Overview

• Currency conversion API built with Clean Architecture. Includes EF Core (code-first), HttpClient to Open Exchange Rates, in-memory caching, Swagger, ProblemDetails, and rate limiting.

Requirements

• .NET SDK 9 or later
• SQLite (bundled)
• Open Exchange Rates API key

Setup and Run

• Configure the OpenExchangeRates__ApiKey via environment or configuration.
• Start the API from the Api project; database migrations are applied automatically at startup.
• Start backend and frontend using docker-compose. Set the docker-compose project as Startup project and run.

Endpoints

• POST /api/conversion — perform and persist a conversion
• GET /api/conversion/history — paged history (skip, take, sort, userId)
• GET /api/currencies — list available currency codes
• GET /api/rates/{base} — exchange rates for the base currency

Configuration

• Connection string defaults to SQLite file database.
• Enable CORS for the Angular origin if required (for example, http://localhost:4200).

Architecture

• Domain (entities), Application (interfaces and services), Infrastructure (EF Core, provider, DI), API (controllers, DTOs, middleware). Patterns: Repository, Service, Factory. SOLID and DRY principles followed.

Testing

• Unit tests with xUnit, Moq, and AutoFixture for ConversionController. Only 3 requested. Similaraly, unit tests should be implemented per project.

Assumptions and Notes

• UserId defaults to candidate when omitted.
• On free plan, provider returns USD base; cross-rates are computed.

Submission Checklist

• Builds and runs
• Swagger available
• Automatic migrations applied
• Unit tests included
• README present

OpenApi Specification under Helsinki.Api\openapi.json. Import to Postman as Collection.