UrlShortenerAPI

A small URL shortener REST API built with ASP.NET Core 8, EF Core, and PostgreSQL. Post a long URL, get back an 8-character token; request the token and get a 302 redirect to the original. Links expire after 30 days.

Stack

Runtime	.NET 8 (net8.0)
Web	ASP.NET Core, attribute-routed controllers
Data	EF Core 8.0.30 + Npgsql 8.0.11, PostgreSQL
Tests	xUnit + Moq + EF Core InMemory — 13 tests

API

Method	Route	Body / Param	Response
POST	/api/urls	{ "originalUrl": "https://example.com" }	200 { shortUrlToken, fullShortUrl } · 400 on empty or malformed URL
GET	/api/urls/{shortUrl}	short token in path	302 redirect to the original · 404 if unknown or expired

Posting a URL that already exists returns the existing token rather than minting a second one.

Quickstart

You need the .NET 8 SDK and a reachable PostgreSQL instance.

git clone https://github.com/Ar4gornn/UrlShortenerAPI.git
cd UrlShortenerAPI

The connection string is not in source control. Create UrlShortenerAPI/appsettings.Development.json (already gitignored):

{
  "ConnectionStrings": {
    "UrlShortenerDB": "Host=localhost;Port=5432;Database=urlshortener;Username=postgres;Password=your-password"
  }
}

Apply the migrations and run:

dotnet ef database update --project UrlShortenerAPI/UrlShortenerAPI.csproj
dotnet run --project UrlShortenerAPI/UrlShortenerAPI.csproj

The API listens on http://localhost:5251. Try it:

curl -X POST http://localhost:5251/api/urls \
  -H "Content-Type: application/json" \
  -d '{"originalUrl":"https://learn.microsoft.com/aspnet/core"}'

curl -i http://localhost:5251/api/urls/<token>

Run the tests:

dotnet test

Architecture

A thin three-layer slice. UrlsController handles HTTP concerns only — model validation and mapping exceptions to status codes. UrlShortenerService holds the business rules: URL well-formedness via Uri.IsWellFormedUriString, deduplication against existing rows, token generation, and the expiry check on read. UrlShortenerContext is the EF Core boundary, with three migrations tracked in Migrations/. The service is registered scoped and injected through IUrlShortenerService, so the controller tests mock the interface and the service tests run against an in-memory provider.

Tokens are the first 8 characters of a Guid, and expiry is 30 days from creation.

Known limitations

Honest list — these are real, and they are the roadmap.

• Token collisions are not handled. Tokens are truncated GUIDs with no uniqueness check before insert, and the read path uses SingleOrDefaultAsync, which throws if a duplicate ever lands.
• fullShortUrl hardcodes http://localhost:5251. The response is wrong anywhere but a local dev machine.
• The Dockerfile does not work. It builds on the .NET 8 SDK image but runs on the ASP.NET 7.0 runtime image, so the published net8.0 assembly will not start. Fix before trusting it.
• CORS is AllowAnyOrigin + any method + any header. Fine for local development, not for a public deployment.
• No Swagger UI. Microsoft.AspNetCore.OpenApi is referenced but never wired up in Program.cs.
• AppConstants.LinkExpirationDays and the private GenerateUniqueGuidToken() helper are both dead code — the 30-day window is inlined in the service instead.

Roadmap

• Collision-safe token generation (retry loop or a counter-based encoding), plus a unique index
• Base URL from configuration instead of a hardcoded localhost string
• Fix the Dockerfile runtime tag and add a docker compose with PostgreSQL
• Swagger/OpenAPI
• Tighten CORS to a configured origin list
• Hit counter per link

License

MIT — see LICENSE.