Issue 7471 - Add an API for working with blocks of filters

abp/filters/blocks.py

Index: abp/filters/blocks.py
===================================================================
new file mode 100644
--- /dev/null
+++ b/abp/filters/blocks.py
@@ -0,0 +1,83 @@
+# This file is part of Adblock Plus <https://adblockplus.org/>,
+# Copyright (C) 2006-present eyeo GmbH
+#
+# Adblock Plus is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 3 as
+# published by the Free Software Foundation.
+#
+# Adblock Plus 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Extract blocks of filters separated by comments."""
+
+from __future__ import unicode_literals
+
+import re
+
+from abp.filters.parser import ParseError
+
+VAR_REGEXP = re.compile(r'^:(\w+)=(.*)$')
+
+
+class FilterBlock(object):
+    """A block of filters.
+
+    Blocks are consecutive groups of filters separated by comments.
+
+    """
+
+    def __init__(self, comments, filters):
+        self.filters = filters
+        descr_lines = []
+        for comment in comments:
+            match = VAR_REGEXP.search(comment.text)
+            if match:
+                name, value = match.groups()
+                if name.startswith('_') or name in {'filters', 'description'}:
+                    raise ParseError('Invalid variable name',
+                                     comment.to_string())
+                setattr(self, name, value)
+            else:
+                descr_lines.append(comment.text)
+        self.description = '\n'.join(descr_lines)
+
+    def _asdict(self):
+        ret = dict(self.__dict__)
+        ret['filters'] = [f._asdict() for f in ret['filters']]
+        return ret
+
+
+def to_blocks(parsed_lines):
+    """Convert a sequence of parser filter list lines to blocks.
+
+    Parameters
+    ----------
+    parsed_lines : iterable of namedtuple
+        Parsed filter list (see `parser.py` for details on how it's
+        represented).
+
+    Returns
+    -------
+    blocks : iterable of FilterBlock.
+
+    """
+    comments = []
+    filters = []
+
+    for line in parsed_lines:
+        if line.type == 'comment':
+            if filters:
+                yield FilterBlock(comments, filters)
+                comments = []
+                filters = []
+            comments.append(line)
+        elif line.type == 'filter':
+            filters.append(line)
+
+    if filters:
+        yield FilterBlock(comments, filters)