feat: Initialize NestJS backend project with Prisma, core modules, configuration, and common utilities.

src/app.controller.spec.ts

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+import { Test, TestingModule } from '@nestjs/testing';
+import { AppController } from './app.controller';
+import { AppService } from './app.service';
+
+describe('AppController', () => {
+  let appController: AppController;
+
+  beforeEach(async () => {
+    const app: TestingModule = await Test.createTestingModule({
+      controllers: [AppController],
+      providers: [AppService],
+    }).compile();
+
+    appController = app.get<AppController>(AppController);
+  });
+
+  describe('root', () => {
+    it('should return "Hello World!"', () => {
+      expect(appController.getHello()).toBe('Hello World!');
+    });
+  });
+});

src/app.controller.ts

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+import { Controller, Get } from '@nestjs/common';
+import { ApiTags, ApiOperation, ApiResponse } from '@nestjs/swagger';
+import { AppService } from './app.service';
+
+@ApiTags('Health')
+@Controller()
+export class AppController {
+  constructor(private readonly appService: AppService) {}
+
+  @Get()
+  @ApiOperation({ summary: 'Get API welcome message' })
+  @ApiResponse({ status: 200, description: 'API is running' })
+  getHello(): string {
+    return this.appService.getHello();
+  }
+
+  @Get('health')
+  @ApiOperation({ summary: 'Health check endpoint' })
+  @ApiResponse({ status: 200, description: 'Service is healthy' })
+  getHealth() {
+    return this.appService.getHealth();
+  }
+}

src/app.module.ts

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+import { Module } from '@nestjs/common';
+import { ConfigModule } from '@nestjs/config';
+import { ThrottlerModule, ThrottlerGuard } from '@nestjs/throttler';
+import { APP_GUARD } from '@nestjs/core';
+import { ScheduleModule } from '@nestjs/schedule';
+import { EventEmitterModule } from '@nestjs/event-emitter';
+
+import { configuration } from './config';
+import { PrismaModule } from './prisma';
+import { AppController } from './app.controller';
+import { AppService } from './app.service';
+
+@Module({
+  imports: [
+    // Configuration
+    ConfigModule.forRoot({
+      isGlobal: true,
+      load: [configuration],
+      envFilePath: ['.env.local', '.env'],
+    }),
+
+    // Rate Limiting
+    ThrottlerModule.forRoot([
+      {
+        ttl: 60000, // 60 seconds
+        limit: 100, // 100 requests per minute
+      },
+    ]),
+
+    // Task Scheduling
+    ScheduleModule.forRoot(),
+
+    // Event Emitter
+    EventEmitterModule.forRoot(),
+
+    // Database
+    PrismaModule,
+
+    // Feature Modules (will be added as we develop them)
+    // AuthModule,
+    // UsersModule,
+    // AgentsModule,
+  ],
+  controllers: [AppController],
+  providers: [
+    AppService,
+    // Global Rate Limiting Guard
+    {
+      provide: APP_GUARD,
+      useClass: ThrottlerGuard,
+    },
+  ],
+})
+export class AppModule {}

src/app.service.ts

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+import { Injectable } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { PrismaService } from './prisma';
+
+@Injectable()
+export class AppService {
+  constructor(
+    private readonly configService: ConfigService,
+    private readonly prisma: PrismaService,
+  ) {}
+
+  getHello(): string {
+    return 'Real Estate Agent Platform API v1.0';
+  }
+
+  async getHealth() {
+    const dbHealthy = await this.checkDatabaseHealth();
+
+    return {
+      status: 'ok',
+      timestamp: new Date().toISOString(),
+      environment: this.configService.get<string>('app.env'),
+      version: '1.0.0',
+      services: {
+        database: dbHealthy ? 'healthy' : 'unhealthy',
+      },
+    };
+  }
+
+  private async checkDatabaseHealth(): Promise<boolean> {
+    try {
+      await this.prisma.$queryRaw`SELECT 1`;
+      return true;
+    } catch {
+      return false;
+    }
+  }
+}

src/common/filters/http-exception.filter.ts

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+import {
+  ExceptionFilter,
+  Catch,
+  ArgumentsHost,
+  HttpException,
+  HttpStatus,
+  Logger,
+} from '@nestjs/common';
+import { Request, Response } from 'express';
+
+@Catch()
+export class AllExceptionsFilter implements ExceptionFilter {
+  private readonly logger = new Logger(AllExceptionsFilter.name);
+
+  catch(exception: unknown, host: ArgumentsHost) {
+    const ctx = host.switchToHttp();
+    const response = ctx.getResponse<Response>();
+    const request = ctx.getRequest<Request>();
+
+    let status: number;
+    let message: string | object;
+    let error: string;
+
+    if (exception instanceof HttpException) {
+      status = exception.getStatus();
+      const exceptionResponse = exception.getResponse();
+
+      if (typeof exceptionResponse === 'object') {
+        message = (exceptionResponse as any).message || exception.message;
+        error = (exceptionResponse as any).error || 'Error';
+      } else {
+        message = exceptionResponse;
+        error = 'Error';
+      }
+    } else {
+      status = HttpStatus.INTERNAL_SERVER_ERROR;
+      message = 'Internal server error';
+      error = 'Internal Server Error';
+
+      // Log unexpected errors
+      this.logger.error(
+        `Unexpected error: ${exception}`,
+        exception instanceof Error ? exception.stack : undefined,
+      );
+    }
+
+    const errorResponse = {
+      statusCode: status,
+      timestamp: new Date().toISOString(),
+      path: request.url,
+      method: request.method,
+      error,
+      message,
+    };
+
+    response.status(status).json(errorResponse);
+  }
+}

