Feat/add redirect url (#8)

Redirect users when they hit the shorten url to the original url

Author: selimyanat

api/src/infrastructure/repository/in-memory-url.repository.ts

@@ -5,13 +5,15 @@ import { Injectable, Logger } from '@nestjs/common';
 export class InMemoryUrlRepository implements ShortenUrlRepository {
   private urls: Map<string, string> = new Map();
 
-  create(url: string, shortenedUrl: string): Promise<void> {
-    this.urls.set(url, shortenedUrl);
+  create(url: string, encodedUrl: string): Promise<void> {
+    this.urls.set(url, encodedUrl);
     return Promise.resolve(undefined);
   }
 
-  findURL(url: string): Promise<string | null> {
-    const shortenedUrl = this.urls.get(url);
-    return Promise.resolve(shortenedUrl);
+  findOriginalURL(encodedUrl: string): Promise<string | null> {
+    const originalUrl = Array.from(this.urls.keys()).find(
+      (key) => this.urls.get(key) === encodedUrl,
+    );
+    return Promise.resolve(originalUrl || null);
   }
 }

api/src/infrastructure/repository/redis-url.repository.ts

@@ -14,9 +14,9 @@ export class RedisUrlRepository
 {
   private readonly DEFAULT_TTL = 100;
 
-  private redisClient: RedisClientType;
+  private readonly redisTTL: number;
 
-  private redisTTL: number;
+  private redisClient: RedisClientType;
 
   constructor(private readonly configService: ConfigService) {
     const redisUrl = this.configService.get<string>('REDIS_URL');
@@ -30,12 +30,18 @@ export class RedisUrlRepository
     );
   }
 
-  async create(url: string, shortenedUrl: string): Promise<void> {
-    await this.redisClient.set(url, shortenedUrl, { EX: this.redisTTL });
+  async create(url: string, encodedUrl: string): Promise<void> {
+    await this.redisClient.set(
+      `encodedUrl: ${encodedUrl}`,
+      `originalUrl: ${url}`,
+      {
+        EX: this.redisTTL,
+      },
+    );
   }
 
-  async findURL(url: string): Promise<string | null> {
-    return await this.redisClient.get(url);
+  async findOriginalURL(encodedUrl: string): Promise<string | null> {
+    return await this.redisClient.get(`encodedUrl:${encodedUrl}`);
   }
 
   async onModuleInit() {

api/src/infrastructure/repository/repository.provider.ts

@@ -9,7 +9,6 @@ import { RedisUrlRepository } from './redis-url.repository';
  */
 export const RepositoryProvider: Provider = {
   // TODO: Use a constant for the key
-  //provide: 'ShortenUrlRepository',
   provide: ShortenUrlRepository,
   useFactory: (configService: ConfigService) => {
     const persistenceType = configService.get<string>(

api/src/shorten-url/shorten-url.controller.spec.ts renamed to api/src/shorten-url/create-shorten-url/create-shorten-url.controller.spec.ts

@@ -1,17 +1,17 @@
 import { Test, TestingModule } from '@nestjs/testing';
-import { ShortenUrlController } from './shorten-url.controller';
+import { CreateShortenUrlController } from './create-shorten-url.controller';
 import { ConfigModule } from '@nestjs/config';
-import { ShortenUrlModule } from './shorten-url.module';
+import { ShortenUrlModule } from '../shorten-url.module';
 
 describe('ShortenUrl controller', () => {
-  let underTest: ShortenUrlController;
+  let underTest: CreateShortenUrlController;
 
   beforeEach(async () => {
     const app: TestingModule = await Test.createTestingModule({
       imports: [await ConfigModule.forRoot(), ShortenUrlModule],
     }).compile();
 
-    underTest = app.get<ShortenUrlController>(ShortenUrlController);
+    underTest = app.get<CreateShortenUrlController>(CreateShortenUrlController);
   });
 
   describe('shortenUrl', () => {

api/src/shorten-url/shorten-url.controller.ts renamed to api/src/shorten-url/create-shorten-url/create-shorten-url.controller.ts

@@ -1,18 +1,18 @@
 import { Body, Controller, Logger, Post } from '@nestjs/common';
-import { ShortenUrlUsecase } from './shorten-url.usecase';
+import { CreateShortenUrlUsecase } from './create-shorten-url.usecase';
 import { CreateShortenUrlDto } from './create-shorten-url.dto';
 
 @Controller('/shorten-url')
-export class ShortenUrlController {
-  constructor(private readonly shortenUrlUsecase: ShortenUrlUsecase) {}
+export class CreateShortenUrlController {
+  constructor(private readonly shortenUrlUsecase: CreateShortenUrlUsecase) {}
 
   @Post()
   async shortenUrl(
     @Body() request: CreateShortenUrlDto,
   ): Promise<{ shortenedUrl: string }> {
-    Logger.log(`Received url ${request.url} to shorten`);
     // TODO perhaps it is worth converting the URL from string to URL object
-    const shortenedUrl = await this.shortenUrlUsecase.shortenUrl(request.url);
-    return { shortenedUrl };
+    const url = new URL(request.url);
+    const shortenedUrl = await this.shortenUrlUsecase.shortenUrl(url);
+    return { shortenedUrl: shortenedUrl.toString() };
   }
 }

api/src/shorten-url/create-shorten-url.dto.ts renamed to api/src/shorten-url/create-shorten-url/create-shorten-url.dto.ts

