--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/donations/views.py	Sat May 05 17:10:48 2012 -0500
@@ -0,0 +1,221 @@
+"""
+Views for the donations application.
+"""
+import urllib2
+import decimal
+import datetime
+import logging
+
+from django.shortcuts import render_to_response
+from django.template import RequestContext
+from django.conf import settings
+from django.contrib.sites.models import Site
+from django.http import HttpResponse
+from django.http import HttpResponseServerError
+from django.contrib.auth.models import User
+from django.views.decorators.csrf import csrf_exempt
+
+
+from donations.models import Donation
+
+PP_DATE_FMT = '%H:%M:%S %b %d, %Y'
+
+def paypal_params():
+    """
+    This function returns a tuple where the 1st element is the Paypal
+    URL and the 2nd element is the Paypal business email. This information
+    depends on the setting DONATIONS_DEBUG.
+    """
+    if settings.DONATIONS_DEBUG:
+        form_action = 'https://www.sandbox.paypal.com/cgi-bin/webscr'
+        business = settings.DONATIONS_BUSINESS_DEBUG
+    else:
+        form_action = 'https://www.paypal.com/cgi-bin/webscr'
+        business = settings.DONATIONS_BUSINESS
+
+    return form_action, business
+
+
+def verify_request(params):
+    """
+    Send the parameters back to Paypal and return the response string.
+    """
+    # If we are doing localhost-type unit tests, just return whatever
+    # the test wants us to...
+    if hasattr(settings, 'DONATIONS_DEBUG_VERIFY_RESPONSE'):
+        return settings.DONATIONS_DEBUG_VERIFY_RESPONSE
+
+    req = urllib2.Request(paypal_params()[0], params)
+    req.add_header("Content-type", "application/x-www-form-urlencoded")
+    try:
+        response = urllib2.urlopen(req)
+    except URLError, e:
+        logging.exception('IPN: exception verifying IPN: %s', e)
+        return None
+
+    return response.read()
+
+
+def index(request):
+    gross, net, donations = Donation.objects.monthly_stats()
+    current_site = Site.objects.get_current()
+    form_action, business = paypal_params()
+
+    return render_to_response('donations/index.html', {
+        'goal': settings.DONATIONS_GOAL,
+        'gross': gross,
+        'net': net,
+        'left': settings.DONATIONS_GOAL - net,
+        'donations': donations,
+        'form_action': form_action,
+        'business': business,
+        'anonymous': settings.DONATIONS_ANON_NAME,
+        'item_name': settings.DONATIONS_ITEM_NAME,
+        'item_number': settings.DONATIONS_ITEM_NUM,
+        'item_anon_number': settings.DONATIONS_ITEM_ANON_NUM,
+        'domain': current_site.domain,
+        },
+        context_instance = RequestContext(request))
+
+
+@csrf_exempt
+def ipn(request):
+    """
+    This function is the IPN listener and handles the IPN POST from Paypal.
+    The algorithm here roughly follows the outline described in chapter 2
+    of Paypal's IPNGuide.pdf "Implementing an IPN Listener".
+
+    """
+    # Log some info about this IPN event
+    ip = request.META.get('REMOTE_ADDR', '?')
+    parameters = request.POST.copy()
+    logging.info('IPN from %s; post data: %s', ip, parameters.urlencode())
+
+    # Now we follow the instructions in chapter 2 of the Paypal IPNGuide.pdf.
+    # Create a request that contains exactly the same IPN variables and values in
+    # the same order, preceded with cmd=_notify-validate
+    parameters['cmd']='_notify-validate'
+
+    # Post the request back to Paypal (either to the sandbox or the real deal),
+    # and read the response:
+    status = verify_request(parameters.urlencode())
+    if status != 'VERIFIED':
+        logging.warning('IPN: Payapl did not verify; status was %s', status)
+        return HttpResponse()
+
+    # Response was VERIFIED; act on this if it is a Completed donation, 
+    # otherwise don't handle it (we are just a donations application. Here
+    # is where we could be expanded to be a more general payment processor).
+
+    payment_status = parameters.get('payment_status')
+    if payment_status != 'Completed':
+        logging.info('IPN: payment_status is %s; we are done.', payment_status)
+        return HttpResponse()
+
+    # Is this a donation to the site?
+    item_number = parameters.get('item_number')
+    if (item_number == settings.DONATIONS_ITEM_NUM or
+        item_number == settings.DONATIONS_ITEM_ANON_NUM):
+        process_donation(item_number, parameters)
+    else:
+        logging.info('IPN: not a donation; done.')
+
+    return HttpResponse()
+
+
+def process_donation(item_number, params):
+    """
+    A few validity and duplicate checks are made on the donation params.
+    If everything is ok, construct a donation object from the parameters and
+    store it in the database.
+
+    """
+    # Has this transaction been processed before?
+    txn_id = params.get('txn_id')
+    if txn_id is None:
+        logging.error('IPN: missing txn_id')
+        return
+
+    try:
+        donation = Donation.objects.get(txn_id__exact=txn_id)
+    except Donation.DoesNotExist:
+        pass
+    else:
+        logging.warning('IPN: duplicate txn_id')
+        return      # no exception, this is a duplicate
+
+    # Is the email address ours?
+    business = params.get('business')
+    if business != paypal_params()[1]:
+        logging.warning('IPN: invalid business: %s', business)
+        return
+
+    # is this a payment received?
+    txn_type = params.get('txn_type')
+    if txn_type != 'web_accept':
+        logging.warning('IPN: invalid txn_type: %s', txn_type)
+        return
+
+    # Looks like a donation, save it to the database.
+    # Determine which user this came from, if any.
+    # The username is stored in the custom field if the user was logged in when
+    # the donation was made.
+    user = None
+    if 'custom' in params and params['custom']:
+        try:
+            user = User.objects.get(username__exact=params['custom'])
+        except User.DoesNotExist:
+            pass
+
+    is_anonymous = item_number == settings.DONATIONS_ITEM_ANON_NUM
+    test_ipn = params.get('test_ipn') == '1'
+
+    first_name = params.get('first_name', '')
+    last_name = params.get('last_name', '')
+    payer_email = params.get('payer_email', '')
+    payer_id = params.get('payer_id', '')
+    memo = params.get('memo', '')
+    payer_status = params.get('payer_status', '')
+
+    try:
+        mc_gross = decimal.Decimal(params['mc_gross'])
+        mc_fee = decimal.Decimal(params['mc_fee'])
+    except KeyError, decimal.InvalidOperation:
+        logging.error('IPN: invalid/missing mc_gross or mc_fee')
+        return
+
+    payment_date = params.get('payment_date')
+    if payment_date is None:
+        logging.error('IPN: missing payment_date')
+        return
+
+    # strip off the timezone
+    payment_date = payment_date[:-4]
+    try:
+        payment_date = datetime.datetime.strptime(payment_date, PP_DATE_FMT)
+    except ValueError:
+        logging.error('IPN: invalid payment_date "%s"', params['payment_date'])
+        return
+
+    try:
+        donation = Donation(
+            user=user,
+            is_anonymous=is_anonymous,
+            test_ipn=test_ipn,
+            txn_id=txn_id,
+            txn_type=txn_type,
+            first_name=first_name,
+            last_name=last_name,
+            payer_email=payer_email,
+            payer_id=payer_id,
+            memo=memo,
+            payer_status=payer_status,
+            mc_gross=mc_gross,
+            mc_fee=mc_fee,
+            payment_date=payment_date)
+    except:
+        logging.exception('IPN: exception during donation creation')
+    else:
+        donation.save()
+        logging.info('IPN: donation saved')
+