add currency exchange rates

liberapay/cron.py

@@ -8,6 +8,7 @@
 logger = logging.getLogger('liberapay.cron')
 
 
+Daily = namedtuple('Daily', 'hour')
 Weekly = namedtuple('Weekly', 'weekday hour')
 
 
@@ -20,7 +21,7 @@ def __init__(self, website):
  self.exclusive_jobs = []
 
  def __call__(self, period, func, exclusive=False):
- if isinstance(period, int) and period <= 0:
+ if not self.website.env.run_cron_jobs:
  return
  if exclusive and not self.has_lock:
  self.exclusive_jobs.append((period, func))
@@ -45,6 +46,21 @@ def f():
  except Exception as e:
  self.website.tell_sentry(e, {})
  sleep(86400 * 6)
+ elif isinstance(period, Daily):
+ while True:
+ now = datetime.utcnow()
+ then = now.replace(hour=period.hour, minute=0, second=0)
+ seconds = (then - now).total_seconds()
+ if seconds > 0:
+ # later today
+ sleep(seconds)
+ elif seconds < -3600:
+ # tomorrow
+ sleep(3600 * 24 + seconds)
+ try:
+ func()
+ except Exception as e:
+ self.website.tell_sentry(e, {})
  else:
  while True:
  try:

liberapay/main.py

@@ -20,12 +20,13 @@
 
 from liberapay import utils, wireup
 from liberapay.billing.payday import Payday, create_payday_issue
-from liberapay.cron import Cron, Weekly
+from liberapay.cron import Cron, Daily, Weekly
 from liberapay.models.community import Community
 from liberapay.models.participant import Participant
 from liberapay.models.repository import refetch_repos
 from liberapay.security import authentication, csrf, set_default_security_headers
 from liberapay.utils import b64decode_s, b64encode_s, erase_cookie, http_caching, i18n, set_cookie
+from liberapay.utils.currencies import fetch_currency_exchange_rates
 from liberapay.utils.state_chain import (
  attach_environ_to_request, create_response_object, canonize, insert_constants,
  _dispatch_path_to_filesystem, merge_exception_into_response, return_500_for_exception,
@@ -94,7 +95,7 @@ def _assert(x):
 # =============
 
 conf = website.app_conf
-if env.run_cron_jobs and conf:
+if conf:
  cron = Cron(website)
  cron(conf.check_db_every, website.db.self_check, True)
  cron(conf.dequeue_emails_every, Participant.dequeue_emails, True)
@@ -103,6 +104,7 @@ def _assert(x):
  cron(Weekly(weekday=3, hour=2), create_payday_issue, True)
  cron(conf.clean_up_counters_every, website.db.clean_up_counters, True)
  cron(conf.update_cached_amounts_every, Payday.update_cached_amounts, True)
+ cron(Daily(hour=16), lambda: fetch_currency_exchange_rates(website.db), True)
 
 
 # Website Algorithm

liberapay/utils/currencies.py

@@ -0,0 +1,46 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from decimal import Decimal, ROUND_UP
+
+from mangopay.utils import Money
+import requests
+import xmltodict
+
+from liberapay.constants import D_CENT, D_ZERO
+from liberapay.website import website
+
+
+def _convert(self, c):
+ if self.currency == c:
+ return self
+ amount = self.amount * website.currency_exchange_rates[(self.currency, c)]
+ return Money(amount.quantize(D_CENT), c)
+
+
+Money.convert = _convert
+
+
+def fetch_currency_exchange_rates(db):
+ currencies = set(db.one("SELECT array_to_json(enum_range(NULL::currency))"))
+ r = requests.get('https://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml')
+ rates = xmltodict.parse(r.text)['gesmes:Envelope']['Cube']['Cube']['Cube']
+ for fx in rates:
+ currency = fx['@currency']
+ if currency not in currencies:
+ continue
+ db.run("""
+ INSERT INTO currency_exchange_rates
+ (source_currency, target_currency, rate)
+ VALUES ('EUR', %(target)s, %(rate)s)
+ , (%(target)s, 'EUR', 1 / %(rate)s)
+ ON CONFLICT (source_currency, target_currency) DO UPDATE
+ SET rate = excluded.rate
+ """, dict(target=currency, rate=Decimal(fx['@rate'])))
+
+
+def get_currency_exchange_rates(db):
+ r = {(r[0], r[1]): r[2] for r in db.all("SELECT * FROM currency_exchange_rates")}
+ if r:
+ return r
+ fetch_currency_exchange_rates(db)
+ return get_currency_exchange_rates(db)

liberapay/wireup.py

@@ -42,6 +42,7 @@
 from liberapay.models import DB
 from liberapay.security.authentication import ANON
 from liberapay.utils import find_files, markdown, mkdir_p
+from liberapay.utils.currencies import get_currency_exchange_rates
 from liberapay.utils.emails import compile_email_spt
 from liberapay.utils.http_caching import asset_etag
 from liberapay.utils.i18n import (
@@ -636,6 +637,10 @@ def s3(env):
  return {'s3': s3}
 
 
+def currency_exchange_rates(db):
+ return {'currency_exchange_rates': get_currency_exchange_rates(db)}
+
+
 minimal_algorithm = Algorithm(
  env,
  make_sentry_teller,
@@ -657,6 +662,7 @@ def s3(env):
  load_scss_variables,
  s3,
  trusted_proxies,
+ currency_exchange_rates,
 )
 
 

sql/app-conf-tests.sql

@@ -15,3 +15,7 @@ END;
 $$;
 
 DROP FUNCTION update_app_conf(text, jsonb);
+
+INSERT INTO currency_exchange_rates
+ VALUES ('EUR', 'USD', 1.2)
+ , ('USD', 'EUR', 1 / 1.2);

sql/currencies.sql

@@ -238,3 +238,33 @@ CREATE OPERATOR <= (
  commutator = >=,
  negator = >
 );
+
+
+-- Exchange rates
+
+CREATE TABLE currency_exchange_rates
+( source_currency currency NOT NULL
+, target_currency currency NOT NULL
+, rate numeric NOT NULL
+, UNIQUE (source_currency, target_currency)
+);
+
+
+-- Currency conversion function
+
+CREATE FUNCTION convert(currency_amount, currency) RETURNS currency_amount AS $$
+ DECLARE
+ rate numeric;
+ BEGIN
+ IF ($1.currency = $2) THEN RETURN $1; END IF;
+ rate := (
+ SELECT r.rate
+ FROM currency_exchange_rates r
+ WHERE r.source_currency = $1.currency
+ );
+ IF (rate IS NULL) THEN
+ RAISE 'missing exchange rate %->%', $1.currency, $2;
+ END IF;
+ RETURN ($1.amount / rate, $2);
+ END;
+$$ LANGUAGE plpgsql STRICT;

tests/test.env

@@ -6,3 +6,4 @@ CACHE_STATIC=yes
 CLEAN_ASSETS=yes
 OVERRIDE_QUERY_CACHE=yes
 ASPEN_CHANGES_RELOAD=no
+RUN_CRON_JOBS=no