NexaFX Backend

NexaFX is a Web3-powered currency exchange platform that supports real-time fiat and crypto conversions. The backend is built using NestJS and interfaces with smart contracts written in Rust on the Stellar network.

🚀 Features

JWT-based authentication and authorization
Role-based access control (Admin, User, Tutor)
Multi-currency exchange system
Blockchain integration with Stellar smart contracts
Real-time and historical transactions tracking
Modular, scalable NestJS architecture
Exportable transaction data (CSV, Excel, PDF)

🏗️ Project Structure

nexafx-backend/
├── src/
│   ├── admin/                # Admin panel and controls
│   ├── audit-logs/           # Audit trail and logging
│   ├── auth/                 # JWT authentication & authorization
│   ├── beneficiaries/        # Beneficiary management
│   ├── blockchain/           # Stellar blockchain integration
│   ├── common/               # Shared guards, interceptors, decorators, services
│   ├── currencies/           # Fiat and crypto currency management
│   ├── database/             # Database seeding scripts
│   ├── exchange-rates/       # Real-time exchange rate providers
│   ├── fees/                 # Transaction fee management
│   ├── health/               # Health check endpoints
│   ├── kyc/                  # KYC/AML compliance
│   ├── notifications/        # Push & email notifications
│   ├── otps/                 # One-time passwords for 2FA
│   ├── push-notifications/   # Firebase push notifications
│   ├── rate-alerts/          # Rate change alerts (utility)
│   ├── receipts/             # Transaction receipts
│   ├── referrals/            # Referral program
│   ├── scheduled-jobs/       # Background scheduled tasks
│   ├── tokens/               # Refresh token management (utility)
│   ├── transactions/         # Transaction processing & tracking
│   ├── two-factor/           # Two-factor authentication
│   ├── users/                # User management (CRUD, roles, profiles)
│   ├── app.module.ts         # Root application module
│   ├── app.controller.ts     # Root application controller
│   ├── app.service.ts        # Root application service
│   └── main.ts               # Application entry point
├── migrations/               # TypeORM migration files
├── test/                     # E2E and integration tests
├── .env.example              # Environment configuration template
├── package.json              # Dependencies and scripts
├── tsconfig.json             # TypeScript configuration
└── README.md                 # This file

📦 Tech Stack

Backend Framework: NestJS 11, TypeScript 5.7
Database ORM: TypeORM 0.3 (PostgreSQL)
Authentication: JWT (Passport.js), Bcrypt, TOTP
Blockchain: Stellar SDK with Horizon API integration
Background Jobs: NestJS Schedule (@nestjs/schedule)
Notifications: Mailgun (email), Firebase (push notifications)
Rate Limiting: NestJS Throttler
Documentation: Swagger/OpenAPI
Testing: Jest, Supertest
Code Quality: ESLint, Prettier

🚀 Getting Started

Prerequisites

Node.js: v18+ (LTS recommended)
PostgreSQL: v12+ running locally or via Docker
npm or yarn

1. Clone the Repository

git clone https://github.com/Nexacore-Org/NexaFx-backend.git
cd NexaFx-backend

2. Install Dependencies

npm install

3. Setup Environment Variables

Copy the .env.example file and create a .env file:

cp .env.example .env

Edit .env and configure your variables (see Environment Variables section below).

4. Setup Database with TypeORM

Initialize the PostgreSQL database and apply migrations:

# Ensure PostgreSQL is running and DATABASE_URL is configured in .env
# TypeORM will auto-synchronize schema on startup if synchronize: true

# Create the database (first time only)
npm run typeorm:db:create

# Run migrations
npm run typeorm:migration:run

# OR generate a new migration after schema changes
npm run typeorm:migration:generate -- src/migrations/my-migration-name

# To revert the last migration
npm run typeorm:migration:revert

Note: The application uses TypeORM with autoLoadEntities: true, which automatically loads all entity metadata. Ensure all .entity.ts files are properly decorated with @Entity().

