Implement CNB exchange rate provider - Natalia Dorofeieva

[NataliaDorofeieva]

Exchange Rate Provider for Czech National Bank.

ASP.NET Core Web API built on .NET 10 that fetches daily exchange rates from the
Czech National Bank and exposes an endpoint for consumers.
I use https://api.cnb.cz/cnbapi/exrates/daily API with default parameters to retrieve rates.

Architecture

• Minimal API
• Clean separation between:
  • API layer
  • Application layer
  • Infrastructure

Infrastructure

• Cnb api parameters are stored in appsettings.json
• ILogger from Microsoft.Extensions.Logging is used to log warnings and errors.
• Provided currency codes are compared with CNB currency codes ignoring case.
• AbstractValidator from FluentValidation is used to validate input parameters.

Tests

• xUnit
• Unit tests for services and api client
• Integration tests using WebApplicationFactory
• External API calls are mocked

Future improvements

• Add caching for exchange rates
• Implement resilience policies for external API calls
• Add option to change parameters for CNB API
• Improve exception handling
• Write rates to database for persistency and historical data audit

How to run

CLI

dotnet run --project ExchangeRateUpdater.Api

Swagger

Swagger UI is available at /swagger/index.html once the application is running.
The exact port is shown in the application startup logs.

HTTP requests

The file ExchangeRateUpdater.Api.http can be used to send requests
to the API directly from the IDE.

API

GET /exchange-rates

Query parameters:

• currencies: list of currency codes

Example:

GET /exchange-rates?currencies=usd&currencies=eur