fund-wikihouse.py

import logging

from cgi import escape
from decimal import Decimal
from json import loads as decode_json

from google.appengine.api import memcache
from google.appengine.api.urlfetch import fetch as urlfetch, POST
from google.appengine.ext import db

create_key = db.Key.from_path

CAMPAIGNS = [
    ('sketchup', 500000, 'SketchUp Extension', 'Blah blah blah'),
    ('hardware', 25000000, 'Hardware Designs', 'More blah blah'),
    ('platform', 18000000, 'Platform Development', 'Even more blah'),
]

CAMPAIGN_KEYS = {}

for _campaign in CAMPAIGNS:
    CAMPAIGN_KEYS[_campaign[0]] = create_key('C', _campaign[0])
del _campaign

CURRENCIES = frozenset(['GBP', 'EUR', 'USD'])
PAYPAL_ACCOUNT = '[email protected]'

class C(db.Model): # key=campaign_id
    v = db.IntegerProperty(default=0)
    c = db.IntegerProperty(default=0)                  # count of funders
    t1 = db.IntegerProperty(default=0)                 # total raised (GBP)
    t2 = db.IntegerProperty(default=0)                 # total raised (EUR)
    t3 = db.IntegerProperty(default=0)                 # total raised (USD)

Campaign = C

class P(db.Model): # key=txn_id
    v = db.IntegerProperty(default=0)
    c = db.StringProperty(default='', indexed=False)   # campaign id
    d = db.DateTimeProperty(auto_now_add=True)         # date created
    e = db.StringProperty(default='', indexed=False)   # payer email
    f = db.StringProperty(default='', indexed=False)   # fee
    g = db.StringProperty(default='', indexed=False)   # gross
    h = db.BooleanProperty(default=False)              # handled
    i = db.TextProperty()                              # info payload
    m = db.DateTimeProperty(auto_now=True)             # modified date
    n = db.StringProperty(default='', indexed=False)   # net
    p = db.StringProperty(default='', indexed=False)   # payer name
    t = db.StringProperty(default='', indexed=False)   # currency type

PayPalTransaction = P

class T(db.Model): # parent=campaign_id, key=txn_id
    """Stub entity to synchronise accounted transactions."""

TransactionReceipt = T

# This handler needs to be served at the path: /ipn
#
# The required parameters are:
#
#       post_body — The body of the POST request that PayPal made to /ipn
#                   This would have been encoded in windows-1252 and we
#                   shouldn't corrupt it by trying to treat it as utf-8
#
#       kwargs — The key/value pairs from the parsed POST body.
#
# The returned string value from this handler needs to be served with a
# 200 OK code.
def handle_ipn(post_body, **kwargs):
    resp = do_actual_ipn_handling(post_body, kwargs)
    if resp != "OK":
        logging.info("IPN RETCODE: %s" % resp)
    return resp

def do_actual_ipn_handling(txn_info, kwargs):
    if kwargs['payment_status'] != 'Completed':
        return '1'
    resp = urlfetch(
        url="https://www.paypal.com/cgi-bin/webscr",
        method=POST,
        payload=('cmd=_notify-validate&' + txn_info)
        )
    if resp.content != 'VERIFIED':
        return '2'
    campaign = kwargs['custom']
    if not campaign:
        return '3'
    if not campaign.startswith('wikihouse.'):
        return '4'
    campaign = campaign.split('.', 1)[1].strip()
    if campaign not in CAMPAIGN_KEYS:
        return '5'
    receiver = kwargs['receiver_email']
    if receiver != PAYPAL_ACCOUNT:
        return '6'
    currency = kwargs['mc_currency']
    if currency not in CURRENCIES:
        return '7'
    gross = kwargs['mc_gross']
    fee = kwargs['mc_fee']
    gross_d = Decimal(gross)
    fee_d = Decimal(fee)
    net = gross_d - fee_d
    if net <= 0:
        return '8'
    txn_id = kwargs['txn_id']
    first_name = kwargs.get('first_name')
    if first_name:
        first_name += ' '
    payer_name = (first_name + kwargs.get('last_name', '')).strip()
    payer_email = kwargs['payer_email']
    txn = PayPalTransaction.get_or_insert(
        key_name=txn_id, c=campaign, e=payer_email, f=fee, g=gross, i=txn_info,
        n=str(net), p=payer_name, t=currency
        )
    db.run_in_transaction(
        update_campaign_tallies, campaign, txn_id, currency, net
        )
    txn.h = True
    txn.put()
    return 'OK'

