Renew Backend Code Test

Problem

Implement a simple URL shortening web service (like tinyurl) using the Python Flask framework. This service will allow clients to create and delete unique identifiers for an arbitrary set of URLs and, provided a valid identifier, redirect a client to the target URL.

Requirements

1. Expose an endpoint to create a new shortened URL.
   • must optionally accept a user-provided ID for the shortened URL, otherwise generate one randomly
   • must not accept or generate a duplicate ID
   • must validate that IDs are non-empty and only contain alphanumeric characters
   • must include in the response a unique "authorization" token, which is different from the URL ID and may be used to delete or get additional stats about the shortened URL
   • must include in the response the shortened URL, constructed as follows: http://{serverHostname}:{serverPort}/{urlId}
2. Expose an endpoint to delete an existing shortened URL.
   • must only allow deletion if the "authorization" token that was generated on creation is provided with the request
3. Redirect valid, shortened URLs to the original full URL.
   • must keep track of successful redirects, per unique client IP address
4. Expose an endpoint to retrieve stats about successful redirects for a shortened URL.
   • must only return stats if the "authorization" token that was generated on creation is provided with the request
   • must report counts of successful redirects per unique client IP address over the lifetime of the shortened URL

Additional Requirements

• Your code is expected to run on Python 3.5+.
• You must use Flask as the web framework.
• You are free to use any third-party Python modules that are installable via pip. If you do, you must add the relevant dependencies to the requirements.txt file.
• You may use the provided sqlite.py module to interface with SQLite as your backing datastore, but you may use PostgreSQL or another relational database if you prefer. In this case, you must write code to setup the database schema and document your database configuration or any additional setup that is required to run your application.

For bonus points

Note: These features are completely optional - don't feel obligated to implement them!

• Set a default expiration time when a shortened URL is created. After the time has expired, the shortened URL should fail to redirect, and the web service should not allow further operations on the expired URL ID, but should allow a new shortened URL to be created with that ID.
• Prevent simple DoS or brute force attacks by restricting the number of requests a particular client can make to the service within a certain timeframe.

Example

For example, assuming a web application running on localhost:8080, it would support the following interaction:

curl -v -XPOST \
     -H"Content-type: application/json" \
     -d'{"url":"http://www.renew.com"}' \
     http://localhost:8080/create
> POST /create HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.54.0
> Accept: */*
> Content-Length: 30
> Content-Type: application/json
>
< HTTP/1.0 200 OK
< Content-Type: application/json
< Content-Length: 95
< Server: Werkzeug/0.12.2 Python/3.5.2
< Date: Thu, 12 Jan 2017 00:00:00 GMT
{"shortUrl":"http://localhost:8080/hrms3zw", "urlId":"hrms3zw", "authToken":"donjo2ef938gfo2h"}

curl -v http://localhost:8080/hrms3zw
> GET /hrms3zw HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.54.0
> Accept: */*
>
< HTTP/1.1 301 Moved Permanently
< Location: http://www.renew.com
< Server: Werkzeug/0.12.2 Python/3.5.2
< Date: Thu, 12 Jan 2017 00:00:01 GMT

curl -v -H"Authorization: donjo2ef938gfo2h" \
     http://localhost:8080/hrms3zw/stats
> GET /hrms3zw/stats HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.54.0
> Accept: */*
>
< HTTP/1.1 200 OK
< Content-Type: application/json
< Content-Length: 15
< Server: Werkzeug/0.12.2 Python/3.5.2
< Date: Thu, 12 Jan 2017 00:00:02 GMT
{"10.0.0.12":1}

curl -v -XDELETE \
     -H"Authorization: donjo2ef938gfo2h" \
     http://localhost:8080/hrms3zw
> DELETE /hrms3zw HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.54.0
> Accept: */*
>
< HTTP/1.1 204 No Content
< Server: Werkzeug/0.12.2 Python/3.5.2
< Date: Thu, 12 Jan 2017 00:00:03 GMT

Endpoint Specification

POST /create

Generate and return a new, unique ID that can later be used to redirect to the provided URL. The url parameter must be a well-formed URL, but does not necessarily need to exist or be available.

A successful request must return with a status code 200 and a JSON object with valid urlId, shortUrl, and authToken values.

Otherwise, an invalid request must return with a status code 400 and a plain text error message.

Request

application/json

Body Parameters:

url     (required - string): A well-formatted URL
id      (optional - string): A non-empty string identifier for URL

Example:

{
    "url": "http://www.renew.com"
}

Responses

Status 200 (success): application/json

{
    "shortUrl": "string",
    "urlId": "string",
    "authToken": "string"
}

Status 400 (error):

Error Message

---

GET /{urlId}

Given a valid urlId, redirect the client to the target URL with a status code 301.

An invalid request must return with a status code 404 and a plain text error message.

Responses

Status 301 (success)

Status 404 (error):

Error Message

---

GET /{urlId}/stats

Given a valid urlId, return with a status code 200 and a JSON object with numeric counts of successful redirects, per unique client IP address.

A request with a missing or incorrect authToken must return with a status code 403 and a plain text error message.

An invalid request must return with a status code 404 and a plain text error message.

Request

Request Headers:

Authorization  (required - string): The authToken associated with the urlId

Responses

Status 200 (success): application/json

{
    "ip_address_1": int,
    "ip_address_2": int,
    ...
}

Status 403 (error):

Error Message

Status 404 (error):

Error Message

---

DELETE /{urlId}

Given a valid urlId, remove the mapping to the target URL. A subsequent GET request with the urlId should yield a 404 response.

A request with a missing or incorrect authToken must return with a status code 403 and a plain text error message.

An invalid request must return with a status code 404 and a plain text error message.

Request

Request Headers:

Authorization  (required - string): The authToken associated with the urlId

Responses

Status 204 (success)

Status 403 (error):

Error Message

Status 404 (error):

Error Message

Project Structure

The following modules are provided for you as a starting point for your web application:

.
├── README.md
├── requirements.txt
├── run.py
└── src
    └── db
        ├── __init__.py
        └── sqlite.py
    ├── __init__.py
    └── routes.py

You may modify any of the provided application code and define new modules and/or functions as long as your application starts a webserver bound to port 8080 on localhost and is runnable via the following command from the top-level directory:

python -m run

Modules

run.py

Imports the routes module and runs the webserver on localhost:8080. You can run the webserver from the top-level directory with the following command: python -m run

src/__init__.py

The Flask application object is initialized in this file.

src/routes.py

Module where the routes, as specified in the Endpoint Specification section, are defined - these are the functions that you must implement.

src/db/sqlite.py

Module providing a simple wrapper around an sqlite3 database connection. You are free to use this module as-is, modify it, or ignore it.