5. Run the Application

# Development (watch mode)
npm run start:dev

# Debug mode
npm run start:debug

# Production
npm run build
npm run start:prod

The API will be available at http://localhost:3000 API documentation: http://localhost:3000/api/docs

⚙️ Environment Variables

Copy .env.example to .env and configure the following variables:

Database Configuration

Variable	Type	Required	Example	Description
`DATABASE_URL`	string	✅ Yes	`postgresql://user:pass@localhost:5432/nexafx`	PostgreSQL connection string
`DB_HOST`	string	✅ Yes	`localhost`	Database host address
`DB_PORT`	number	✅ Yes	`5432`	Database port
`DB_USERNAME`	string	✅ Yes	`postgres`	Database user
`DB_PASSWORD`	string	✅ Yes	`secure_password`	Database password
`DB_NAME`	string	✅ Yes	`nexafx`	Database name

Application Configuration

Variable	Type	Required	Example	Description
`NODE_ENV`	string	✅ Yes	`development`	Runtime environment: `development`, `staging`, `production`
`PORT`	number	✅ Yes	`3000`	Server port

JWT & Authentication

Variable	Type	Required	Min Length	Description
`JWT_SECRET`	string	✅ Yes	32 chars	Secret key for signing JWT tokens (keep secure in production)
`JWT_EXPIRES_IN`	string	✅ Yes	N/A	JWT expiration time (e.g., `15m`, `1h`, `7d`)
`REFRESH_TOKEN_SECRET`	string	✅ Yes	32 chars	Secret for refresh token signing
`REFRESH_TOKEN_EXPIRES_DAYS`	number	✅ Yes	N/A	Refresh token lifespan in days (default: 30)

OTP & Two-Factor Authentication

Variable	Type	Required	Description
`OTP_SECRET`	string	✅ Yes	HMAC secret for TOTP generation (min 32 chars)
`OTP_EXPIRES_MINUTES`	number	✅ Yes	OTP validity period in minutes (default: 10)

Stellar Blockchain

Variable	Type	Required	Description
`STELLAR_NETWORK`	string	✅ Yes	Network: `TESTNET` or `PUBLIC`
`STELLAR_HORIZON_URL`	string	✅ Yes	Horizon API endpoint (testnet: `https://horizon-testnet.stellar.org`)
`STELLAR_BASE_FEE`	number	✅ Yes	Base transaction fee in stroops (typically 100)
`STELLAR_HOT_WALLET_SECRET`	string	✅ Yes	Secret key for Stellar hot wallet (keep secure!)

Wallet Encryption

Variable	Type	Required	Description
`WALLET_ENCRYPTION_KEY`	string	✅ Yes	64-character hex key for wallet encryption. Generate: `openssl rand -hex 32`

Email Service (Mailgun)

Variable	Type	Required	Description
`MAILGUN_API_KEY`	string	✅ Yes	Mailgun API key from dashboard
`MAILGUN_DOMAIN`	string	✅ Yes	Verified Mailgun domain (e.g., `mail.nexafx.com`)
`MAILGUN_FROM_EMAIL`	string	✅ Yes	Sender email address (e.g., `noreply@nexafx.com`)
`MAILGUN_FROM_NAME`	string	❌ No	Display name for emails (default: `NexaFX`)
`SKIP_EMAIL_SENDING`	boolean	❌ No	Skip email sending in development (default: `false`)

Frontend Configuration

Variable	Type	Required	Description
`FRONTEND_URL`	string	✅ Yes	Frontend URL for CORS and email links (e.g., `http://localhost:3001`)

Rate Limiting

Variable	Type	Required	Description
`THROTTLE_TTL`	number	✅ Yes	Time window in seconds (default: 60)
`THROTTLE_LIMIT`	number	✅ Yes	Max requests per window (default: 100)
`THROTTLE_AUTH_LIMIT`	number	✅ Yes	Max auth attempts per window (default: 5)

