first commit

modules/currency/ecb.py

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+# This file is part of Tryton.  The COPYRIGHT file at the top level of
+# this repository contains the full copyright notices and license terms.
+
+import datetime as dt
+import ssl
+import sys
+
+try:
+    from lxml import etree as ET
+except ImportError:
+    try:
+        import xml.etree.cElementTree as ET
+    except ImportError:
+        import xml.etree.ElementTree as ET
+
+from decimal import Decimal
+from urllib.error import HTTPError
+from urllib.request import urlopen
+
+_URL = 'https://www.ecb.europa.eu/stats/eurofxref/'
+_URL_TODAY = _URL + 'eurofxref-daily.xml'
+_URL_90 = _URL + 'eurofxref-hist-90d.xml'
+_URL_HIST = _URL + 'eurofxref-hist.xml'
+_START_DATE = dt.date(1999, 1, 4)
+_CUBE_TAG = '{http://www.ecb.int/vocabulary/2002-08-01/eurofxref}Cube'
+
+
+class RatesNotAvailableError(Exception):
+    pass
+
+
+class UnsupportedCurrencyError(Exception):
+    pass
+
+
+def _parse_time(time):
+    return dt.datetime.strptime(time, '%Y-%m-%d').date()
+
+
+def _find_time(source, time=None):
+    for _, element in ET.iterparse(source):
+        if element.tag == _CUBE_TAG and 'time' in element.attrib:
+            if time and _parse_time(element.attrib.get('time')) <= time:
+                return element
+            elif time is None:
+                return element
+            element.clear()
+
+
+def get_rates(currency='EUR', date=None):
+    if date is None:
+        date = dt.date.today()
+    if date < _START_DATE:
+        date = _START_DATE
+    context = ssl.create_default_context()
+    try:
+        with urlopen(_URL_TODAY, context=context) as response:
+            element = _find_time(response)
+            last_date = _parse_time(element.attrib['time'])
+            if last_date < date:
+                raise RatesNotAvailableError()
+            elif last_date == date:
+                return _compute_rates(element, currency, date)
+
+        if last_date - date < dt.timedelta(days=90):
+            url = _URL_90
+        else:
+            url = _URL_HIST
+        with urlopen(url, context=context) as response:
+            element = _find_time(response, date)
+            if element is None and url == _URL_90:
+                with urlopen(_URL_HIST, context=context) as response:
+                    element = _find_time(response, date)
+            return _compute_rates(element, currency, date)
+    except HTTPError as e:
+        raise RatesNotAvailableError() from e
+
+
+def _compute_rates(element, currency, date):
+    currencies = {}
+    for cur in element:
+        currencies[cur.attrib['currency']] = Decimal(cur.attrib['rate'])
+    if currency != 'EUR':
+        currencies['EUR'] = Decimal(1)
+        try:
+            base_rate = currencies.pop(currency)
+        except KeyError:
+            raise UnsupportedCurrencyError(f'{currency} is not available')
+        for cur, rate in currencies.items():
+            currencies[cur] = (rate / base_rate).quantize(Decimal('.0001'))
+    return currencies
+
+
+if __name__ == '__main__':
+    currency = 'EUR'
+    if len(sys.argv) > 1:
+        currency = sys.argv[1]
+    date = None
+    if len(sys.argv) > 2:
+        date = dt.datetime.strptime(sys.argv[2], '%Y-%m-%d').date()
+    print(get_rates(currency, date))