Webcash merchant demo using python/flask

merchantcash.py

"""
A small Flask web application to demonstrate a shopping cart with simple checkout.

This file was written mostly by Github Co-pilot!
Only the webcash API endpoint was specialized knowledge.
"""

import secrets
import datetime
import json

# pip3 install requests webcash flask
import requests
from webcash import SecretWebcash
from flask import Flask, render_template, request, redirect, url_for, flash, session, render_template_string


def replace_webcash(webcash):
    """
    Make a request to the webcash server to replace the given webcash with a new secret value.
    """
    if not isinstance(webcash, SecretWebcash):
        webcash = SecretWebcash.deserialize(webcash)

    # generate a new webcash secret
    secret_value = secrets.token_hex(32)
    new_webcash = SecretWebcash(amount=webcash.amount, secret_value=secret_value)

    # make a request to the webcash server to replace the webcash
    replace_data = {
        "webcashes": [str(webcash)],
        "new_webcashes": [str(new_webcash)],
        "legalese": {"terms": True},   
    }

    response = requests.post("https://webcash.tech/api/v1/replace", json=replace_data)
    if response.status_code != 200:
        raise Exception("Replace webcash failed: {}".format(response.text))
    
    # Seems that it worked!
    return new_webcash

# Create the application object
app = Flask(__name__)

# Create a secret key for session
app.secret_key = 'my precious'

# Create a list of products
products = [
    {"SKU": 1001, "name": "T-Shirt", "price": 10},
    {"SKU": 1002, "name": "Jeans", "price": 60},
    {"SKU": 1003, "name": "Socks", "price": 7},
]

# Create a flask endpoint to display the homepage from a static file (index.html)
@app.route('/')
def homepage():
    """
    Display the homepage.
    """
    #return render_template('index.html')

    output = """
        <div>
            <h1>Welcome to the Flask/Webcash Shopping Cart demo</h1>
            <p>Browse our selection of products and pay with webcash!</p>
            <a href="{products_url}">Products</a> | <a href="{shopping_cart_url}">Shopping Cart</a>
        </div>
    """.format(products_url=url_for('products_view'), shopping_cart_url=url_for('shopping_cart'))

    return render_template_string(output)

# Create a flask endpoint to display the products
@app.route('/products')
def products_view():
    """
    Display the products.
    """
    #return render_template('products.html', products=products)

    output = ""

    for product in products:
        add_to_cart_url = url_for('add_to_cart', product_id=product['SKU'])
        output += f"<p><a href=\"{add_to_cart_url}\">{product['name']} - {product['price']}</a></p>"

    # render output in the products.html template
    return render_template_string(output)
    #return render_template('products.html', products=output)

# Create a flask endpoint to add a product to the user's shopping cart
@app.route('/add_to_cart/<int:product_id>')
def add_to_cart(product_id):
    """
    Add a product to the user's shopping cart.
    """
    # Check if the user's shopping cart is in the session
    if 'shopping_cart' not in session:
        # If not, create a new shopping cart
        session['shopping_cart'] = []

    # Add the product to the shopping cart
    session['shopping_cart'].append(product_id)

    # Display a flash message to the user
    flash('Product added to cart.')

    # Redirect the user to the shopping cart
    return redirect(url_for('shopping_cart'))

# Create a flask endpoint to display the contents of the user's shopping cart
@app.route('/shopping_cart')
def shopping_cart():
    """
    Display the contents of the user's shopping cart.
    """
    # Check if the user's shopping cart is in the session
    if 'shopping_cart' not in session:
        # If not, create a new shopping cart
        session['shopping_cart'] = []

    # Display the shopping cart
    #return render_template('shopping_cart.html', products=products, shopping_cart=session['shopping_cart'])

