.migrate()

core/server/web/maintenance/index.js

@@ -1,13 +1,10 @@
 const hbs = require('express-hbs');
-const compress = require('compression');
-const debug = require('ghost-ignition').debug('web:maintenance');
-const constants = require('@tryghost/constants');
-const errors = require('@tryghost/errors');
 const {i18n} = require('../../lib/common');
 const logging = require('../../../shared/logging');
 const express = require('../../../shared/express');
 const config = require('../../../shared/config');
-const {servePublicFile} = require('../site/middleware');
+const {servePublicFile, serveFavicon} = require('../site/middleware');
+const MaintenanceApp = require('./maintenance-app');
 
 const createHbsEngine = () => {
     const engine = hbs.create();
@@ -16,45 +13,13 @@ const createHbsEngine = () => {
     return engine.express4();
 };
 
-module.exports = function setupMaintenanceApp() {
+module.exports = new MaintenanceApp({
-    debug('MaintenanceApp setup start');
+    logging,
-    const app = express('maintenance');
+    i18n,
-
+    express,
-    // enabled gzip compression by defaulti
+    viewEngine: createHbsEngine(),
-    if (config.get('compress') !== false) {
+    compress: config.get('compress'),
-        app.use(compress());
+    views: config.get('paths').defaultViews,
-    }
+    servePublicFile,
-
+    serveFavicon
-    app.engine('hbs', createHbsEngine());
+}).app;
-    app.set('view engine', 'hbs');
-    app.set('views', config.get('paths').defaultViews);
-
-    // Serve stylesheets for default templates
-    app.use(servePublicFile('public/ghost.css', 'text/css', constants.ONE_HOUR_S));
-    app.use(servePublicFile('public/ghost.min.css', 'text/css', constants.ONE_YEAR_S));
-
-    // Serve images for default templates
-    app.use(servePublicFile('public/404-ghost@2x.png', 'image/png', constants.ONE_HOUR_S));
-    app.use(servePublicFile('public/404-ghost.png', 'image/png', constants.ONE_HOUR_S));
-
-    app.use('/', (req, res) => {
-        const error = new errors.MaintenanceError({
-            message: i18n.t('errors.general.maintenance')
-        });
-
-        logging.error({req: req, res: res, err: error});
-
-        // never cache errors
-        res.set({
-            'Cache-Control': 'no-cache, private, no-store, must-revalidate, max-stale=0, post-check=0, pre-check=0'
-        });
-        res.status(error.statusCode);
-        res.render('error', error, (err, html) => {
-            return res.send(html);
-        });
-    });
-
-    debug('MaintenanceApp setup end');
-
-    return app;
-};

core/server/web/maintenance/maintenance-app.js

@@ -0,0 +1,53 @@
+const compression = require('compression');
+const errors = require('@tryghost/errors');
+const constants = require('@tryghost/constants');
+const debug = require('ghost-ignition').debug('web:admin:app');
+
+class MaintenanceApp {
+    constructor({logging, i18n, express, viewEngine, compress, views, servePublicFile, serveFavicon}) {
+        debug('MaintenanceApp setup start');
+        const app = express('maintenance');
+
+        if (compress !== false) {
+            app.use(compression());
+        }
+
+        app.engine('hbs', viewEngine);
+        app.set('view engine', 'hbs');
+        app.set('views', views);
+
+        // Serve favicon.ico and favicon.png
+        app.use(serveFavicon());
+
+        // Serve stylesheets for default templates
+        app.use(servePublicFile('public/ghost.css', 'text/css', constants.ONE_HOUR_S));
+        app.use(servePublicFile('public/ghost.min.css', 'text/css', constants.ONE_YEAR_S));
+
+        // Serve images for default templates
+        app.use(servePublicFile('public/404-ghost@2x.png', 'image/png', constants.ONE_HOUR_S));
+        app.use(servePublicFile('public/404-ghost.png', 'image/png', constants.ONE_HOUR_S));
+
+        app.use('/', (req, res) => {
+            const error = new errors.MaintenanceError({
+                message: i18n.t('errors.general.maintenance')
+            });
+
+            logging.error({req: req, res: res, err: error});
+
+            res.render('error', error, (err, html) => {
+                // never cache errors
+                res.set({
+                    'Cache-Control': 'no-cache, private, no-store, must-revalidate, max-stale=0, post-check=0, pre-check=0'
+                });
+                res.status(error.statusCode);
+                return res.send(html);
+            });
+        });
+
+        debug('MaintenanceApp setup end');
+
+        this.app = app;
+    }
+}
+
+module.exports = MaintenanceApp;