URL Shortener - TASK — README

Simple URL shortener service implemented in Go. This repo contains a small HTTP API to shorten URLs and redirect short codes to original URLs. The service uses an in-memory storage implementation and is packaged with Docker and Docker Compose.

Quick links (workspace)

• Files:

  • docker-compose.yaml
  • Dockerfile
  • go.mod
  • Readme.md
  • cmd/server/main.go
  • internals/handler/handler.go
  • internals/service/service.go
  • internals/storage/memory.go
  • internals/storage/storage.go
  • test/service_test.go
  • test/handler_test.go

• Important symbols:

  • service.NewURLService
  • service.URLService.ShortenURL
  • service.URLService.GetLongURL
  • service.URLService.GenerateShortCode
  • service.ErrInvalidURL
  • handler.NewHandler
  • handler.Handler.ShortenURL
  • handler.Handler.RedirectURL
  • storage.NewMemoryStorage
  • storage.Storage interface
  • storage.ErrNotFound

Requirements

• Docker & Docker Compose
• (Optional) Go 1.24 or newer for running tests locally (module set in go.mod)

How to run the code

1. Run with Docker Compose (recommended)

• Build and start (background):

docker compose up --build -d

• Check container logs:

docker compose logs -f app

• Stop and remove:

docker compose down

Notes:

• The service listens on port 8080 (host port mapped in docker-compose.yaml).
• Base URL is set via the BASE_URL environment variable in docker-compose.yaml and defaults to http://localhost:8080. The server code that reads these is in cmd/server/main.go.

2. Run locally (without Docker)

• With Go installed (recommended for development):

# from repo root
go run ./cmd/server
# or build binary
go build -o urlshort ./cmd/server
./urlshort

• Environment variables:
  • PORT (default 8080)
  • BASE_URL (default http://localhost:8080) The app is wired in cmd/server/main.go which creates the storage storage.NewMemoryStorage, the service service.NewURLService and the handlers handler.NewHandler.

3. Run tests

• Locally (requires Go toolchain):

go test ./... -v

Tests are in test/service_test.go and test/handler_test.go.

• Inside a container (no local Go):

docker run --rm -v "$(pwd):/app" -w /app golang:1.24 go test ./... -v

4. Manual / API testing (curl or Postman)

• Shorten a URL (POST):

curl -s -X POST -H "Content-Type: application/json" \
  -d '{"url":"https://example.com"}' \
  http://localhost:8080/api/shorten
# -> {"short_url":"http://localhost:8080/EAaArVRs","long_url":"https://example.com"}

• Inspect redirect headers (HEAD):

curl -I http://localhost:8080/<shortCode>
# -> HTTP/1.1 302 Found, Location: https://example.com

• Follow redirect (GET):

curl -L http://localhost:8080/<shortCode>

Postman:

• Create environment variable base_url = http://localhost:8080.
• POST {{base_url}}/api/shorten with JSON body { "url": "https://example.com" }.
• For redirect request GET {{base_url}}/{{short_code}} — disable auto-follow redirects to inspect the 302 Location header.

Behavior summary

• POST /api/shorten: returns JSON { "short_url": "...", "long_url": "..." }. Implemented in handler.Handler.ShortenURL and uses service.URLService.ShortenURL.
• GET /{shortCode}: returns HTTP 302 with Location header on success. Implemented in handler.Handler.RedirectURL and resolves via service.URLService.GetLongURL.
• Storage is in-memory via storage.NewMemoryStorage — restarting the app clears stored mappings.