URL shortener

The job of a URL shortener is to take a long URL (e.g. "https://www.cockroachlabs.com/docs/stable/build-a-go-app-with-cockroachdb.html") and turn it into something shorter (e.g. "https://bit.ly/2QLUQIu").

A simple URL shortener with no special rules is very simple and consists of 2 endpoints:

One to generate a short version of a URL given a long version of a URL.
One to handle a call to the short version of a URL and redirect the user to the long (original) version of the URL.

Create a simple URL shortening API with the following endpoints:

POST /

A POST endpoint that accepts a JSON body describing the URL to shorten. Your URL shortener should generate a short version of the URL and keep track of the mapping between short and long URLs. For example:

   $ curl -X POST 'localhost:8080' \
   -H 'Content-Type: application/json' \
   -d '{
       "long": "https://www.cockroachlabs.com/docs/stable/build-a-go-app-with-cockroachdb.html"
   }'

Should returning something similar to:

   http://localhost:8080/9eXmFnuj

GET /:short

A GET endpoint that accepts a short version of the URL in the URL path and redirects the user to the original URL. For example:

   $ curl -L http://localhost:3000/9eXmFnuj

Should redirect the user to the original URL:

   <!DOCTYPE html>
   <html lang="en">
   ...

Rules:

Store the short -> long mappings in any way you like. In-memory is fine.
There are no auth requirements. Your API can be completely open.

Crystal

<lang ruby>require "kemal"

CHARS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".chars entries = Hash(String, String).new

post "/" do |env|

 short = Random::Secure.random_bytes(8).map{|b| CHARS[b % CHARS.size]}.join
 entries[short] = env.params.json["long"].as(String)
 "http://localhost:3000/#{short}"

end

get "/:short" do |env|

 if long = entries[env.params.url["short"]]?
   env.redirect long
 else
   env.response.status_code = 404
 end

end

error 404 do

 "invalid short url"

end

Kemal.run</lang>