feat(backend): implement Google OAuth strategy and endpoints

Author: Arun-kushwaha007

apps/backend/src/auth/auth.controller.ts

@@ -1,16 +1,21 @@
-import { Body, Controller, Get, Logger, Post, Req, Res } from '@nestjs/common';
+import { Body, Controller, Get, Logger, Post, Req, Res, UseGuards } from '@nestjs/common';
 import { Throttle } from '@nestjs/throttler';
 import { Request, Response } from 'express';
 import { AuthService } from './auth.service';
 import { RegisterDto } from './dto/register.dto';
 import { LoginDto } from './dto/login.dto';
 import { GoogleLoginDto } from './dto/google-login.dto';
+import { GoogleOAuthGuard } from './guards/google-oauth.guard';
+import { AppConfigService } from '../config/app-config.service';
 
 @Controller('auth')
 export class AuthController {
   private readonly logger = new Logger(AuthController.name);
 
-  constructor(private readonly authService: AuthService) {}
+  constructor(
+    private readonly authService: AuthService,
+    private readonly config: AppConfigService,
+  ) {}
 
   @Get('csrf-token')
   getCsrfToken(@Req() req: Request & { csrfToken?: () => string }) {
@@ -45,6 +50,28 @@ export class AuthController {
     return payload;
   }
 
+  @Get('google')
+  @UseGuards(GoogleOAuthGuard)
+  async googleAuth() {
+    // Redirects to Google
+  }
+
+  @Get('google/callback')
+  @UseGuards(GoogleOAuthGuard)
+  async googleAuthRedirect(@Req() req: Request & { user: any }, @Res() res: Response) {
+    this.logger.log(`GET /auth/google/callback email=${req.user.email}`);
+    const payload = await this.authService.googleLogin({
+      email: req.user.email,
+      name: req.user.name,
+      avatarUrl: req.user.avatarUrl,
+    });
+    this.authService.setRefreshTokenCookie(res, payload.refreshToken);
+    
+    // Redirect back to frontend dashboard
+    const frontendUrl = this.config.corsOrigins[0]; // Usually the web frontend is first
+    res.redirect(`${frontendUrl}/dashboard`);
+  }
+
   @Post('refresh')
   async refresh(@Req() req: Request & { cookies?: Record<string, string> }, @Res({ passthrough: true }) res: Response) {
     const token = req.cookies?.refresh_token;

apps/backend/src/auth/auth.module.ts

@@ -7,6 +7,7 @@ import { PrismaModule } from '../common/prisma.module';
 import { AuthController } from './auth.controller';
 import { AuthService } from './auth.service';
 import { JwtStrategy } from './strategies/jwt.strategy';
+import { GoogleStrategy } from './strategies/google.strategy';
 
 import { GroupsModule } from '../groups/groups.module';
 import { RedisModule } from '../redis/redis.module';
@@ -27,7 +28,7 @@ import { RedisModule } from '../redis/redis.module';
     }),
   ],
   controllers: [AuthController],
-  providers: [AuthService, JwtStrategy],
+  providers: [AuthService, JwtStrategy, GoogleStrategy],
   exports: [AuthService],
 })
 export class AuthModule {}

apps/backend/src/auth/guards/google-oauth.guard.ts

@@ -0,0 +1,5 @@
+import { Injectable } from '@nestjs/common';
+import { AuthGuard } from '@nestjs/passport';
+
+@Injectable()
+export class GoogleOAuthGuard extends AuthGuard('google') {}

apps/backend/src/auth/strategies/google.strategy.ts

@@ -0,0 +1,31 @@
+import { Injectable } from '@nestjs/common';
+import { PassportStrategy } from '@nestjs/passport';
+import { Strategy, VerifyCallback } from 'passport-google-oauth20';
+import { AppConfigService } from '../../config/app-config.service';
+
+@Injectable()
+export class GoogleStrategy extends PassportStrategy(Strategy, 'google') {
+  constructor(config: AppConfigService) {
+    super({
+      clientID: config.googleClientId,
+      clientSecret: config.googleClientSecret,
+      callbackURL: `http://localhost:${config.port}/api/v1/auth/google/callback`,
+      scope: ['email', 'profile'],
+    });
+  }
+
+  async validate(
+    accessToken: string,
+    refreshToken: string,
+    profile: any,
+    done: VerifyCallback,
+  ): Promise<any> {
+    const { name, emails, photos } = profile;
+    const user = {
+      email: emails[0].value,
+      name: name.givenName ? `${name.givenName} ${name.familyName || ''}`.trim() : profile.displayName,
+      avatarUrl: photos && photos.length > 0 ? photos[0].value : undefined,
+    };
+    done(null, user);
+  }
+}