Currency Converter Application

A production-ready currency conversion service built with Laravel, featuring real-time exchange rates, comprehensive monitoring, and a modern Vue.js frontend.

🚀 Features

Core Functionality

• Real-time Currency Conversion: Leverages Swop.cx API for exchange rates
• Multi-currency Support: Convert between major world currencies (USD, EUR, GBP, JPY, etc.)
• Input Validation: Robust validation for amounts and currency codes
• Internationalization: Formatted currency display using PHP's NumberFormatter

Performance & Reliability

• Redis Caching: Exchange rates cached for 1 hour to optimize API calls
• Retry Logic: Automatic retry mechanism for failed API requests
• Error Handling: Comprehensive error handling with custom exceptions

Monitoring & Analytics

• InfluxDB Integration: Real-time metrics collection for all conversions and API calls
• Grafana Dashboard: Visual monitoring of conversion rates, API response times, and error rates

Security & Best Practices

• Input Sanitization: All inputs validated and sanitized
• SOLID Principles: Clean architecture with dependency injection
• Interface Segregation: Service contracts for easy testing and swapping

Frontend Experience

• Vue.js 3 Interface: Modern, responsive user interface
• Real-time Feedback: Loading states and error handling

Architecture

Backend Structure

app/
├── Console/Commands/           # Artisan commands
│   └── CheckInfluxDBConnection.php
├── DataTransferObjects/        # Data transfer objects
│   └── CurrencyConversionResult.php
├── Exceptions/                 # Custom exceptions
│   └── CurrencyConversionException.php
├── Http/
│   ├── Controllers/           # API controllers
│   │   └── CurrencyConverterController.php
│   └── Requests/              # Form request validation
│       └── ConvertCurrencyRequest.php
├── Providers/                 # Service providers
│   ├── CurrencyServiceProvider.php
│   └── InfluxDBServiceProvider.php
└── Services/                  # Business logic
    ├── Contracts/
    │   └── CurrencyConverterInterface.php
    ├── InfluxDBService.php
    └── SwopCurrencyConverter.php

Key Design Patterns

• Dependency Injection: Services injected through Laravel's IoC container
• Repository Pattern: Interface-based service layer for easy testing
• Data Transfer Objects: Structured data transfer with type safety
• Service Layer: Business logic separated from controllers

Technology Stack

Backend

• PHP 8.4 - Modern PHP with strong typing
• Laravel 12 - Latest Robust web application framework
• Redis - High-performance caching layer
• InfluxDB 2.7 - Time-series database for metrics

Frontend

• Vue.js 3 - Progressive JavaScript framework
• Composition API - Modern Vue development approach
• Axios - HTTP client for API communication

Infrastructure

• Docker & Docker Compose - Containerized deployment
• Nginx - High-performance web server
• Grafana - Analytics and monitoring dashboards

External Services

• Swop.cx API - Real-time exchange rate provider

Application Screenshots

API Testing (Postman)

Postman test showing successful EUR to USD conversion with formatted output

Vue.js Frontend

Clean, responsive Vue.js interface for currency conversion

Grafana Monitoring Dashboard

Real-time monitoring showing conversion requests, response times, and currency pair analytics

Quick Start

Prerequisites

• Docker & Docker Compose
• Git

Installation

1. Clone the repository

git clone https://github.com/MathewsJose/currency-converter.git
cd currency-converter

2. Environment Setup

cp .env.example .env

3. Start the application

docker-compose up -d

4. Install dependencies

docker-compose exec app composer install
docker-compose exec app php artisan key:generate

5. Install frontend node

cd frontend
npm install

Access Points

• API: http://localhost:8000
• Frontend: http://localhost:8080
• Grafana Dashboard: http://localhost:3000 (admin/admin123)
• InfluxDB UI: http://localhost:8086

API Reference

Convert Currency

POST /api/convert

Request Body

{
    "amount": 100.50,
    "from_currency": "USD",
    "to_currency": "EUR"
}

Response

{
    "success": true,
    "data": {
        "amount": 100.50,
        "from_currency": "USD",
        "to_currency": "EUR",
        "exchange_rate": 0.850000,
        "converted_amount": 85.43,
        "formatted_converted_amount": "€85.43",
        "formatted_exchange_rate": "0.850000"
    }
}

Error Response

{
    "success": false,
    "message": "Validation errors",
    "errors": {
        "amount": ["Amount must be at least 0.01"]
    }
}

Validation Rules

• amount: Required, numeric, minimum 0.01
• from_currency: Required, 3 uppercase letters (e.g., USD)
• to_currency: Required, 3 uppercase letters, different from from_currency

Testing

Run Tests

docker-compose exec app php artisan test

Test Coverage

• Feature Tests: API endpoint validation and response structure
• Unit Tests: Service layer business logic

Health Checks

# Check InfluxDB connection
docker-compose exec app php artisan influxdb:check

Monitoring & Analytics

Metrics Collected

• Conversion Metrics: Success/failure rates, response times
• API Metrics: External API call performance and errors
• Business Metrics: Popular currency pairs, conversion volumes

Grafana Dashboards

Access Grafana at http://localhost:3000 to view:

• Real-time conversion statistics
• API performance metrics
• Error rate monitoring
• Currency pair popularity

InfluxDB Measurements

• currency_conversion: Conversion request metrics
• exchange_rate_api: External API call metrics

Configuration

Cache Configuration

• TTL: 3600 seconds (1 hour) for exchange rates
• Driver: Redis for high performance
• Invalidation: Automatic based on TTL

Development

Code Standards

• SOLID principles implementation
• Clean Architecture patterns
• Type Declarations throughout

Architecture Highlights

• Interface Segregation: CurrencyConverterInterface
• Dependency Injection: Service container usage
• Single Responsibility: Focused service classes
• Open/Closed Principle: Extensible through interfaces