Support ISO8601 duration format for UpdatePolicy PauseTime

Adds a timeutils module in heat common to handle ISO 8601
duration format. Separating this as a different patch per
request.

Change-Id: I2fe6fccde838f4ddac6b898e4518ffb33e2a76fc
Implements: blueprint as-update-policy

heat/common/timeutils.py

@@ -0,0 +1,42 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+"""
+Utilities for handling ISO 8601 duration format.
+"""
+
+import re
+
+
+iso_duration_re = re.compile('PT(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?$')
+
+
+def parse_isoduration(duration):
+    """
+    Convert duration in ISO 8601 format to second(s).
+
+    Year, Month, Week, and Day designators are not supported.
+    Example: 'PT12H30M5S'
+    """
+    result = iso_duration_re.match(duration)
+    if not result:
+        raise ValueError('Only ISO 8601 duration format of the form '
+                         'PT#H#M#S is supported.')
+
+    t = 0
+    t += (3600 * int(result.group(1))) if result.group(1) else 0
+    t += (60 * int(result.group(2))) if result.group(2) else 0
+    t += int(result.group(3)) if result.group(3) else 0
+
+    return t

heat/tests/test_iso8601_utils.py

@@ -0,0 +1,47 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from heat.common import timeutils as util
+from heat.tests.common import HeatTestCase
+from heat.tests import utils
+
+
+class ISO8601UtilityTest(HeatTestCase):
+
+    def setUp(self):
+        super(ISO8601UtilityTest, self).setUp()
+        utils.setup_dummy_db()
+
+    def test_valid_durations(self):
+        self.assertEqual(util.parse_isoduration('PT'), 0)
+        self.assertEqual(util.parse_isoduration('PT1H'), 3600)
+        self.assertEqual(util.parse_isoduration('PT2M'), 120)
+        self.assertEqual(util.parse_isoduration('PT3S'), 3)
+        self.assertEqual(util.parse_isoduration('PT1H5M'), 3900)
+        self.assertEqual(util.parse_isoduration('PT1H5S'), 3605)
+        self.assertEqual(util.parse_isoduration('PT5M3S'), 303)
+        self.assertEqual(util.parse_isoduration('PT1H5M3S'), 3903)
+        self.assertEqual(util.parse_isoduration('PT24H'), 24 * 3600)
+
+    def test_invalid_durations(self):
+        self.assertRaises(ValueError, util.parse_isoduration, 'P1Y')
+        self.assertRaises(ValueError, util.parse_isoduration, 'P1DT12H')
+        self.assertRaises(ValueError, util.parse_isoduration, 'PT1Y1D')
+        self.assertRaises(ValueError, util.parse_isoduration, 'PTAH1M0S')
+        self.assertRaises(ValueError, util.parse_isoduration, 'PT1HBM0S')
+        self.assertRaises(ValueError, util.parse_isoduration, 'PT1H1MCS')
+        self.assertRaises(ValueError, util.parse_isoduration, 'PT1H1H')
+        self.assertRaises(ValueError, util.parse_isoduration, 'PT1MM')
+        self.assertRaises(ValueError, util.parse_isoduration, 'PT1S0S')
+        self.assertRaises(ValueError, util.parse_isoduration, 'ABCDEFGH')