lib.PackageFilter: Add module

Add a package filter abstraction designed to replace the package
filter string tossed around various functions througout jw-pkg.

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/PackageFilter.py

@@ -0,0 +1,26 @@
+# -*- coding: utf-8 -*-
+
+import abc, re
+
+from .Package import Package
+
+class PackageFilter(abc.ABC):
+
+    @abc.abstractmethod
+    def _match(self, package: Package) -> bool:
+        raise NotImplementedError()
+
+    def match(self, package: Package) -> bool:
+        return self._match(package)
+
+class PackageFilterString(PackageFilter):
+
+    def __init__(self, definition: str) -> None:
+        # -- Poor man's parsing for now
+        url_rx_str = re.sub(r'^\s*url\s*=~\s*', '', definition)
+        if url_rx_str == definition:
+            raise Exception(f'Unsupported filter string "{definition}"')
+        self.__definition = url_rx_str
+
+    def _match(self, package: Package) -> bool:
+        return re.search(self.__definition, package.url) is not None