Add tools.capabilities.paste tools for building Paste Backends

It will provide useful functions but as it imposes on the structure of
the backends, it will not be put straight into the Paste capability.

weboob/tools/capabilities/__init__.py

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+

weboob/tools/capabilities/paste.py

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+# -*- coding: utf-8 -*-
+
+# Copyright(C) 2011 Laurent Bachelier
+#
+# This file is part of weboob.
+#
+# weboob is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# weboob is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with weboob. If not, see <http://www.gnu.org/licenses/>.
+
+
+from __future__ import with_statement
+
+from weboob.capabilities.paste import ICapPaste
+
+
+class BasePasteBackend(ICapPaste):
+    EXPIRATIONS = {}
+    """
+    List of expirations and their corresponding remote codes (any type can be used).
+    The expirations, i.e. the keys, are integers representing the duration
+    in seconds. There also can be one False key, for the "forever" expiration.
+    """
+
+    def get_closest_expiration(self, max_age):
+        """
+        Get the expiration closest (and less or equal to) max_age (int, in seconds).
+        max_age set to False means we want it to never expire.
+
+        @return int or False if found, else None
+        """
+        # "forever"
+        if max_age is False and False in self.EXPIRATIONS:
+            return max_age
+        # get timed expirations, longest first
+        expirations = sorted([e for e in self.EXPIRATIONS if e is not False], reverse=True)
+        # find the first expiration that is below or equal to the maximum wanted age
+        for e in expirations:
+            if max_age is False or max_age >= e:
+                return e
+
+def test():
+    class MockPasteBackend(BasePasteBackend):
+        def __init__(self, expirations):
+            self.EXPIRATIONS = expirations
+
+    # all expirations are too high
+    assert MockPasteBackend({1337: '', 42: '', False: ''}).get_closest_expiration(1) is None
+    # we found a suitable lower or equal expiration
+    assert MockPasteBackend({1337: '', 42: '', False: ''}).get_closest_expiration(84) is 42
+    assert MockPasteBackend({1337: '', 42: '', False: ''}).get_closest_expiration(False) is False
+    assert MockPasteBackend({1337: '', 42: ''}).get_closest_expiration(False) is 1337
+    assert MockPasteBackend({1337: '', 42: '', False: ''}).get_closest_expiration(1336) is 42
+    assert MockPasteBackend({1337: '', 42: '', False: ''}).get_closest_expiration(1337) is 1337
+    assert MockPasteBackend({1337: '', 42: '', False: ''}).get_closest_expiration(1338) is 1337
+    # this format should work, though of doubtful usage
+    assert MockPasteBackend([1337, 42, False]).get_closest_expiration(84) is 42