    # Calculate the total price of the user's shopping cart
    total_price = 0
    for product_id in session['shopping_cart']:
        for product in products:
            if product['SKU'] == product_id:
                total_price += product['price']

    output = """
    <div id="shopping-cart">
        <a href="{products_url}">Products</a>
        <h2>Shopping Cart</h2>
        Total: {total}
        <form action="{action}" method="POST">
            First name: <input type="text" name="first_name"><br />
            Last name: <input type="text" name="last_name"><br />
            Your email: <input type="text" name="email"><br />
            <table class="table table-striped">
                <thead>
                    <tr>
                        <th>Product</th>
                        <th>Price</th>
                        <th>Quantity</th>
                        <th>Actions</th>
                    </tr>
                </thead>
                <tbody>
    """.format(action=url_for('checkout'), total=total_price, products_url=url_for("products_view"))

    # Loop through the shopping cart
    for product_id in session['shopping_cart']:
        # Get the product
        product = [p for p in products if p['SKU'] == product_id][0]
        # Render the product
        output += """
                    <tr>
                        <td>{name}</td>
                        <td>{price}</td>
                        <td>1</td>
                        <td><a href="{remove}">Remove from cart</a></td>
                    </tr>
        """.format(name=product['name'], price=product['price'], remove=url_for('remove_from_cart', product_id=product['SKU']))

    output += """
                </tbody>      
            </table>

            Your webcash payment: <input type="text" name="webcash" autoComplete=no><br />
            <input type=submit value="Checkout" />            
        </form>
    </div>
    """.format(url_for('checkout'))

    # render the output for flask
    # tell flask to render "output" as html
    #return render_template('shopping_cart.html', output=output)

    return render_template_string(output)

# Create a flask endpoint to remove a product from the user's shopping cart
@app.route('/remove_from_cart/<int:product_id>')
def remove_from_cart(product_id):
    """
    Remove a product from the user's shopping cart.
    """
    # Check if the user's shopping cart is in the session
    if 'shopping_cart' not in session:
        # If not, create a new shopping cart
        session['shopping_cart'] = []

    # Remove the product from the shopping cart
    session['shopping_cart'].remove(product_id)

    # Display a flash message to the user
    flash('Product removed from cart.')

    # Redirect the user to the shopping cart
    return redirect(url_for('shopping_cart'))

# Create a flask endpoint to submit the checkout form
@app.route('/checkout', methods=['POST'])
def checkout():
    """
    Process the checkout form.
    """
    # Check if the user's shopping cart is in the session
    if 'shopping_cart' not in session:
        # If not, create a new shopping cart
        session['shopping_cart'] = []
        flash("Your shopping cart is empty.")
        return redirect(url_for('shopping_cart'))

    # Calculate the total price of the user's shopping cart
    total_price = 0
    for product_id in session['shopping_cart']:
        for product in products:
            if product['SKU'] == product_id:
                total_price += product['price']

    # Get the user's webcash from the request
    webcash = request.form['webcash']
    webcash = SecretWebcash.deserialize(webcash)

    # Check that the webcash is sufficient
    # If not, display a flash message to the user
    # If so, process the payment
    if webcash.amount != total_price:
        flash('Insufficient webcash. You might want to re-insert it: {}'.format(str(webcash)))
    else:
        # Replace the given webcash with a new value. Note that this is kind of
        # dangerous because the new secret is not deterministic and there's no
        # way to get it back if the process dies while processing the payment.
        new_webcash = replace_webcash(webcash)
        print("new_webcash: " + str(new_webcash))

        # Take the shopping cart information and the new webcash, and prepare an email to send to the merchant.
        order_data = {
            'timestamp': datetime.datetime.now(datetime.timezone.utc).strftime("%Y-%m-%d %H:%M:%S"),
            'shopping_cart': str(session['shopping_cart']),
            'computed_total': str(total_price),
            'webcash': str(new_webcash),
            'original_webcash': str(webcash),
            'first_name': request.form['first_name'],
            'last_name': request.form['last_name'],
            'email': request.form['email'],
        }

        # Send the order data to the merchant by email
        email_address = "orders@myshop.com"
        email_subject = "New order"
        #email_body = render_template('order_email.html', order_data=order_data)
        #send_email(email_address, email_subject, email_body)

        # Write the order data to a file using json.
        with open('orders.json', 'a') as f:
            f.write(json.dumps(order_data))

        # Display a flash message to the user
        flash('Payment successful. Thank you for shopping with us!')

    # Redirect the user to the homepage
    return redirect(url_for('homepage'))

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