#3 added util func to validate url on post request

backend/.env

 DB_CONN_STRING="mongodb://localhost:27017"
 DB_NAME="linksDB"
 LINKS_COLLECTION_NAME="links"
-PORT='3000'
\ No newline at end of file
+PORT='3000'
+BASE_URL='http://localhost:3000'
\ No newline at end of file

backend/Util/util.ts

+export const validateUrl = (url: string): boolean => {
+  const urlPattern: RegExp = new RegExp(
+    '^(https?:\\/\\/)?' +
+      '((([a-z\\d]([a-z\\d-]*[a-z\\d])*)\\.)+[a-z]{2,}|' +
+      '((\\d{1,3}\\.){3}\\d{1,3}))' +
+      '(\\:\\d+)?(\\/[-a-z\\d%_.~+]*)*' +
+      '(\\?[;&a-z\\d%_.~+=-]*)?' +
+      '(\\#[-a-z\\d_]*)?$',
+    'i'
+  );
+
+  return !!urlPattern.test(url);
+};

backend/package-lock.json

@@ -13,11 +13,13 @@
         "cors": "^2.8.5",
         "dotenv": "^16.0.3",
         "express": "^4.18.2",
-        "mongodb": "^5.1.0"
+        "mongodb": "^5.1.0",
+        "shortid": "^2.2.16"
       },
       "devDependencies": {
         "@types/cors": "^2.8.13",
         "@types/express": "^4.17.17",
+        "@types/shortid": "^0.0.29",
         "ts-node-dev": "^2.0.0"
       }
     },
@@ -166,6 +168,12 @@
         "@types/node": "*"
       }
     },
+    "node_modules/@types/shortid": {
+      "version": "0.0.29",
+      "resolved": "https://registry.npmjs.org/@types/shortid/-/shortid-0.0.29.tgz",
+      "integrity": "sha512-9BCYD9btg2CY4kPcpMQ+vCR8U6V8f/KvixYD5ZbxoWlkhddNF5IeZMVL3p+QFUkg+Hb+kPAG9Jgk4bnnF1v/Fw==",
+      "dev": true
+    },
     "node_modules/@types/strip-bom": {
       "version": "3.0.0",
       "resolved": "https://registry.npmjs.org/@types/strip-bom/-/strip-bom-3.0.0.tgz",
@@ -931,6 +939,11 @@
       "resolved": "https://registry.npmjs.org/ms/-/ms-2.0.0.tgz",
       "integrity": "sha512-Tpp60P6IUJDTuOq/5Z8cdskzJujfwqfOTkrwIwj7IRISpnkJnT6SyJ4PCPnGMoFjC9ddhal5KVIYtAt97ix05A=="
     },
+    "node_modules/nanoid": {
+      "version": "2.1.11",
+      "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-2.1.11.tgz",
+      "integrity": "sha512-s/snB+WGm6uwi0WjsZdaVcuf3KJXlfGl2LcxgwkEwJF0D/BWzVWAZW/XY4bFaiR7s0Jk3FPvlnepg1H1b1UwlA=="
+    },
     "node_modules/negotiator": {
       "version": "0.6.3",
       "resolved": "https://registry.npmjs.org/negotiator/-/negotiator-0.6.3.tgz",
@@ -1204,6 +1217,14 @@
       "resolved": "https://registry.npmjs.org/setprototypeof/-/setprototypeof-1.2.0.tgz",
       "integrity": "sha512-E5LDX7Wrp85Kil5bhZv46j8jOeboKq5JMmYM3gVGdGH8xFpPWXUMsNrlODCrkoxMEeNi/XZIwuRvY4XNwYMJpw=="
     },
+    "node_modules/shortid": {
+      "version": "2.2.16",
+      "resolved": "https://registry.npmjs.org/shortid/-/shortid-2.2.16.tgz",
+      "integrity": "sha512-Ugt+GIZqvGXCIItnsL+lvFJOiN7RYqlGy7QE41O3YC1xbNSeDGIRO7xg2JJXIAj1cAGnOeC1r7/T9pgrtQbv4g==",
+      "dependencies": {
+        "nanoid": "^2.1.0"
+      }
+    },
     "node_modules/side-channel": {
       "version": "1.0.4",
       "resolved": "https://registry.npmjs.org/side-channel/-/side-channel-1.0.4.tgz",
@@ -1675,6 +1696,12 @@
         "@types/node": "*"
       }
     },
+    "@types/shortid": {
+      "version": "0.0.29",
+      "resolved": "https://registry.npmjs.org/@types/shortid/-/shortid-0.0.29.tgz",
+      "integrity": "sha512-9BCYD9btg2CY4kPcpMQ+vCR8U6V8f/KvixYD5ZbxoWlkhddNF5IeZMVL3p+QFUkg+Hb+kPAG9Jgk4bnnF1v/Fw==",
+      "dev": true
+    },
     "@types/strip-bom": {
       "version": "3.0.0",
       "resolved": "https://registry.npmjs.org/@types/strip-bom/-/strip-bom-3.0.0.tgz",
@@ -2246,6 +2273,11 @@
       "resolved": "https://registry.npmjs.org/ms/-/ms-2.0.0.tgz",
       "integrity": "sha512-Tpp60P6IUJDTuOq/5Z8cdskzJujfwqfOTkrwIwj7IRISpnkJnT6SyJ4PCPnGMoFjC9ddhal5KVIYtAt97ix05A=="
     },
+    "nanoid": {
+      "version": "2.1.11",
+      "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-2.1.11.tgz",
+      "integrity": "sha512-s/snB+WGm6uwi0WjsZdaVcuf3KJXlfGl2LcxgwkEwJF0D/BWzVWAZW/XY4bFaiR7s0Jk3FPvlnepg1H1b1UwlA=="
+    },
     "negotiator": {
       "version": "0.6.3",
       "resolved": "https://registry.npmjs.org/negotiator/-/negotiator-0.6.3.tgz",
@@ -2441,6 +2473,14 @@
       "resolved": "https://registry.npmjs.org/setprototypeof/-/setprototypeof-1.2.0.tgz",
       "integrity": "sha512-E5LDX7Wrp85Kil5bhZv46j8jOeboKq5JMmYM3gVGdGH8xFpPWXUMsNrlODCrkoxMEeNi/XZIwuRvY4XNwYMJpw=="
     },
+    "shortid": {
+      "version": "2.2.16",
+      "resolved": "https://registry.npmjs.org/shortid/-/shortid-2.2.16.tgz",
+      "integrity": "sha512-Ugt+GIZqvGXCIItnsL+lvFJOiN7RYqlGy7QE41O3YC1xbNSeDGIRO7xg2JJXIAj1cAGnOeC1r7/T9pgrtQbv4g==",
+      "requires": {
+        "nanoid": "^2.1.0"
+      }
+    },
     "side-channel": {
       "version": "1.0.4",
       "resolved": "https://registry.npmjs.org/side-channel/-/side-channel-1.0.4.tgz",

