Merge pull request #365 from Real-Dev-Squad/doc/backendflow

Created Backend Flow doc of website-backend

Author: ankurnarkhede

docs/backendFlow.md

@@ -0,0 +1,252 @@
+# **Backend Flow 🕸️**
+
+<br>
+
+> ## Explaining the flow using `Users` created in the project ✌️
+
+<br>
+
+- [**Backend Flow 🕸️**](#backend-flow-️)
+  - [server.js](#serverjs)
+  - [Base or Global Route](#base-or-global-route)
+  - [Different HTTP Routes](#different-http-routes)
+  - [Middlewares](#middlewares)
+  - [Controllers](#controllers)
+  - [Models](#models)
+  - [config.js](#configjs)
+  - [test](#test)
+  - [package.json file](#packagejson-file)
+  - [Want to Contribute ??](#want-to-contribute-)
+
+## server.js
+
+<br>
+
+> Entry point for the project
+
+- `Config` and `logger` are added to the global object
+- Creating the server, and other server helper functions
+- Makes use of `http` module of node.js
+
+💡 Know How: [Build http-server](https://nodejs.dev/learn/build-an-http-server "Create Http-server")
+
+<br>
+
+## Base or Global Route
+
+- In project, base route `'/users'` means this is the base for every users route
+  [ From: `routes> index.js` ]
+
+👀 Example:
+
+`routes/index.js`
+
+```
+app.use('/users', require('./users.js'))
+```
+
+Description:
+
+- To access details of user with `userId`, the route will be `/users/userId` and so on.
+
+👀 Example:
+
+`router.get('/:username', users.getUser)`
+
+<br>
+
+## Different HTTP Routes
+
+- Defines the path of the users request (can be, `GET` | `POST` | `PUT` | `PATCH` | `DELETE` etc.)
+- Each route can have one or more handler functions, which are executed when the route is matched
+
+<br>
+
+More on HTTP Methods: [MDN HTTP Methods](https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods "HTTP Methods") <br>
+Routing Basics: [Express Router](https://expressjs.com/en/guide/routing.html "Express way Routing")
+
+<br>
+
+👀 Example:
+
+`GET /users Route`
+
+```
+router.get('/', authenticate, usersController.getUsers)
+```
+
+<br>
+
+## Middlewares
+
+- Middleware function has access to request object and response object
+- And it has the `next()` [ mandatory to add ] which calls to the next middleware, if any assigned
+
+💡 Know How: [Express Middleware](https://expressjs.com/en/guide/writing-middleware.html "Middleware Docs")
+
+<br>
+
+👀 Example:
+
+`authenticate middleware`
+
+```JS
+module.exports = async (req, res, next) => {
+  try {
+    let token = req.cookies[config.get('userToken.cookieName')]
+
+    /**
+     * Enable Bearer Token authentication for NON-PRODUCTION environments
+     * This is enabled as Swagger UI does not support cookie authe
+     */
+    if (process.env.NODE_ENV !== 'production' && !token) {
+      token = req.headers.authorization.split(' ')[1]
+    }
+
+    const { userId } = authService.verifyAuthToken(token)
+
+    // add user data to `req.userData` for further use
+    const userData = await users.fetchUser({ userId })
+    req.userData = userData.user
+
+    return next()
+  } catch (err) {
+    logger.error(err)
+
+    if (err.name === 'TokenExpiredError') {
+      const refreshTtl = config.get('userToken.refreshTtl')
+      const token = req.cookies[config.get('userToken.cookieName')]
+      const { userId, iat } = authService.decodeAuthToken(token)
+      const newToken = authService.generateAuthToken({ userId })
+      const rdsUiUrl = new URL(config.get('services.rdsUi.baseUrl'))
+
+      // add new JWT to the response if it satisfies the refreshTtl time
+      if (Math.floor(Date.now() / 1000) - iat <= refreshTtl) {
+        res.cookie(config.get('userToken.cookieName'), newToken, {
+          domain: rdsUiUrl.hostname,
+          expires: new Date(Date.now() + config.get('userToken.ttl') * 1000),
+          httpOnly: true,
+          secure: true
+        })
+
+        // add user data to `req.userData` for further use
+        req.userData = await users.fetchUser({ userId })
+
+        return next()
+      } else {
+        return res.boom.unauthorized('Unauthenticated User')
+      }
+    } else {
+      return res.boom.unauthorized('Unauthenticated User')
+    }
+  }
+}
+```
+
+<br>
+
+## Controllers
+
+- Contains the business logic
+- Here the request and response are handled
+
+👀 Example:
+
+`getUsers Controller`
+
+```JS
+const getUsers = async (req, res) => {
+  try {
+    const allUsers = await userQuery.fetchUsers(req.query)
+    return res.json({
+      message: 'Users returned successfully!',
+      users: allUsers
+    })
+  } catch (error) {
+    logger.error(`Error while fetching all users: ${error}`)
+    return res.boom.serverUnavailable('Something went wrong please contact admin')
+  }
+}
+```
+
+<br>
+
+## Models
+
+- Interacts with the database, Ex. [Firebase](https://firebase.google.com/docs/guides "Firebase Docs")
+- Triggers database calls
+
+👀 Example:
+
+`fetchUsers Model`
+
+```JS
+const fetchUsers = async (query) => {
+  try {
+    const snapshot = await userModel
+      .limit(parseInt(query.size) || 100)
+      .offset((parseInt(query.size) || 100) * (parseInt(query.page) || 0))
+      .get()
+
+    const allUsers = []
+
+    snapshot.forEach((doc) => {
+      allUsers.push({
+        id: doc.id,
+        ...doc.data(),
+        phone: undefined,
+        email: undefined,
+        tokens: undefined
+      })
+    })
+
+    return allUsers
+  } catch (err) {
+    logger.error('Error retrieving user data', err)
+    throw err
+  }
+}
+```
+
+<br>
+
+## config.js
+
+- Configuring Environmental Variables
+  <br>
+
+💡 Know How: [Config](https://github.com/lorenwest/node-config/wiki/Configuration-Files "Setup the Configuration files")
+<br>
+
+## test
+
+<br>
+
+> Includes Integration and Unit Test for the backend routes
+
+Tests are written using:
+
+- [mocha](https://mochajs.org/ "Mocha Framework") : Test Framework
+- [chai](https://www.chaijs.com/ "Chai Library") : Asserion Library
+- [sinon](https://sinonjs.org/ "Sinon") : JavaScript test spies, stubs and mocks
+- [nock](https://github.com/nock/nock/blob/main/README.md "Nock") : HTTP requests mocking
+
+<br>
+
+## package.json file
+
+<br>
+
+> Gives the overiew of the project requirements
+
+- `scripts` : For different scripts needed for development & others
+- `Dependencies` : Modules needed for the project to work/ be functional
+- `devDependencies` : Dependencies only needed for the devlopment purpose
+ 
+<br>
+
+---
+
+## Want to Contribute ??
+
+[Guide](https://github.com/Real-Dev-Squad/website-backend/blob/develop/CONTRIBUTING.md "Follow the guidelines")