src/common/filters/index.ts

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+export * from './http-exception.filter';

src/common/interceptors/index.ts

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+export * from './transform.interceptor';

src/common/interceptors/transform.interceptor.ts

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+import {
+  Injectable,
+  NestInterceptor,
+  ExecutionContext,
+  CallHandler,
+} from '@nestjs/common';
+import { Observable } from 'rxjs';
+import { map } from 'rxjs/operators';
+
+export interface Response<T> {
+  success: boolean;
+  data: T;
+  timestamp: string;
+}
+
+@Injectable()
+export class TransformInterceptor<T>
+  implements NestInterceptor<T, Response<T>>
+{
+  intercept(
+    context: ExecutionContext,
+    next: CallHandler,
+  ): Observable<Response<T>> {
+    return next.handle().pipe(
+      map((data) => ({
+        success: true,
+        data,
+        timestamp: new Date().toISOString(),
+      })),
+    );
+  }
+}

src/config/configuration.ts

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+export default () => ({
+  // Application
+  app: {
+    name: process.env.APP_NAME || 'Real Estate Agent Platform',
+    env: process.env.NODE_ENV || 'development',
+    port: parseInt(process.env.PORT || '3001', 10),
+    apiUrl: process.env.API_URL || 'http://localhost:3001',
+    frontendUrl: process.env.FRONTEND_URL || 'http://localhost:3000',
+    adminUrl: process.env.ADMIN_URL || 'http://localhost:3002',
+  },
+
+  // Database
+  database: {
+    url: process.env.DATABASE_URL,
+  },
+
+  // JWT Authentication
+  jwt: {
+    secret: process.env.JWT_SECRET || 'super-secret-key',
+    accessExpiration: process.env.JWT_ACCESS_EXPIRATION || '15m',
+    refreshExpiration: process.env.JWT_REFRESH_EXPIRATION || '7d',
+  },
+
+  // Password Hashing
+  bcrypt: {
+    saltRounds: parseInt(process.env.BCRYPT_SALT_ROUNDS || '12', 10),
+  },
+
+  // Google OAuth
+  google: {
+    clientId: process.env.GOOGLE_CLIENT_ID,
+    clientSecret: process.env.GOOGLE_CLIENT_SECRET,
+    callbackUrl: process.env.GOOGLE_CALLBACK_URL,
+  },
+
+  // Facebook OAuth
+  facebook: {
+    appId: process.env.FACEBOOK_APP_ID,
+    appSecret: process.env.FACEBOOK_APP_SECRET,
+    callbackUrl: process.env.FACEBOOK_CALLBACK_URL,
+  },
+
+  // AWS S3
+  aws: {
+    accessKeyId: process.env.AWS_ACCESS_KEY_ID,
+    secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
+    region: process.env.AWS_REGION || 'us-east-1',
+    s3Bucket: process.env.AWS_S3_BUCKET,
+  },
+
+  // Email
+  mail: {
+    host: process.env.MAIL_HOST,
+    port: parseInt(process.env.MAIL_PORT || '587', 10),
+    user: process.env.MAIL_USER,
+    password: process.env.MAIL_PASSWORD,
+    from: process.env.MAIL_FROM,
+  },
+
+  // Stripe
+  stripe: {
+    secretKey: process.env.STRIPE_SECRET_KEY,
+    webhookSecret: process.env.STRIPE_WEBHOOK_SECRET,
+    publishableKey: process.env.STRIPE_PUBLISHABLE_KEY,
+  },
+
+  // Firebase
+  firebase: {
+    projectId: process.env.FIREBASE_PROJECT_ID,
+    clientEmail: process.env.FIREBASE_CLIENT_EMAIL,
+    privateKey: process.env.FIREBASE_PRIVATE_KEY?.replace(/\\n/g, '\n'),
+  },
+
+  // Redis
+  redis: {
+    host: process.env.REDIS_HOST || 'localhost',
+    port: parseInt(process.env.REDIS_PORT || '6379', 10),
+    password: process.env.REDIS_PASSWORD || undefined,
+    db: parseInt(process.env.REDIS_DB || '0', 10),
+  },
+
+  // Rate Limiting
+  throttle: {
+    ttl: parseInt(process.env.THROTTLE_TTL || '60', 10),
+    limit: parseInt(process.env.THROTTLE_LIMIT || '100', 10),
+  },
+
+  // Logging
+  logging: {
+    level: process.env.LOG_LEVEL || 'debug',
+  },
+
+  // CORS
+  cors: {
+    origins: process.env.CORS_ORIGINS?.split(',') || [
+      'http://localhost:3000',
+      'http://localhost:3002',
+    ],
+  },
+});