backend/package.json

@@ -14,11 +14,13 @@
     "cors": "^2.8.5",
     "dotenv": "^16.0.3",
     "express": "^4.18.2",
-    "mongodb": "^5.1.0"
+    "mongodb": "^5.1.0",
+    "shortid": "^2.2.16"
   },
   "devDependencies": {
     "@types/cors": "^2.8.13",
     "@types/express": "^4.17.17",
+    "@types/shortid": "^0.0.29",
     "ts-node-dev": "^2.0.0"
   }
 }

backend/src/models/links.ts

 import {ObjectId} from 'mongodb';
 
 export default class Link {
-  constructor(public originalUrl: string, public id?: ObjectId) {}
+  constructor(
+    public originalUrl: string,
+    public shortUrl: string,
+    public id?: ObjectId
+  ) {}
 }

backend/src/routes/links.router.ts

@@ -2,12 +2,15 @@ import express, {Router, Request, Response} from 'express';
 import {ObjectId} from 'mongodb';
 import {collections} from '../services/database.service';
 import Link from '../models/links';
+import shortid from 'shortid';
+import {validateUrl} from '../../Util/util';
 
 export const linksRouter: Router = express.Router();
 
-linksRouter.get('/', (req: Request, res: Response) => {
+linksRouter.get('/', async (req: Request, res: Response) => {
   try {
-    res.send('Hello');
+    const links = await collections.links?.find({}).toArray();
+    res.status(200).send(links);
   } catch (error: unknown) {
     const err = error as Error;
     res.status(500).send(err.message);
@@ -17,14 +20,37 @@ linksRouter.get('/', (req: Request, res: Response) => {
 linksRouter.post('/', async (req: Request, res: Response) => {
   try {
     const newLink = req.body as Link;
-    const result = await collections.links?.insertOne(newLink);
-    if (result) {
-      res
-        .status(201)
-        .send(`Successfully created a new link with id ${result.insertedId}`);
-    } else {
-      res.status(500).send('Failed to create a new link.');
+
+    if (!validateUrl(newLink.originalUrl)) {
+      res.status(400).send('Invalid url link');
+      return;
+    }
+
+    const originalLinkExists = await collections.links?.findOne({
+      originalUrl: newLink.originalUrl,
+    });
+
+    if (originalLinkExists) {
+      res.status(200).send(originalLinkExists);
+      return;
+    }
+    let shortUrl;
+
+    while (true) {
+      const urlId = shortid.generate();
+      shortUrl = `${process.env.BASE_URL}/${urlId}`;
+
+      const shortUlrExists = await collections.links?.findOne({
+        shortUrl: shortUrl,
+      });
+
+      if (!shortUlrExists) {
+        break;
+      }
     }
+    newLink.shortUrl = shortUrl;
+    await collections.links?.insertOne(newLink);
+    res.status(200).send(newLink);
   } catch (err: unknown) {
     const error = err as Error;
     res.status(500).send(error.message);

backend/src/types/environment.d.ts

@@ -5,6 +5,7 @@ declare global {
       DB_CONN_STRING: string;
       DB_NAME: string;
       LINKS_COLLECTION_NAME: string;
+      BASE_URL: string;
     }
   }
 }