Build a URL shortener web service using Express.js

Build a URL-shortener service like bit.ly or goo.gl using Express.js.

At a very high level, the URL shortener works by taking an entered URL and creating a relatively shortened version simplified into an easy to share format.

In this assignment, you need to implement two API endpoints:

POST /shorten-url

The body of the HTTP request should be an JSON object containing one field url, e.g.

{
   "url": "https://facebook.github.io/jest/docs/en/asynchronous.html"
}

The response body is an JSON object containing one field hash, e.g.

{
   "hash": "MTAwMDA="
}

Requirements:

The hash in the response is a unique value for each given url (i.e. two different URLs should maps to different hash values)
Calling the API multiple times with the same url value should get back the same hash value. Each time this API is called, the HTTP status code in the response should be 200, even if the url has been shortened before

Hint: the trick here is how to generate a hash value that's short and unique.

One of the solution is:

keep a counter on the server side
assign a unique counter value for each new URL submitted
generate base64 encoding of the counter value as the hash value

GET /expand-url?hash=someHash

There is a query parameter to the URL called hash, e.g.

GET /expand-url?hash=MTAwMDA%3D

Note that the query parameter MTAwMDA%3D is url-encoded value of MTAwMDA=. It has to be encoded so that it can be used as part of URL.

There are two scenarios you need to handle:

Scenario 1

Suppose the given hash value does not correspond to any valid URLs registered with /shorten-url, the API should return HTTP status code 404 and the response body should look like

{
  "error": "There is no long URL registered for hash value 'MTAwMDA='";
}

Scenario 2

Suppose the given hash value maps to an existing URL registered with /shorten-url, the API should return HTTP status code 200 with a JSON string in body:

{
   "url": "https://facebook.github.io/jest/docs/en/asynchronous.html"
}

DELETE /expand-url?hash=someHash

Suppose someone wants to delete the record of the shortened URL (people do that when they don't want their bitly link to be accessible anymore). The API should delete the record if it exists and return a HTTP status code 200 and a JSON string in body.

{
   "message": "URL with hash value 'MTAwMDA=' deleted successfully";
}

If the record doesn't exist, it should return a HTTP status code 404 and a JSON string in body.

{
   "message": "URL with hash value 'MTAwMDA=' does not exist";
}

You can try make a HTTP request (GET /expand-url?hash=someHash) to verify that the record was deleted successfully

songguoqiang / express-url-shortener