src/config/index.ts

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+export { default as configuration } from './configuration';

src/main.ts

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+import { NestFactory } from '@nestjs/core';
+import { ValidationPipe, Logger } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { SwaggerModule, DocumentBuilder } from '@nestjs/swagger';
+import helmet from 'helmet';
+import * as cookieParser from 'cookie-parser';
+import { AppModule } from './app.module';
+import { AllExceptionsFilter } from './common/filters';
+import { TransformInterceptor } from './common/interceptors';
+
+async function bootstrap() {
+  const logger = new Logger('Bootstrap');
+  const app = await NestFactory.create(AppModule);
+
+  const configService = app.get(ConfigService);
+  const port = configService.get<number>('app.port') || 3001;
+  const appEnv = configService.get<string>('app.env') || 'development';
+  const corsOrigins = configService.get<string[]>('cors.origins') || [];
+
+  // Security
+  app.use(helmet());
+  app.use(cookieParser());
+
+  // CORS
+  app.enableCors({
+    origin: corsOrigins,
+    credentials: true,
+    methods: ['GET', 'POST', 'PUT', 'PATCH', 'DELETE', 'OPTIONS'],
+    allowedHeaders: ['Content-Type', 'Authorization', 'X-Requested-With'],
+  });
+
+  // Global prefix
+  app.setGlobalPrefix('api/v1');
+
+  // Global pipes
+  app.useGlobalPipes(
+    new ValidationPipe({
+      whitelist: true,
+      forbidNonWhitelisted: true,
+      transform: true,
+      transformOptions: {
+        enableImplicitConversion: true,
+      },
+    }),
+  );
+
+  // Global filters
+  app.useGlobalFilters(new AllExceptionsFilter());
+
+  // Global interceptors
+  app.useGlobalInterceptors(new TransformInterceptor());
+
+  // Swagger documentation (only in development)
+  if (appEnv !== 'production') {
+    const config = new DocumentBuilder()
+      .setTitle('Real Estate Agent Platform API')
+      .setDescription('API documentation for the Real Estate Agent Platform')
+      .setVersion('1.0')
+      .addBearerAuth(
+        {
+          type: 'http',
+          scheme: 'bearer',
+          bearerFormat: 'JWT',
+          name: 'JWT',
+          description: 'Enter JWT token',
+          in: 'header',
+        },
+        'JWT-auth',
+      )
+      .addTag('Auth', 'Authentication endpoints')
+      .addTag('Users', 'User management endpoints')
+      .addTag('Agents', 'Agent management endpoints')
+      .addTag('Health', 'Health check endpoints')
+      .build();
+
+    const document = SwaggerModule.createDocument(app, config);
+    SwaggerModule.setup('api/docs', app, document, {
+      swaggerOptions: {
+        persistAuthorization: true,
+      },
+    });
+
+    logger.log(`Swagger documentation available at http://localhost:${port}/api/docs`);
+  }
+
+  await app.listen(port);
+  logger.log(`Application is running on: http://localhost:${port}`);
+  logger.log(`Environment: ${appEnv}`);
+}
+
+bootstrap();

src/prisma/index.ts

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+export * from './prisma.module';
+export * from './prisma.service';

src/prisma/prisma.module.ts

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+import { Global, Module } from '@nestjs/common';
+import { PrismaService } from './prisma.service';
+
+@Global()
+@Module({
+  providers: [PrismaService],
+  exports: [PrismaService],
+})
+export class PrismaModule {}

src/prisma/prisma.service.ts

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+import { Injectable, OnModuleInit, OnModuleDestroy } from '@nestjs/common';
+import { PrismaClient } from '@prisma/client';
+
+@Injectable()
+export class PrismaService
+  extends PrismaClient
+  implements OnModuleInit, OnModuleDestroy
+{
+  constructor() {
+    super({
+      log:
+        process.env.NODE_ENV === 'development'
+          ? ['query', 'info', 'warn', 'error']
+          : ['error'],
+    });
+  }
+
+  async onModuleInit() {
+    await this.$connect();
+  }
+
+  async onModuleDestroy() {
+    await this.$disconnect();
+  }
+
+  async cleanDatabase() {
+    if (process.env.NODE_ENV === 'production') {
+      throw new Error('cleanDatabase is not allowed in production');
+    }
+
+    const models = Reflect.ownKeys(this).filter(
+      (key) => typeof key === 'string' && !key.startsWith('_') && !key.startsWith('$'),
+    );
+
+    return Promise.all(
+      models.map((modelKey) => {
+        const model = this[modelKey as string];
+        if (model && typeof model.deleteMany === 'function') {
+          return model.deleteMany();
+        }
+        return Promise.resolve();
+      }),
+    );
+  }
+}