Simplify JSON response (openshift-knative#10)

The simplified response is so it contains a short JSON, and the
additional data is delivered via headers:

```
HTTP/1.1 200 OK
content-length: 52
Content-Type: application/json
Server: Quarkus/2.13.5.Final-redhat-00002 Java/17.0.5
X-Config: {"sink":"http://localhost:38859","greet":"Welcome","delay":0}
X-Version: feature-event-receiver-8540b9b

{
  "artifact":"knative-showcase",
  "greeting":"Welcome"
}
```

expressjs/.env

@@ -1,5 +1 @@
-K_SINK=http://localhost:31111
-PORT=8080
-GREETING=Hello
-DELAY=0
 CONTAINER_BASENAME=quay.io/openshift-knative/

expressjs/package.json

@@ -43,6 +43,7 @@
     "express-handlebars": "^6.0.6",
     "express-prom-bundle": "^6.6.0",
     "git-describe": "^4.1.1",
+    "joi": "^17.8.3",
     "morgan": "^1.10.0",
     "prom-client": "^14.1.1",
     "semver": "^7.3.8"

expressjs/src/domain/entity/project.js

@@ -1,7 +1,7 @@
 const semver = require('semver')
 
 class Platform {
-  constructor({ node, npm }) {
+  constructor({ node, express }) {
 
     /**
      * @type {string}
@@ -11,7 +11,11 @@ class Platform {
     /**
      * @type {string}
      */
-    this.npm = npm
+    this.express = express
+  }
+
+  toString() {
+    return `Express/${this.express} Node/${this.node}`
   }
 }
 

expressjs/src/index.js

@@ -1,7 +1,7 @@
 (async () => {
   const app = await require('./app').createApp()
 
-  const port = process.env.PORT
+  const port = require('./services/config').port()
 
   app.listen(port, () => {
     console.log(`Listening at http://localhost:${port}/`)

expressjs/src/routes/index.js

@@ -2,17 +2,22 @@ const { oapi } = require('../middlewares/openapi')
 const { resolveProject } = require('../services/project')
 const config = require('../services/config')
 
+/**
+ * @param {express.Express} app
+ */
 module.exports = app => {
-  const project = resolveProject()
   app.get('/', getDoc(), async (req, res) => {
     try {
+      const project = await resolveProject()
+      const idx = new Index({
+        artifact: project.artifact,
+        greeting: config.greet(),
+      })
+      addResponseHeaders(res, project)
       if (shouldRenderJson(req)) {
-        return res.json(await project)
-      }
-      const data = {
-        project: await project,
-        config,
+        return res.json(idx)
       }
+      const data = { project, config }
       res.render('index', data)
     } catch (err) {
       console.error(err)
@@ -23,7 +28,13 @@ module.exports = app => {
 
   app.options('/', optionsDoc(), async (_, res) => {
     try {
-      res.json(await project)
+      const project = await resolveProject()
+      const idx = new Index({
+        artifact: project.artifact,
+        greeting: config.greet(),
+      })
+      addResponseHeaders(res, project)
+      res.json(idx)
     } catch (err) {
       console.error(err)
       res.status(500)
@@ -32,6 +43,38 @@ module.exports = app => {
   })
 }
 
+class Index {
+  constructor({ artifact, greeting }) {
+
+    /**
+     * @type {string}
+     */
+    this.artifact = artifact
+
+    /**
+     * @type {string}
+     */
+    this.greeting = greeting
+  }
+}
+
+/**
+ * Adds response headers
+ *
+ * @param {*} res the response object
+ * @param {Project} project holds project info
+ */
+function addResponseHeaders(res, project) {
+  const { sink, greet, delay } = config
+  res.header('Server', project.platform)
+    .header('X-Version', project.version)
+    .header('X-Config', JSON.stringify({
+      sink: sink(),
+      greet: greet(),
+      delay: delay(),
+    }))
+}
+
 function shouldRenderJson(req) {
   const ua = req.header('user-agent')
   if (ua && ua.startsWith('Mozilla')) {
@@ -67,23 +110,12 @@ function optionsDoc() {
             schema: {
               type: 'object',
               properties: {
-                version: { type: 'string' },
-                artifact: { type: 'string' },
-                platform: {
-                  type: 'object',
-                  properties: {
-                    node: { type: 'string' },
-                    npm: { type: 'string' }
-                  }
-                }
+                greeting: { type: 'string' },
+                artifact: { type: 'string' }
               },
               example: {
-                version: 'v1.3.1',
-                artifact: '@openshift/knative-showcase',
-                platform: {
-                  node: 'v12.19.0',
-                  npm: 'v6.14.8'
-                }
+                greeting: 'Welcome',
+                artifact: 'knative-showcase'
               }
             }
           }

expressjs/src/services/config.js

@@ -1,21 +1,54 @@
+const Joi = require('joi')
+
 function sink() {
-  return process.env.K_SINK
+  return process.env.K_SINK || 'http://localhost:31111'
 }
 
-function greeting() {
-  return process.env.GREETING
+function greet() {
+  return process.env.GREET || 'Welcome'
 }
 
 function delay() {
-  let d = parseInt(process.env.DELAY, 10)
-  if (isNaN(d) || d < 0) {
-    return 0
-  }
-  return d
+  return parseInt(process.env.DELAY || '0', 10)
+}
+
+function port() {
+  return process.env.PORT || 8080
 }
 
-module.exports = {
+const config = {
   sink,
-  greeting,
-  delay
+  greet,
+  delay,
+  port
 }
+
+const schema = Joi.object({
+  sink: Joi.string()
+    .uri({ scheme: /https?/ })
+    .required(),
+
+  greet: Joi.string()
+    .pattern(new RegExp('^[A-Z][a-z]+$'))
+    .required(),
+
+  delay: Joi.number()
+    .min(0)
+    .required(),
+
+  port: Joi.number()
+    .min(0)
+    .required()
+})
+
+const { error } = schema.validate({
+  sink: config.sink(),
+  greet: config.greet(),
+  delay: config.delay(),
+  port: config.port()
+})
+if (error) {
+  throw error
+}
+
+module.exports = config

expressjs/src/services/greeter.js

@@ -4,7 +4,7 @@ const { Notifier } = require('./notifier')
 let number = 0
 
 class Greeter {
-  constructor({ sink, greeting, delay }) {
+  constructor({ sink, greet, delay }) {
 
     /**
      * @type {Notifier}
@@ -14,7 +14,7 @@ class Greeter {
     /**
      * @type {() => string}
      */
-    this.greeting = greeting
+    this.greet = greet
 
     /**
      * @type {() => Number}
@@ -28,7 +28,7 @@ class Greeter {
    */
   async hello(who) {
     const hello = new Hello({
-      greeting: this.greeting(),
+      greeting: this.greet(),
       who,
       number: ++number
     })