Khipu payment form

gistfile1.py

# coding=utf-8
import hashlib

from django import forms

from .khipu_settings import USER_ID, USER_KEY


class KhipuPaymentForm(forms.Form):

    receiver_id = forms.CharField(required=True, widget=forms.HiddenInput())
    subject = forms.CharField(required=True, widget=forms.HiddenInput())
    body = forms.CharField(required=True, widget=forms.HiddenInput())
    amount = forms.IntegerField(required=True, widget=forms.HiddenInput())
    payer_email = forms.CharField(required=False, widget=forms.HiddenInput())
    transaction_id = forms.CharField(required=False, widget=forms.HiddenInput())
    custom = forms.CharField(required=False, widget=forms.HiddenInput())
    notify_url = forms.CharField(required=False, widget=forms.HiddenInput())
    return_url = forms.CharField(required=False, widget=forms.HiddenInput())
    cancel_url = forms.CharField(required=False, widget=forms.HiddenInput())
    picture_url = forms.CharField(required=False, widget=forms.HiddenInput())
    hash = forms.CharField(required=False, widget=forms.HiddenInput())

    def __init__(self, subject, body, amount, notify_url='', return_url='', cancel_url='', transaction_id='',
                 payer_email='', picture_url='', custom='', *args, **kwargs):

        super(KhipuPaymentForm, self).__init__(*args, **kwargs)

        params = [
            ('receiver_id', USER_ID),
            ('subject', subject),
            ('body', body),
            ('amount', int(amount)),
            ('payer_email', payer_email),
            ('transaction_id', transaction_id),
            ('custom', custom),
            ('notify_url', notify_url),
            ('return_url', return_url),
            ('cancel_url', cancel_url),
            ('picture_url', picture_url),
        ]

        for param in params:
            self.fields[param[0]].initial = param[1]

        self.fields['hash'].initial = self.generate_hash(params)
        
    def generate_hash(self, params):
        """ Implements the hashing function described in https://khipu.com/page/api
        :param params Any paramater you wish to encode
        :return A string representing the hash of an api call
        """

        string = ''
        for param in params:
            string += '%s=%s&' % (str(param[0]), str(param[1]))
        string += 'secret=' + USER_KEY
        return hashlib.sha1(string).hexdigest()
        
# Luego en un template se usa así:
#
#<form action="https://khipu.com/api/1.1/createPaymentPage" method="post">
#  {{ khipu_form }}
#  <input type="submit" value="Pagar con khipu"/>
#</form>