Exchange Rates Provider

Variable	Type	Required	Description
`EXCHANGE_RATES_PROVIDER_BASE_URL`	string	✅ Yes	Provider API base URL (default: `https://api.exchangerate.host`)
`EXCHANGE_RATES_PROVIDER_API_KEY`	string	❌ No	API key if required by provider
`EXCHANGE_RATES_PROVIDER_TIMEOUT_MS`	number	✅ Yes	Request timeout in milliseconds (default: 5000)
`EXCHANGE_RATES_CACHE_TTL_SECONDS`	number	✅ Yes	Cache duration in seconds (default: 600 = 10 min)
`EXCHANGE_RATES_CACHE_MAX_SIZE`	number	✅ Yes	Max cached rates (default: 1000)

🧪 Running Tests

# Unit & Integration
npm run test

# E2E
npm run test:e2e

# Coverage
npm run test:cov

🔐 Role-Based Access Control

The application implements role-based access control (RBAC) with the following roles:

USER: Can perform standard exchange operations, manage own profile, view transactions
ADMIN: Full control of all resources, user management, configuration, audit logs
SUPER_ADMIN: System-level administrative access (future)

Guards are applied at controller and route levels using custom decorators (@RequireRole(), @Permissions()) and NestJS Guards.

📁 Module Overview & Architecture

All major modules are fully implemented and integrated:

Module	File Location	Purpose	Status
auth	`src/auth/`	JWT authentication, password reset, OAuth2 strategies. Implements Passport.js strategies and JWT verification	✅ Complete
admin	`src/admin/`	Admin dashboard, user moderation, system controls, configuration management	✅ Complete
users	`src/users/`	User CRUD operations, profile management, roles, KYC status, personal data storage	✅ Complete
currencies	`src/currencies/`	Fiat and crypto currency registry, metadata, pairs, support matrix	✅ Complete
transactions	`src/transactions/`	Core exchange transactions, Stellar blockchain integration, settlement tracking, reversals	✅ Complete
exchange-rates	`src/exchange-rates/`	Real-time rate fetching, multi-provider aggregation, in-memory caching	✅ Complete
beneficiaries	`src/beneficiaries/`	Manage recipient accounts, wallets, bank details for transactions	✅ Complete
kyc	`src/kyc/`	KYC/AML workflows, document collection, verification, compliance status	✅ Complete
notifications	`src/notifications/`	Email & SMS system via Mailgun, verification codes, alerts, announcements	✅ Complete
push-notifications	`src/push-notifications/`	Firebase Cloud Messaging (FCM) integration for mobile push notifications	✅ Complete
referrals	`src/referrals/`	Referral program tracking, unique codes, rewards, commission calculation	✅ Complete
receipts	`src/receipts/`	Transaction receipt generation and export (PDF via pdfkit, CSV, Excel via exceljs)	✅ Complete
fees	`src/fees/`	Dynamic fee calculation, fee matrices, tier-based pricing, settlement	✅ Complete
audit-logs	`src/audit-logs/`	Comprehensive audit trail for compliance, debugging, user activity tracking	✅ Complete
scheduled-jobs	`src/scheduled-jobs/`	Background tasks: rate updates, data cleanup, notification batching, reconciliation	✅ Complete
common	`src/common/`	Shared infrastructure: global guards, interceptors, decorators, pipes, error filters, shared services	✅ Complete
health	`src/health/`	Health check endpoints for monitoring, load balancer integration, readiness/liveness probes	✅ Complete
blockchain	`src/blockchain/`	Stellar SDK integration, Horizon API communication, contract deployment, transaction signing	✅ Complete
two-factor	`src/two-factor/`	TOTP-based 2FA, recovery codes, backup authentication methods	✅ Complete
otps	`src/otps/`	One-time password generation, validation, expiration, retry limits	✅ Complete

📄 API Documentation

Swagger/OpenAPI documentation is available when the backend is running:

URL: http://localhost:3000/api/docs
Features: Interactive API explorer, request/response examples, schema definitions
Auto-generated from NestJS decorators

