Refactor the big monster into pieces

refactor-monster-pieces-ugly.py

def create_order(products, user):
    # Start a connection
    connection = db_connection()
    connection.begin_transaction()

    # Create a mail message
    mail = mailer.create_message()
    mail.to = user.email
    mail.from_ = 'The store'

    try:
        item_repository = item_repository_for(connection)
        order_repository = order_repository_for(connection)
        payment_repository = payment_repository_for(connection)

        # Calculate the amount for the total order
        amount = Decimal('0')
        for product in products:
            amount += product.price

        # Create an order with the data
        order = order_repository.create()
        order.amount = amount
        order.user = user
        order.date = today()

        # Create one item for each product
        for product in products:
            item = item_repository.create()
            item.name = product.name
            item.price = product.price
            item.date = today()
            item.order = order
            item_repository.add(item)

        # Create a payment
        payment = payment_repository.create()
        payment.amount = amount
        payment.user = user

        # Authorize the payment in the gateway
        authorized = payment_gateway.authorize(payment)
        if not authorized:
            raise Exception('You cannot buy that!')

        # Save the payment with the authorization results
        payment.transaction_id = authorized.transaction_id
        payment_repository.add(payment)
    except Exception as e:
        connection.rollback()
        mail.message = 'Order failed : %s' % e
    else:
        connection.commit()
        mail.message = 'Order successful!'
    finally:
        connection.close()

    mail.send()