"""
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')