🧱 Blockchain Integration

Stellar Network provides the foundation for trustless, fast international transfers:

Smart Contracts: Rust-based contracts deployed on Stellar
Horizon API: Communication layer for account, ledger, and transaction queries
Asset Creation: Native and custom asset support
Multi-Signature Accounts: Enhanced security for hot wallets
Transaction Flow: NestJS service → Stellar SDK → Horizon → Ledger

Current implementation:

🧪 Testing Strategy

Unit & Integration Tests

npm run test           # Run all tests
npm run test:watch    # Watch mode (re-run on file changes)
npm run test:cov      # Generate coverage report

Test files follow the pattern: *.spec.ts
Coverage reports are generated in coverage/ directory

E2E Tests

npm run test:e2e       # Run end-to-end tests
npm run test:debug     # Debug mode (use Chrome DevTools on port 9229)

E2E test suite: test/jest-e2e.json

Best Practices

Use describe() blocks for logical grouping
Mock external services (Stellar, Mailgun, etc.)
Test controller endpoints with supertest
Test services in isolation with mocked repositories
Aim for 80%+ coverage for critical paths

📝 Development Workflow

Commit Message Format

Follow Conventional Commits:

type(scope): subject

# Types: feat, fix, docs, style, refactor, perf, test, chore
# Scopes: auth, users, transactions, etc.

# Examples:
git commit -m "feat(transactions): add Stellar integration"
git commit -m "fix(auth): validate JWT expiration"
git commit -m "docs(readme): update setup instructions"  
git commit -m "chore(deps): upgrade NestJS to 11.0.2"

Pull Request Workflow

Create feature branch: git checkout -b feature/your-feature-name
Make changes and write tests
Submit PR with description and linked issue
Wait for CI/CD checks and code review
Merge after approval

📌 Project Roadmap

✅ Completed

🚧 In Progress

Advanced payment routing (path payments)
DAO governance and voting
Smart contract optimization

📋 Planned

🛠️ Troubleshooting

Common Setup Issues

1. Database Connection Error

Error: connect ECONNREFUSED 127.0.0.1:5432

Solution:

Verify PostgreSQL is running: brew services list (macOS) or sudo systemctl status postgresql (Linux)
Check DATABASE_URL in .env
Default: postgresql://postgres:postgres@localhost:5432/nexafx
Create database if missing: createdb nexafx

2. TypeORM Migrations Fail

Error: migrations not found

Solution:

# Ensure migration scripts exist in package.json
npm run typeorm:migration:run  # Run pending migrations
npm run typeorm:migration:create -- src/migrations/fresh-migration

3. JWT Token Verification Failed

Error: jwt malformed

Solution:

Verify JWT_SECRET is set in .env (minimum 32 characters)
Ensure token format: Authorization: Bearer <token>
Check token expiration: JWT_EXPIRES_IN (default: 15m)

4. Stellar Network Connection Error

Error: ECONNREFUSED (Horizon endpoint)

Solution:

Verify STELLAR_HORIZON_URL: testnet=https://horizon-testnet.stellar.org
Check internet connectivity
Verify STELLAR_NETWORK is set to TESTNET or PUBLIC
Testnet transactions: browse at https://stellar.expert/explorer/testnet

5. Email Sending Not Working

Error: Mailgun credentials invalid

Solution:

Verify Mailgun API key and domain in .env
Check MAILGUN_DOMAIN is verified in Mailgun dashboard
Test: SKIP_EMAIL_SENDING=true to bypass sending locally
Ensure MAILGUN_FROM_EMAIL matches verified sender

6. Port 3000 Already in Use

Error: listen EADDRINUSE :::3000

Solution:

# Kill the process
lsof -ti:3000 | xargs kill -9       # macOS/Linux
netstat -ano | findstr :3000        # Windows

# Or use a different port
PORT=3001 npm run start:dev

7. Module Not Found Error

Error: Cannot find module '@nestjs/typeorm'

