1 files changed, 117 insertions, 0 deletions
diff --git a/slog/slog_filter.py b/slog/slog_filter.py
new file mode 100644
index 0000000..1115f05
--- /dev/null
+++ b/slog/slog_filter.py
@@ -0,0 +1,117 @@
+# slog_filter.py - structured logging filtering
+#
+# Copyright 2017  QvarnLabs Ab
+#
+# This program 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.
+#
+# This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+import re
+
+
+class FilterRule:  # pragma: no cover
+
+    def allow(self, log_obj):
+        raise NotImplementedError()
+
+
+class FilterAllow(FilterRule):
+
+    def allow(self, log_obj):
+        return True
+
+
+class FilterDeny(FilterRule):
+
+    def allow(self, log_obj):
+        return False
+
+
+class FilterHasField(FilterRule):
+
+    def __init__(self, field_name):
+        self._field_name = field_name
+
+    def allow(self, log_obj):
+        return self._field_name in log_obj
+
+
+class FilterFieldHasValue(FilterRule):
+
+    def __init__(self, field, value):
+        self._field = field
+        self._value = value
+
+    def allow(self, log_obj):
+        return self._field in log_obj and log_obj[self._field] == self._value
+
+
+class FilterFieldValueRegexp(FilterRule):
+
+    def __init__(self, field, pattern):
+        self._field = field
+        self._pattern = pattern
+
+    def allow(self, log_obj):
+        if self._field not in log_obj:
+            return False
+        value = str(log_obj[self._field])
+        return re.search(self._pattern, value) is not None
+
+
+class FilterInclude(FilterRule):
+
+    def __init__(self, rule_dict, rule):
+        self._rule = rule
+        self._include = rule_dict.get('include', True)
+
+    def allow(self, log_obj):
+        allow = self._rule.allow(log_obj)
+        return (self._include and allow) or (not self._include and not allow)
+
+
+class FilterAny(FilterRule):
+
+    def __init__(self, rules):
+        self._rules = rules
+
+    def allow(self, log_obj):
+        return any(rule.allow(log_obj) for rule in self._rules)
+
+
+def construct_log_filter(filters):
+    if not filters:
+        raise NoFilter()
+    rules = []
+    for spec in filters:
+        rule = None
+        if 'field' in spec:
+            if 'value' in spec:
+                rule = FilterFieldHasValue(spec['field'], spec['value'])
+            elif 'regexp' in spec:
+                rule = FilterFieldValueRegexp(
+                    spec['field'], spec['regexp'])
+            elif 'field' in spec:
+                rule = FilterHasField(spec['field'])
+            else:  # pragma: no cover
+                rule = FilterAllow()
+        if 'include' in spec:
+            rule = FilterInclude(spec, rule)
+        rules.append(rule)
+    return FilterAny(rules)
+
+
+class NoFilter(Exception):
+
+    def __init__(self):
+        super(NoFilter, self).__init__('No log filter specified')