feat: implement URL path configuration for static files and routes

- Added support for a configurable URL path in the application, allowing static files and routes to be served under a specified path.
- Implemented redirection from the root to the configured URL path.
- Updated socket.io initialization to respect the URL path configuration.
- Enhanced middleware to prevent redirection for the URL path itself.

This change improves flexibility in routing and enhances the application's structure.

Author: Yukaii

app.js

@@ -69,7 +69,9 @@ app.use(morgan('combined', {
 }))
 
 // socket io
-var io = require('socket.io')(server)
+var io = require('socket.io')(server, config.urlPath ? {
+  path: `/${config.urlPath}/socket.io`
+} : {})
 io.engine.ws = new (require('ws').Server)({
   noServer: true,
   perMessageDeflate: false
@@ -132,13 +134,29 @@ app.use(cookieParser())
 
 app.use(i18n.init)
 
-// routes without sessions
-// static files
-app.use('/', express.static(path.join(__dirname, '/public'), { maxAge: config.staticCacheTime, index: false }))
-app.use('/docs', express.static(path.resolve(__dirname, config.docsPath), { maxAge: config.staticCacheTime }))
-app.use('/uploads', express.static(path.resolve(__dirname, config.uploadsPath), { maxAge: config.staticCacheTime }))
-app.use('/default.md', express.static(path.resolve(__dirname, config.defaultNotePath), { maxAge: config.staticCacheTime }))
-app.use(require('./lib/metrics').router)
+// Handle URL path configuration
+if (config.urlPath) {
+  // Redirect from root to URL path (with trailing slash)
+  app.get('/', function (req, res) {
+    res.redirect(301, `/${config.urlPath}/`)
+  })
+  
+  // Mount static files and routes under URL path
+  const urlPathPrefix = `/${config.urlPath}`
+  app.use(urlPathPrefix + '/', express.static(path.join(__dirname, '/public'), { maxAge: config.staticCacheTime, index: false }))
+  app.use(urlPathPrefix + '/docs', express.static(path.resolve(__dirname, config.docsPath), { maxAge: config.staticCacheTime }))
+  app.use(urlPathPrefix + '/uploads', express.static(path.resolve(__dirname, config.uploadsPath), { maxAge: config.staticCacheTime }))
+  app.use(urlPathPrefix + '/default.md', express.static(path.resolve(__dirname, config.defaultNotePath), { maxAge: config.staticCacheTime }))
+  app.use(urlPathPrefix, require('./lib/metrics').router)
+} else {
+  // routes without sessions
+  // static files
+  app.use('/', express.static(path.join(__dirname, '/public'), { maxAge: config.staticCacheTime, index: false }))
+  app.use('/docs', express.static(path.resolve(__dirname, config.docsPath), { maxAge: config.staticCacheTime }))
+  app.use('/uploads', express.static(path.resolve(__dirname, config.uploadsPath), { maxAge: config.staticCacheTime }))
+  app.use('/default.md', express.static(path.resolve(__dirname, config.defaultNotePath), { maxAge: config.staticCacheTime }))
+  app.use(require('./lib/metrics').router)
+}
 
 // session
 app.use(session({
@@ -227,7 +245,11 @@ app.locals.enableDropBoxSave = config.isDropboxEnable
 app.locals.enableGitHubGist = config.isGitHubEnable
 app.locals.enableGitlabSnippets = config.isGitlabSnippetsEnable
 
-app.use(require('./lib/routes').router)
+if (config.urlPath) {
+  app.use(`/${config.urlPath}`, require('./lib/routes').router)
+} else {
+  app.use(require('./lib/routes').router)
+}
 
 // response not found if no any route matxches
 app.get('*', function (req, res) {

lib/middleware/redirectWithoutTrailingSlashes.js

@@ -4,13 +4,15 @@ const config = require('../config')
 
 module.exports = function (req, res, next) {
   if (req.method === 'GET' && req.path.substr(-1) === '/' && req.path.length > 1) {
+    // Don't redirect if this is the URL path itself (e.g., /codimd/)
+    if (config.urlPath && req.path === `/${config.urlPath}/`) {
+      next()
+      return
+    }
+    
     const queryString = req.url.slice(req.path.length)
     const urlPath = req.path.slice(0, -1)
-    let serverURL = config.serverURL
-    if (config.urlPath) {
-      serverURL = serverURL.slice(0, -(config.urlPath.length + 1))
-    }
-    res.redirect(301, serverURL + urlPath + queryString)
+    res.redirect(301, urlPath + queryString)
   } else {
     next()
   }