Solution:

# Reinstall dependencies
rm -rf node_modules package-lock.json
npm install
npm run build

Debugging Tips

Enable Debug Logging:

DEBUG=* npm run start:dev

TypeORM Query Logging: Add to .env:

TYPEORM_LOGGING=true

Check Application State:

curl http://localhost:3000/health

View API Docs:

http://localhost:3000/api/docs

🔗 Related Repositories & Resources

Resource	URL	Purpose
Frontend	NexaFx-frontend	Next.js 14 web UI with React, Tailwind CSS
Smart Contracts	NexaFx-contract	Rust smart contracts deployed on Stellar
API Docs	http://localhost:3000/api/docs	Interactive Swagger documentation (local)
Stellar Testnet Explorer	stellar.expert/explorer/testnet	View transactions and accounts on Stellar testnet
Stellar Horizon API	horizon-testnet.stellar.org	Official Stellar Horizon API endpoint

📜 License

This project is licensed under the MIT License. See the LICENSE file for details.

📧 Support & Community

Have questions, need help, or want to contribute? Here's how to reach us:

Channel	Link	Purpose
Email	contact@nexacore.org	Business inquiries, partnerships
Telegram	t.me/NexaFx	Community chat, quick support
GitHub Issues	Issues	Bug reports, feature requests
Discussions	Discussions	Technical questions, ideas

👥 Contributing

We welcome contributions from the community! Please start with:

Fork the repository
Create a feature branch: git checkout -b feature/your-feature
Commit changes: git commit -m "feat(module): description" (see Commit Format)
Push to your fork: git push origin feature/your-feature
Open a Pull Request with your changes

Before submitting:

Tests pass: npm run test
Linting passes: npm run lint
Coverage is adequate
Updated README if adding major features

See CONTRIBUTING.md for detailed guidelines.

Happy coding! 🚀

Name		Name	Last commit message	Last commit date
Latest commit History 407 Commits
src		src
test		test
.env.example		.env.example
.gitignore		.gitignore
.prettierrc		.prettierrc
CONTRIBUTING.md		CONTRIBUTING.md
ENV.md		ENV.md
README.md		README.md
docker-compose.yml		docker-compose.yml
eslint.config.mjs		eslint.config.mjs
jest-out.txt		jest-out.txt
jest_error.json		jest_error.json
nest-cli.json		nest-cli.json
package-lock.json		package-lock.json
package.json		package.json
tsc_final.txt		tsc_final.txt
tsc_output.txt		tsc_output.txt
tsconfig.build.json		tsconfig.build.json
tsconfig.json		tsconfig.json

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NexaFX Backend

🚀 Features

🏗️ Project Structure

📦 Tech Stack

🚀 Getting Started

Prerequisites

1. Clone the Repository

2. Install Dependencies

3. Setup Environment Variables

4. Setup Database with TypeORM

5. Run the Application

⚙️ Environment Variables

Database Configuration

Application Configuration

JWT & Authentication

OTP & Two-Factor Authentication

Stellar Blockchain

Wallet Encryption

Email Service (Mailgun)

Frontend Configuration

Rate Limiting

Exchange Rates Provider

🧪 Running Tests

🔐 Role-Based Access Control

📁 Module Overview & Architecture

📄 API Documentation

🧱 Blockchain Integration

🧪 Testing Strategy

Unit & Integration Tests

E2E Tests

Best Practices

📝 Development Workflow

Commit Message Format

Pull Request Workflow

📌 Project Roadmap

✅ Completed

🚧 In Progress

📋 Planned

🛠️ Troubleshooting

Common Setup Issues

1. Database Connection Error

2. TypeORM Migrations Fail

3. JWT Token Verification Failed

4. Stellar Network Connection Error

5. Email Sending Not Working

6. Port 3000 Already in Use

7. Module Not Found Error

Debugging Tips

🔗 Related Repositories & Resources

📜 License

📧 Support & Community

👥 Contributing

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