README.md

How to run

This app is highly recommended to run in a virtualenv.

• Install requirements:

$ pip install -r requirements.txt

• Run the app, this app listens on port 5000 by default, ensure port available

$ python urlshorten.py

Tests

This app doesn't support a frontend page, we will use curl to verify

• Send a POST request with form style

$ curl -X POST -F 'original_url=google.com' localhost:5000/api/v1/url
{
  "shorten_url": "http://localhost:5000/6wASiB"
}

• Send a GET request with shorten url, expected an HTTP 302 return

$ curl http://localhost:5000/6wASiB -I
HTTP/1.0 302 FOUND
Content-Type: text/html; charset=utf-8
Content-Length: 241
Location: http://google.com
Server: Werkzeug/0.12.1 Python/2.7.9
Date: Sun, 07 May 2017 01:48:29 GMT

The Locaton header points out the request should be redirected to http://google.com. To follow the redrection in curl, use option -L

• Send a POST request to shorten google.com again, expect the same issued shorten url returned

$ curl -X POST -F 'original_url=google.com' localhost:5000/api/v1/url
{
  "shorten_url": "http://localhost:5000/6wASiB"
}

requirements.txt

appdirs==1.4.3
click==6.7
Flask==0.12.1
Flask-SQLAlchemy==2.2
itsdangerous==0.24
Jinja2==2.9.6
MarkupSafe==1.0
packaging==16.8
pyparsing==2.2.0
six==1.10.0
SQLAlchemy==1.1.9
Werkzeug==0.12.1

urlshorten.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import string
from random import SystemRandom as SR
from datetime import datetime

from flask import Flask, request, jsonify, url_for, make_response, redirect
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/url.db'
db = SQLAlchemy(app)

# length of shorten uri
URI_LENGTH = 6


class Url(db.Model):
    shorten_url = db.Column(db.String(URI_LENGTH), primary_key=True)
    original_url = db.Column(db.String(255), nullable=False)
    created_at = db.Column(db.DateTime, default=datetime.utcnow)

    def __init__(self, original_url, shorten_url):
        self.original_url = original_url
        self.shorten_url = shorten_url

    def __repr__(self):
        return '<ShortenUrl: %r with OrignalUrl: %r>' % (self.shorten_url,
                                                         self.original_url)
# create database
db.create_all()


def generate_uri(length=URI_LENGTH):
    """Generate a random string with `length` chacracter
    """
    return ''.join(SR().choice(string.ascii_letters + string.digits)
                   for _ in range(length))


@app.route("/", methods=['GET'])
def index():
    return "URL Shorten application"


@app.route("/<string:url>", methods=['GET'])
def read(url):
    """This API receives an HTTP GET request with shorten url passed and
    lookup the shorten url in database. If original url is found, redirects
    user to original url. Otherwise, return JSON reponse of HTTP code 404
    """
    url = Url.query.filter_by(shorten_url=url).first()
    if url:
        original_url = url.original_url
        if not original_url.startswith('http'):
            original_url = 'http://' + original_url
        return redirect(original_url)
    else:
        resp = jsonify({'original_url': 'Not found'})
        return make_response(resp, 404)


@app.route("/api/v1/url", methods=['POST'])
def write():
    """Write API receives original url and return shorten url
    """
    # if original url already shorten, grab shorten url and return
    original_url = request.form['original_url']
    url = Url.query.filter_by(original_url=original_url).first()
    if url:
        shorten_url = url_for("read", url=url.shorten_url, _external=True)
        resp = jsonify({'shorten_url': shorten_url})
    else:
        # if shorten uri already existed, re-generate
        while True:
            shorten_uri = generate_uri()
            uri = Url.query.filter_by(shorten_url=shorten_uri).first()
            if shorten_uri != uri:
                break

        shorten_url = url_for("read", url=shorten_uri, _external=True)
        i = Url(original_url, shorten_uri)
        db.session.add(i)
        db.session.commit()
        resp = jsonify({'shorten_url': shorten_url})
    return make_response(resp, 201)

if __name__ == '__main__':
    app.run(debug=True)