Currency Conversion Service

A professional currency conversion service that supports multiple fiat currencies and converts between fiat and cryptocurrencies (XLM, USDC).

Features

• 150+ Fiat Currencies: Support for major world currencies
• Real-time Crypto Prices: Live XLM and USDC prices
• Intelligent Caching: 5-minute cache for optimal performance
• Fallback Support: Graceful degradation when APIs are unavailable
• Decimal Precision: Accurate calculations using Decimal.js
• Comprehensive Testing: Full unit and integration test coverage

API Endpoints

GET /currency/rates

Get current exchange rates for all supported currencies.

Response:

{
  "USD": 1,
  "EUR": 0.85,
  "GBP": 0.73,
  "XLM": 0.22,
  "USDC": 1.00
}

POST /currency/convert

Convert amount from one currency to another.

Request Body:

{
  "amount": 100,
  "from": "USD",
  "to": "EUR"
}

Response:

{
  "amount": 117.65,
  "rate": 1.1765,
  "from": "USD",
  "to": "EUR"
}

GET /currency/supported

Get list of all supported currencies.

Response:

["USD", "EUR", "GBP", "JPY", "XLM", "USDC", ...]

GET /currency/format

Format amount with currency symbol.

Query Parameters:

• amount: Number to format
• currency: Currency code

Response:

{
  "formatted": "$100.50"
}

POST /currency/cache/clear

Clear the exchange rate cache (admin use).

Response:

{
  "message": "Exchange rate cache cleared successfully"
}

Supported Conversions

• Fiat to Fiat: USD to EUR, EUR to GBP, etc.
• Fiat to Crypto: USD to XLM, EUR to USDC, etc.
• Crypto to Fiat: XLM to USD, USDC to EUR, etc.
• Crypto to Crypto: XLM to USDC, USDC to XLM

Configuration

The service uses the following external APIs:

• Exchange Rates: https://api.exchangerate-api.com/v4/latest/USD
• Crypto Prices: https://api.coingecko.com/api/v3/simple/price

Error Handling

• API Failures: Automatically falls back to predefined rates
• Invalid Currencies: Returns descriptive error messages
• Invalid Amounts: Validates amounts are greater than 0
• Cache Issues: Continues operation even if cache fails

Testing

Run the test suite:

npm test

Run tests with coverage:

npm run test:coverage

Architecture

• CurrencyService: Core business logic and API integration
• CurrencyController: HTTP endpoints and validation
• CurrencyModule: NestJS module configuration
• Caching: Built-in NestJS cache manager with 5-minute TTL