shorten.py

from bidict import bidict
from django.core.exceptions import ValidationError
from django.core.validators import URLValidator
from flask import Flask, request, redirect
from flask_restful import Resource, Api
from random import randrange


class Redirects(Resource):
    def get(self, short):
        if not store.get(short, None):
            return 'Not found.', 404
        return redirect(store.get(short))


class Shorten(Resource):
    def post(self):
        url = request.form['v']
        if not url.startswith('http://') and not url.startswith('https://'):
            return {'status': 'NOK', 'message': 'Only available for http/https URLs.'}, 400
        if len(url) < 10:
            return {'status': 'NOK', 'message': 'URL too short.'}, 400
        try:
            validator(url)
        except ValidationError as e:
            return 'Invalid URL.', 400
        if store.inverse.get(url, None):
            return {'status': 'OK', 'short': store.inverse[url]}, 409
        short = str()
        while True:
            for x in range(6):
                short += base64[randrange(2 ** 6)]
            if short not in store:
                break
            short = str()
        store.put(short, url)
        return {'status': 'OK', 'short': short}, 201


base64 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_'
app = Flask(__name__)
api = Api(app)
store = bidict()
validator = URLValidator()
api.add_resource(Shorten, '/')
api.add_resource(Redirects, '/<short>')

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