from flask import Flask, request, redirect, render_template, url_for
from flask_sqlalchemy import SQLAlchemy
import string
import random

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

class URLMapping(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    original_url = db.Column(db.String(500), nullable=False)
    short_url = db.Column(db.String(10), unique=True, nullable=False)

    def __repr__(self):
        return f'<URLMapping {self.short_url}>'

def generate_short_url():
    return ''.join(random.choices(string.ascii_letters + string.digits, k=6))

@app.route('/')
def index():
    return render_template('index.html')

@app.route('/shorten', methods=['POST'])
def shorten_url():
    original_url = request.form['url'].strip()
    
    if not original_url.startswith(('http://', 'https://')):
        original_url = 'http://' + original_url
    
    short_url = generate_short_url()
    
    new_url = URLMapping(original_url=original_url, short_url=short_url)
    db.session.add(new_url)
    db.session.commit()

    full_short_url = request.host_url + short_url
    
    return f'Short URL: <a href="{full_short_url}">{full_short_url}</a>'

@app.route('/<short_url>')
def redirect_to_url(short_url):
    url_mapping = URLMapping.query.filter_by(short_url=short_url).first()
    if url_mapping:
        return redirect(url_mapping.original_url)
    return 'URL not found!'

if __name__ == '__main__':
    with app.app_context():
        db.create_all()
    app.run(debug=False, host='0.0.0.0', port=80)