@@ -0,0 +1,48 @@
+import { Inject, Injectable } from '@nestjs/common';
+import { ShortenUrlIdGeneratorService } from './shorten-url.id-generator.service';
+import { ShortenUrlRepository } from '../shorten-url.repository';
+import { ConfigService } from '@nestjs/config';
+
+@Injectable()
+export class CreateShortenUrlUsecase {
+  private static BASE62_CHARACTERS =
+    '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
+
+  private static BASE62 = CreateShortenUrlUsecase.BASE62_CHARACTERS.length;
+
+  private readonly shortenedBaseUrl: string;
+
+  constructor(
+    private readonly configService: ConfigService,
+    private readonly idGenerator: ShortenUrlIdGeneratorService,
+    @Inject('ShortenUrlRepository')
+    private readonly shortenUrlRepository: ShortenUrlRepository,
+  ) {
+    if (!this.configService.get<number>('SHORTENED_BASE_URL'))
+      throw new Error(
+        'SHORTENED_BASE_URL is not defined in the environment variables',
+      );
+    this.shortenedBaseUrl =
+      this.configService.get<string>('SHORTENED_BASE_URL');
+  }
+
+  async shortenUrl(originalURL: URL): Promise<URL> {
+    const id = this.idGenerator.generateId();
+    const encodedUrl = this.encodeBase62(Number(id));
+    await this.shortenUrlRepository.create(originalURL.toString(), encodedUrl);
+    const shortenedUrl = new URL(encodedUrl, this.shortenedBaseUrl);
+    return shortenedUrl;
+  }
+
+  private encodeBase62(id: number): string {
+    if (id === 0) return CreateShortenUrlUsecase.BASE62_CHARACTERS[0];
+
+    let encoded = '';
+    while (id > 0) {
+      const remainder = id % CreateShortenUrlUsecase.BASE62;
+      encoded = CreateShortenUrlUsecase.BASE62_CHARACTERS[remainder] + encoded;
+      id = Math.floor(id / CreateShortenUrlUsecase.BASE62);
+    }
+    return encoded;
+  }
+}

api/src/shorten-url/create-shorten-url/create-shorten-url.usecase.ts

@@ -0,0 +1,52 @@
+import { CreateShortenUrlController } from '../create-shorten-url/create-shorten-url.controller';
+import { RedirectToOriginalUrlController } from './redirect-to-original-url.controller';
+import { Test, TestingModule } from '@nestjs/testing';
+import { ConfigModule } from '@nestjs/config';
+import { ShortenUrlModule } from '../shorten-url.module';
+
+describe('Redirect to original url controller', () => {
+  let shortenUrlController: CreateShortenUrlController;
+  let underTest: RedirectToOriginalUrlController;
+
+  beforeEach(async () => {
+    const app: TestingModule = await Test.createTestingModule({
+      imports: [await ConfigModule.forRoot(), ShortenUrlModule],
+    }).compile();
+
+    shortenUrlController = app.get<CreateShortenUrlController>(
+      CreateShortenUrlController,
+    );
+    underTest = app.get<RedirectToOriginalUrlController>(
+      RedirectToOriginalUrlController,
+    );
+  });
+
+  describe('Redirect to original url', () => {
+    it('should return the original URL for a given shortened URL', async () => {
+      const longUrl =
+        'https://zapper.xyz/very-long-url/very-long-url/very-long-url';
+
+      // Use the shorten URL controller to create the shortened URL
+      const shortenedResponse = await shortenUrlController.shortenUrl({
+        url: longUrl,
+      });
+
+      // Extract the slug from the shortened URL
+      const shortenedUrl = shortenedResponse.shortenedUrl;
+      const slug = shortenedUrl.split('/').pop();
+
+      // Now retrieve the original URL using GetOriginalUrlController
+      const response = await underTest.redirectToOriginalUrl(slug);
+
+      // TODO check with an integration / e2e test the redirection code (302)
+      expect(response).toEqual({ url: longUrl });
+    });
+  });
+
+  it('should return 404 if the shortened URL is not found', async () => {
+    const slug = 'does-not-exist';
+    await expect(underTest.redirectToOriginalUrl(slug)).rejects.toThrow(
+      'Shortened URL "does-not-exist" not found',
+    );
+  });
+});

api/src/shorten-url/shorten-url.id-generator.service.ts renamed to api/src/shorten-url/create-shorten-url/shorten-url.id-generator.service.ts

@@ -0,0 +1,28 @@
+import {
+  Controller,
+  Get,
+  NotFoundException,
+  Param,
+  Redirect,
+} from '@nestjs/common';
+import { RedirectToOriginalUrlUsecase } from './redirect-to-original-url.usecase';
+
+@Controller()
+export class RedirectToOriginalUrlController {
+  constructor(
+    private readonly getOriginalUrlUsecase: RedirectToOriginalUrlUsecase,
+  ) {}
+
+  @Get(':slug')
+  @Redirect(undefined, 302)
+  async redirectToOriginalUrl(@Param('slug') slug: string) {
+    const originalUrl = await this.getOriginalUrlUsecase.redirectToOriginalUrl(
+      slug,
+    );
+    if (!originalUrl) {
+      throw new NotFoundException(`Shortened URL "${slug}" not found`);
+    }
+    // Use temporary redirect to original URL so that we can capture analytics
+    return { url: originalUrl.toString() };
+  }
+}