Project: API Response and Middleware Formats

This project defines standardized response formats and middleware utilities for handling authentication, notifications, payments, courier tracking, and HTTP requests/responses.

Installation

Ensure you have NestJS and Express installed in your project before using these interfaces and middleware.

npm install @nestjs/common @nestjs/core @nestjs/jwt @nestjs/config express

or using yarn

yarn add @nestjs/common @nestjs/core @nestjs/jwt @nestjs/config express

Response Formats

1. Courier Response Format

This defines the structure for tracking shipments via courier services such as DHL.

export interface CourierResponse {
    trackingId: string;
    status: string;
    estimatedDelivery: string;
    currentLocation: string;
    origin: string;
    destination: string;
    history: Array<{
        status: string;
        location: string;
        timestamp: string;
    }>;
}

2. Notification Response Format

Defines the structure of notification events for server-side events.

export interface NotificationResponse<T> {
    event: string; // "order_update" | "payment_status" | "shipment_tracking" | etc.
    message: string;
    timestamp: string;
    data?: T;
}

3. Payment Response Format

Defines the structure for payment processing responses using Trust Payments.

export interface PaymentResponse {
    status: string; // "success" | "failed" | "pending"
    transactionId: string;
    amount: number;
    currency: string;
    message: string;
    paymentMethod: string; // "credit_card", "paypal", etc.
    createdAt: string;
}

4. HTTP Response Format

A generic HTTP response wrapper to standardize API responses.

export class HttpResponse<T> {
    public data: T;
    public error: boolean;
    public message?: string;
  
    constructor(data: T, error: boolean = false, message?: string) {
      this.data = data;
      this.error = error;
      if (message) {
        this.message = message;
      }
    }
}

Middleware

1. Authentication Middleware

A NestJS AuthGuard for protecting routes using JWT authentication.

import {
    CanActivate,
    ExecutionContext,
    Injectable,
    UnauthorizedException,
} from '@nestjs/common';
import { Request } from 'express';
import { Reflector } from '@nestjs/core';
import { JwtService } from '@nestjs/jwt';
import { ConfigService } from '@nestjs/config';
import { IS_PUBLIC_KEY } from '../decorators/public.decorator';

@Injectable()
export class AuthGuard implements CanActivate {
    constructor(
        private jwtService: JwtService,
        private reflector: Reflector,
        private configService: ConfigService,
    ) { }

    async canActivate(context: ExecutionContext): Promise<boolean> {
        const isPublic = this.reflector.getAllAndOverride<boolean>(IS_PUBLIC_KEY, [
            context.getHandler(),
            context.getClass(),
        ]);
        if (isPublic) {
            return true;
        }

        const request = context.switchToHttp().getRequest();
        const token = this.extractTokenFromHeader(request);
        if (!token) {
            throw new UnauthorizedException();
        }
        try {
            const payload = await this.jwtService.verifyAsync(token, {
                secret: this.configService.get<string>('JWT_SECRET'),
            });
            request.body = payload;
        } catch {
            throw new UnauthorizedException();
        }
        return true;
    }

    private extractTokenFromHeader(request: Request): string | undefined {
        const [type, token] = request.headers.authorization?.split(' ') ?? [];
        return type === 'Bearer' ? token : undefined;
    }
}

2. Request Interface for Express

Defines a custom request interface that includes a body property for authenticated requests.

import { Request } from 'express';

export interface RequestWithUser extends Request {
    body: any;
}

Usage

Using the AuthGuard in NestJS

import { Controller, Get, UseGuards, Req } from '@nestjs/common';
import { AuthGuard } from './middleware/auth.guard';
import { RequestWithUser } from './req/index';

@Controller('/secure')
export class SecureController {
  @UseGuards(AuthGuard)
  @Get('/')
  getSecureData() {
    return { message: 'Secure data accessed' };
  }

  @UseGuards(AuthGuard)
  @Get('/secure_user')
  getSecureDataByUser(@Req() req: RequestWithUser) {
    return { message: 'Secure data accessed' };
  }
}

Example API Response

{
  "data": {
    "trackingId": "123456789",
    "status": "In Transit",
    "estimatedDelivery": "2025-02-20T10:00:00Z",
    "currentLocation": "New York, USA"
  },
  "error": false,
  "message": "Tracking details fetched successfully"
}

License

MIT License