def update_campaign_tallies(campaign_id, txn_id, currency, amount):
    amount_in_pence = int(amount * 100)
    campaign_key = CAMPAIGN_KEYS[campaign_id]
    receipt = db.get(create_key('T', txn_id, parent=campaign_key))
    if receipt:
        return
    receipt = TransactionReceipt(key_name=txn_id, parent=campaign_key)
    campaign = Campaign.get(campaign_key)
    campaign.c += 1
    if currency == 'GBP':
        campaign.t1 += amount_in_pence
    elif currency == 'EUR':
        campaign.t2 += amount_in_pence
    elif currency == 'USD':
        campaign.t3 += amount_in_pence
    db.put([campaign, receipt])
    return

def render_number_with_commas(n):
    result = ''
    while n >= 1000:
        n, r = divmod(n, 1000)
        result = ",%03d%s" % (r, result)
    return "%d%s" % (n, result)

def get_exchange_rate_to_gbp(currency, cache={}):
    if currency == 'GBP':
        return 1
    if currency in cache:
        return cache[currency]
    rate = memcache.get('exchange:%s' % currency)
    if rate:
        return cache.setdefault(currency, rate)
    url = "http://rate-exchange.appspot.com/currency?from=%s&to=GBP" % currency
    try:
        rate = decode_json(urlfetch(url).content)['rate']
    except Exception, err:
        logging.error("currency conversion: %s" % err)
        return 0
    memcache.set('exchange:%s' % currency, rate)
    return cache.setdefault(currency, rate)

def gen_fund_form():
    html = []; out = html.append
    entities = dict(
        (ent.key().name(), ent)
        for ent in Campaign.get(sorted(CAMPAIGN_KEYS))
        )
    for campaign in CAMPAIGNS:
        campaign_id = campaign[0]
        ent = entities[campaign_id]
        if ent.c == 1:
            backers = '1 Backer'
        else:
            backers = '%d Backers' % ent.c
        target = campaign[1]
        total = ent.t1
        if ent.t2:
            total += (ent.t2 * get_exchange_rate_to_gbp('EUR'))
        if ent.t3:
            total += (ent.t3 * get_exchange_rate_to_gbp('USD'))
        raised = int(total)
        if raised >= target:
            pct = 100
        else:
            pct = (raised * 100)/target
        kwargs = dict(
            backers=backers,
            campaign=campaign_id,
            email=PAYPAL_ACCOUNT,
            info=escape(campaign[3]),
            pct=pct * 1, # multiply by 2 if width == 200px, etc.
            raised=render_number_with_commas(raised/100),
            target=render_number_with_commas(target/100),
            title=escape(campaign[2])
            )
        out("""<div class="campaign">
    <div class="campaign-title">%(title)s</div>
    <div class="campaign-info">%(info)s</div>
    <div class="campaign-backers">%(backers)s</div>
    <div class="campaign-raised">Raised: £%(raised)s</div>
    <div class="campaign-target">%(pct)s%% of target £%(target)s</div>
    <form action="https://www.paypal.com/uk/cgi-bin/webscr" method="post">
    <input type="hidden" name="charset" value="utf-8">
    <input type="hidden" name="cmd" value="_donations">
    <input type="hidden" name="business" value="%(email)s">
    <input type="hidden" name="item_name" value="Fund WikiHouse">
    <input type="hidden" name="item_number" value="wikihouse.%(campaign)s">
    <input type="hidden" name="custom" value="wikihouse.%(campaign)s">
    <input type="hidden" name="return" value="http://www.wikihouse.cc/thank-you">
    <input type="hidden" name="rm" value="1">
    <input type="hidden" name="cancel_return" value="http://www.wikihouse.cc/">
    <input type="hidden" name="notify_url" value="https://wikihouse-cc.appspot.com/ipn">
    <input type="text" name="amount" value="" placeholder="Amount, e.g. 30.00">
    <select name="currency_code">
        <option value="USD">US Dollars ($)</option>
        <option value="GBP">British Pounds (£)</option>
        <option value="EUR">Euros (€)</option>
    </select>
    <input type="submit" name="submit" value=" Back This! ">
    </form></div>""" % kwargs)
    return ''.join(html)